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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Kaaret%2C+P&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Kaaret%2C+P&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Kaaret%2C+P&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> <li> <a href="/search/?searchtype=author&query=Kaaret%2C+P&start=100" class="pagination-link " aria-label="Page 3" aria-current="page">3 </a> </li> <li> <a href="/search/?searchtype=author&query=Kaaret%2C+P&start=150" class="pagination-link " aria-label="Page 4" aria-current="page">4 </a> </li> <li> <a href="/search/?searchtype=author&query=Kaaret%2C+P&start=200" class="pagination-link " aria-label="Page 5" aria-current="page">5 </a> </li> <li><span class="pagination-ellipsis">…</span></li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.16868">arXiv:2411.16868</a> <span> [<a href="https://arxiv.org/pdf/2411.16868">pdf</a>, <a href="https://arxiv.org/format/2411.16868">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> IXPE Observation of the Low-Synchrotron Peaked Blazar S4 0954+65 During An Optical-X-ray Flare </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kouch%2C+P+M">Pouya M. Kouch</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Fenu%2C+F">Francesco Fenu</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+H">Haocheng Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Boula%2C+S">Stella Boula</a>, <a href="/search/astro-ph?searchtype=author&query=Middei%2C+R">Riccardo Middei</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Gesu%2C+L">Laura Di Gesu</a>, <a href="/search/astro-ph?searchtype=author&query=Paraschos%2C+G+F">Georgios F. Paraschos</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Lindfors%2C+E">Elina Lindfors</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">Henric Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Hu%2C+K">Kun Hu</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Cavazzuti%2C+E">Elisabetta Cavazzuti</a>, <a href="/search/astro-ph?searchtype=author&query=Errando%2C+M">Manel Errando</a>, <a href="/search/astro-ph?searchtype=author&query=Blinov%2C+D">Dmitry Blinov</a>, <a href="/search/astro-ph?searchtype=author&query=Gourni%2C+A">Anastasia Gourni</a>, <a href="/search/astro-ph?searchtype=author&query=Kiehlmann%2C+S">Sebastian Kiehlmann</a>, <a href="/search/astro-ph?searchtype=author&query=Kourtidis%2C+A">Angelos Kourtidis</a>, <a href="/search/astro-ph?searchtype=author&query=Mandarakas%2C+N">Nikos Mandarakas</a>, <a href="/search/astro-ph?searchtype=author&query=Triantafyllou%2C+N">Nikolaos Triantafyllou</a>, <a href="/search/astro-ph?searchtype=author&query=Vervelaki%2C+A">Anna Vervelaki</a> , et al. (112 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.16868v1-abstract-short" style="display: inline;"> The X-ray polarization observations made possible with the Imaging X-ray Polarimetry Explorer (IXPE) offer new ways of probing high-energy emission processes in astrophysical jets from blazars. Here we report on the first X-ray polarization observation of the blazar S4 0954+65 in a high optical and X-ray state. During our multi-wavelength campaign on the source, we detected an optical flare whose… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.16868v1-abstract-full').style.display = 'inline'; document.getElementById('2411.16868v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.16868v1-abstract-full" style="display: none;"> The X-ray polarization observations made possible with the Imaging X-ray Polarimetry Explorer (IXPE) offer new ways of probing high-energy emission processes in astrophysical jets from blazars. Here we report on the first X-ray polarization observation of the blazar S4 0954+65 in a high optical and X-ray state. During our multi-wavelength campaign on the source, we detected an optical flare whose peak coincided with the peak of an X-ray flare. This optical-X-ray flare most likely took place in a feature moving along the parsec-scale jet, imaged at 43 GHz by the Very Long Baseline Array. The 43 GHz polarization angle of the moving component underwent a rotation near the time of the flare. In the optical band, prior to the IXPE observation, we measured the polarization angle to be aligned with the jet axis. In contrast, during the optical flare the optical polarization angle was perpendicular to the jet axis; after the flare, it reverted to being parallel to the jet axis. Due to the smooth behavior of the optical polarization angle during the flare, we favor shocks as the main acceleration mechanism. We also infer that the ambient magnetic field lines in the jet were parallel to the jet position angle. The average degree of optical polarization during the IXPE observation was (14.3$\pm$4.1)%. Despite the flare, we only detected an upper limit of 14% (at 3$蟽$ level) on the X-ray polarization degree; although a reasonable assumption on the X-ray polarization angle results in an upper limit of 8.8% ($3蟽$). We model the spectral energy distribution (SED) and spectral polarization distribution (SPD) of S4 0954+65 with leptonic (synchrotron self-Compton) and hadronic (proton and pair synchrotron) models. The constraints we obtain with our combined multi-wavelength polarization observations and SED modeling tentatively disfavor hadronic models for the X-ray emission in S4 0954+65. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.16868v1-abstract-full').style.display = 'none'; document.getElementById('2411.16868v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Submitted to A&A, 16 pages, 5 figures, and 7 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.10353">arXiv:2411.10353</a> <span> [<a href="https://arxiv.org/pdf/2411.10353">pdf</a>, <a href="https://arxiv.org/format/2411.10353">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> First spectropolarimetric observation of the neutron star low-mass X-ray binary GX 3+1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gnarini%2C+A">Andrea Gnarini</a>, <a href="/search/astro-ph?searchtype=author&query=Farinelli%2C+R">Ruben Farinelli</a>, <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">Francesco Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+M">Mason Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Tarana%2C+A">Antonella Tarana</a>, <a href="/search/astro-ph?searchtype=author&query=Bobrikova%2C+A">Anna Bobrikova</a>, <a href="/search/astro-ph?searchtype=author&query=Cocchi%2C+M">Massimo Cocchi</a>, <a href="/search/astro-ph?searchtype=author&query=Fabiani%2C+S">Sergio Fabiani</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Ravi%2C+S">Swati Ravi</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2411.10353v1-abstract-short" style="display: inline;"> We report the first simultaneous X-ray spectropolarimetric observation of the bright atoll neutron star low-mass X-ray binary GX 3+1, performed by the Imaging X-ray Polarimetry Explorer (IXPE) joint with NICER and NuSTAR. The source does not exhibit significant polarization in the 2-8 keV energy band, with an upper limit of 1.3% at a 99% confidence level on the polarization degree. The observed sp… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.10353v1-abstract-full').style.display = 'inline'; document.getElementById('2411.10353v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.10353v1-abstract-full" style="display: none;"> We report the first simultaneous X-ray spectropolarimetric observation of the bright atoll neutron star low-mass X-ray binary GX 3+1, performed by the Imaging X-ray Polarimetry Explorer (IXPE) joint with NICER and NuSTAR. The source does not exhibit significant polarization in the 2-8 keV energy band, with an upper limit of 1.3% at a 99% confidence level on the polarization degree. The observed spectra can be well described by a combination of thermal disk emission, the hard Comptonization component, and reflected photons off the accretion disk. In particular, from the broad Fe K$伪$ line profile, we were able to determine the inclination of the system ($i \approx 36^\circ$), which is crucial for comparing the observed polarization with theoretical models. Both the spectral and polarization properties of GX 3+1 are consistent with those of other atoll sources observed by IXPE. Therefore, we may expect a similar geometrical configuration for the accreting system and the hot Comptonizing region. The low polarization is also consistent with the low inclination of the system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.10353v1-abstract-full').style.display = 'none'; document.getElementById('2411.10353v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 6 figures, 4 tables. Accepted for publication in Astronomy & Astrophysics. arXiv admin note: text overlap with arXiv:2408.02309</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.23140">arXiv:2410.23140</a> <span> [<a href="https://arxiv.org/pdf/2410.23140">pdf</a>, <a href="https://arxiv.org/format/2410.23140">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Insights from the first flaring activity of a high-synchrotron-peaked blazar with X-ray polarization and VHE gamma rays </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Abe%2C+K">K. Abe</a>, <a href="/search/astro-ph?searchtype=author&query=Abe%2C+S">S. Abe</a>, <a href="/search/astro-ph?searchtype=author&query=Abhir%2C+J">J. Abhir</a>, <a href="/search/astro-ph?searchtype=author&query=Abhishek%2C+A">A. Abhishek</a>, <a href="/search/astro-ph?searchtype=author&query=Acciari%2C+V+A">V. A. Acciari</a>, <a href="/search/astro-ph?searchtype=author&query=Aguasca-Cabot%2C+A">A. Aguasca-Cabot</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">I. Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Aniello%2C+T">T. Aniello</a>, <a href="/search/astro-ph?searchtype=author&query=Ansoldi%2C+S">S. Ansoldi</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">L. A. Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Engels%2C+A+A">A. Arbet Engels</a>, <a href="/search/astro-ph?searchtype=author&query=Arcaro%2C+C">C. Arcaro</a>, <a href="/search/astro-ph?searchtype=author&query=Asano%2C+K">K. Asano</a>, <a href="/search/astro-ph?searchtype=author&query=Babi%C4%87%2C+A">A. Babi膰</a>, <a href="/search/astro-ph?searchtype=author&query=de+Almeida%2C+U+B">U. Barres de Almeida</a>, <a href="/search/astro-ph?searchtype=author&query=Barrio%2C+J+A">J. A. Barrio</a>, <a href="/search/astro-ph?searchtype=author&query=Barrios-Jim%C3%A9nez%2C+L">L. Barrios-Jim茅nez</a>, <a href="/search/astro-ph?searchtype=author&query=Batkovi%C4%87%2C+I">I. Batkovi膰</a>, <a href="/search/astro-ph?searchtype=author&query=Baxter%2C+J">J. Baxter</a>, <a href="/search/astro-ph?searchtype=author&query=Gonz%C3%A1lez%2C+J+B">J. Becerra Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Bednarek%2C+W">W. Bednarek</a>, <a href="/search/astro-ph?searchtype=author&query=Bernardini%2C+E">E. Bernardini</a>, <a href="/search/astro-ph?searchtype=author&query=Bernete%2C+J">J. Bernete</a>, <a href="/search/astro-ph?searchtype=author&query=Berti%2C+A">A. Berti</a>, <a href="/search/astro-ph?searchtype=author&query=Besenrieder%2C+J">J. Besenrieder</a> , et al. (228 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.23140v1-abstract-short" style="display: inline;"> We study a flaring activity of the HSP Mrk421 that was characterized from radio to very-high-energy (VHE; E $>0.1$TeV) gamma rays with MAGIC, Fermi-LAT, Swift, XMM-Newton and several optical and radio telescopes. These observations included, for the first time for a gamma-ray flare of a blazar, simultaneous X-ray polarization measurements with IXPE. We find substantial variability in both X-rays a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.23140v1-abstract-full').style.display = 'inline'; document.getElementById('2410.23140v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.23140v1-abstract-full" style="display: none;"> We study a flaring activity of the HSP Mrk421 that was characterized from radio to very-high-energy (VHE; E $>0.1$TeV) gamma rays with MAGIC, Fermi-LAT, Swift, XMM-Newton and several optical and radio telescopes. These observations included, for the first time for a gamma-ray flare of a blazar, simultaneous X-ray polarization measurements with IXPE. We find substantial variability in both X-rays and VHE gamma rays throughout the campaign, with the highest VHE flux above 0.2 TeV occurring during the IXPE observing window, and exceeding twice the flux of the Crab Nebula. However, the VHE and X-ray spectra are on average softer, and the correlation between these two bands weaker that those reported in previous flares of Mrk421. IXPE reveals an X-ray polarization degree significantly higher than that at radio and optical frequencies. The X-ray polarization angle varies by $\sim$100$^\circ$ on timescales of days, and the polarization degree changes by more than a factor 4. The highest X-ray polarization degree reaches 26%, around which a X-ray counter-clockwise hysteresis loop is measured with XMM-Newton. It suggests that the X-ray emission comes from particles close to the high-energy cutoff, hence possibly probing an extreme case of the Turbulent Extreme Multi-Zone model. We model the broadband emission with a simplified stratified jet model throughout the flare. The polarization measurements imply an electron distribution in the X-ray emitting region with a very high minimum Lorentz factor, which is expected in electron-ion plasma, as well as a variation of the emitting region size up to a factor of three during the flaring activity. We find no correlation between the fluxes and the evolution of the model parameters, which indicates a stochastic nature of the underlying physical mechanism. Such behaviour would be expected in a highly turbulent electron-ion plasma crossing a shock front. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.23140v1-abstract-full').style.display = 'none'; document.getElementById('2410.23140v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Submitted to Astronomy and Astrophysics. Corresponding authors: Axel Arbet-Engels, Lea Heckmann, David Paneque</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.20582">arXiv:2410.20582</a> <span> [<a href="https://arxiv.org/pdf/2410.20582">pdf</a>, <a href="https://arxiv.org/format/2410.20582">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Evidence for a shock-compressed magnetic field in the northwestern rim of Vela Jr. from X-ray polarimetry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Prokhorov%2C+D+A">Dmitry A. Prokhorov</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+Y">Yi-Jung Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Ferrazzoli%2C+R">Riccardo Ferrazzoli</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J">Jacco Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Slane%2C+P">Patrick Slane</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Silvestri%2C+S">Stefano Silvestri</a>, <a href="/search/astro-ph?searchtype=author&query=Zhou%2C+P">Ping Zhou</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccol貌 Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Doroshenko%2C+V">Victor Doroshenko</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Marin%2C+F">Fr茅d茅ric Marin</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno%2C+T">Tsunefumi Mizuno</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+C">Chi-Yung Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Pesce-Rollins%2C+M">Melissa Pesce-Rollins</a>, <a href="/search/astro-ph?searchtype=author&query=Sgr%C3%B2%2C+C">Carmelo Sgr貌</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Swartz%2C+D+A">Douglas A. Swartz</a>, <a href="/search/astro-ph?searchtype=author&query=Tamagawa%2C+T">Toru Tamagawa</a> , et al. (75 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.20582v1-abstract-short" style="display: inline;"> Synchrotron X-ray emission has been detected from nearly a dozen young supernova remnants (SNRs). X-rays of synchrotron origin exhibit linear polarization in a regular, non-randomly oriented magnetic field. The significant polarized X-ray emission from four such SNRs has already been reported on the basis of observations with the Imaging X-ray Polarimetry Explorer (IXPE). The magnetic-field struct… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.20582v1-abstract-full').style.display = 'inline'; document.getElementById('2410.20582v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.20582v1-abstract-full" style="display: none;"> Synchrotron X-ray emission has been detected from nearly a dozen young supernova remnants (SNRs). X-rays of synchrotron origin exhibit linear polarization in a regular, non-randomly oriented magnetic field. The significant polarized X-ray emission from four such SNRs has already been reported on the basis of observations with the Imaging X-ray Polarimetry Explorer (IXPE). The magnetic-field structure as derived from IXPE observations is radial for Cassiopeia A, Tycho's SNR, and SN 1006, and tangential for RX J1713.7-3946. The latter together with the recent detection of a tangential magnetic field in SNR 1E 0102.2-7219 by the Australia Telescope Compact Array in the radio band shows that tangential magnetic fields can also be present in young SNRs. Thus, the dichotomy in polarization between young and middle-aged SNRs (radial magnetic fields in young SNRs, but tangential magnetic fields in middle-aged SNRs), previously noticed in the radio band, deserves additional attention. The present analysis of IXPE observations determines, for the first time, a magnetic-field structure in the northwestern rim of Vela Jr, also known as RX J0852.0-4622, and provides a new example of a young SNR with a tangential magnetic field. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.20582v1-abstract-full').style.display = 'none'; document.getElementById('2410.20582v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Astronomy and Astrophysics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.19983">arXiv:2410.19983</a> <span> [<a href="https://arxiv.org/pdf/2410.19983">pdf</a>, <a href="https://arxiv.org/format/2410.19983">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> A Two-Week $IXPE$ Monitoring Campaign on Mrk 421 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maksym%2C+W+P">W. Peter Maksym</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Saade%2C+M+L">M. Lynne Saade</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Middei%2C+R">Riccardo Middei</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Gesu%2C+L">Laura Di Gesu</a>, <a href="/search/astro-ph?searchtype=author&query=Kiehlmann%2C+S">Sebastian Kiehlmann</a>, <a href="/search/astro-ph?searchtype=author&query=Matzeu%2C+G">Gabriele Matzeu</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">Herman L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Pacciani%2C+L">Luigi Pacciani</a>, <a href="/search/astro-ph?searchtype=author&query=Perri%2C+M">Matteo Perri</a>, <a href="/search/astro-ph?searchtype=author&query=Puccetti%2C+S">Simonetta Puccetti</a>, <a href="/search/astro-ph?searchtype=author&query=Kouch%2C+P+M">Pouya M. Kouch</a>, <a href="/search/astro-ph?searchtype=author&query=Lindfors%2C+E">Elina Lindfors</a>, <a href="/search/astro-ph?searchtype=author&query=Aceituno%2C+F+J">Francisco Jos茅 Aceituno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonnoli%2C+G">Giacomo Bonnoli</a>, <a href="/search/astro-ph?searchtype=author&query=Casanova%2C+V">V铆ctor Casanova</a>, <a href="/search/astro-ph?searchtype=author&query=Escudero%2C+J">Juan Escudero</a>, <a href="/search/astro-ph?searchtype=author&query=Ag%C3%ADs-Gonz%C3%A1lez%2C+B">Beatriz Ag铆s-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Husillos%2C+C">C茅sar Husillos</a> , et al. (131 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.19983v1-abstract-short" style="display: inline;"> X-ray polarization is a unique new probe of the particle acceleration in astrophysical jets made possible through the Imaging X-ray Polarimetry Explorer. Here we report on the first dense X-ray polarization monitoring campaign on the blazar Mrk 421. Our observations were accompanied by an even denser radio and optical polarization campaign. We find significant short-timescale variability in both X… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.19983v1-abstract-full').style.display = 'inline'; document.getElementById('2410.19983v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.19983v1-abstract-full" style="display: none;"> X-ray polarization is a unique new probe of the particle acceleration in astrophysical jets made possible through the Imaging X-ray Polarimetry Explorer. Here we report on the first dense X-ray polarization monitoring campaign on the blazar Mrk 421. Our observations were accompanied by an even denser radio and optical polarization campaign. We find significant short-timescale variability in both X-ray polarization degree and angle, including a $\sim90^\circ$ angle rotation about the jet axis. We attribute this to random variations of the magnetic field, consistent with the presence of turbulence but also unlikely to be explained by turbulence alone. At the same time, the degree of lower-energy polarization is significantly lower and shows no more than mild variability. Our campaign provides further evidence for a scenario in which energy-stratified shock-acceleration of relativistic electrons, combined with a turbulent magnetic field, is responsible for optical to X-ray synchrotron emission in blazar jets. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.19983v1-abstract-full').style.display = 'none'; document.getElementById('2410.19983v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">23 pages, including 8 pages of appendices. 12 figures, 3 tables. Submitted to ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2409.16116">arXiv:2409.16116</a> <span> [<a href="https://arxiv.org/pdf/2409.16116">pdf</a>, <a href="https://arxiv.org/format/2409.16116">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Magnetic field geometry of the gamma-ray binary PSR B1259-63 revealed via X-ray polarization </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Roberts%2C+O+J">Oliver J. Roberts</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Swartz%2C+D+A">Douglas A. Swartz</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Saade%2C+M+L">M. Lynne Saade</a>, <a href="/search/astro-ph?searchtype=author&query=O%27Dell%2C+S+L">Stephen L. O'Dell</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+C">Chien-Ting Chen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2409.16116v1-abstract-short" style="display: inline;"> Some X-ray binaries containing an energetic pulsar in orbit around a normal star accelerate particles to high energies in the shock cone formed where the pulsar and stellar winds collide. The magnetic field geometry in the acceleration region in such binaries is unknown. We performed the first measurement of the polarization of the X-ray synchrotron emission from a gamma-ray emitting binary system… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.16116v1-abstract-full').style.display = 'inline'; document.getElementById('2409.16116v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2409.16116v1-abstract-full" style="display: none;"> Some X-ray binaries containing an energetic pulsar in orbit around a normal star accelerate particles to high energies in the shock cone formed where the pulsar and stellar winds collide. The magnetic field geometry in the acceleration region in such binaries is unknown. We performed the first measurement of the polarization of the X-ray synchrotron emission from a gamma-ray emitting binary system. We observed PSR B1259-63 with the Imaging X-ray Polarimetry Explorer (IXPE) during an X-ray bright phase following the periastron passage in June 2024. X-ray polarization is detected with a polarization degree of $8.3\% \pm 1.5\%$ at a significance of $5.3 蟽$. The X-ray polarization angle is aligned with the axis of the shock cone at the time of the observation. This indicates that the predominant component of the magnetic field in the acceleration region is oriented perpendicular to the shock cone axis. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2409.16116v1-abstract-full').style.display = 'none'; document.getElementById('2409.16116v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 September, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, to appear in the Astrophysical Journal Letters</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.16713">arXiv:2408.16713</a> <span> [<a href="https://arxiv.org/pdf/2408.16713">pdf</a>, <a href="https://arxiv.org/format/2408.16713">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> X-ray spectropolarimetry of the bright atoll Serpens X-1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">F. Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Gnarini%2C+A">A. Gnarini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">S. Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bobrikova%2C+A">A. Bobrikova</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">F. Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Cocchi%2C+M">M. Cocchi</a>, <a href="/search/astro-ph?searchtype=author&query=Fabiani%2C+S">S. Fabiani</a>, <a href="/search/astro-ph?searchtype=author&query=Farinelli%2C+R">R. Farinelli</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">P. Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">G. Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+M">M. Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">J. Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Ravi%2C+S">S. Ravi</a>, <a href="/search/astro-ph?searchtype=author&query=Tarana%2C+A">A. Tarana</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2408.16713v1-abstract-short" style="display: inline;"> We present simultaneous X-ray polarimetric and spectral observations of the bright atoll source Ser~X-1 carried out with the Imaging X-ray Polarimetry Explorer (IXPE), NICER, and NuSTAR. We obtain an upper limit of 2% (99% confidence level) on the polarization degree in the 2--8 keV energy band. We detect four type-I X-ray bursts, two of which during the IXPE observation. This is the first time th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.16713v1-abstract-full').style.display = 'inline'; document.getElementById('2408.16713v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.16713v1-abstract-full" style="display: none;"> We present simultaneous X-ray polarimetric and spectral observations of the bright atoll source Ser~X-1 carried out with the Imaging X-ray Polarimetry Explorer (IXPE), NICER, and NuSTAR. We obtain an upper limit of 2% (99% confidence level) on the polarization degree in the 2--8 keV energy band. We detect four type-I X-ray bursts, two of which during the IXPE observation. This is the first time that has IXPE observed type-I X-ray bursts, and it allows us to place an upper limit on their polarization degree; however, due to the limited total number of counts in each burst, we obtain a relatively high upper limit (80%). We confirm the presence of reflection features in the X-ray spectrum, notably a broad iron line. Fitting the data with a relativistic reflection model, we derive a disk inclination of 25 deg. The spectral and polarization properties are comparable with other atolls observed by IXPE, suggesting a similar accretion geometry, and the relatively low polarization is consistent with the low inclination. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.16713v1-abstract-full').style.display = 'none'; document.getElementById('2408.16713v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted by A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.12746">arXiv:2408.12746</a> <span> [<a href="https://arxiv.org/pdf/2408.12746">pdf</a>, <a href="https://arxiv.org/format/2408.12746">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> A Comparison of the X-ray Polarimetric Properties of Stellar and Supermassive Black Holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Saade%2C+M+L">M. Lynne Saade</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2408.12746v1-abstract-short" style="display: inline;"> X-ray polarization provides a new way to probe accretion geometry in black hole systems. If the accretion geometry of black holes is similar regardless of mass, we should expect the same to be true of their polarization properties. We compare the polarimetric properties of all non-blazar black holes observed with IXPE. We find that their polarization properties are very similar, particularly in th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.12746v1-abstract-full').style.display = 'inline'; document.getElementById('2408.12746v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.12746v1-abstract-full" style="display: none;"> X-ray polarization provides a new way to probe accretion geometry in black hole systems. If the accretion geometry of black holes is similar regardless of mass, we should expect the same to be true of their polarization properties. We compare the polarimetric properties of all non-blazar black holes observed with IXPE. We find that their polarization properties are very similar, particularly in the hard state, where the corona dominates. This tentatively supports the idea that stellar and supermassive black holes share a common coronal geometry. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.12746v1-abstract-full').style.display = 'none'; document.getElementById('2408.12746v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.02309">arXiv:2408.02309</a> <span> [<a href="https://arxiv.org/pdf/2408.02309">pdf</a>, <a href="https://arxiv.org/format/2408.02309">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202450716">10.1051/0004-6361/202450716 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraining the geometry of the dipping atoll 4U 1624-49 with X-ray spectroscopy and polarimetry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gnarini%2C+A">Andrea Gnarini</a>, <a href="/search/astro-ph?searchtype=author&query=Saade%2C+M+L">M. Lynne Saade</a>, <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">Francesco Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+W">Wenda Zhang</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2408.02309v2-abstract-short" style="display: inline;"> We present the spectro-polarimetric results obtained from simultaneous X-ray observations with IXPE, NuSTAR and NICER of the dipping neutron star X-ray binary 4U 1624-49. This source is the most polarized Atoll source so far observed with IXPE, with a polarization degree of 2.7% $\pm$ 0.9% in the 2-8 keV band during the non-dip phase and marginal evidence of an increasing trend with energy. The hi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.02309v2-abstract-full').style.display = 'inline'; document.getElementById('2408.02309v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.02309v2-abstract-full" style="display: none;"> We present the spectro-polarimetric results obtained from simultaneous X-ray observations with IXPE, NuSTAR and NICER of the dipping neutron star X-ray binary 4U 1624-49. This source is the most polarized Atoll source so far observed with IXPE, with a polarization degree of 2.7% $\pm$ 0.9% in the 2-8 keV band during the non-dip phase and marginal evidence of an increasing trend with energy. The higher polarization degree compared to other Atolls can be explained by the high inclination of the system ($i \approx 60$掳). The spectra are well described by the combination of a soft thermal emission, a Comptonized component, plus reflection of soft photons off the accretion disk. During the dips, the hydrogen column density of the highly-ionized absorber increases while the ionization state decreases. The Comptonized radiation seems to be the dominant contribution to the polarized signal, with additional reflected photons which significantly contribute even if their fraction in the total flux is not high. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.02309v2-abstract-full').style.display = 'none'; document.getElementById('2408.02309v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 7 figures, 5 tables. Accepted for publication in Astronomy & Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 690, A230 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.16518">arXiv:2407.16518</a> <span> [<a href="https://arxiv.org/pdf/2407.16518">pdf</a>, <a href="https://arxiv.org/format/2407.16518">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Experiment">hep-ex</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> </div> </div> <p class="title is-5 mathjax"> An indirect search for dark matter with a combined analysis of dwarf spheroidal galaxies from VERITAS </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Acharyya%2C+A">A. Acharyya</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+C+B">C. B. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Bangale%2C+P">P. Bangale</a>, <a href="/search/astro-ph?searchtype=author&query=Bartkoske%2C+J+T">J. T. Bartkoske</a>, <a href="/search/astro-ph?searchtype=author&query=Batista%2C+P">P. Batista</a>, <a href="/search/astro-ph?searchtype=author&query=Benbow%2C+W">W. Benbow</a>, <a href="/search/astro-ph?searchtype=author&query=Christiansen%2C+J+L">J. L. Christiansen</a>, <a href="/search/astro-ph?searchtype=author&query=Chromey%2C+A+J">A. J. Chromey</a>, <a href="/search/astro-ph?searchtype=author&query=Duerr%2C+A">A. Duerr</a>, <a href="/search/astro-ph?searchtype=author&query=Errando%2C+M">M. Errando</a>, <a href="/search/astro-ph?searchtype=author&query=Falcone%2C+A">A. Falcone</a>, <a href="/search/astro-ph?searchtype=author&query=Feng%2C+Q">Q. Feng</a>, <a href="/search/astro-ph?searchtype=author&query=Foote%2C+G+M">G. M. Foote</a>, <a href="/search/astro-ph?searchtype=author&query=Fortson%2C+L">L. Fortson</a>, <a href="/search/astro-ph?searchtype=author&query=Furniss%2C+A">A. Furniss</a>, <a href="/search/astro-ph?searchtype=author&query=Hanlon%2C+W">W. Hanlon</a>, <a href="/search/astro-ph?searchtype=author&query=Hanna%2C+D">D. Hanna</a>, <a href="/search/astro-ph?searchtype=author&query=Hervet%2C+O">O. Hervet</a>, <a href="/search/astro-ph?searchtype=author&query=Hinrichs%2C+C+E">C. E. Hinrichs</a>, <a href="/search/astro-ph?searchtype=author&query=Holder%2C+J">J. Holder</a>, <a href="/search/astro-ph?searchtype=author&query=Humensky%2C+T+B">T. B. Humensky</a>, <a href="/search/astro-ph?searchtype=author&query=Jin%2C+W">W. Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Johnson%2C+M+N">M. N. Johnson</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">P. Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Kertzman%2C+M">M. Kertzman</a> , et al. (37 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.16518v2-abstract-short" style="display: inline;"> Understanding the nature and identity of dark matter is a key goal in the physics community. In the case that TeV-scale dark matter particles decay or annihilate into standard model particles, very-high-energy (VHE) gamma rays (greater than 100 GeV) will be present in the final state. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an imaging atmospheric Cherenkov telescop… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.16518v2-abstract-full').style.display = 'inline'; document.getElementById('2407.16518v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.16518v2-abstract-full" style="display: none;"> Understanding the nature and identity of dark matter is a key goal in the physics community. In the case that TeV-scale dark matter particles decay or annihilate into standard model particles, very-high-energy (VHE) gamma rays (greater than 100 GeV) will be present in the final state. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an imaging atmospheric Cherenkov telescope array that can indirectly detect VHE gamma rays in an energy range of 100 GeV to > 30 TeV. Dwarf spheroidal galaxies (dSphs) are ideal candidates in the search for dark matter due to their high dark matter content, high mass-to-light ratios, and their low gamma-ray fluxes from astrophysical processes. This study uses a legacy data set of 638 hours collected on 17 dSphs, built over 11 years with an observing strategy optimized according to the dark matter content of the targets. The study addresses a broad dark matter particle mass range, extending from 200 GeV to 30 PeV. In the absence of a detection, we set the upper limits on the dark matter velocity-weighted annihilation cross section. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.16518v2-abstract-full').style.display = 'none'; document.getElementById('2407.16518v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages, 7 figures, 3 tables, accepted in PRD</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.12779">arXiv:2407.12779</a> <span> [<a href="https://arxiv.org/pdf/2407.12779">pdf</a>, <a href="https://arxiv.org/format/2407.12779">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Analysis of Crab X-ray Polarization using Deeper IXPE Observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Wong%2C+J">Josephine Wong</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno%2C+T">Tsunefumi Mizuno</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccol贸 Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Romani%2C+R+W">Roger W. Romani</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+Y">Yi-Jung Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+K">Kuan Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Deng%2C+W">Wei Deng</a>, <a href="/search/astro-ph?searchtype=author&query=Goya%2C+K">Kazuho Goya</a>, <a href="/search/astro-ph?searchtype=author&query=Xie%2C+F">Fei Xie</a>, <a href="/search/astro-ph?searchtype=author&query=Pilia%2C+M">Maura Pilia</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Silvestri%2C+S">Stefano Silvestri</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+C+-">C. -Y. Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+C">Chien-Ting Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio A. Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W+H">Wayne H. Baumgartner</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+R">Ronaldo Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bongiorno%2C+S+D">Stephen D. Bongiorno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonino%2C+R">Raffaella Bonino</a>, <a href="/search/astro-ph?searchtype=author&query=Brez%2C+A">Alessandro Brez</a> , et al. (76 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.12779v1-abstract-short" style="display: inline;"> We present Crab X-ray polarization measurements using IXPE data with a total exposure of 300ks, three times more than the initial 2022 discovery paper. Polarization is detected in three times more pulsar phase bins, revealing an S-shaped $+40^\circ$ polarization angle sweep in the main pulse and ${>}1蟽$ departures from the OPTIMA optical polarization in both pulses, suggesting different radiation… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.12779v1-abstract-full').style.display = 'inline'; document.getElementById('2407.12779v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.12779v1-abstract-full" style="display: none;"> We present Crab X-ray polarization measurements using IXPE data with a total exposure of 300ks, three times more than the initial 2022 discovery paper. Polarization is detected in three times more pulsar phase bins, revealing an S-shaped $+40^\circ$ polarization angle sweep in the main pulse and ${>}1蟽$ departures from the OPTIMA optical polarization in both pulses, suggesting different radiation mechanisms or sites for the polarized emission at the two wavebands. Our polarization map of the inner nebula reveals a toroidal magnetic field, as seen in prior IXPE analyses. Along the southern jet, the magnetic field orientation relative to the jet axis changes from perpendicular to parallel and the polarization degree decreases by ${\sim}6\%$. These observations may be explained by kink instabilities along the jet or a collision with a dense, jet-deflecting medium at the tip. Using spectropolarimetric analysis, we find asymmetric polarization in the four quadrants of the inner nebula, as expected for a toroidal field geometry, and a spatial correlation between polarization degree and photon index. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.12779v1-abstract-full').style.display = 'none'; document.getElementById('2407.12779v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 7 figures, 3 tables. Accepted by The Astrophysical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.11848">arXiv:2407.11848</a> <span> [<a href="https://arxiv.org/pdf/2407.11848">pdf</a>, <a href="https://arxiv.org/format/2407.11848">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> A multi-wavelength study to decipher the 2017 flare of the blazar OJ 287 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Acharyya%2C+A">A. Acharyya</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+C+B">C. B. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Archer%2C+A">A. Archer</a>, <a href="/search/astro-ph?searchtype=author&query=Bangale%2C+P">P. Bangale</a>, <a href="/search/astro-ph?searchtype=author&query=Bartkoske%2C+J+T">J. T. Bartkoske</a>, <a href="/search/astro-ph?searchtype=author&query=Batista%2C+P">P. Batista</a>, <a href="/search/astro-ph?searchtype=author&query=Benbow%2C+W">W. Benbow</a>, <a href="/search/astro-ph?searchtype=author&query=Brill%2C+A">A. Brill</a>, <a href="/search/astro-ph?searchtype=author&query=Caldwell%2C+J+P">J. P. Caldwell</a>, <a href="/search/astro-ph?searchtype=author&query=Carini%2C+M">M. Carini</a>, <a href="/search/astro-ph?searchtype=author&query=Christiansen%2C+J+L">J. L. Christiansen</a>, <a href="/search/astro-ph?searchtype=author&query=Chromey%2C+A+J">A. J. Chromey</a>, <a href="/search/astro-ph?searchtype=author&query=Errando%2C+M">M. Errando</a>, <a href="/search/astro-ph?searchtype=author&query=Falcone%2C+A">A. Falcone</a>, <a href="/search/astro-ph?searchtype=author&query=Feng%2C+Q">Q. Feng</a>, <a href="/search/astro-ph?searchtype=author&query=Finley%2C+J+P">J. P. Finley</a>, <a href="/search/astro-ph?searchtype=author&query=Foote%2C+J">J. Foote</a>, <a href="/search/astro-ph?searchtype=author&query=Fortson%2C+L">L. Fortson</a>, <a href="/search/astro-ph?searchtype=author&query=Furniss%2C+A">A. Furniss</a>, <a href="/search/astro-ph?searchtype=author&query=Gallagher%2C+G">G. Gallagher</a>, <a href="/search/astro-ph?searchtype=author&query=Hanlon%2C+W">W. Hanlon</a>, <a href="/search/astro-ph?searchtype=author&query=Hanna%2C+D">D. Hanna</a>, <a href="/search/astro-ph?searchtype=author&query=Hervet%2C+O">O. Hervet</a>, <a href="/search/astro-ph?searchtype=author&query=Hinrichs%2C+C+E">C. E. Hinrichs</a>, <a href="/search/astro-ph?searchtype=author&query=Hoang%2C+J">J. Hoang</a> , et al. (49 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.11848v3-abstract-short" style="display: inline;"> In February 2017, the blazar OJ~287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3-10 keV) band, as measured by Swift-XRT. This event coincides with a very-high-energy (VHE) $纬$-ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of $10蟽$ (from 2016 December 9 to 2017 March 31). The time-averag… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.11848v3-abstract-full').style.display = 'inline'; document.getElementById('2407.11848v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.11848v3-abstract-full" style="display: none;"> In February 2017, the blazar OJ~287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3-10 keV) band, as measured by Swift-XRT. This event coincides with a very-high-energy (VHE) $纬$-ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of $10蟽$ (from 2016 December 9 to 2017 March 31). The time-averaged VHE $纬$-ray spectrum was consistent with a soft power law ($螕= -3.81 \pm 0.26$) and an integral flux corresponding to $\sim2.4\%$ that of the Crab Nebula above the same energy. Contemporaneous data from multiple instruments across the electromagnetic spectrum reveal complex flaring behavior, primarily in the soft X-ray and VHE bands. To investigate the possible origin of such an event, our study focuses on three distinct activity states: before, during, and after the February 2017 peak. The spectral energy distributions during these periods suggest the presence of at least two non-thermal emission zones, with the more compact one responsible for the observed flare. Broadband modeling results and observations of a new radio knot in the jet of OJ~287 in 2017 are consistent with a flare originating from a strong recollimation shock outside the radio core. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.11848v3-abstract-full').style.display = 'none'; document.getElementById('2407.11848v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 7 figures, accepted for publication in The Astrophysical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2407.11128">arXiv:2407.11128</a> <span> [<a href="https://arxiv.org/pdf/2407.11128">pdf</a>, <a href="https://arxiv.org/format/2407.11128">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> X-ray and multiwavelength polarization of Mrk 501 from 2022 to 2023 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Chen%2C+C+J">Chien-Ting J. Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Middei%2C+R">Riccardo Middei</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Gesu%2C+L">Laura Di Gesu</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Errando%2C+M">Manel Errando</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+K">Kinwah Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno%2C+T">Tsunefumi Mizuno</a>, <a href="/search/astro-ph?searchtype=author&query=Kouch%2C+P+M">Pouya M. Kouch</a>, <a href="/search/astro-ph?searchtype=author&query=Lindfors%2C+E">Elina Lindfors</a>, <a href="/search/astro-ph?searchtype=author&query=Borman%2C+G+A">George A. Borman</a>, <a href="/search/astro-ph?searchtype=author&query=Grishina%2C+T+S">Tatiana S. Grishina</a>, <a href="/search/astro-ph?searchtype=author&query=Kopatskaya%2C+E+N">Evgenia N. Kopatskaya</a>, <a href="/search/astro-ph?searchtype=author&query=Larionova%2C+E+G">Elena G. Larionova</a>, <a href="/search/astro-ph?searchtype=author&query=Morozova%2C+D+A">Daria A. Morozova</a>, <a href="/search/astro-ph?searchtype=author&query=Savchenko%2C+S+S">Sergey S. Savchenko</a>, <a href="/search/astro-ph?searchtype=author&query=Troitsky%2C+I+S">Ivan S. Troitsky</a>, <a href="/search/astro-ph?searchtype=author&query=Troitskaya%2C+Y+V">Yulia V. Troitskaya</a> , et al. (121 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2407.11128v1-abstract-short" style="display: inline;"> We present multiwavelength polarization measurements of the luminous blazar Mrk~501 over a 14-month period. The 2--8 keV X-ray polarization was measured with the Imaging X-ray Polarimetry Explorer (IXPE) with six 100-ks observations spanning from 2022 March to 2023 April. Each IXPE observation was accompanied by simultaneous X-ray data from NuSTAR, Swift/XRT, and/or XMM-Newton. Complementary optic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.11128v1-abstract-full').style.display = 'inline'; document.getElementById('2407.11128v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.11128v1-abstract-full" style="display: none;"> We present multiwavelength polarization measurements of the luminous blazar Mrk~501 over a 14-month period. The 2--8 keV X-ray polarization was measured with the Imaging X-ray Polarimetry Explorer (IXPE) with six 100-ks observations spanning from 2022 March to 2023 April. Each IXPE observation was accompanied by simultaneous X-ray data from NuSTAR, Swift/XRT, and/or XMM-Newton. Complementary optical-infrared polarization measurements were also available in the B, V, R, I, and J bands, as were radio polarization measurements from 4.85 GHz to 225.5 GHz. Among the first five IXPE observations, we did not find significant variability in the X-ray polarization degree and angle with IXPE. However, the most recent sixth observation found an elevated polarization degree at $>3蟽$ above the average of the other five observations. The optical and radio measurements show no apparent correlations with the X-ray polarization properties. Throughout the six IXPE observations, the X-ray polarization degree remained higher than, or similar to, the R-band optical polarization degree, which remained higher than the radio value. This is consistent with the energy-stratified shock scenario proposed to explain the first two IXPE observations, in which the polarized X-ray, optical, and radio emission arises from different regions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.11128v1-abstract-full').style.display = 'none'; document.getElementById('2407.11128v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 July, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.15554">arXiv:2406.15554</a> <span> [<a href="https://arxiv.org/pdf/2406.15554">pdf</a>, <a href="https://arxiv.org/format/2406.15554">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202451037">10.1051/0004-6361/202451037 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Kiehlmann%2C+S">Sebastian Kiehlmann</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+H">Haocheng Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Blinov%2C+D">Dmitry Blinov</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Ben%C3%ADtez%2C+E">Erika Ben铆tez</a>, <a href="/search/astro-ph?searchtype=author&query=Berdyugin%2C+A">Andrei Berdyugin</a>, <a href="/search/astro-ph?searchtype=author&query=Bonnoli%2C+G">Giacomo Bonnoli</a>, <a href="/search/astro-ph?searchtype=author&query=Casadio%2C+C">Carolina Casadio</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+C">Chien-Ting Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+W">Wen-Ping Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Escudero%2C+J">Juan Escudero</a>, <a href="/search/astro-ph?searchtype=author&query=Grishina%2C+T+S">Tatiana S. Grishina</a>, <a href="/search/astro-ph?searchtype=author&query=Hiriart%2C+D">David Hiriart</a>, <a href="/search/astro-ph?searchtype=author&query=Hsu%2C+A">Angela Hsu</a>, <a href="/search/astro-ph?searchtype=author&query=Imazawa%2C+R">Ryo Imazawa</a>, <a href="/search/astro-ph?searchtype=author&query=Jermak%2C+H+E">Helen E. Jermak</a>, <a href="/search/astro-ph?searchtype=author&query=Jose%2C+J">Jincen Jose</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Kopatskaya%2C+E+N">Evgenia N. Kopatskaya</a>, <a href="/search/astro-ph?searchtype=author&query=Lalchand%2C+B">Bhavana Lalchand</a>, <a href="/search/astro-ph?searchtype=author&query=Larionova%2C+E+G">Elena G. Larionova</a> , et al. (22 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.15554v1-abstract-short" style="display: inline;"> Variability can be the pathway to understanding the physical processes in astrophysical jets, however, the high-cadence observations required to test particle acceleration models are still missing. Here we report on the first attempt to produce continuous, >24 hour polarization light curves of blazars using telescopes distributed across the globe and the rotation of the Earth to avoid the rising S… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.15554v1-abstract-full').style.display = 'inline'; document.getElementById('2406.15554v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.15554v1-abstract-full" style="display: none;"> Variability can be the pathway to understanding the physical processes in astrophysical jets, however, the high-cadence observations required to test particle acceleration models are still missing. Here we report on the first attempt to produce continuous, >24 hour polarization light curves of blazars using telescopes distributed across the globe and the rotation of the Earth to avoid the rising Sun. Our campaign involved 16 telescopes in Asia, Europe, and North America. We observed BL Lacertae and CGRaBS J0211+1051 for a combined 685 telescope hours. We find large variations in the polarization degree and angle for both sources in sub-hour timescales as well as a ~180 degree rotation of the polarization angle in CGRaBS J0211+1051 in less than two days. We compared our high-cadence observations to Particle-In-Cell magnetic reconnection and turbulent plasma simulations. We find that although the state of the art simulation frameworks can produce a large fraction of the polarization properties, they do not account for the entirety of the observed polarization behavior in blazar jets. