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class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.00100">arXiv:2411.00100</a> <span> [<a href="https://arxiv.org/pdf/2411.00100">pdf</a>, <a href="https://arxiv.org/format/2411.00100">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> The formation and stability of a cold disc made out of stellar winds in the Galactic Centre </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Calder%C3%B3n%2C+D">Diego Calder贸n</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Burkert%2C+A">Andreas Burkert</a>, <a href="/search/?searchtype=author&query=Rosswog%2C+S">Stephan Rosswog</a>, <a href="/search/?searchtype=author&query=Balakrishnan%2C+M">Mayura Balakrishnan</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="2411.00100v1-abstract-short" style="display: inline;"> The reported discovery of a cold ($\sim$10$^4~\text{K}$) disc-like structure around the super-massive black hole at the centre of the Milk Way, Sagittarius A* (Sgr A*), has challenged our understanding of the gas dynamics and thermodynamic state of the plasma in its immediate vicinity. State-of-the-art simulations do not agree on whether or not such a disc can indeed be a product of the multiple s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.00100v1-abstract-full').style.display = 'inline'; document.getElementById('2411.00100v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.00100v1-abstract-full" style="display: none;"> The reported discovery of a cold ($\sim$10$^4~\text{K}$) disc-like structure around the super-massive black hole at the centre of the Milk Way, Sagittarius A* (Sgr A*), has challenged our understanding of the gas dynamics and thermodynamic state of the plasma in its immediate vicinity. State-of-the-art simulations do not agree on whether or not such a disc can indeed be a product of the multiple stellar wind interactions of the mass-losing stars in the region. This study aims to constrain the conditions for the formation of a cold disc as a natural outcome of the system of the mass-losing stars orbiting around Sgr A*, to investigate if the disc is a transient or long-lasting structure, and to assess the validity of the model through direct comparisons with observations. We conduct a set of hydrodynamic simulations of the observed Wolf-Rayet (WR) stars feeding Sgr A* using the finite-volume adaptive mesh-refinement code Ramses. We focus, for the first time, on the impact of the chemical composition of the plasma emanating from the WR stars. The simulations show that the chemical composition of the plasma affects the radiative cooling enough to impact the properties of the medium such as density and temperature and, as a consequence, the rate at which the material inflows onto Sgr A*. We demonstrated that the formation of a cold disc from the stellar winds is possible for certain chemical compositions that are consistent with the current observational constraints. However, even in such a case, it is not possible to reproduce the reported properties of the observed disc-like structure, namely its inclination and hydrogen recombination line fluxes. We conclude that the stellar winds on their own cannot form the cold disc around Sgr A* inferred from the observations. Either relevant ingredients are still missing in the model, or the interpretation of the observed data needs to be revised. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.00100v1-abstract-full').style.display = 'none'; document.getElementById('2411.00100v1-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 October, 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, 17 pages, 11 figures (+2 pages, +2 figures in Appendix)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.14631">arXiv:2406.14631</a> <span> [<a href="https://arxiv.org/pdf/2406.14631">pdf</a>, <a href="https://arxiv.org/format/2406.14631">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"> Multistructured accretion flow of Sgr A* II: Signatures of a Cool Accretion Disk in Hydrodynamic Simulations of Stellar Winds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Balakrishnan%2C+M">Mayura Balakrishnan</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Corrales%2C+L">Lia Corrales</a>, <a href="/search/?searchtype=author&query=Calder%C3%B3n%2C+D">Diego Calder贸n</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</a>, <a href="/search/?searchtype=author&query=Haggard%2C+D">Daryl Haggard</a>, <a href="/search/?searchtype=author&query=Markoff%2C+S">Sera Markoff</a>, <a href="/search/?searchtype=author&query=Neilsen%2C+J">Joey Neilsen</a>, <a href="/search/?searchtype=author&query=Nowak%2C+M">Michael Nowak</a>, <a href="/search/?searchtype=author&query=Wang%2C+Q+D">Q. Daniel Wang</a>, <a href="/search/?searchtype=author&query=Baganoff%2C+F">Fred Baganoff</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="2406.14631v1-abstract-short" style="display: inline;"> Hydrodynamic simulations of the stellar winds from Wolf-Rayet stars within the Galactic Center can provide predictions for the X-ray spectrum of supermassive black hole Sgr A*. Herein, we present results from updated smooth particle hydrodynamics simulations, building on the architecture of Cuadra et al. (2015); Russell et al. (2017), finding that a cold gas disk forms around Sgr A* with a simulat… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.14631v1-abstract-full').style.display = 'inline'; document.getElementById('2406.14631v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.14631v1-abstract-full" style="display: none;"> Hydrodynamic simulations of the stellar winds from Wolf-Rayet stars within the Galactic Center can provide predictions for the X-ray spectrum of supermassive black hole Sgr A*. Herein, we present results from updated smooth particle hydrodynamics simulations, building on the architecture of Cuadra et al. (2015); Russell et al. (2017), finding that a cold gas disk forms around Sgr A* with a simulation runtime of 3500 years. This result is consistent with previous grid-based simulations, demonstrating that a cold disk can form regardless of numerical method. We examine the plasma scenarios arising from an environment with and without this cold disk, by generating synthetic spectra for comparison to the quiescent Fe K alpha Sgr A* spectrum from Chandra HETG-S, taken through the Chandra X-ray Visionary Program. We find that current and future X-ray missions are unlikely to distinguish between the kinematic signatures in the plasma in these two scenarios. Nonetheless, the stellar wind plasma model presents a good fit to the dispersed Chandra spectra within 1.5" of Sgr A*. We compare our results to the Radiatively Inefficient Accretion Flow (RIAF) model fit to the HETG-S spectrum presented in Paper I and find that the Bayesian model evidence does not strongly favor either model. With 9" angular resolution and high spectral resolution of the X-IFU, NewAthena will offer a clearer differentiation between the RIAF plasma model and hydrodynamic simulations, but only a future X-ray mission with arcsecond resolution will significantly advance our understanding of Sgr A*'s accretion flow in