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.15554v1-abstract-full').style.display = 'none'; document.getElementById('2406.15554v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, 15 figures, 2 tables, accepted for publication in A&A. The data used in the paper are available here: https://doi.org/10.7910/DVN/IETSXS</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 689, A200 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.12014">arXiv:2406.12014</a> <span> [<a href="https://arxiv.org/pdf/2406.12014">pdf</a>, <a href="https://arxiv.org/format/2406.12014">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> An IXPE-Led X-ray Spectro-Polarimetric Campaign on the Soft State of Cygnus X-1: X-ray Polarimetric Evidence for Strong Gravitational Lensing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+J+F">James F. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Nathan%2C+E">Edward Nathan</a>, <a href="/search/astro-ph?searchtype=author&query=Hu%2C+K">Kun Hu</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">Henric Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Dovciak%2C+M">Michal Dovciak</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">Jiri Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Alabarta%2C+K">Kevin Alabarta</a>, <a href="/search/astro-ph?searchtype=author&query=Parra%2C+M">Maxime Parra</a>, <a href="/search/astro-ph?searchtype=author&query=Bhargava%2C+Y">Yash Bhargava</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Petrucci%2C+P">Pierre-Olivier Petrucci</a>, <a href="/search/astro-ph?searchtype=author&query=Tennant%2C+A+F">Allyn F. Tennant</a>, <a href="/search/astro-ph?searchtype=author&query=Baglio%2C+M+C">M. Cristina Baglio</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Barnier%2C+S">Samuel Barnier</a>, <a href="/search/astro-ph?searchtype=author&query=Bhattacharyya%2C+S">Sudip Bhattacharyya</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Brigitte%2C+M">Maimouna Brigitte</a>, <a href="/search/astro-ph?searchtype=author&query=Cabezas%2C+M">Mauricio Cabezas</a>, <a href="/search/astro-ph?searchtype=author&query=Cangemi%2C+F">Floriane Cangemi</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Casey%2C+J">Jacob Casey</a> , et al. (112 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.12014v1-abstract-short" style="display: inline;"> We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May-June. Companion multiwavelength data during the campaign are likewise shown. The 2-8 keV X-rays exhibit a net polarization degree PD=1.99%+/-0.13% (68% confidence). The polarization signal is found to increase with energy across IXPE's 2-8 keV… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.12014v1-abstract-full').style.display = 'inline'; document.getElementById('2406.12014v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.12014v1-abstract-full" style="display: none;"> We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May-June. Companion multiwavelength data during the campaign are likewise shown. The 2-8 keV X-rays exhibit a net polarization degree PD=1.99%+/-0.13% (68% confidence). The polarization signal is found to increase with energy across IXPE's 2-8 keV bandpass. The polarized X-rays exhibit an energy-independent polarization angle of PA=-25.7+/-1.8 deg. East of North (68% confidence). This is consistent with being aligned to Cyg X-1's AU-scale compact radio jet and its pc-scale radio lobes. In comparison to earlier hard-state observations, the soft state exhibits a factor of 2 lower polarization degree, but a similar trend with energy and a similar (also energy-independent) position angle. When scaling by the natural unit of the disk temperature, we find the appearance of a consistent trendline in the polarization degree between soft and hard states. Our favored polarimetric model indicates Cyg X-1's spin is likely high (a* above ~0.96). The substantial X-ray polarization in Cyg X-1's soft state is most readily explained as resulting from a large portion of X-rays emitted from the disk returning and reflecting off the disk surface, generating a high polarization degree and a polarization direction parallel to the black hole spin axis and radio jet. In IXPE's bandpass, the polarization signal is dominated by the returning reflection emission. This constitutes polarimetric evidence for strong gravitational lensing of X-rays close to the black hole. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.12014v1-abstract-full').style.display = 'none'; document.getElementById('2406.12014v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, accepted for publication in ApJL</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.08988">arXiv:2406.08988</a> <span> [<a href="https://arxiv.org/pdf/2406.08988">pdf</a>, <a href="https://arxiv.org/format/2406.08988">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202450937">10.1051/0004-6361/202450937 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the polarized emission from SMC X-1: the brightest X-ray pulsar observed by IXPE </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Forsblom%2C+S+V">Sofia V. Forsblom</a>, <a href="/search/astro-ph?searchtype=author&query=Tsygankov%2C+S+S">Sergey S. Tsygankov</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Doroshenko%2C+V">Victor Doroshenko</a>, <a href="/search/astro-ph?searchtype=author&query=Mushtukov%2C+A+A">Alexander A. Mushtukov</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+M">Mason Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Ravi%2C+S">Swati Ravi</a>, <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">Herman L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=La+Monaca%2C+F">Fabio La Monaca</a>, <a href="/search/astro-ph?searchtype=author&query=Malacaria%2C+C">Christian Malacaria</a>, <a href="/search/astro-ph?searchtype=author&query=Mastroserio%2C+G">Guglielmo Mastroserio</a>, <a href="/search/astro-ph?searchtype=author&query=Loktev%2C+V">Vladislav Loktev</a>, <a href="/search/astro-ph?searchtype=author&query=Possenti%2C+A">Andrea Possenti</a>, <a href="/search/astro-ph?searchtype=author&query=Suleimanov%2C+V+F">Valery F. Suleimanov</a>, <a href="/search/astro-ph?searchtype=author&query=Taverna%2C+R">Roberto Taverna</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Ivan Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio A. Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W+H">Wayne H. Baumgartner</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+R">Ronaldo Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bongiorno%2C+S+D">Stephen D. Bongiorno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonino%2C+R">Raffaella Bonino</a> , et al. (79 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.08988v1-abstract-short" style="display: inline;"> Recent observations of X-ray pulsars (XRPs) performed by the Imaging X-ray Polarimetry Explorer (IXPE) have made it possible to investigate the intricate details of these objects in a new way, thanks to the added value of X-ray polarimetry. Here we present the results of the IXPE observations of SMC X-1, a member of the small group of XRPs displaying super-orbital variability. SMC X-1 was observed… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.08988v1-abstract-full').style.display = 'inline'; document.getElementById('2406.08988v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.08988v1-abstract-full" style="display: none;"> Recent observations of X-ray pulsars (XRPs) performed by the Imaging X-ray Polarimetry Explorer (IXPE) have made it possible to investigate the intricate details of these objects in a new way, thanks to the added value of X-ray polarimetry. Here we present the results of the IXPE observations of SMC X-1, a member of the small group of XRPs displaying super-orbital variability. SMC X-1 was observed by IXPE three separate times during the high state of its super-orbital period. The observed luminosity in the 2-8 keV energy band of $L=2\times10^{38}$ erg/s makes SMC X-1 the brightest XRP ever observed by IXPE. We detect significant polarization in all three observations, with values of the phase-averaged polarization degree (PD) and polarization angle (PA) of $3.2\pm0.8$% and $97掳\pm8掳$ for Observation 1, $3.0\pm0.9$% and $90掳\pm8掳$ for Observation 2, and $5.5\pm1.1$% and $80掳\pm6掳$ for Observation 3, for the spectro-polarimetric analysis. The observed PD shows an increase over time with decreasing luminosity, while the PA decreases in decrements of 10掳. The phase-resolved spectro-polarimetric analysis reveals significant detection of polarization in three out of seven phase bins, with the PD ranging between 2% and 10%, and a corresponding range in the PA from $\sim$70掳 to $\sim$100掳. The pulse-phase resolved PD displays an apparent anti-correlation with the flux. Using the rotating vector model, we obtain constraints on the pulsar's geometrical properties for the individual observations. The position angle of the pulsar displays an evolution over time supporting the idea that we observe changes related to different super-orbital phases. Scattering in the wind of the precessing accretion disk may be responsible for the behavior of the polarimetric properties observed during the high-state of SMC X-1's super-orbital period. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.08988v1-abstract-full').style.display = 'none'; document.getElementById('2406.08988v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 11 figures, submitted to A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 691, A216 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.01693">arXiv:2406.01693</a> <span> [<a href="https://arxiv.org/pdf/2406.01693">pdf</a>, <a href="https://arxiv.org/format/2406.01693">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202449166">10.1051/0004-6361/202449166 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> IXPE observation of PKS 2155-304 reveals the most highly polarized blazar </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kouch%2C+P+M">Pouya M. Kouch</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Middei%2C+R">Riccardo Middei</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Tavecchio%2C+F">Fabrizio Tavecchio</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">Herman L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Gesu%2C+L">Laura Di Gesu</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Madejski%2C+G+M">Grzegorz M. Madejski</a>, <a href="/search/astro-ph?searchtype=author&query=Romani%2C+R+W">Roger W. Romani</a>, <a href="/search/astro-ph?searchtype=author&query=Errando%2C+M">Manel Errando</a>, <a href="/search/astro-ph?searchtype=author&query=Lindfors%2C+E">Elina Lindfors</a>, <a href="/search/astro-ph?searchtype=author&query=Nilsson%2C+K">Kari Nilsson</a>, <a href="/search/astro-ph?searchtype=author&query=Toppari%2C+E">Ella Toppari</a>, <a href="/search/astro-ph?searchtype=author&query=Potter%2C+S+B">Stephen B. Potter</a>, <a href="/search/astro-ph?searchtype=author&query=Imazawa%2C+R">Ryo Imazawa</a>, <a href="/search/astro-ph?searchtype=author&query=Sasada%2C+M">Mahito Sasada</a>, <a href="/search/astro-ph?searchtype=author&query=Fukazawa%2C+Y">Yasushi Fukazawa</a>, <a href="/search/astro-ph?searchtype=author&query=Kawabata%2C+K+S">Koji S. Kawabata</a>, <a href="/search/astro-ph?searchtype=author&query=Uemura%2C+M">Makoto Uemura</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno%2C+T">Tsunefumi Mizuno</a>, <a href="/search/astro-ph?searchtype=author&query=Nakaoka%2C+T">Tatsuya Nakaoka</a> , et al. (111 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.01693v1-abstract-short" style="display: inline;"> We report the X-ray polarization properties of the high-synchrotron-peaked (HSP) blazar PKS 2155$-$304 based on observations with the Imaging X-ray Polarimetry Explorer (IXPE). We observed the source between Oct 27 and Nov 7, 2023. We also conducted an extensive contemporaneous multiwavelength (MW) campaign. We find that during the first half ($T_1$) of the IXPE pointing, the source exhibited the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.01693v1-abstract-full').style.display = 'inline'; document.getElementById('2406.01693v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.01693v1-abstract-full" style="display: none;"> We report the X-ray polarization properties of the high-synchrotron-peaked (HSP) blazar PKS 2155$-$304 based on observations with the Imaging X-ray Polarimetry Explorer (IXPE). We observed the source between Oct 27 and Nov 7, 2023. We also conducted an extensive contemporaneous multiwavelength (MW) campaign. We find that during the first half ($T_1$) of the IXPE pointing, the source exhibited the highest X-ray polarization degree detected for an HSP blazar thus far, (30.7$\pm$2.0)%, which dropped to (15.3$\pm$2.1)% during the second half ($T_2$). The X-ray polarization angle remained stable during the IXPE pointing at 129.4$^\circ$$\pm$1.8$^\circ$ and 125.4$^\circ$$\pm$3.9$^\circ$ during $T_1$ and $T_2$, respectively. Meanwhile, the optical polarization degree remained stable during the IXPE pointing, with average host-galaxy-corrected values of (4.3$\pm$0.7)% and (3.8$\pm$0.9)% during the $T_1$ and $T_2$, respectively. During the IXPE pointing, the optical polarization angle changed achromatically from $\sim$140$^\circ$ to $\sim$90$^\circ$ and back to $\sim$130$^\circ$. Despite several attempts, we only detected (99.7% conf.) the radio polarization once (during $T_2$, at 225.5 GHz): with degree (1.7$\pm$0.4)% and angle 112.5$^\circ$$\pm$5.5$^\circ$. The direction of the broad pc-scale jet is rather ambiguous and has been found to point to the east and south at different epochs; however, on larger scales (> 1.5 pc) the jet points toward the southeast ($\sim$135$^\circ$), similar to all of the MW polarization angles. Moreover, the X-ray to optical polarization degree ratios of $\sim$7 and $\sim$4 during $T_1$ and $T_2$, respectively, are similar to previous IXPE results for several HSP blazars. These findings, combined with the lack of correlation of temporal variability between the MW polarization properties, agree with an energy-stratified shock-acceleration scenario in HSP blazars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.01693v1-abstract-full').style.display = 'none'; document.getElementById('2406.01693v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">17 pages, 10 figures, 4 tables, Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 689, A119 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.13192">arXiv:2405.13192</a> <span> [<a href="https://arxiv.org/pdf/2405.13192">pdf</a>, <a href="https://arxiv.org/format/2405.13192">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> X-rays from the Nearby Compact Emission Line Galaxy NGC 2366 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Prestwich%2C+A">Andrea Prestwich</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.13192v1-abstract-short" style="display: inline;"> Luminous, compact emission-line galaxies (LCGs) are the most abundant class of confirmed Lyman continuum (LyC) emitters. An optical integral field study of the nearby LCG NGC 2366 reveals an outflow originating at the star cluster 'knot B' thought to clear a channel via mechanical feedback that enables LyC escape. We observed NGC 2366 with the Chandra X-ray Observatory and detect X-ray emission fr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.13192v1-abstract-full').style.display = 'inline'; document.getElementById('2405.13192v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.13192v1-abstract-full" style="display: none;"> Luminous, compact emission-line galaxies (LCGs) are the most abundant class of confirmed Lyman continuum (LyC) emitters. An optical integral field study of the nearby LCG NGC 2366 reveals an outflow originating at the star cluster 'knot B' thought to clear a channel via mechanical feedback that enables LyC escape. We observed NGC 2366 with the Chandra X-ray Observatory and detect X-ray emission from a point source coincident with the apex of the outflow at knot B. The point-like nature and variability of the X-ray emission suggests accretion onto a compact object. The accretion could produce sufficient kinetic energy to power the outflow. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.13192v1-abstract-full').style.display = 'none'; document.getElementById('2405.13192v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, to appear in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.08107">arXiv:2405.08107</a> <span> [<a href="https://arxiv.org/pdf/2405.08107">pdf</a>, <a href="https://arxiv.org/format/2405.08107">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202450696">10.1051/0004-6361/202450696 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Studying geometry of the ultraluminous X-ray pulsar Swift J0243.6+6124 using X-ray and optical polarimetry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Tsygankov%2C+S+S">Sergey S. Tsygankov</a>, <a href="/search/astro-ph?searchtype=author&query=Doroshenko%2C+V">Victor Doroshenko</a>, <a href="/search/astro-ph?searchtype=author&query=Forsblom%2C+S+V">Sofia V. Forsblom</a>, <a href="/search/astro-ph?searchtype=author&query=Jenke%2C+P">Peter Jenke</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Berdyugin%2C+A+V">Andrei V. Berdyugin</a>, <a href="/search/astro-ph?searchtype=author&query=Blinov%2C+D">Dmitry Blinov</a>, <a href="/search/astro-ph?searchtype=author&query=Kravtsov%2C+V">Vadim Kravtsov</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Tzouvanou%2C+A">Anastasia Tzouvanou</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=La+Monaca%2C+F">Fabio La Monaca</a>, <a href="/search/astro-ph?searchtype=author&query=Mushtukov%2C+A+A">Alexander A. Mushtukov</a>, <a href="/search/astro-ph?searchtype=author&query=Pavlov%2C+G+G">George G. Pavlov</a>, <a href="/search/astro-ph?searchtype=author&query=Salganik%2C+A">Alexander Salganik</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Zane%2C+S">Silvia Zane</a>, <a href="/search/astro-ph?searchtype=author&query=Loktev%2C+V">Vladislav Loktev</a>, <a href="/search/astro-ph?searchtype=author&query=Suleimanov%2C+V+F">Valery F. Suleimanov</a>, <a href="/search/astro-ph?searchtype=author&query=Wilson-Hodge%2C+C">Colleen Wilson-Hodge</a>, <a href="/search/astro-ph?searchtype=author&query=Berdyugina%2C+S+V">Svetlana V. Berdyugina</a>, <a href="/search/astro-ph?searchtype=author&query=Kagitani%2C+M">Masato Kagitani</a> , et al. (86 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.08107v2-abstract-short" style="display: inline;"> Discovery of pulsations from a number of ULXs proved that accretion onto neutron stars can produce luminosities exceeding the Eddington limit by several orders of magnitude. The conditions necessary to achieve such high luminosities as well as the exact geometry of the accretion flow in the neutron star vicinity are, however, a matter of debate. The pulse phase-resolved polarization measurements t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.08107v2-abstract-full').style.display = 'inline'; document.getElementById('2405.08107v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.08107v2-abstract-full" style="display: none;"> Discovery of pulsations from a number of ULXs proved that accretion onto neutron stars can produce luminosities exceeding the Eddington limit by several orders of magnitude. The conditions necessary to achieve such high luminosities as well as the exact geometry of the accretion flow in the neutron star vicinity are, however, a matter of debate. The pulse phase-resolved polarization measurements that became possible with the launch of the Imaging X-ray Polarimetry Explorer (IXPE) can be used to determine the pulsar geometry and its orientation relative to the orbital plane. They provide an avenue to test different theoretical models of ULX pulsars. In this paper we present the results of three IXPE observations of the first Galactic ULX pulsar Swift J0243.6+6124 during its 2023 outburst. We find strong variations in the polarization characteristics with the pulsar phase. The average polarization degree increases from about 5% to 15% as the flux dropped by a factor of three in the course of the outburst. The polarization angle (PA) as a function of the pulsar phase shows two peaks in the first two observations, but changes to a characteristic sawtooth pattern in the remaining data set. This is not consistent with a simple rotating vector model. Assuming the existence of an additional constant polarized component, we were able to fit the three observations with a common rotating vector model and obtain constraints on the pulsar geometry. In particular, we find the pulsar angular momentum inclination with respect to the line of sight of 15-40 deg, the magnetic obliquity of 60-80 deg, and the pulsar spin position angle of -50 deg, which significantly differs from the constant component PA of about 10 deg. Combining these X-ray measurements with the optical PA, we find evidence for at least a 30 deg misalignment between the pulsar angular momentum and the binary orbital axis. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.08107v2-abstract-full').style.display = 'none'; document.getElementById('2405.08107v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 7 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages, 10 figures, version published in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 691, A123 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.07577">arXiv:2405.07577</a> <span> [<a href="https://arxiv.org/pdf/2405.07577">pdf</a>, <a href="https://arxiv.org/format/2405.07577">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/ad4a68">10.3847/2041-8213/ad4a68 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Discovery of a shock-compressed magnetic field in the north-western rim of the young supernova remnant RX J1713.7-3946 with X-ray polarimetry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ferrazzoli%2C+R">Riccardo Ferrazzoli</a>, <a href="/search/astro-ph?searchtype=author&query=Prokhorov%2C+D">Dmitry Prokhorov</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccol貌 Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Slane%2C+P">Patrick Slane</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J">Jacco Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Cardillo%2C+M">Martina Cardillo</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+Y">Yi-Jung Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Silvestri%2C+S">Stefano Silvestri</a>, <a href="/search/astro-ph?searchtype=author&query=Zhou%2C+P">Ping Zhou</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Omodei%2C+N">Nicola Omodei</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+C+-">C. -Y. Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Doroshenko%2C+V">Victor Doroshenko</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Marin%2C+F">Fr茅d茅ric Marin</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno%2C+T">Tsunefumi Mizuno</a>, <a href="/search/astro-ph?searchtype=author&query=Pesce-Rollins%2C+M">Melissa Pesce-Rollins</a>, <a href="/search/astro-ph?searchtype=author&query=Sgr%C3%B2%2C+C">Carmelo Sgr貌</a>, <a href="/search/astro-ph?searchtype=author&query=Swartz%2C+D+A">Douglas A. Swartz</a> , et al. (77 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.07577v2-abstract-short" style="display: inline;"> Supernova remnants (SNRs) provide insights into cosmic-ray acceleration and magnetic field dynamics at shock fronts. Recent X-ray polarimetric measurements by the Imaging X-ray Polarimetry Explorer (IXPE) have revealed radial magnetic fields near particle acceleration sites in young SNRs, including Cassiopeia A, Tycho, and SN 1006. We present here the spatially-resolved IXPE X-ray polarimetric obs… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.07577v2-abstract-full').style.display = 'inline'; document.getElementById('2405.07577v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.07577v2-abstract-full" style="display: none;"> Supernova remnants (SNRs) provide insights into cosmic-ray acceleration and magnetic field dynamics at shock fronts. Recent X-ray polarimetric measurements by the Imaging X-ray Polarimetry Explorer (IXPE) have revealed radial magnetic fields near particle acceleration sites in young SNRs, including Cassiopeia A, Tycho, and SN 1006. We present here the spatially-resolved IXPE X-ray polarimetric observation of the northwestern rim of SNR RX J1713.7-3946. For the first time, our analysis shows that the magnetic field in particle acceleration sites of this SNR is oriented tangentially with respect to the shock front. Because of the lack of precise Faraday-rotation measurements in the radio band, this was not possible before. The average measured polarization degree (PD) of the synchtrotron emission is 12.5 {\pm} 3.3%, lower than the one measured by IXPE in SN 1006, comparable to the Tycho one, but notably higher than the one in Cassiopeia A. On sub-parsec scales, localized patches within RX J1713.7-3946 display PD up to 41.5 {\pm} 9.5%. These results are compatible with a shock-compressed magnetic field. However, in order to explain the observed PD, either the presence of a radial net magnetic field upstream of the shock, or partial reisotropization of the turbulence downstream by radial magneto-hydrodynamical instabilities, can be invoked. From comparison of PD and magnetic field distribution with 纬-rays and 12 CO data, our results provide new inputs in favor of a leptonic origin of the 纬-ray emission. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.07577v2-abstract-full').style.display = 'none'; document.getElementById('2405.07577v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">18 pages, 6 figures, 2 tables, published in ApJ Letters</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJL 967 L38 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2404.19601">arXiv:2404.19601</a> <span> [<a href="https://arxiv.org/pdf/2404.19601">pdf</a>, <a href="https://arxiv.org/format/2404.19601">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202450566">10.1051/0004-6361/202450566 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Recovery of the X-ray polarisation of Swift J1727.8$-$1613 after the soft-to-hard spectral transition </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Podgorn%C3%BD%2C+J">J. Podgorn媒</a>, <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">J. Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Dov%C4%8Diak%2C+M">M. Dov膷iak</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">A. Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">J. Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">P. Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">S. Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Ingram%2C+A">A. Ingram</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">F. Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Datta%2C+S+R">S. R. Datta</a>, <a href="/search/astro-ph?searchtype=author&query=Egron%2C+E">E. Egron</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">H. Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">G. Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">F. Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Petrucci%2C+P+-">P. -O. Petrucci</a>, <a href="/search/astro-ph?searchtype=author&query=Russell%2C+T+D">T. D. Russell</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+J+F">J. F. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Bollemeijer%2C+N">N. Bollemeijer</a>, <a href="/search/astro-ph?searchtype=author&query=Brigitte%2C+M">M. Brigitte</a>, <a href="/search/astro-ph?searchtype=author&query=Segura%2C+N+C">N. Castro Segura</a>, <a href="/search/astro-ph?searchtype=author&query=Emami%2C+R">R. Emami</a>, <a href="/search/astro-ph?searchtype=author&query=Garc%C3%ADa%2C+J+A">J. A. Garc铆a</a>, <a href="/search/astro-ph?searchtype=author&query=Hu%2C+K">K. Hu</a>, <a href="/search/astro-ph?searchtype=author&query=Iacolina%2C+M+N">M. N. Iacolina</a>, <a href="/search/astro-ph?searchtype=author&query=Kravtsov%2C+V">V. Kravtsov</a> , et al. (12 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2404.19601v2-abstract-short" style="display: inline;"> We report on the detection of X-ray polarisation in the black-hole X-ray binary Swift J1727.8$-$1613 during its dim hard spectral state by the Imaging X-ray Polarimetry Explorer (IXPE). This is the first detection of X-ray polarisation at the transition from the soft to the hard state in an X-ray binary. We find an averaged 2$-$8 keV polarisation degree of (3.3 ${\pm}$ 0.4) % and a corresponding p… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.19601v2-abstract-full').style.display = 'inline'; document.getElementById('2404.19601v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.19601v2-abstract-full" style="display: none;"> We report on the detection of X-ray polarisation in the black-hole X-ray binary Swift J1727.8$-$1613 during its dim hard spectral state by the Imaging X-ray Polarimetry Explorer (IXPE). This is the first detection of X-ray polarisation at the transition from the soft to the hard state in an X-ray binary. We find an averaged 2$-$8 keV polarisation degree of (3.3 ${\pm}$ 0.4) % and a corresponding polarisation angle of 3掳 ${\pm}$ 4掳, which matches the polarisation detected during the rising stage of the outburst, in September$-$October 2023, within 1$蟽$ uncertainty. The observational campaign complements previous studies of this source and enables comparison of the X-ray polarisation properties of a single transient across the X-ray hardness-intensity diagram. The complete recovery of the X-ray polarisation properties, including the energy dependence, came after a dramatic drop in the X-ray polarisation during the soft state. The new IXPE observations in the dim hard state at the reverse transition indicate that the accretion properties, including the geometry of the corona, appear to be strikingly similar to the bright hard state during the outburst rise despite the X-ray luminosities differing by two orders of magnitude. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.19601v2-abstract-full').style.display = 'none'; document.getElementById('2404.19601v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 30 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, 6 figures. Accepted for publication in A&A Letters</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 686, L12 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2404.17623">arXiv:2404.17623</a> <span> [<a href="https://arxiv.org/pdf/2404.17623">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> Broadband Multi-wavelength Properties of M87 during the 2018 EHT Campaign including a Very High Energy Flaring Episode </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Algaba%2C+J+C">J. C. Algaba</a>, <a href="/search/astro-ph?searchtype=author&query=Balokovic%2C+M">M. Balokovic</a>, <a href="/search/astro-ph?searchtype=author&query=Chandra%2C+S">S. Chandra</a>, <a href="/search/astro-ph?searchtype=author&query=Cheong%2C+W+Y">W. Y. Cheong</a>, <a href="/search/astro-ph?searchtype=author&query=Cui%2C+Y+Z">Y. Z. Cui</a>, <a href="/search/astro-ph?searchtype=author&query=D%27Ammando%2C+F">F. D'Ammando</a>, <a href="/search/astro-ph?searchtype=author&query=Falcone%2C+A+D">A. D. Falcone</a>, <a href="/search/astro-ph?searchtype=author&query=Ford%2C+N+M">N. M. Ford</a>, <a href="/search/astro-ph?searchtype=author&query=Giroletti%2C+M">M. Giroletti</a>, <a href="/search/astro-ph?searchtype=author&query=Goddi%2C+C">C. Goddi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurwell%2C+M+A">M. A. Gurwell</a>, <a href="/search/astro-ph?searchtype=author&query=Hada%2C+K">K. Hada</a>, <a href="/search/astro-ph?searchtype=author&query=Haggard%2C+D">D. Haggard</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S">S. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Kaur%2C+A">A. Kaur</a>, <a href="/search/astro-ph?searchtype=author&query=Kawashima%2C+T">T. Kawashima</a>, <a href="/search/astro-ph?searchtype=author&query=Kerby%2C+S">S. Kerby</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+J+Y">J. Y. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Kino%2C+M">M. Kino</a>, <a href="/search/astro-ph?searchtype=author&query=Kravchenko%2C+E+V">E. V. Kravchenko</a>, <a href="/search/astro-ph?searchtype=author&query=Lee%2C+S+S">S. S. Lee</a>, <a href="/search/astro-ph?searchtype=author&query=Lu%2C+R+S">R. S. Lu</a>, <a href="/search/astro-ph?searchtype=author&query=Markoff%2C+S">S. Markoff</a>, <a href="/search/astro-ph?searchtype=author&query=Michail%2C+J">J. Michail</a>, <a href="/search/astro-ph?searchtype=author&query=Neilsen%2C+J">J. Neilsen</a> , et al. (721 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2404.17623v3-abstract-short" style="display: inline;"> The nearby elliptical galaxy M87 contains one of the only two supermassive black holes whose emission surrounding the event horizon has been imaged by the Event Horizon Telescope (EHT). In 2018, more than two dozen multi-wavelength (MWL) facilities (from radio to gamma-ray energies) took part in the second M87 EHT campaign. The goal of this extensive MWL campaign was to better understand the physi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.17623v3-abstract-full').style.display = 'inline'; document.getElementById('2404.17623v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2404.17623v3-abstract-full" style="display: none;"> The nearby elliptical galaxy M87 contains one of the only two supermassive black holes whose emission surrounding the event horizon has been imaged by the Event Horizon Telescope (EHT). In 2018, more than two dozen multi-wavelength (MWL) facilities (from radio to gamma-ray energies) took part in the second M87 EHT campaign. The goal of this extensive MWL campaign was to better understand the physics of the accreting black hole M87*, the relationship between the inflow and inner jets, and the high-energy particle acceleration. Understanding the complex astrophysics is also a necessary first step towards performing further tests of general relativity. The MWL campaign took place in April 2018, overlapping with the EHT M87* observations. We present a new, contemporaneous spectral energy distribution (SED) ranging from radio to very high energy (VHE) gamma-rays, as well as details of the individual observations and light curves. We also conduct phenomenological modelling to investigate the basic source properties. We present the first VHE gamma-ray flare from M87 detected since 2010. The flux above 350 GeV has more than doubled within a period of about 36 hours. We find that the X-ray flux is enhanced by about a factor of two compared to 2017, while the radio and millimetre core fluxes are consistent between 2017 and 2018. We detect evidence for a monotonically increasing jet position angle that corresponds to variations in the bright spot of the EHT image. Our results show the value of continued MWL monitoring together with precision imaging for addressing the origins of high-energy particle acceleration. While we cannot currently pinpoint the precise location where such acceleration takes place, the new VHE gamma-ray flare already presents a challenge to simple one-zone leptonic emission model approaches, and emphasises the need for combined image and spectral modelling. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2404.17623v3-abstract-full').style.display = 'none'; document.getElementById('2404.17623v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 December, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">46 pages, 23 figures, accepted by Astronomy & Astrophysics on August. 29, 2024</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2403.04689">arXiv:2403.04689</a> <span> [<a href="https://arxiv.org/pdf/2403.04689">pdf</a>, <a href="https://arxiv.org/format/2403.04689">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/ad402e">10.3847/2041-8213/ad402e <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Dramatic Drop in the X-Ray Polarization of Swift J1727.8$-$1613 in the Soft Spectral State </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">Ji艡铆 Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Dov%C4%8Diak%2C+M">Michal Dov膷iak</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+J+F">James F. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Podgorn%C3%BD%2C+J">Jakub Podgorn媒</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Taverna%2C+R">Roberto Taverna</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">Henric Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Brigitte%2C+M">Ma茂mouna Brigitte</a>, <a href="/search/astro-ph?searchtype=author&query=Datta%2C+S+R">Sudeb Ranjan Datta</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Segura%2C+N+C">Noel Castro Segura</a>, <a href="/search/astro-ph?searchtype=author&query=Garc%C3%ADa%2C+J+A">Javier A. Garc铆a</a>, <a href="/search/astro-ph?searchtype=author&query=Ingram%2C+A">Adam Ingram</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Mu%C3%B1oz-Darias%2C+T">Teo Mu帽oz-Darias</a>, <a href="/search/astro-ph?searchtype=author&query=Nathan%2C+E">Edward Nathan</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Altamirano%2C+D">Diego Altamirano</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Bollemeijer%2C+N">Niek Bollemeijer</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Egron%2C+E">Elise Egron</a> , et al. (12 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2403.04689v2-abstract-short" style="display: inline;"> Black-hole X-ray binaries exhibit different spectral and timing properties in different accretion states. The X-ray outburst of a recently discovered and extraordinarily bright source, Swift$~$J1727.8$-$1613, has enabled the first investigation of how the X-ray polarization properties of a source evolve with spectral state. The 2$-$8 keV polarization degree was previously measured by the Imaging X… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.04689v2-abstract-full').style.display = 'inline'; document.getElementById('2403.04689v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2403.04689v2-abstract-full" style="display: none;"> Black-hole X-ray binaries exhibit different spectral and timing properties in different accretion states. The X-ray outburst of a recently discovered and extraordinarily bright source, Swift$~$J1727.8$-$1613, has enabled the first investigation of how the X-ray polarization properties of a source evolve with spectral state. The 2$-$8 keV polarization degree was previously measured by the Imaging X-ray Polarimetry Explorer (IXPE) to be $\approx$ 4% in the hard and hard intermediate states. Here we present new IXPE results taken in the soft state, with the X-ray flux dominated by the thermal accretion-disk emission. We find that the polarization degree has dropped dramatically to $\lesssim$ 1%. This result indicates that the measured X-ray polarization is largely sensitive to the accretion state and the polarization fraction is significantly higher in the hard state when the X-ray emission is dominated by up-scattered radiation in the X-ray corona. The combined polarization measurements in the soft and hard states disfavor a very high or low inclination of the system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.04689v2-abstract-full').style.display = 'none'; document.getElementById('2403.04689v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 7 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal Letters, 2024, 966, L35 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2403.02061">arXiv:2403.02061</a> <span> [<a href="https://arxiv.org/pdf/2403.02061">pdf</a>, <a href="https://arxiv.org/format/2403.02061">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202449760">10.1051/0004-6361/202449760 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-ray polarization measurement of the gold standard of radio-quiet active galactic nuclei : NGC 1068 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Marin%2C+F">F. Marin</a>, <a href="/search/astro-ph?searchtype=author&query=Marinucci%2C+A">A. Marinucci</a>, <a href="/search/astro-ph?searchtype=author&query=Laurenti%2C+M">M. Laurenti</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">D. E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Barnouin%2C+T">T. Barnouin</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">A. Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">F. Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">S. Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Ravi%2C+S">S. Ravi</a>, <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">H. L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">G. Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+C+-">C. -T. Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Gianolli%2C+V+E">V. E. Gianolli</a>, <a href="/search/astro-ph?searchtype=author&query=Ingram%2C+A">A. Ingram</a>, <a href="/search/astro-ph?searchtype=author&query=Maksym%2C+W+P">W. P. Maksym</a>, <a href="/search/astro-ph?searchtype=author&query=Panagiotou%2C+C">C. Panagiotou</a>, <a href="/search/astro-ph?searchtype=author&query=Podgorny%2C+J">J. Podgorny</a>, <a href="/search/astro-ph?searchtype=author&query=Puccetti%2C+S">S. Puccetti</a>, <a href="/search/astro-ph?searchtype=author&query=Ratheesh%2C+A">A. Ratheesh</a>, <a href="/search/astro-ph?searchtype=author&query=Tombesi%2C+F">F. Tombesi</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">I. Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">L. A. Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">M. Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">L. Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W">W. Baumgartner</a> , et al. (80 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2403.02061v2-abstract-short" style="display: inline;"> We used the Imaging X-ray Polarimetry Explorer (IXPE) satellite to measure, for the first time, the 2-8 keV polarization of NGC 1068. We pointed IXPE for a net exposure time of 1.15 Ms on the target, in addition to two ~ 10 ks each Chandra snapshots in order to account for the potential impact of several ultraluminous X-ray source (ULXs) within IXPE's field-of-view. We measured a 2 - 8 keV polariz… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.02061v2-abstract-full').style.display = 'inline'; document.getElementById('2403.02061v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2403.02061v2-abstract-full" style="display: none;"> We used the Imaging X-ray Polarimetry Explorer (IXPE) satellite to measure, for the first time, the 2-8 keV polarization of NGC 1068. We pointed IXPE for a net exposure time of 1.15 Ms on the target, in addition to two ~ 10 ks each Chandra snapshots in order to account for the potential impact of several ultraluminous X-ray source (ULXs) within IXPE's field-of-view. We measured a 2 - 8 keV polarization degree of 12.4% +/- 3.6% and an electric vector polarization angle of 101掳 +/- 8掳 at 68% confidence level. If we exclude the spectral region containing the bright Fe K lines and other soft X-ray lines where depolarization occurs, the polarization fraction rises up to 21.3% +/- 6.7% in the 3.5 - 6.0 keV band, with a similar polarization angle. The observed polarization angle is found to be perpendicular to the parsec scale radio jet. Using a combined Chandra and IXPE analysis plus multi-wavelength constraints, we estimated that the circumnuclear "torus" may sustain a half-opening angle of 50掳 - 55掳 (from the vertical axis of the system). Thanks to IXPE, we have measured the X-ray polarization of NGC 1068 and found comparable results, both in terms of polarization angle orientation with respect to the radio-jet and torus half-opening angle, to the X-ray polarimetric measurement achieved for the other archetypal Compton-thick AGN : the Circinus galaxy. Probing the geometric arrangement of parsec-scale matter in extragalactic object is now feasible thanks to X-ray polarimetry. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2403.02061v2-abstract-full').style.display = 'none'; document.getElementById('2403.02061v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 5 figures, 2 tables, submited to A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">MSC Class:</span> 85-06 <span class="has-text-black-bis has-text-weight-semibold">ACM Class:</span> J.2.3; J.2.9 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 689, A238 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.02504">arXiv:2402.02504</a> <span> [<a href="https://arxiv.org/pdf/2402.02504">pdf</a>, <a href="https://arxiv.org/format/2402.02504">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> First detection of polarization in X-rays for PSR B0540-69 and its nebula </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Xie%2C+F">Fei Xie</a>, <a href="/search/astro-ph?searchtype=author&query=Wong%2C+J">Josephine Wong</a>, <a href="/search/astro-ph?searchtype=author&query=La+Monaca%2C+F">Fabio La Monaca</a>, <a href="/search/astro-ph?searchtype=author&query=Romani%2C+R+W">Roger W. Romani</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccol貌 Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+K">Kuan Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+C">Chi-Yung Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Lalla%2C+N">Niccol貌 Di Lalla</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Pilia%2C+M">Maura Pilia</a>, <a href="/search/astro-ph?searchtype=author&query=Rankin%2C+J">John Rankin</a>, <a href="/search/astro-ph?searchtype=author&query=Fabiani%2C+S">Sergio Fabiani</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio A. Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W+H">Wayne H. Baumgartner</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+R">Ronaldo Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a> , et al. (78 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2402.02504v1-abstract-short" style="display: inline;"> We report on X-ray polarization measurements of the extra-galactic Crab-like PSR B0540-69 and its Pulsar Wind Nebula (PWN) in the Large Magellanic Cloud (LMC), using a ~850 ks Imaging X-ray Polarimetry Explorer (IXPE) exposure. The PWN is unresolved by IXPE. No statistically significant polarization is detected for the image-averaged data, giving a 99% confidence polarization upper limit (MDP99) o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.02504v1-abstract-full').style.display = 'inline'; document.getElementById('2402.02504v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.02504v1-abstract-full" style="display: none;"> We report on X-ray polarization measurements of the extra-galactic Crab-like PSR B0540-69 and its Pulsar Wind Nebula (PWN) in the Large Magellanic Cloud (LMC), using a ~850 ks Imaging X-ray Polarimetry Explorer (IXPE) exposure. The PWN is unresolved by IXPE. No statistically significant polarization is detected for the image-averaged data, giving a 99% confidence polarization upper limit (MDP99) of 5.3% in 2-8 keV energy range. However, a phase-resolved analysis detects polarization for both the nebula and pulsar in the 4-6 keV energy range. For the PWN defined as the off-pulse phases, the polarization degree (PD) of (24.5 ${\pm}$ 5.3)% and polarization angle (PA) of (78.1 ${\pm}$ 6.2)掳 is detected at 4.6$蟽$ significance level, consistent with the PA observed in the optical band. In a single on-pulse window, a hint of polarization is measured at 3.8$蟽$ with polarization degree of (50.0 ${\pm}$ 13.1)% and polarization angle of (6.2 ${\pm}$ 7.4)掳. A 'simultaneous' PSR/PWN analysis finds two bins at the edges of the pulse exceeding 3$蟽$ PD significance, with PD of (68 ${\pm}$ 20)% and (62 ${\pm}$ 20)%; intervening bins at 2-3$蟽$ significance have lower PD, hinting at additional polarization structure. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.02504v1-abstract-full').style.display = 'none'; document.getElementById('2402.02504v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 7 figures, 4 tables, author's version of the paper accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.13058">arXiv:2401.13058</a> <span> [<a href="https://arxiv.org/pdf/2401.13058">pdf</a>, <a href="https://arxiv.org/format/2401.13058">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202449318">10.1051/0004-6361/202449318 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Discovery of a strong rotation of the X-ray polarization angle in the galactic burster GX 13+1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bobrikova%2C+A">Anna Bobrikova</a>, <a href="/search/astro-ph?searchtype=author&query=Forsblom%2C+S+V">Sofia V. Forsblom</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=La+Monaca%2C+F">Fabio La Monaca</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+M">Mason Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Ravi%2C+S">Swati Ravi</a>, <a href="/search/astro-ph?searchtype=author&query=Loktev%2C+V">Vladislav Loktev</a>, <a href="/search/astro-ph?searchtype=author&query=Kajava%2C+J+J+E">Jari J. E. Kajava</a>, <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">Francesco Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Rogantini%2C+D">Daniele Rogantini</a>, <a href="/search/astro-ph?searchtype=author&query=Salmi%2C+T">Tuomo Salmi</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Done%2C+C">Chris Done</a>, <a href="/search/astro-ph?searchtype=author&query=Fabiani%2C+S">Sergio Fabiani</a>, <a href="/search/astro-ph?searchtype=author&query=Gnarini%2C+A">Andrea Gnarini</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Nitindala%2C+A+P">Anagha P. Nitindala</a>, <a href="/search/astro-ph?searchtype=author&query=Rankin%2C+J">John Rankin</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a> , et al. (84 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.13058v2-abstract-short" style="display: inline;"> Weakly magnetized neutron stars in X-ray binaries show complex phenomenology with several spectral components that can be associated with the accretion disk, boundary and/or spreading layer, a corona, and a wind. Spectroscopic information alone is, however, not enough to disentangle these components. Additional information about the nature of the spectral components and in particular the geometry… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.13058v2-abstract-full').style.display = 'inline'; document.getElementById('2401.13058v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.13058v2-abstract-full" style="display: none;"> Weakly magnetized neutron stars in X-ray binaries show complex phenomenology with several spectral components that can be associated with the accretion disk, boundary and/or spreading layer, a corona, and a wind. Spectroscopic information alone is, however, not enough to disentangle these components. Additional information about the nature of the spectral components and in particular the geometry of the emission region can be provided by X-ray polarimetry. One of the objects of the class, a bright, persistent, and rather peculiar galactic Type I X-ray burster was observed with the Imaging X-ray Polarimetry Explorer (IXPE) and the X-ray Multi-Mirror Mission Newton (XMM-Newton). Using the XMM-Newton data we estimated the current state of the source as well as detected strong absorption lines associated with the accretion disk wind. IXPE data showed the source to be significantly polarized in the 2-8 keV energy band with the overall polarization degree (PD) of 1.4% at a polarization angle (PA) of -2 degrees (errors at 68% confidence level). During the two-day long observation, we detected rotation of the PA by about 70 degrees with the corresponding changes in the PD from 2% to non-detectable and then up to 5%. These variations in polarization properties are not accompanied by visible changes in spectroscopic characteristics. The energy-resolved polarimetric analysis showed a significant change in polarization, from being strongly dependent on energy at the beginning of the observation to being almost constant with energy in the later parts of the observation. As a possible interpretation, we suggest the presence of a constant component of polarization, strong wind scattering, or different polarization of the two main spectral components with individually peculiar behavior. The rotation of the PA suggests a 30-degree misalignment of the neutron star spin from the orbital axis. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.13058v2-abstract-full').style.display = 'none'; document.getElementById('2401.13058v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 12 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 688, A170 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.04420">arXiv:2401.04420</a> <span> [<a href="https://arxiv.org/pdf/2401.04420">pdf</a>, <a href="https://arxiv.org/format/2401.04420">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ad1ce4">10.3847/1538-4357/ad1ce4 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Detection of X-ray Polarization from the Blazar 1ES 1959+650 with the Imaging X-ray Polarimetry Explorer </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Errando%2C+M">Manel Errando</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">Herman L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Middei%2C+R">Riccardo Middei</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Peirson%2C+A+L">Abel Lawrence Peirson</a>, <a href="/search/astro-ph?searchtype=author&query=Perri%2C+M">Matteo Perri</a>, <a href="/search/astro-ph?searchtype=author&query=Puccetti%2C+S">Simonetta Puccetti</a>, <a href="/search/astro-ph?searchtype=author&query=Rabinowitz%2C+P+L">Pazit L. Rabinowitz</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Savchenko%2C+S+S">Sergey S. Savchenko</a>, <a href="/search/astro-ph?searchtype=author&query=Blinov%2C+D">Dmitry Blinov</a>, <a href="/search/astro-ph?searchtype=author&query=Bourbah%2C+I+G">Ioakeim G. Bourbah</a>, <a href="/search/astro-ph?searchtype=author&query=Kiehlmann%2C+S">Sebastian Kiehlmann</a>, <a href="/search/astro-ph?searchtype=author&query=Kontopodis%2C+E">Evangelos Kontopodis</a>, <a href="/search/astro-ph?searchtype=author&query=Mandarakas%2C+N">Nikos Mandarakas</a>, <a href="/search/astro-ph?searchtype=author&query=Romanopoulos%2C+S">Stylianos Romanopoulos</a>, <a href="/search/astro-ph?searchtype=author&query=Skalidis%2C+R">Raphael Skalidis</a>, <a href="/search/astro-ph?searchtype=author&query=Vervelaki%2C+A">Anna Vervelaki</a>, <a href="/search/astro-ph?searchtype=author&query=Aceituno%2C+F+J">Francisco Jos茅 Aceituno</a>, <a href="/search/astro-ph?searchtype=author&query=Bernardos%2C+M+I">Maria I. Bernardos</a>, <a href="/search/astro-ph?searchtype=author&query=Bonnoli%2C+G">Giacomo Bonnoli</a>, <a href="/search/astro-ph?searchtype=author&query=Casanova%2C+V">V铆ctor Casanova</a> , et al. (121 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.04420v1-abstract-short" style="display: inline;"> Observations of linear polarization in the 2-8 keV energy range with the Imaging X-ray Polarimetry Explorer (IXPE) explore the magnetic field geometry and dynamics of the regions generating non-thermal radiation in relativistic jets of blazars. These jets, particularly in blazars whose spectral energy distribution peaks at X-ray energies, emit X-rays via synchrotron radiation from high-energy part… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.04420v1-abstract-full').style.display = 'inline'; document.getElementById('2401.04420v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.04420v1-abstract-full" style="display: none;"> Observations of linear polarization in the 2-8 keV energy range with the Imaging X-ray Polarimetry Explorer (IXPE) explore the magnetic field geometry and dynamics of the regions generating non-thermal radiation in relativistic jets of blazars. These jets, particularly in blazars whose spectral energy distribution peaks at X-ray energies, emit X-rays via synchrotron radiation from high-energy particles within the jet. IXPE observations of the X-ray selected BL Lac-type blazar 1ES 1959+650 in 2022 May 3-4 showed a significant linear polarization degree of $螤_\mathrm{x} = 8.0\% \pm 2.3\%$ at an electric-vector position angle $蠄_\mathrm{x} = 123^\circ \pm 8^\circ$. However, in 2022 June 9-12, only an upper limit of $螤_\mathrm{x} \leq 5.1\%$ could be derived (at the 99% confidence level). The degree of optical polarization at that time $螤_\mathrm{O} \sim 5\%$ is comparable to the X-ray measurement. We investigate possible scenarios for these findings, including temporal and geometrical depolarization effects. Unlike some other X-ray selected BL Lac objects, there is no significant chromatic dependence of the measured polarization in 1ES 1959+650, and its low X-ray polarization may be attributed to turbulence in the jet flow with dynamical timescales shorter than 1 day. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.04420v1-abstract-full').style.display = 'none'; document.getElementById('2401.04420v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages, 4 figures, accepted for publication in The Astrophysical Journal</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, 963 (2024) 5 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.01853">arXiv:2401.01853</a> <span> [<a href="https://arxiv.org/pdf/2401.01853">pdf</a>, <a href="https://arxiv.org/format/2401.01853">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> </div> <p class="title is-5 mathjax"> An Angular Diameter Measurement of $尾$ UMa via Stellar Intensity Interferometry with the VERITAS Observatory </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Acharyya%2C+A">A. Acharyya</a>, <a href="/search/astro-ph?searchtype=author&query=Aufdenberg%2C+J+P">J. P. Aufdenberg</a>, <a href="/search/astro-ph?searchtype=author&query=Bangale%2C+P">P. Bangale</a>, <a href="/search/astro-ph?searchtype=author&query=Bartkoske%2C+J+T">J. T. Bartkoske</a>, <a href="/search/astro-ph?searchtype=author&query=Batista%2C+P">P. Batista</a>, <a href="/search/astro-ph?searchtype=author&query=Benbow%2C+W">W. Benbow</a>, <a href="/search/astro-ph?searchtype=author&query=Chromey%2C+A+J">A. J. Chromey</a>, <a href="/search/astro-ph?searchtype=author&query=Davis%2C+J+D">J. D. Davis</a>, <a href="/search/astro-ph?searchtype=author&query=Feng%2C+Q">Q. Feng</a>, <a href="/search/astro-ph?searchtype=author&query=Foote%2C+G+M">G. M. Foote</a>, <a href="/search/astro-ph?searchtype=author&query=Furniss%2C+A">A. Furniss</a>, <a href="/search/astro-ph?searchtype=author&query=Hanlon%2C+W">W. Hanlon</a>, <a href="/search/astro-ph?searchtype=author&query=Hinrichs%2C+C+E">C. E. Hinrichs</a>, <a href="/search/astro-ph?searchtype=author&query=Holder%2C+J">J. Holder</a>, <a href="/search/astro-ph?searchtype=author&query=Jin%2C+W">W. Jin</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">P. Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Kertzman%2C+M">M. Kertzman</a>, <a href="/search/astro-ph?searchtype=author&query=Kieda%2C+D">D. Kieda</a>, <a href="/search/astro-ph?searchtype=author&query=Kleiner%2C+T+K">T. K. Kleiner</a>, <a href="/search/astro-ph?searchtype=author&query=Korzoun%2C+N">N. Korzoun</a>, <a href="/search/astro-ph?searchtype=author&query=LeBohec%2C+T">T. LeBohec</a>, <a href="/search/astro-ph?searchtype=author&query=Lisa%2C+M+A">M. A. Lisa</a>, <a href="/search/astro-ph?searchtype=author&query=Lundy%2C+M">M. Lundy</a>, <a href="/search/astro-ph?searchtype=author&query=Matthews%2C+N">N. Matthews</a>, <a href="/search/astro-ph?searchtype=author&query=McGrath%2C+C+E">C. E McGrath</a> , et al. (22 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.01853v1-abstract-short" style="display: inline;"> We use the VERITAS imaging air Cherenkov Telescope (IACT) array to obtain the first measured angular diameter of $尾$ UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak ($尾$ UMa), an A1-type subgiant… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.01853v1-abstract-full').style.display = 'inline'; document.getElementById('2401.01853v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.01853v1-abstract-full" style="display: none;"> We use the VERITAS imaging air Cherenkov Telescope (IACT) array to obtain the first measured angular diameter of $尾$ UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak ($尾$ UMa), an A1-type subgiant, by comparing effective temperature and luminosity constraints to model stellar evolution tracks. Previous interferometric limb-darkened angular-diameter measurements of $尾$ UMa in the near-infrared (CHARA Array, $1.149 \pm 0.014$ mas) and mid-infrared (Keck Nuller, $1.08 \pm 0.07$ mas), together with the measured parallax and bolometric flux, have constrained the effective temperature. This paper presents current VERITAS-SII observation and analysis procedures to derive squared visibilities from correlation functions. We fit the resulting squared visibilities to find a limb-darkened angular diameter of $1.07 \pm 0.04 {\rm (stat)} \pm 0.05$ (sys) mas, using synthetic visibilities from a stellar atmosphere model that provides a good match to the spectrum of $尾$ UMa in the optical wave band. The VERITAS-SII limb-darkened angular diameter yields an effective temperature of $9700\pm200\pm 200$ K, consistent with ultraviolet spectrophotometry, and an age of $390\pm 29 \pm 32 $ Myr, using MESA Isochrones and Stellar Tracks (MIST). This age is consistent with $408 \pm 6$ Myr from the CHARA Array angular diameter. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.01853v1-abstract-full').style.display = 'none'; document.getElementById('2401.01853v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.11655">arXiv:2312.11655</a> <span> [<a href="https://arxiv.org/pdf/2312.11655">pdf</a>, <a href="https://arxiv.org/format/2312.11655">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> X-Ray Polarimetry of the Dipping Accreting Neutron Star 4U 1624-49 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Saade%2C+M+L">M. Lynne Saade</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Gnarini%2C+A">Andrea Gnarini</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">Francesco Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bobrikova%2C+A">Anna Bobrikova</a>, <a href="/search/astro-ph?searchtype=author&query=La+Monaca%2C+F">Fabio La Monaca</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Ivan Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio A. Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W+H">Wayne H. Baumgartner</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+R">Ronaldo Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bongiorno%2C+S+D">Stephen D. Bongiorno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonino%2C+R">Raffaella Bonino</a>, <a href="/search/astro-ph?searchtype=author&query=Brez%2C+A">Alessandro Brez</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccolo Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Castellano%2C+S">Simone Castellano</a>, <a href="/search/astro-ph?searchtype=author&query=Cavazzuti%2C+E">Elisabetta Cavazzuti</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+C">Chien-Ting Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Ciprini%2C+S">Stefano Ciprini</a> , et al. (76 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.11655v3-abstract-short" style="display: inline;"> We present the first X-ray polarimetric study of the dipping accreting neutron star 4U 1624$-$49 with the Imaging X-ray Polarimetry Explorer (IXPE). We report a detection of polarization in the non-dip time intervals with a confidence level of 99.99%. We find an average polarization degree (PD) of $3.1\pm0.7$% and a polarization angle of $81\pm6$ degrees east of north in the 2-8 keV band. We repor… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.11655v3-abstract-full').style.display = 'inline'; document.getElementById('2312.11655v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.11655v3-abstract-full" style="display: none;"> We present the first X-ray polarimetric study of the dipping accreting neutron star 4U 1624$-$49 with the Imaging X-ray Polarimetry Explorer (IXPE). We report a detection of polarization in the non-dip time intervals with a confidence level of 99.99%. We find an average polarization degree (PD) of $3.1\pm0.7$% and a polarization angle of $81\pm6$ degrees east of north in the 2-8 keV band. We report an upper limit on the PD of 22% during the X-ray dips with 95% confidence. The PD increases with energy, reaching from $3.0\pm0.9$% in the 4-6 keV band to $6\pm2$% in the 6-8 keV band. This indicates the polarization likely arises from Comptonization. The high PD observed is unlikely to be produced by Comptonization in the boundary layer or spreading layer alone. It can be produced by the addition of an extended geometrically thin slab corona covering part of the accretion disk, as assumed in previous models of dippers, and/or a reflection component from the accretion disk. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.11655v3-abstract-full').style.display = 'none'; document.getElementById('2312.11655v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.04421">arXiv:2312.04421</a> <span> [<a href="https://arxiv.org/pdf/2312.04421">pdf</a>, <a href="https://arxiv.org/format/2312.04421">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202349080">10.1051/0004-6361/202349080 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Pulsar-wind-nebula-powered Galactic center X-ray filament G0.13-0.11: Proof of the synchrotron nature by IXPE </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Churazov%2C+E">Eugene Churazov</a>, <a href="/search/astro-ph?searchtype=author&query=Khabibullin%2C+I">Ildar Khabibullin</a>, <a href="/search/astro-ph?searchtype=author&query=Barnouin%2C+T">Thibault Barnouin</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccol貌 Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Gesu%2C+L">Laura Di Gesu</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Ferrazzoli%2C+R">Riccardo Ferrazzoli</a>, <a href="/search/astro-ph?searchtype=author&query=Forman%2C+W">William Forman</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Kolodziejczak%2C+J+J">Jeffery J. Kolodziejczak</a>, <a href="/search/astro-ph?searchtype=author&query=Kraft%2C+R">Ralph Kraft</a>, <a href="/search/astro-ph?searchtype=author&query=Marin%2C+F">Fr茅d茅ric Marin</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Romani%2C+R+W">Roger W. Romani</a>, <a href="/search/astro-ph?searchtype=author&query=Silvestri%2C+S">Stefano Silvestri</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Sunyaev%2C+R">Rashid Sunyaev</a>, <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">Jiri Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Vikhlinin%2C+A">Alexey Vikhlinin</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Xie%2C+F">Fei Xie</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a> , et al. (81 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.04421v2-abstract-short" style="display: inline;"> We report the discovery of X-ray polarization from the X-ray-bright filament. G0.13-0.11 in the Galactic center (GC) region. This filament features a bright, hard X-ray source that is most plausibly a pulsar wind nebula (PWN) and an extended and structured diffuse component. Combining the polarization signal from IXPE with the imaging/spectroscopic data from Chandra, we find that X-ray emission of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.04421v2-abstract-full').style.display = 'inline'; document.getElementById('2312.04421v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.04421v2-abstract-full" style="display: none;"> We report the discovery of X-ray polarization from the X-ray-bright filament. G0.13-0.11 in the Galactic center (GC) region. This filament features a bright, hard X-ray source that is most plausibly a pulsar wind nebula (PWN) and an extended and structured diffuse component. Combining the polarization signal from IXPE with the imaging/spectroscopic data from Chandra, we find that X-ray emission of G0.13-0.11 is highly polarized PD=$57(\pm18)$% in the 3-6 keV band, while the polarization angle is PA=$21^\circ(\pm9^\circ)$. This high degree of polarization proves the synchrotron origin of the X-ray emission from G0.13-0.11. In turn, the measured polarization angle implies that the X-ray emission is polarized approximately perpendicular to a sequence of nonthermal radio filaments that may be part of the GC Radio Arc. The magnetic field on the order of $100\,{\rm渭G}$ appears to be preferentially ordered along the filaments. The above field strength is the fiducial value that makes our model self-consistent, while the other conclusions are largely model independent. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.04421v2-abstract-full').style.display = 'none'; document.getElementById('2312.04421v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 686, A14 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.02551">arXiv:2312.02551</a> <span> [<a href="https://arxiv.org/pdf/2312.02551">pdf</a>, <a href="https://arxiv.org/ps/2312.02551">ps</a>, <a href="https://arxiv.org/format/2312.02551">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> Soft X-ray Energy Spectra in the Wide-Field Galactic Disk Area Revealed with HaloSat </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ampuku%2C+K">Kazuki Ampuku</a>, <a href="/search/astro-ph?searchtype=author&query=Mitsuishi%2C+I">Ikuyuki Mitsuishi</a>, <a href="/search/astro-ph?searchtype=author&query=Sakuta%2C+K">Koki Sakuta</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=LaRocca%2C+D+M">Daniel M. LaRocca</a>, <a href="/search/astro-ph?searchtype=author&query=Angelini%2C+L">Lorella Angelini</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.02551v1-abstract-short" style="display: inline;"> We analyzed data from HaloSat observations for five fields in the Galactic disk located far away from the Galactic center (135$^{\circ}$ $<$ $l$ $<$ 254$^{\circ}$) to understand the nature of soft X-ray energy emission in the Galactic disk. The fields have 14$^{\circ}$ diameter and were selected to contain no significant high-flux X-ray sources. All five HaloSat soft X-ray energy spectra (0.4--7 k… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.02551v1-abstract-full').style.display = 'inline'; document.getElementById('2312.02551v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.02551v1-abstract-full" style="display: none;"> We analyzed data from HaloSat observations for five fields in the Galactic disk located far away from the Galactic center (135$^{\circ}$ $<$ $l$ $<$ 254$^{\circ}$) to understand the nature of soft X-ray energy emission in the Galactic disk. The fields have 14$^{\circ}$ diameter and were selected to contain no significant high-flux X-ray sources. All five HaloSat soft X-ray energy spectra (0.4--7 keV with energy resolution of $<$100 eV below 1 keV) show a possibility of the presence of unresolved high-temperature plasma in the Galactic disk (UHTPGD) with a temperature of 0.8--1.0 keV and an emission measure of (8--11)$\times10^{-4} \rm cm^{-6} pc$ in addition to the soft X-ray diffuse background components mainly studied at higher galactic latitudes (solar wind charge exchange emission, local hot bubble, Milky Way halo emission, and the cosmic X-ray background). This suggests that the UHTPGD is present across the whole Galactic disk. We also observed UHTPGD emission in a region with no bright sources in an {\it XMM-Newton} field contained within one of the {\it HaloSat} fields. The temperature and emission measure are consistent with those measured with {\it HaloSat}. Moreover, the stacked spectra of the X-ray point-like sources and NIR-identified point sources such as stars in the {\it XMM-Newton} field also show a spectral feature similar to the UHTPGD emission. This suggests that the UHTPGD may partly originate from point-like sources such as stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.02551v1-abstract-full').style.display = 'none'; document.getElementById('2312.02551v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in ApJ. 11 pages and 4 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.16313">arXiv:2311.16313</a> <span> [<a href="https://arxiv.org/pdf/2311.16313">pdf</a>, <a href="https://arxiv.org/format/2311.16313">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> X-ray Polarization of the Eastern Lobe of SS 433 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Ferrazzoli%2C+R">Riccardo Ferrazzoli</a>, <a href="/search/astro-ph?searchtype=author&query=Silvestri%2C+S">Stefano Silvestri</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Manfreda%2C+A">Alberto Manfreda</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+K">Kinwah Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Safi-Harb%2C+S">Samar Safi-Harb</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Slane%2C+P">Patrick Slane</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Ingram%2C+A">Adam Ingram</a>, <a href="/search/astro-ph?searchtype=author&query=Romani%2C+R+W">Roger W. Romani</a>, <a href="/search/astro-ph?searchtype=author&query=Cibrario%2C+N">Nicolo Cibrario</a>, <a href="/search/astro-ph?searchtype=author&query=Mac+Intyre%2C+B">Brydyn Mac Intyre</a>, <a href="/search/astro-ph?searchtype=author&query=Mikusincova%2C+R">Romana Mikusincova</a>, <a href="/search/astro-ph?searchtype=author&query=Ratheesh%2C+A">Ajay Ratheesh</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+J+F">James F. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">Jiri Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Tugliani%2C+S">Stefano Tugliani</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Ivan Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio A. Antonelli</a> , et al. (81 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.16313v1-abstract-short" style="display: inline;"> How astrophysical systems translate the kinetic energy of bulk motion into the acceleration of particles to very high energies is a pressing question. SS 433 is a microquasar that emits TeV gamma-rays indicating the presence of high-energy particles. A region of hard X-ray emission in the eastern lobe of SS 433 was recently identified as an acceleration site. We observed this region with the Imagi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.16313v1-abstract-full').style.display = 'inline'; document.getElementById('2311.16313v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.16313v1-abstract-full" style="display: none;"> How astrophysical systems translate the kinetic energy of bulk motion into the acceleration of particles to very high energies is a pressing question. SS 433 is a microquasar that emits TeV gamma-rays indicating the presence of high-energy particles. A region of hard X-ray emission in the eastern lobe of SS 433 was recently identified as an acceleration site. We observed this region with the Imaging X-ray Polarimetry Explorer and measured a polarization degree in the range 38% to 77%. The high polarization degree indicates the magnetic field has a well ordered component if the X-rays are due to synchrotron emission. The polarization angle is in the range -12 to +10 degrees (east of north) which indicates that the magnetic field is parallel to the jet. Magnetic fields parallel to the bulk flow have also been found in supernova remnants and the jets of powerful radio galaxies. This may be caused by interaction of the flow with the ambient medium. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.16313v1-abstract-full').style.display = 'none'; document.getElementById('2311.16313v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, accepted in the Astrophysical Journal Letters</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.06359">arXiv:2311.06359</a> <span> [<a href="https://arxiv.org/pdf/2311.06359">pdf</a>, <a href="https://arxiv.org/format/2311.06359">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/ad132d">10.3847/2041-8213/ad132d <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=La+Monaca%2C+F">Fabio La Monaca</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Motta%2C+S+E">Sara E. Motta</a>, <a href="/search/astro-ph?searchtype=author&query=Papitto%2C+A">Alessandro Papitto</a>, <a href="/search/astro-ph?searchtype=author&query=Pilia%2C+M">Maura Pilia</a>, <a href="/search/astro-ph?searchtype=author&query=Xie%2C+F">Fei Xie</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bobrikova%2C+A">Anna Bobrikova</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Deng%2C+W">Wei Deng</a>, <a href="/search/astro-ph?searchtype=author&query=Ge%2C+M">Mingyu Ge</a>, <a href="/search/astro-ph?searchtype=author&query=Illiano%2C+G">Giulia Illiano</a>, <a href="/search/astro-ph?searchtype=author&query=Jia%2C+S">Shu-Mei Jia</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">Henric Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Lai%2C+E+V">Eleonora V. Lai</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+K">Kuan Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Mastroserio%2C+G">Guglielmo Mastroserio</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Rankin%2C+J">John Rankin</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Ambrosino%2C+F">Filippo Ambrosino</a>, <a href="/search/astro-ph?searchtype=author&query=Del+Santo%2C+M">Melania Del Santo</a> , et al. (94 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.06359v3-abstract-short" style="display: inline;"> The Imaging X-ray Polarimetry Explorer (IXPE) measured with high significance the X-ray polarization of the brightest Z-source Scorpius X-1, resulting in the nominal 2-8 keV energy band in a polarization degree of 1.0(0.2)% and a polarization angle of 8(6)掳 at 90% of confidence level. This observation was strictly simultaneous with observations performed by NICER, NuSTAR, and Insight-HXMT, which a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.06359v3-abstract-full').style.display = 'inline'; document.getElementById('2311.06359v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.06359v3-abstract-full" style="display: none;"> The Imaging X-ray Polarimetry Explorer (IXPE) measured with high significance the X-ray polarization of the brightest Z-source Scorpius X-1, resulting in the nominal 2-8 keV energy band in a polarization degree of 1.0(0.2)% and a polarization angle of 8(6)掳 at 90% of confidence level. This observation was strictly simultaneous with observations performed by NICER, NuSTAR, and Insight-HXMT, which allowed for a precise characterization of its broad-band spectrum from soft to hard X-rays. The source has been observed mainly in its soft state, with short periods of flaring. We also observed low-frequency quasi-periodic oscillations. From a spectro-polarimetric analysis, we associate a polarization to the accretion disk at <3.2% at 90% of confidence level, compatible with expectations for an electron-scattering dominated optically thick atmosphere at the Sco X-1 inclination of 44掳; for the higher-energy Comptonized component, we obtain a polarization of 1.3(0.4)%, in agreement with expectations for a slab of Thomson optical depth of ~7 and an electron temperature of ~3 keV. A polarization rotation with respect to previous observations by OSO-8 and PolarLight, and also with respect to the radio-jet position angle, is observed. This result may indicate a variation of the polarization with the source state that can be related to relativistic precession or to a change in the corona geometry with the accretion flow. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.06359v3-abstract-full').style.display = 'none'; document.getElementById('2311.06359v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJL 960 L11 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.05497">arXiv:2311.05497</a> <span> [<a href="https://arxiv.org/pdf/2311.05497">pdf</a>, <a href="https://arxiv.org/format/2311.05497">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Tracking the X-ray Polarization of the Black Hole Transient Swift J1727.8-1613 during a State Transition </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ingram%2C+A">Adam Ingram</a>, <a href="/search/astro-ph?searchtype=author&query=Bollemeijer%2C+N">Niek Bollemeijer</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Dovciak%2C+M">Michal Dovciak</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Egron%2C+E">Elise Egron</a>, <a href="/search/astro-ph?searchtype=author&query=Russell%2C+T+D">Thomas D. Russell</a>, <a href="/search/astro-ph?searchtype=author&query=Trushkin%2C+S+A">Sergei A. Trushkin</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Ratheesh%2C+A">Ajay Ratheesh</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Connors%2C+R">Riley Connors</a>, <a href="/search/astro-ph?searchtype=author&query=Neilsen%2C+J">Joseph Neilsen</a>, <a href="/search/astro-ph?searchtype=author&query=Kraus%2C+A">Alexander Kraus</a>, <a href="/search/astro-ph?searchtype=author&query=Iacolina%2C+M+N">Maria Noemi Iacolina</a>, <a href="/search/astro-ph?searchtype=author&query=Pellizzoni%2C+A">Alberto Pellizzoni</a>, <a href="/search/astro-ph?searchtype=author&query=Pilia%2C+M">Maura Pilia</a>, <a href="/search/astro-ph?searchtype=author&query=Carotenuto%2C+F">Francesco Carotenuto</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Mastroserio%2C+G">Guglielmo Mastroserio</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Garcia%2C+J+A">Javier A. Garcia</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+K">Kinwah Wu</a> , et al. (98 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.05497v3-abstract-short" style="display: inline;"> We report on an observational campaign on the bright black hole X-ray binary Swift J1727.8$-$1613 centered around five observations by the Imaging X-ray Polarimetry Explorer (IXPE). These observations track for the first time the evolution of the X-ray polarization of a black hole X-ray binary across a hard to soft state transition. The 2--8 keV polarization degree decreased from $\sim$4\% to… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.05497v3-abstract-full').style.display = 'inline'; document.getElementById('2311.05497v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.05497v3-abstract-full" style="display: none;"> We report on an observational campaign on the bright black hole X-ray binary Swift J1727.8$-$1613 centered around five observations by the Imaging X-ray Polarimetry Explorer (IXPE). These observations track for the first time the evolution of the X-ray polarization of a black hole X-ray binary across a hard to soft state transition. The 2--8 keV polarization degree decreased from $\sim$4\% to $\sim$3\% across the five observations, but the polarization angle remained oriented in the North-South direction throughout. Based on observations with the Australia Telescope Compact Array (ATCA), we find that the intrinsic 7.25 GHz radio polarization aligns with the X-ray polarization. Assuming the radio polarization aligns with the jet direction (which can be tested in the future with higher spatial resolution images of the jet), our results imply that the X-ray corona is extended in the disk plane, rather than along the jet axis, for the entire hard intermediate state. This in turn implies that the long ($\gtrsim$10 ms) soft lags that we measure with the Neutron star Interior Composition ExploreR (NICER) are dominated by processes other than pure light-crossing delays. Moreover, we find that the evolution of the soft lag amplitude with spectral state does not follow the trend seen for other sources, implying that Swift J1727.8$-$1613 is a member of a hitherto under-sampled sub-population. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.05497v3-abstract-full').style.display = 'none'; document.getElementById('2311.05497v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in ApJ. 21 pages, 8 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.04632">arXiv:2311.04632</a> <span> [<a href="https://arxiv.org/pdf/2311.04632">pdf</a>, <a href="https://arxiv.org/format/2311.04632">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/ad1832">10.3847/2041-8213/ad1832 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-Ray Polarized View on the Accretion Geometry in the X-Ray Binary Circinus X-1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Rankin%2C+J">John Rankin</a>, <a href="/search/astro-ph?searchtype=author&query=La+Monaca%2C+F">Fabio La Monaca</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Bobrikova%2C+A">Anna Bobrikova</a>, <a href="/search/astro-ph?searchtype=author&query=Kravtsov%2C+V">Vadim Kravtsov</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Pilia%2C+M">Maura Pilia</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Fender%2C+R">Rob Fender</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Marinucci%2C+A">Andrea Marinucci</a>, <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">Herman L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Papitto%2C+A">Alessandro Papitto</a>, <a href="/search/astro-ph?searchtype=author&query=Tennant%2C+A+F">Allyn F. Tennant</a>, <a href="/search/astro-ph?searchtype=author&query=Tsygankov%2C+S+S">Sergey S. Tsygankov</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+K">Kinwah Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Zane%2C+S">Silvia Zane</a>, <a href="/search/astro-ph?searchtype=author&query=Ambrosino%2C+F">Filippo Ambrosino</a>, <a href="/search/astro-ph?searchtype=author&query=Farinelli%2C+R">Ruben Farinelli</a>, <a href="/search/astro-ph?searchtype=author&query=Gnarini%2C+A">Andrea Gnarini</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio A. Antonelli</a> , et al. (79 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.04632v2-abstract-short" style="display: inline;"> Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric $\sim$16.6 days orbit. There are also strong variations in the spectral state, and historically it has shown both atoll and Z state properties. We observed the source with the Imaging X-ray Polarimetry Explorer during two orbital segments, 6 days apart, for a total of 263~ks. We find an X-ray pol… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.04632v2-abstract-full').style.display = 'inline'; document.getElementById('2311.04632v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.04632v2-abstract-full" style="display: none;"> Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric $\sim$16.6 days orbit. There are also strong variations in the spectral state, and historically it has shown both atoll and Z state properties. We observed the source with the Imaging X-ray Polarimetry Explorer during two orbital segments, 6 days apart, for a total of 263~ks. We find an X-ray polarization degree in these segments of $1.6\%\pm0.3\%$ and $1.4\%\pm0.3\%$ at polarization angles of $37^\circ\pm5^\circ$ and $-12^\circ\pm7^\circ$, respectively. Thus we observed a rotation of the polarization angle by $49^\circ\pm8^\circ$ along the orbit. Because variations of accretion flow, and then of the hardness ratio, are expected during the orbit, we also studied the polarization binned in hardness ratio, and found the polarization angle differing by $67^\circ\pm11^\circ$ between the lowest and highest values of the hardness ratio. We discuss possible interpretations of this result that could indicate a possible misalignment between the symmetry axes of the accretion disk and the Comptonizing region caused by the misalignment of the neutron star's angular momentum with respect to the orbital one. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.04632v2-abstract-full').style.display = 'none'; document.getElementById('2311.04632v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 8 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 6 figures, Accepted for publication in ApJL</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJL 961 L8 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.03667">arXiv:2311.03667</a> <span> [<a href="https://arxiv.org/pdf/2311.03667">pdf</a>, <a href="https://arxiv.org/format/2311.03667">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> X-ray Polarization Reveals the Precessions of the Neutron Star in Hercules X-1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Doroshenko%2C+V">Victor Doroshenko</a>, <a href="/search/astro-ph?searchtype=author&query=Gonz%C3%A1lez-Caniulef%2C+D">Denis Gonz谩lez-Caniulef</a>, <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Mushtukov%2C+A">Alexander Mushtukov</a>, <a href="/search/astro-ph?searchtype=author&query=Tsygankov%2C+S+S">Sergey S. Tsygankov</a>, <a href="/search/astro-ph?searchtype=author&query=Kirmizibayrak%2C+D">Demet Kirmizibayrak</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Pavlov%2C+G+G">George G. Pavlov</a>, <a href="/search/astro-ph?searchtype=author&query=Forsblom%2C+S+V">Sofia V. Forsblom</a>, <a href="/search/astro-ph?searchtype=author&query=Malacaria%2C+C">Christian Malacaria</a>, <a href="/search/astro-ph?searchtype=author&query=Suleimanov%2C+V+F">Valery F. Suleimanov</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio Angelo Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W+H">Wayne H. Baumgartner</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+R">Ronaldo Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bongiorno%2C+S+D">Stephen D. Bongiorno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonino%2C+R">Raffaella Bonino</a>, <a href="/search/astro-ph?searchtype=author&query=Brez%2C+A">Alessandro Brez</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccol貌 Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Castellano%2C+S">Simone Castellano</a> , et al. (78 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.03667v1-abstract-short" style="display: inline;"> In an accreting X-ray pulsar, a neutron star accretes matter from a stellar companion through an accretion disk. The high magnetic field of the rotating neutron star disrupts the inner edge of the disc, funneling the gas to flow onto the magnetic poles on its surface. Hercules X-1 is in many ways the prototypical X-ray pulsar; it shows persistent X-ray emission and it resides with its companion HZ… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.03667v1-abstract-full').style.display = 'inline'; document.getElementById('2311.03667v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.03667v1-abstract-full" style="display: none;"> In an accreting X-ray pulsar, a neutron star accretes matter from a stellar companion through an accretion disk. The high magnetic field of the rotating neutron star disrupts the inner edge of the disc, funneling the gas to flow onto the magnetic poles on its surface. Hercules X-1 is in many ways the prototypical X-ray pulsar; it shows persistent X-ray emission and it resides with its companion HZ Her, a two-solar-mass star, at about 7~kpc from Earth. Its emission varies on three distinct timescales: the neutron star rotates every 1.2~seconds, it is eclipsed by its companion each 1.7~days, and the system exhibits a superorbital period of 35~days which has remained remarkably stable since its discovery. Several lines of evidence point to the source of this variation as the precession of the accretion disc, the precession of the neutron star or both. Despite the many hints over the past fifty years, the precession of the neutron star itself has yet not been confirmed or refuted. We here present X-ray polarization measurements with the Imaging X-ray Polarimetry Explorer (IXPE) which probe the spin geometry of the neutron star. These observations provide direct evidence that the 35-day-period is set by the free precession of the neutron star crust, which has the important implication that its crust is somewhat asymmetric fractionally by a few parts per ten million. Furthermore, we find indications that the basic spin geometry of the neutron star is altered by torques on timescale of a few hundred days. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.03667v1-abstract-full').style.display = 'none'; document.getElementById('2311.03667v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">37 pages</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.03637">arXiv:2311.03637</a> <span> [<a href="https://arxiv.org/pdf/2311.03637">pdf</a>, <a href="https://arxiv.org/format/2311.03637">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> The detection of polarized x-ray emission from the magnetar 1E 2259+586 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Taverna%2C+R">Roberto Taverna</a>, <a href="/search/astro-ph?searchtype=author&query=Turolla%2C+R">Roberto Turolla</a>, <a href="/search/astro-ph?searchtype=author&query=Israel%2C+G+L">Gian Luca Israel</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+M">Mason Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Kirmizibayrak%2C+D">Demet Kirmizibayrak</a>, <a href="/search/astro-ph?searchtype=author&query=Gonz%C3%A1lez-Caniulef%2C+D">Denis Gonz谩lez-Caniulef</a>, <a href="/search/astro-ph?searchtype=author&query=Caiazzo%2C+I">Ilaria Caiazzo</a>, <a href="/search/astro-ph?searchtype=author&query=Zane%2C+S">Silvia Zane</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio Angelo Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W+H">Wayne H. Baumgartner</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+R">Ronaldo Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bongiorno%2C+S+D">Stephen D. Bongiorno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonino%2C+R">Raffaella Bonino</a>, <a href="/search/astro-ph?searchtype=author&query=Brez%2C+A">Alessandro Brez</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccol貌 Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Castellano%2C+S">Simone Castellano</a>, <a href="/search/astro-ph?searchtype=author&query=Cavazzuti%2C+E">Elisabetta Cavazzuti</a> , et al. (76 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.03637v1-abstract-short" style="display: inline;"> We report on IXPE, NICER and XMM-Newton observations of the magnetar 1E 2259+586. We find that the source is significantly polarized at about or above 20% for all phases except for the secondary peak where it is more weakly polarized. The polarization degree is strongest during the primary minimum which is also the phase where an absorption feature has been identified previously (Pizzocaro et al.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.03637v1-abstract-full').style.display = 'inline'; document.getElementById('2311.03637v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.03637v1-abstract-full" style="display: none;"> We report on IXPE, NICER and XMM-Newton observations of the magnetar 1E 2259+586. We find that the source is significantly polarized at about or above 20% for all phases except for the secondary peak where it is more weakly polarized. The polarization degree is strongest during the primary minimum which is also the phase where an absorption feature has been identified previously (Pizzocaro et al. 2019). The polarization angle of the photons are consistent with a rotating vector model with a mode switch between the primary minimum and the rest of the rotation of the neutron star. We propose a scenario in which the emission at the source is weakly polarized (as in a condensed surface) and, as the radiation passes through a plasma arch, resonant cyclotron scattering off of protons produces the observed polarized radiation. This confirms the magnetar nature of the source with a surface field greater than about 10<sup>15</sup> G <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.03637v1-abstract-full').style.display = 'none'; document.getElementById('2311.03637v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 pages, 13 figures, 5 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2310.11510">arXiv:2310.11510</a> <span> [<a href="https://arxiv.org/pdf/2310.11510">pdf</a>, <a href="https://arxiv.org/format/2310.11510">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Observations of Low and Intermediate Spectral Peak Blazars with the Imaging X-ray Polarimetry Explorer </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">Herman L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Lalla%2C+N">Niccolo Di Lalla</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Middei%2C+R">Riccardo Middei</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Omodei%2C+N">Nicola Omodei</a>, <a href="/search/astro-ph?searchtype=author&query=Peirson%2C+A+L">Abel L. Peirson</a>, <a href="/search/astro-ph?searchtype=author&query=Perri%2C+M">Matteo Perri</a>, <a href="/search/astro-ph?searchtype=author&query=Puccetti%2C+S">Simonetta Puccetti</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Ivan Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Bonnoli%2C+G">Giacomo Bonnoli</a>, <a href="/search/astro-ph?searchtype=author&query=Berdyugin%2C+A+V">Andrei V. Berdyugin</a>, <a href="/search/astro-ph?searchtype=author&query=Cavazzuti%2C+E">Elisabetta Cavazzuti</a>, <a href="/search/astro-ph?searchtype=author&query=Cavero%2C+N+R">Nicole Rodriguez Cavero</a>, <a href="/search/astro-ph?searchtype=author&query=Donnarumma%2C+I">Immacolata Donnarumma</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Gesu%2C+L">Laura Di Gesu</a>, <a href="/search/astro-ph?searchtype=author&query=Jormanainen%2C+J">Jenni Jormanainen</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">Henric Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Lindfors%2C+E">Elina Lindfors</a>, <a href="/search/astro-ph?searchtype=author&query=Marin%2C+F">Frederic Marin</a>, <a href="/search/astro-ph?searchtype=author&query=Massaro%2C+F">Francesco Massaro</a>, <a href="/search/astro-ph?searchtype=author&query=Pacciani%2C+L">Luigi Pacciani</a> , et al. (133 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2310.11510v2-abstract-short" style="display: inline;"> We present X-ray polarimetry observations from the Imaging X-ray Polarimetry Explorer (IXPE) of three low spectral peak and one intermediate spectral peak blazars, namely 3C 273, 3C 279, 3C 454.3, and S5 0716+714. For none of these objects was IXPE able to detect X-ray polarization at the 3$蟽$ level. However, we placed upper limits on the polarization degree at $\sim$10-30\%. The undetected polari… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.11510v2-abstract-full').style.display = 'inline'; document.getElementById('2310.11510v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.11510v2-abstract-full" style="display: none;"> We present X-ray polarimetry observations from the Imaging X-ray Polarimetry Explorer (IXPE) of three low spectral peak and one intermediate spectral peak blazars, namely 3C 273, 3C 279, 3C 454.3, and S5 0716+714. For none of these objects was IXPE able to detect X-ray polarization at the 3$蟽$ level. However, we placed upper limits on the polarization degree at $\sim$10-30\%. The undetected polarizations favor models where the X-ray band is dominated by unpolarized photons upscattered by relativistic electrons in the jets of blazars, although hadronic models are not completely eliminated. We discuss the X-ray polarization upper limits in the context of our contemporaneous multiwavelength polarization campaigns. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.11510v2-abstract-full').style.display = 'none'; document.getElementById('2310.11510v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 10 figures, 6 tables; submitted to the Astrophysical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2310.11125">arXiv:2310.11125</a> <span> [<a href="https://arxiv.org/pdf/2310.11125">pdf</a>, <a href="https://arxiv.org/format/2310.11125">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> IXPE observation confirms a high spin in the accreting black hole 4U 1957+115 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Marra%2C+L">L. Marra</a>, <a href="/search/astro-ph?searchtype=author&query=Brigitte%2C+M">M. Brigitte</a>, <a href="/search/astro-ph?searchtype=author&query=Cavero%2C+N+R">N. Rodriguez Cavero</a>, <a href="/search/astro-ph?searchtype=author&query=Chun%2C+S">S. Chun</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+J+F">J. F. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Dov%C4%8Diak%2C+M">M. Dov膷iak</a>, <a href="/search/astro-ph?searchtype=author&query=Nowak%2C+M">M. Nowak</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">S. Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">F. Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Ingram%2C+A">A. Ingram</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">G. Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">F. Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Podgorn%C3%BD%2C+J">J. Podgorn媒</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">J. Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">J. Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Taverna%2C+R">R. Taverna</a>, <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">F. Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">A. Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=De+Rosa%2C+A">A. De Rosa</a>, <a href="/search/astro-ph?searchtype=author&query=Garcia%2C+J+A">J. A. Garcia</a>, <a href="/search/astro-ph?searchtype=author&query=Lutovinov%2C+A+A">A. A. Lutovinov</a>, <a href="/search/astro-ph?searchtype=author&query=Mereminskiy%2C+I+A">I. A. Mereminskiy</a>, <a href="/search/astro-ph?searchtype=author&query=Farinelli%2C+R">R. Farinelli</a>, <a href="/search/astro-ph?searchtype=author&query=Gunji%2C+S">S. Gunji</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">P. Kaaret</a> , et al. (91 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2310.11125v2-abstract-short" style="display: inline;"> We present the results of the first X-ray polarimetric observation of the low-mass X-ray binary 4U 1957+115, performed with the Imaging X-ray Polarimetry Explorer in May 2023. The binary system has been in a high-soft spectral state since its discovery and is thought to host a black hole. The $\sim$571 ks observation reveals a linear polarisation degree of $1.9\% \pm 0.6\%$ and a polarisation angl… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.11125v2-abstract-full').style.display = 'inline'; document.getElementById('2310.11125v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.11125v2-abstract-full" style="display: none;"> We present the results of the first X-ray polarimetric observation of the low-mass X-ray binary 4U 1957+115, performed with the Imaging X-ray Polarimetry Explorer in May 2023. The binary system has been in a high-soft spectral state since its discovery and is thought to host a black hole. The $\sim$571 ks observation reveals a linear polarisation degree of $1.9\% \pm 0.6\%$ and a polarisation angle of $-41^\circ.8 \pm 7^\circ.9$ in the 2-8 keV energy range. Spectral modelling is consistent with the dominant contribution coming from the standard accretion disc, while polarimetric data suggest a significant role of returning radiation: photons that are bent by strong gravity effects and forced to return to the disc surface, where they can be reflected before eventually reaching the observer. In this setting, we find that models with a black hole spin lower than 0.96 and an inclination lower than $50^\circ$ are disfavoured. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.11125v2-abstract-full').style.display = 'none'; document.getElementById('2310.11125v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 10 figures, 2 tables, accepted for publication in A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2310.06788">arXiv:2310.06788</a> <span> [<a href="https://arxiv.org/pdf/2310.06788">pdf</a>, <a href="https://arxiv.org/ps/2310.06788">ps</a>, <a href="https://arxiv.org/format/2310.06788">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Discovery of a variable energy-dependent X-ray polarization in the accreting neutron star GX 5-1 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fabiani%2C+S">Sergio Fabiani</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Iaria%2C+R">Rosario Iaria</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Gnarini%2C+A">Andrea Gnarini</a>, <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">Francesco Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Farinelli%2C+R">Ruben Farinelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bobrikova%2C+A">Anna Bobrikova</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+J+F">James F. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">Jiri Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Anitra%2C+A">Alessio Anitra</a>, <a href="/search/astro-ph?searchtype=author&query=Baglio%2C+M+C">Maria C. Baglio</a>, <a href="/search/astro-ph?searchtype=author&query=Carotenuto%2C+F">Francesco Carotenuto</a>, <a href="/search/astro-ph?searchtype=author&query=Del+Santo%2C+M">Melania Del Santo</a>, <a href="/search/astro-ph?searchtype=author&query=Ferrigno%2C+C">Carlo Ferrigno</a>, <a href="/search/astro-ph?searchtype=author&query=Lewis%2C+F">Fraser Lewis</a>, <a href="/search/astro-ph?searchtype=author&query=Russell%2C+D+M">David M. Russell</a>, <a href="/search/astro-ph?searchtype=author&query=Russell%2C+T+D">Thomas D. Russell</a>, <a href="/search/astro-ph?searchtype=author&query=Eijnden%2C+J+v+d">Jakob van den Eijnden</a>, <a href="/search/astro-ph?searchtype=author&query=Cocchi%2C+M">Massimo Cocchi</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=La+Monaca%2C+F">Fabio La Monaca</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+K">Kuan Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Rankin%2C+J">John Rankin</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a> , et al. (94 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2310.06788v2-abstract-short" style="display: inline;"> We report on the coordinated observations of the neutron star low-mass X-ray binary (NS-LMXB) \gx in X-rays (IXPE, NICER, Nustar and INTEGRAL), optical (REM and LCO), near-infrared (REM), mid-infrared (VLT VISIR), and radio (ATCA). This Z-source was observed by \IXPE twice in March-April 2023 (Obs. 1 and 2). In the radio band, the source was detected, but only upper-limits to the linear polarizati… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.06788v2-abstract-full').style.display = 'inline'; document.getElementById('2310.06788v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.06788v2-abstract-full" style="display: none;"> We report on the coordinated observations of the neutron star low-mass X-ray binary (NS-LMXB) \gx in X-rays (IXPE, NICER, Nustar and INTEGRAL), optical (REM and LCO), near-infrared (REM), mid-infrared (VLT VISIR), and radio (ATCA). This Z-source was observed by \IXPE twice in March-April 2023 (Obs. 1 and 2). In the radio band, the source was detected, but only upper-limits to the linear polarization were obtained at a $3蟽$ level of $6.1\%$ at 5.5 GHz and $5.9\%$ at 9 GHz in Obs.~1 and $12.5\%$ at 5.5~GHz and $20\%$ at 9~GHz in Obs.~2. The mid-IR, near-IR and optical observations suggest the presence of a compact jet which peaks in the mid- or far-IR. The X-ray polarization degree was found to be $3.7\% \pm 0.4 \%$ (at $90\%$ confidence level) during Obs.~1 when the source was in the horizontal branch of the Z-track and $1.8\% \pm 0.4 \%$ during Obs.~2 when the source was in the normal-flaring branch. These results confirm the variation of polarization degree as a function of the position of the source in the color-color diagram as for previously observed Z-track sources (Cyg~X-2 and XTE~1701$-$462). Evidence for a variation of the polarization angle $\sim 20^\circ$ with energy is found in both observations, likely related to the different, non-orthogonal polarization angles of the disk and Comptonization components which peak at different energies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.06788v2-abstract-full').style.display = 'none'; document.getElementById('2310.06788v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Submitted to Astronomy and Astrophysics on 06 July 2023. Accepted on 21 November 2023</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2310.06097">arXiv:2310.06097</a> <span> [<a href="https://arxiv.org/pdf/2310.06097">pdf</a>, <a href="https://arxiv.org/format/2310.06097">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202347408">10.1051/0004-6361/202347408 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Magnetic Field Properties inside the Jet of Mrk 421: Multiwavelength Polarimetry Including the Imaging X-ray Polarimetry Explorer </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Gesu%2C+L">Laura Di Gesu</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Midde%2C+R">Riccardo Midde</a>, <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">Herman L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Pacciani%2C+L">Luigi Pacciani</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Tavecchio%2C+F">Fabrizio Tavecchio</a>, <a href="/search/astro-ph?searchtype=author&query=Cibrario%2C+N">Nicol貌 Cibrario</a>, <a href="/search/astro-ph?searchtype=author&query=Tugliani%2C+S">Stefano Tugliani</a>, <a href="/search/astro-ph?searchtype=author&query=Bonino%2C+R">Raffaella Bonino</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Puccetti%2C+S">Simonetta Puccetti</a>, <a href="/search/astro-ph?searchtype=author&query=Tombesi%2C+F">Francesco Tombesi</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Donnarumma%2C+I">Immacolata Donnarumma</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno%2C+T">Tsunefumi Mizuno</a>, <a href="/search/astro-ph?searchtype=author&query=Fukazawa%2C+Y">Yasushi Fukazawa</a>, <a href="/search/astro-ph?searchtype=author&query=Kawabata%2C+K+S">Koji S. Kawabata</a>, <a href="/search/astro-ph?searchtype=author&query=Nakaoka%2C+T">Tatsuya Nakaoka</a>, <a href="/search/astro-ph?searchtype=author&query=Uemura%2C+M">Makoto Uemura</a>, <a href="/search/astro-ph?searchtype=author&query=Imazawa%2C+R">Ryo Imazawa</a> , et al. (111 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2310.06097v1-abstract-short" style="display: inline;"> We conducted a polarimetry campaign from radio to X-ray wavelengths of the high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging X-ray Polarimetry Explorer (IXPE) measurements on 2022 December 6-8. We detected X-ray polarization of Mrk 421 with a degree of $螤_{\rm X}$=14$\pm$1$\%$ and an electric-vector position angle $蠄_{\rm X}$=107$\pm$3$^{\circ}$ in the 2-8 keV band. From the time varia… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.06097v1-abstract-full').style.display = 'inline'; document.getElementById('2310.06097v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.06097v1-abstract-full" style="display: none;"> We conducted a polarimetry campaign from radio to X-ray wavelengths of the high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging X-ray Polarimetry Explorer (IXPE) measurements on 2022 December 6-8. We detected X-ray polarization of Mrk 421 with a degree of $螤_{\rm X}$=14$\pm$1$\%$ and an electric-vector position angle $蠄_{\rm X}$=107$\pm$3$^{\circ}$ in the 2-8 keV band. From the time variability analysis, we find a significant episodic variation in $蠄_{\rm X}$. During 7 months from the first IXPE pointing of Mrk 421 in 2022 May, $蠄_{\rm X}$ varied across the range of 0$^{\circ}$ to 180$^{\circ}$, while $螤_{\rm X}$ maintained similar values within $\sim$10-15$\%$. Furthermore, a swing in $蠄_{\rm X}$ in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that the X-ray polarization degree was generally $\sim$2-3 times greater than that at longer wavelengths, while the polarization angle fluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that rotation of $蠄$ occurred in the opposite direction with respect to the rotation of $蠄_{\rm X}$ over longer timescales at similar epochs. The polarization behavior observed across multiple wavelengths is consistent with previous IXPE findings for HSP blazars. This result favors the energy-stratified shock model developed to explain variable emission in relativistic jets. The accompanying spectral variation during the $蠄_{\rm X}$ rotation can be explained by a fluctuation in the physical conditions, e.g., in the energy distribution of relativistic electrons. The opposite rotation direction of $蠄$ between the X-ray and longer-wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.06097v1-abstract-full').style.display = 'none'; document.getElementById('2310.06097v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">17 pages, 13 figures, 4 tables; Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 681, A12 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2310.04512">arXiv:2310.04512</a> <span> [<a href="https://arxiv.org/pdf/2310.04512">pdf</a>, <a href="https://arxiv.org/format/2310.04512">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> A multi-wavelength investigation of PSR J2229+6114 and its pulsar wind nebula in the radio, X-ray, and gamma-ray bands </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Pope%2C+I">I. Pope</a>, <a href="/search/astro-ph?searchtype=author&query=Mori%2C+K">K. Mori</a>, <a href="/search/astro-ph?searchtype=author&query=Abdelmaguid%2C+M">M. Abdelmaguid</a>, <a href="/search/astro-ph?searchtype=author&query=Gelfand%2C+J+D">J. D. Gelfand</a>, <a href="/search/astro-ph?searchtype=author&query=Reynolds%2C+S+P">S. P. Reynolds</a>, <a href="/search/astro-ph?searchtype=author&query=Safi-Harb%2C+S">S. Safi-Harb</a>, <a href="/search/astro-ph?searchtype=author&query=Hailey%2C+C+J">C. J. Hailey</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+H">H. An</a>, <a href="/search/astro-ph?searchtype=author&query=Collaboration%2C+V">VERITAS Collaboration</a>, <a href="/search/astro-ph?searchtype=author&query=%3A"> :</a>, <a href="/search/astro-ph?searchtype=author&query=Bangale%2C+P">P. Bangale</a>, <a href="/search/astro-ph?searchtype=author&query=Batista%2C+P">P. Batista</a>, <a href="/search/astro-ph?searchtype=author&query=Benbow%2C+W">W. Benbow</a>, <a href="/search/astro-ph?searchtype=author&query=Buckley%2C+J+H">J. H. Buckley</a>, <a href="/search/astro-ph?searchtype=author&query=Capasso%2C+M">M. Capasso</a>, <a href="/search/astro-ph?searchtype=author&query=Christiansen%2C+J+L">J. L. Christiansen</a>, <a href="/search/astro-ph?searchtype=author&query=Chromey%2C+A+J">A. J. Chromey</a>, <a href="/search/astro-ph?searchtype=author&query=Falcone%2C+A">A. Falcone</a>, <a href="/search/astro-ph?searchtype=author&query=Feng%2C+Q">Q. Feng</a>, <a href="/search/astro-ph?searchtype=author&query=Finley%2C+J+P">J. P. Finley</a>, <a href="/search/astro-ph?searchtype=author&query=Foote%2C+G+M">G. M Foote</a>, <a href="/search/astro-ph?searchtype=author&query=Gallagher%2C+G">G. Gallagher</a>, <a href="/search/astro-ph?searchtype=author&query=Hanlon%2C+W+F">W. F Hanlon</a>, <a href="/search/astro-ph?searchtype=author&query=Hanna%2C+D">D. Hanna</a>, <a href="/search/astro-ph?searchtype=author&query=Hervet%2C+O">O. Hervet</a> , et al. (35 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2310.04512v1-abstract-short" style="display: inline;"> G106.3$+$2.7, commonly considered a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct ("head" & "tail") regions in the radio band. A discovery of very-high-energy (VHE) gamma-ray emission ($E_纬> 100$ GeV) followed by the recent detection of ultra-high-energy (UHE) gamma-ray emission ($E_纬> 100$ TeV) from the tail region suggests tha… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.04512v1-abstract-full').style.display = 'inline'; document.getElementById('2310.04512v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.04512v1-abstract-full" style="display: none;"> G106.3$+$2.7, commonly considered a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct ("head" & "tail") regions in the radio band. A discovery of very-high-energy (VHE) gamma-ray emission ($E_纬> 100$ GeV) followed by the recent detection of ultra-high-energy (UHE) gamma-ray emission ($E_纬> 100$ TeV) from the tail region suggests that G106.3$+$2.7 is a PeVatron candidate. We present a comprehensive multi-wavelength study of the Boomerang PWN (100" around PSR J2229+6114) using archival radio and Chandra data obtained from two decades ago, a new NuSTAR X-ray observation from 2020, and upper limits on gamma-ray fluxes obtained by Fermi and VERITAS observatories. The NuSTAR observation allowed us to detect a 51.67 ms spin period from the pulsar PSR J2229+6114 and the PWN emission characterized by a power-law model with $螕= 1.52\pm0.06$ up to 20 keV. Contrary to the previous radio study by Kothes et al. 2006, we prefer a much lower PWN B-field ($B\sim3$ $渭$G) and larger distance ($d \sim 8$ kpc) based on (1) the non-varying X-ray flux over the last two decades, (2) the energy-dependent X-ray PWN size resulting from synchrotron burn-off and (3) the multi-wavelength spectral energy distribution (SED) data. Our SED model suggests that the PWN is currently re-expanding after being compressed by the SNR reverse shock $\sim 1000$ years ago. In this case, the head region should be formed by GeV--TeV electrons injected earlier by the pulsar propagating into the low density environment. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.04512v1-abstract-full').style.display = 'none'; document.getElementById('2310.04512v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2310.01635">arXiv:2310.01635</a> <span> [<a href="https://arxiv.org/pdf/2310.01635">pdf</a>, <a href="https://arxiv.org/format/2310.01635">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> X-ray Polarization of the BL Lac Type Blazar 1ES 0229+200 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Middei%2C+R">Riccardo Middei</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Tavecchio%2C+F">Fabrizio Tavecchio</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Kouch%2C+P+M">Pouya M. Kouch</a>, <a href="/search/astro-ph?searchtype=author&query=Lindfors%2C+E">Elina Lindfors</a>, <a href="/search/astro-ph?searchtype=author&query=Nilsson%2C+K">Kari Nilsson</a>, <a href="/search/astro-ph?searchtype=author&query=Myserlis%2C+I">Ioannis Myserlis</a>, <a href="/search/astro-ph?searchtype=author&query=Gurwell%2C+M">Mark Gurwell</a>, <a href="/search/astro-ph?searchtype=author&query=Rao%2C+R">Ramprasad Rao</a>, <a href="/search/astro-ph?searchtype=author&query=Aceituno%2C+F+J">Francisco Jose Aceituno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonnoli%2C+G">Giacomo Bonnoli</a>, <a href="/search/astro-ph?searchtype=author&query=Casanova%2C+V">Victor Casanova</a>, <a href="/search/astro-ph?searchtype=author&query=Agiz-Gonzalez%2C+B">Beatriz Agiz-Gonzalez</a>, <a href="/search/astro-ph?searchtype=author&query=Escudero%2C+J">Juan Escudero</a>, <a href="/search/astro-ph?searchtype=author&query=Santos%2C+J+O">Jorge Otero Santos</a>, <a href="/search/astro-ph?searchtype=author&query=Sota%2C+A">Alfredo Sota</a>, <a href="/search/astro-ph?searchtype=author&query=Angelakis%2C+E">Emmanouil Angelakis</a>, <a href="/search/astro-ph?searchtype=author&query=Kraus%2C+A">Alexander Kraus</a>, <a href="/search/astro-ph?searchtype=author&query=Keating%2C+G+K">Garrett K. Keating</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio A. Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a> , et al. (88 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2310.01635v1-abstract-short" style="display: inline;"> We present polarization measurements in the $2-8 \thinspace \mathrm{keV}$ band from blazar 1ES 0229+200, the first extreme high synchrotron peaked source to be observed by the Imaging X-ray Polarimetry Explorer (IXPE). Combining two exposures separated by about two weeks, we find the degree of polarization to be $螤_{X} = 17.9 \pm 2.8 \%$ at an electric-vector position angle… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.01635v1-abstract-full').style.display = 'inline'; document.getElementById('2310.01635v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2310.01635v1-abstract-full" style="display: none;"> We present polarization measurements in the $2-8 \thinspace \mathrm{keV}$ band from blazar 1ES 0229+200, the first extreme high synchrotron peaked source to be observed by the Imaging X-ray Polarimetry Explorer (IXPE). Combining two exposures separated by about two weeks, we find the degree of polarization to be $螤_{X} = 17.9 \pm 2.8 \%$ at an electric-vector position angle $蠄_X = 25.0 \pm 4.6^{\circ}$ using a spectropolarimetric fit from joint IXPE and XMM-Newton observations. There is no evidence for the polarization degree or angle varying significantly with energy or time on both short time scales (hours) or longer time scales (days). The contemporaneous polarization degree at optical wavelengths was $>$7$\times$ lower, making 1ES 0229+200 the most strongly chromatic blazar yet observed. This high X-ray polarization compared to the optical provides further support that X-ray emission in high-peaked blazars originates in shock-accelerated, energy-stratified electron populations, but is in tension with many recent modeling efforts attempting to reproduce the spectral energy distribution of 1ES 0229+200 which attribute the extremely high energy synchrotron and Compton peaks to Fermi acceleration in the vicinity of strongly turbulent magnetic fields. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2310.01635v1-abstract-full').style.display = 'none'; document.getElementById('2310.01635v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">17 Pages, 6 Figures, Resubmitted to ApJ after addressing referee comments</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.16067">arXiv:2309.16067</a> <span> [<a href="https://arxiv.org/pdf/2309.16067">pdf</a>, <a href="https://arxiv.org/format/2309.16067">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> The Polarized Cosmic Hand: IXPE Observations of PSR B1509-58/MSH 15-52 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Romani%2C+R+W">Roger W. Romani</a>, <a href="/search/astro-ph?searchtype=author&query=Wong%2C+J">Josephine Wong</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Lalla%2C+N">Niccolo Di Lalla</a>, <a href="/search/astro-ph?searchtype=author&query=Omodei%2C+N">Nicola Omodei</a>, <a href="/search/astro-ph?searchtype=author&query=Xie%2C+F">Fei Xie</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+C+-">C. -Y. Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Ferrazzoli%2C+R">Riccardo Ferrazzoli</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccolo Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Pilia%2C+M">Maura Pilia</a>, <a href="/search/astro-ph?searchtype=author&query=Slane%2C+P">Patrick Slane</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Johnston%2C+S">Simon Johnston</a>, <a href="/search/astro-ph?searchtype=author&query=Burgay%2C+M">Marta Burgay</a>, <a href="/search/astro-ph?searchtype=author&query=Wei%2C+D">Deng Wei</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+Y">Yi-Jung Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+S">Shumeng Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio A. Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W+H">Wayne H. Baumgartner</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+R">Ronaldo Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bongiorno%2C+S+D">Stephen D. Bongiorno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonino%2C+R">Raffaella Bonino</a> , et al. (78 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.16067v1-abstract-short" style="display: inline;"> We describe IXPE polarization observations of the Pulsar Wind Nebula (PWN) MSH15-52, the `Cosmic Hand'. We find X-ray polarization across the PWN, with B field vectors generally aligned with filamentary X-ray structures. High significance polarization is seen in arcs surrounding the pulsar and toward the end of the `jet', with polarization degree PD>70%, thus approaching the maximum allowed synchr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.16067v1-abstract-full').style.display = 'inline'; document.getElementById('2309.16067v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.16067v1-abstract-full" style="display: none;"> We describe IXPE polarization observations of the Pulsar Wind Nebula (PWN) MSH15-52, the `Cosmic Hand'. We find X-ray polarization across the PWN, with B field vectors generally aligned with filamentary X-ray structures. High significance polarization is seen in arcs surrounding the pulsar and toward the end of the `jet', with polarization degree PD>70%, thus approaching the maximum allowed synchrotron value. In contrast, the base of the jet has lower polarization, indicating a complex magnetic field at significant angle to the jet axis. We also detect significant polarization from PSR B1509-58 itself. Although only the central pulse-phase bin of the pulse has high individual significance, flanking bins provide lower significance detections and, in conjunction with the X-ray image and radio polarization, can be used to constrain rotating vector model solutions for the pulsar geometry. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.16067v1-abstract-full').style.display = 'none'; document.getElementById('2309.16067v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">To appear in the Astrophysical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.15928">arXiv:2309.15928</a> <span> [<a href="https://arxiv.org/pdf/2309.15928">pdf</a>, <a href="https://arxiv.org/format/2309.15928">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> Discovery of X-ray Polarization from the Black Hole Transient Swift J1727.8-1613 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Dovciak%2C+M">Michal Dovciak</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Ratheesh%2C+A">Ajay Ratheesh</a>, <a href="/search/astro-ph?searchtype=author&query=Capitanio%2C+F">Fiamma Capitanio</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Tennant%2C+A+F">Allyn F. Tennant</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Ingram%2C+A">Adam Ingram</a>, <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">Jiri Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">Henric Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+J+F">James F. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Garcia%2C+J+A">Javier A. Garcia</a>, <a href="/search/astro-ph?searchtype=author&query=Kravtsov%2C+V">Vadim Kravtsov</a>, <a href="/search/astro-ph?searchtype=author&query=Nitindala%2C+A+P">Anagha P. Nitindala</a>, <a href="/search/astro-ph?searchtype=author&query=Ewing%2C+M">Melissa Ewing</a>, <a href="/search/astro-ph?searchtype=author&query=Mastroserio%2C+G">Guglielmo Mastroserio</a>, <a href="/search/astro-ph?searchtype=author&query=Marinucci%2C+A">Andrea Marinucci</a>, <a href="/search/astro-ph?searchtype=author&query=Ursini%2C+F">Francesco Ursini</a>, <a href="/search/astro-ph?searchtype=author&query=Tombesi%2C+F">Francesco Tombesi</a> , et al. (91 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.15928v1-abstract-short" style="display: inline;"> We report the first detection of the X-ray polarization of the bright transient Swift J1727.8-1613 with the Imaging X-ray Polarimetry Explorer. The observation was performed at the beginning of the 2023 discovery outburst, when the source resided in the bright hard state. We find a time- and energy-averaged polarization degree of 4.1%+/-0.2% and a polarization angle of 2.2+/-1.3 degrees (errors at… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.15928v1-abstract-full').style.display = 'inline'; document.getElementById('2309.15928v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.15928v1-abstract-full" style="display: none;"> We report the first detection of the X-ray polarization of the bright transient Swift J1727.8-1613 with the Imaging X-ray Polarimetry Explorer. The observation was performed at the beginning of the 2023 discovery outburst, when the source resided in the bright hard state. We find a time- and energy-averaged polarization degree of 4.1%+/-0.2% and a polarization angle of 2.2+/-1.3 degrees (errors at 68% confidence level; this translates to about 20-sigma significance of the polarization detection). This finding suggests that the hot corona emitting the bulk of the detected X-rays is elongated, rather than spherical. The X-ray polarization angle is consistent with that found in sub-mm wavelengths. Since the sub-mm polarization was found to be aligned with the jet direction in other X-ray binaries, this indicates that the corona is elongated orthogonal to the jet. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.15928v1-abstract-full').style.display = 'none'; document.getElementById('2309.15928v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 3 figures, submitted</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.10813">arXiv:2309.10813</a> <span> [<a href="https://arxiv.org/pdf/2309.10813">pdf</a>, <a href="https://arxiv.org/format/2309.10813">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ad0842">10.3847/1538-4357/ad0842 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> First X-ray polarization measurement confirms the low black-hole spin in LMC X-3 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Svoboda%2C+J">Ji艡铆 Svoboda</a>, <a href="/search/astro-ph?searchtype=author&query=Dov%C4%8Diak%2C+M">Michal Dov膷iak</a>, <a href="/search/astro-ph?searchtype=author&query=Steiner%2C+J+F">James F. Steiner</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Ingram%2C+A">Adam Ingram</a>, <a href="/search/astro-ph?searchtype=author&query=Yilmaz%2C+A">Anastasiya Yilmaz</a>, <a href="/search/astro-ph?searchtype=author&query=Cavero%2C+N+R">Nicole Rodriguez Cavero</a>, <a href="/search/astro-ph?searchtype=author&query=Marra%2C+L">Lorenzo Marra</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Veledina%2C+A">Alexandra Veledina</a>, <a href="/search/astro-ph?searchtype=author&query=Mojaver%2C+M+R">Mehrnoosh Rahbardar Mojaver</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Garcia%2C+J">Javier Garcia</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">Henric Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Podgorn%C3%BD%2C+J">Jakub Podgorn媒</a>, <a href="/search/astro-ph?searchtype=author&query=Weisskopf%2C+M+C">Martin C. Weisskopf</a>, <a href="/search/astro-ph?searchtype=author&query=Kislat%2C+F">Fabian Kislat</a>, <a href="/search/astro-ph?searchtype=author&query=Petrucci%2C+P">Pierre-Olivier Petrucci</a>, <a href="/search/astro-ph?searchtype=author&query=Brigitte%2C+M">Maimouna Brigitte</a>, <a href="/search/astro-ph?searchtype=author&query=Bursa%2C+M">Michal Bursa</a>, <a href="/search/astro-ph?searchtype=author&query=Fabiani%2C+S">Sergio Fabiani</a>, <a href="/search/astro-ph?searchtype=author&query=Hu%2C+K">Kun Hu</a>, <a href="/search/astro-ph?searchtype=author&query=Chun%2C+S">Sohee Chun</a> , et al. (87 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.10813v1-abstract-short" style="display: inline;"> X-ray polarization is a powerful tool to investigate the geometry of accreting material around black holes, allowing independent measurements of the black hole spin and orientation of the innermost parts of the accretion disk. We perform the X-ray spectro-polarimetric analysis of an X-ray binary system in the Large Magellanic Cloud, LMC X-3, that hosts a stellar-mass black hole, known to be persis… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.10813v1-abstract-full').style.display = 'inline'; document.getElementById('2309.10813v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.10813v1-abstract-full" style="display: none;"> X-ray polarization is a powerful tool to investigate the geometry of accreting material around black holes, allowing independent measurements of the black hole spin and orientation of the innermost parts of the accretion disk. We perform the X-ray spectro-polarimetric analysis of an X-ray binary system in the Large Magellanic Cloud, LMC X-3, that hosts a stellar-mass black hole, known to be persistently accreting since its discovery. We report the first detection of the X-ray polarization in LMC X-3 with the Imaging X-ray Polarimetry Explorer, and find the average polarization degree of 3.2% +- 0.6% and a constant polarization angle -42 deg +- 6 deg over the 2-8 keV range. Using accompanying spectroscopic observations by NICER, NuSTAR, and the Neil Gehrels Swift observatories, we confirm previous measurements of the black hole spin via the X-ray continuum method, a ~ 0.2. From polarization analysis only, we found consistent results with low black-hole spin, with an upper limit of a < 0.7 at a 90% confidence level. A slight increase of the polarization degree with energy, similar to other black-hole X-ray binaries in the soft state, is suggested from the data but with a low statistical significance. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.10813v1-abstract-full').style.display = 'none'; document.getElementById('2309.10813v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 8 figures, submitted to ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, 2024, 960, 3 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.01879">arXiv:2309.01879</a> <span> [<a href="https://arxiv.org/pdf/2309.01879">pdf</a>, <a href="https://arxiv.org/format/2309.01879">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Magnetic structures and turbulence in SN 1006 revealed with imaging X-ray polarimetry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Zhou%2C+P">Ping Zhou</a>, <a href="/search/astro-ph?searchtype=author&query=Prokhorov%2C+D">Dmitry Prokhorov</a>, <a href="/search/astro-ph?searchtype=author&query=Ferrazzoli%2C+R">Riccardo Ferrazzoli</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+Y">Yi-Jung Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Slane%2C+P">Patrick Slane</a>, <a href="/search/astro-ph?searchtype=author&query=Vink%2C+J">Jacco Vink</a>, <a href="/search/astro-ph?searchtype=author&query=Silvestri%2C+S">Stefano Silvestri</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccol貌 Bucciantini</a>, <a href="/search/astro-ph?searchtype=author&query=Reynoso%2C+E">Estela Reynoso</a>, <a href="/search/astro-ph?searchtype=author&query=Moffett%2C+D">David Moffett</a>, <a href="/search/astro-ph?searchtype=author&query=Soffitta%2C+P">Paolo Soffitta</a>, <a href="/search/astro-ph?searchtype=author&query=Swartz%2C+D">Doug Swartz</a>, <a href="/search/astro-ph?searchtype=author&query=Kaaret%2C+P">Philip Kaaret</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Costa%2C+E">Enrico Costa</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+C+-">C. -Y. Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Doroshenko%2C+V">Victor Doroshenko</a>, <a href="/search/astro-ph?searchtype=author&query=Ehlert%2C+S+R">Steven R. Ehlert</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Marin%2C+F">Fr茅d茅ric Marin</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno%2C+T">Tsunefumi Mizuno</a>, <a href="/search/astro-ph?searchtype=author&query=Pesce-Rollins%2C+M">Melissa Pesce-Rollins</a>, <a href="/search/astro-ph?searchtype=author&query=Sgr%C3%B2%2C+C">Carmelo Sgr貌</a>, <a href="/search/astro-ph?searchtype=author&query=Tamagawa%2C+T">Toru Tamagawa</a> , et al. (77 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.01879v1-abstract-short" style="display: inline;"> Young supernova remnants (SNRs) strongly modify surrounding magnetic fields, which in turn play an essential role in accelerating cosmic rays (CRs). X-ray polarization measurements probe magnetic field morphology and turbulence at the immediate acceleration site. We report the X-ray polarization distribution in the northeastern shell of SN1006 from a 1 Ms observation with the Imaging X-ray Polarim… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.01879v1-abstract-full').style.display = 'inline'; document.getElementById('2309.01879v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.01879v1-abstract-full" style="display: none;"> Young supernova remnants (SNRs) strongly modify surrounding magnetic fields, which in turn play an essential role in accelerating cosmic rays (CRs). X-ray polarization measurements probe magnetic field morphology and turbulence at the immediate acceleration site. We report the X-ray polarization distribution in the northeastern shell of SN1006 from a 1 Ms observation with the Imaging X-ray Polarimetry Explorer (IXPE). We found an average polarization degree of $22.4\pm 3.5\%$ and an average polarization angle of $-45.4\pm 4.5^\circ$ (measured on the plane of the sky from north to east). The X-ray polarization angle distribution reveals that the magnetic fields immediately behind the shock in the northeastern shell of SN 1006 are nearly parallel to the shock normal or radially distributed, similar to that in the radio observations, and consistent with the quasi-parallel CR acceleration scenario. The X-ray emission is marginally more polarized than that in the radio band. The X-ray polarization degree of SN 1006 is much larger than that in Cas A and Tycho, together with the relatively tenuous and smooth ambient medium of the remnant, favoring that CR-induced instabilities set the turbulence in SN 1006 and CR acceleration is environment-dependent. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.01879v1-abstract-full').style.display = 'none'; document.getElementById('2309.01879v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 4 Figures, 2 Tables; accepted for publication in The Astrophysical Journal</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.01238">arXiv:2308.01238</a> <span> [<a href="https://arxiv.org/pdf/2308.01238">pdf</a>, <a href="https://arxiv.org/format/2308.01238">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> </div> <p class="title is-5 mathjax"> IXPE and XMM-Newton observations of the Soft Gamma Repeater SGR 1806-20 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Turolla%2C+R">Roberto Turolla</a>, <a href="/search/astro-ph?searchtype=author&query=Taverna%2C+R">Roberto Taverna</a>, <a href="/search/astro-ph?searchtype=author&query=Israel%2C+G+L">Gian Luca Israel</a>, <a href="/search/astro-ph?searchtype=author&query=Muleri%2C+F">Fabio Muleri</a>, <a href="/search/astro-ph?searchtype=author&query=Zane%2C+S">Silvia Zane</a>, <a href="/search/astro-ph?searchtype=author&query=Bachetti%2C+M">Matteo Bachetti</a>, <a href="/search/astro-ph?searchtype=author&query=Heyl%2C+J">Jeremy Heyl</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Marco%2C+A">Alessandro Di Marco</a>, <a href="/search/astro-ph?searchtype=author&query=Gau%2C+E">Ephraim Gau</a>, <a href="/search/astro-ph?searchtype=author&query=Krawczynski%2C+H">Henric Krawczynski</a>, <a href="/search/astro-ph?searchtype=author&query=Ng%2C+M">Mason Ng</a>, <a href="/search/astro-ph?searchtype=author&query=Possenti%2C+A">Andrea Possenti</a>, <a href="/search/astro-ph?searchtype=author&query=Poutanen%2C+J">Juri Poutanen</a>, <a href="/search/astro-ph?searchtype=author&query=Baldini%2C+L">Luca Baldini</a>, <a href="/search/astro-ph?searchtype=author&query=Matt%2C+G">Giorgio Matt</a>, <a href="/search/astro-ph?searchtype=author&query=Negro%2C+M">Michela Negro</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Ivan Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Antonelli%2C+L+A">Lucio Angelo Antonelli</a>, <a href="/search/astro-ph?searchtype=author&query=Baumgartner%2C+W+H">Wayne H. Baumgartner</a>, <a href="/search/astro-ph?searchtype=author&query=Bellazzini%2C+R">Ronaldo Bellazzini</a>, <a href="/search/astro-ph?searchtype=author&query=Bianchi%2C+S">Stefano Bianchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bongiorno%2C+S+D">Stephen D. Bongiorno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonino%2C+R">Raffaella Bonino</a>, <a href="/search/astro-ph?searchtype=author&query=Brez%2C+A">Alessandro Brez</a>, <a href="/search/astro-ph?searchtype=author&query=Bucciantini%2C+N">Niccolo' Bucciantini</a> , et al. (74 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.01238v1-abstract-short" style="display: inline;"> Recent observations with the Imaging X-ray Polarimetry Explorer (IXPE) of two anomalous X-ray pulsars provided evidence that X-ray emission from magnetar sources is strongly polarized. Here we report on the joint IXPE and XMM-Newton observations of the soft 纬-repeater SGR 1806-20. The spectral and timing properties of SGR 1806-20 derived from XMM-Newton data are in broad agreement with previous me… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.01238v1-abstract-full').style.display = 'inline'; document.getElementById('2308.01238v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.01238v1-abstract-full" style="display: none;"> Recent observations with the Imaging X-ray Polarimetry Explorer (IXPE) of two anomalous X-ray pulsars provided evidence that X-ray emission from magnetar sources is strongly polarized. Here we report on the joint IXPE and XMM-Newton observations of the soft 纬-repeater SGR 1806-20. The spectral and timing properties of SGR 1806-20 derived from XMM-Newton data are in broad agreement with previous measurements; however, we found the source at an all-time-low persistent flux level. No significant polarization was measured apart from the 4-5 keV energy range, where a probable detection with PD=31.6\pm 10.5% and PA=-17.6\pm 15 deg was obtained. The resulting polarization signal, together with the upper limits we derive at lower and higher energies 2-4 and 5-8 keV, respectively) is compatible with a picture in which thermal radiation from the condensed star surface is reprocessed by resonant Compton scattering in the magnetosphere, similar to what proposed for the bright magnetar 4U 0142+61. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.01238v1-abstract-full').style.display = 'none'; document.getElementById('2308.01238v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 3 figures, accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.00039">arXiv:2308.00039</a> <span> [<a href="https://arxiv.org/pdf/2308.00039">pdf</a>, <a href="https://arxiv.org/format/2308.00039">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> IXPE and multi-wavelength observations of blazar PG 1553+113 reveal an orphan optical polarization swing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Middei%2C+R">Riccardo Middei</a>, <a href="/search/astro-ph?searchtype=author&query=Perri%2C+M">Matteo Perri</a>, <a href="/search/astro-ph?searchtype=author&query=Puccetti%2C+S">Simonetta Puccetti</a>, <a href="/search/astro-ph?searchtype=author&query=Liodakis%2C+I">Ioannis Liodakis</a>, <a href="/search/astro-ph?searchtype=author&query=Di+Gesu%2C+L">Laura Di Gesu</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Cavero%2C+N+R">Nicole Rodriguez Cavero</a>, <a href="/search/astro-ph?searchtype=author&query=Tavecchio%2C+F">Fabrizio Tavecchio</a>, <a href="/search/astro-ph?searchtype=author&query=Donnarumma%2C+I">Immacolata Donnarumma</a>, <a href="/search/astro-ph?searchtype=author&query=Laurenti%2C+M">Marco Laurenti</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Agudo%2C+I">Iv谩n Agudo</a>, <a href="/search/astro-ph?searchtype=author&query=Marshall%2C+H+L">Herman L. Marshall</a>, <a href="/search/astro-ph?searchtype=author&query=Pacciani%2C+L">Luigi Pacciani</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+D+E">Dawoon E. Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Aceituno%2C+F+J">Francisco Jos茅 Aceituno</a>, <a href="/search/astro-ph?searchtype=author&query=Bonnoli%2C+G">Giacomo Bonnoli</a>, <a href="/search/astro-ph?searchtype=author&query=Casanova%2C+V">V铆ctor Casanova</a>, <a href="/search/astro-ph?searchtype=author&query=Ag%C3%ADs-Gonz%C3%A1lez%2C+B">Beatriz Ag铆s-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Sota%2C+A">Alfredo Sota</a>, <a href="/search/astro-ph?searchtype=author&query=Casadio%2C+C">Carolina Casadio</a>, <a href="/search/astro-ph?searchtype=author&query=Escudero%2C+J">Juan Escudero</a>, <a href="/search/astro-ph?searchtype=author&query=Myserlis%2C+I">Ioannis Myserlis</a>, <a href="/search/astro-ph?searchtype=author&query=Sievers%2C+A">Albrecht Sievers</a>, <a href="/search/astro-ph?searchtype=author&query=Kouch%2C+P+M">Pouya M. Kouch</a> , et al. (97 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.00039v1-abstract-short" style="display: inline;"> The lower energy peak of the spectral energy distribution of blazars has commonly been ascribed to synchrotron radiation from relativistic particles in the jets. Despite the consensus regarding jet emission processes, the particle acceleration mechanism is still debated. Here, we present the first X-ray polarization observations of PG 1553+113, a high-synchrotron-peak blazar observed by the Imagin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.00039v1-abstract-full').style.display = 'inline'; document.getElementById('2308.00039v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.00039v1-abstract-full" style="display: none;"> The lower energy peak of the spectral energy distribution of blazars has commonly been ascribed to synchrotron radiation from relativistic particles in the jets. Despite the consensus regarding jet emission processes, the particle acceleration mechanism is still debated. Here, we present the first X-ray polarization observations of PG 1553+113, a high-synchrotron-peak blazar observed by the Imaging X-ray Polarimetry Explorer (IXPE). We detect an X-ray polarization degree of $(10\pm2)\%$ along an electric-vector position angle of $蠄_X=86^{\circ}\pm8^{\circ}$. At the same time, the radio and optical polarization degrees are lower by a factor of $\sim$3. During our IXPE pointing, we observed the first orphan optical polarization swing of the IXPE era, as the optical angle of PG 1553+113 underwent a smooth monotonic rotation by about 125$^\circ$, with a rate of $\sim$17 degrees per day. We do not find evidence of a similar rotation in either radio or X-rays, which suggests that the X-ray and optically emitting regions are separate or, at most, partially co-spatial. Our spectro-polarimetric results provide further evidence that the steady-state X-ray emission in blazars originates in a shock-accelerated and energy-stratified electron population. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.00039v1-abstract-full').style.display = 'none'; document.getElementById('2308.00039v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 31 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for pubblication in The Astrophysical Journal Letters. 3 Figures, 13 pages</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.17819">arXiv:2306.17819</a> <span> [<a href="https://arxiv.org/pdf/2306.17819">pdf</a>, <a href="https://arxiv.org/format/2306.17819">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Multiwavelength Observations of the Blazar PKS 0735+178 in Spatial and Temporal Coincidence with an Astrophysical Neutrino Candidate IceCube-211208A </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Acharyya%2C+A">A. Acharyya</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+C+B">C. B. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Archer%2C+A">A. Archer</a>, <a href="/search/astro-ph?searchtype=author&query=Bangale%2C+P">P. Bangale</a>, <a href="/search/astro-ph?searchtype=author&query=Bartkoske%2C+J+T">J. T. Bartkoske</a>, <a href="/search/astro-ph?searchtype=author&query=Batista%2C+P">P. Batista</a>, <a href="/search/astro-ph?searchtype=author&query=Benbow%2C+W">W. Benbow</a>, <a href="/search/astro-ph?searchtype=author&query=Brill%2C+A">A. Brill</a>, <a href="/search/astro-ph?searchtype=author&query=Buckley%2C+J+H">J. H. Buckley</a>, <a href="/search/astro-ph?searchtype=author&query=Christiansen%2C+J+L">J. L. Christiansen</a>, <a href="/search/astro-ph?searchtype=author&query=Chromey%2C+A+J">A. J. Chromey</a>, <a href="/search/astro-ph?searchtype=author&query=Errando%2C+M">M. Errando</a>, <a href="/search/astro-ph?searchtype=author&query=Falcone%2C+A">A. Falcone</a>, <a href="/search/astro-ph?searchtype=author&query=Feng%2C+Q">Q. Feng</a>, <a href="/search/astro-ph?searchtype=author&query=Foote%2C+G+M">G. M. Foote</a>, <a href="/search/astro-ph?searchtype=author&query=Fortson%2C+L">L. Fortson</a>, <a href="/search/astro-ph?searchtype=author&query=Furniss%2C+A">A. Furniss</a>, <a href="/search/astro-ph?searchtype=author&query=Gallagher%2C+G">G. Gallagher</a>, <a href="/search/astro-ph?searchtype=author&query=Hanlon%2C+W">W. Hanlon</a>, <a href="/search/astro-ph?searchtype=author&query=Hanna%2C+D">D. Hanna</a>, <a href="/search/astro-ph?searchtype=author&query=Hervet%2C+O">O. Hervet</a>, <a href="/search/astro-ph?searchtype=author&query=Hinrichs%2C+C+E">C. E. Hinrichs</a>, <a href="/search/astro-ph?searchtype=author&query=Hoang%2C+J">J. Hoang</a>, <a href="/search/astro-ph?searchtype=author&query=Holder%2C+J">J. Holder</a>, <a href="/search/astro-ph?searchtype=author&query=Humensky%2C+T+B">T. B. Humensky</a> , et al. (185 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.17819v1-abstract-short" style="display: inline;"> We report on multiwavelength target-of-opportunity observations of the blazar PKS 0735+178, located 2.2$^\circ$ away from the best-fit position of the IceCube neutrino event IceCube-211208A detected on December 8, 2021. The source was in a high-flux state in the optical, ultraviolet, X-ray, and GeV gamma-ray bands around the time of the neutrino event, exhibiting daily variability in the soft X-ra… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.17819v1-abstract-full').style.display = 'inline'; document.getElementById('2306.17819v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.17819v1-abstract-full" style="display: none;"> We report on multiwavelength target-of-opportunity observations of the blazar PKS 0735+178, located 2.2$^\circ$ away from the best-fit position of the IceCube neutrino event IceCube-211208A detected on December 8, 2021. The source was in a high-flux state in the optical, ultraviolet, X-ray, and GeV gamma-ray bands around the time of the neutrino event, exhibiting daily variability in the soft X-ray flux. The X-ray data from Swift-XRT and NuSTAR characterize the transition between the low-energy and high-energy components of the broadband spectral energy distribution (SED), and the gamma-ray data from Fermi -LAT, VERITAS, and H.E.S.S. require a spectral cut-off near 100 GeV. Both X-ray and gamma-ray measurements provide strong constraints on the leptonic and hadronic models. We analytically explore a synchrotron self-Compton model, an external Compton model, and a lepto-hadronic model. Models that are entirely based on internal photon fields face serious difficulties in matching the observed SED. The existence of an external photon field in the source would instead explain the observed gamma-ray spectral cut-off in both leptonic and lepto-hadronic models and allow a proton jet power that marginally agrees with the Eddington limit in the lepto-hadronic model. We show a numerical lepto-hadronic model with external target photons that reproduces the observed SED and is reasonably consistent with the neutrino event despite requiring a high jet power. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.17819v1-abstract-full').style.display = 'none'; document.getElementById('2306.17819v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 3 figures, accepted by ApJ</span> </p> </li> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous 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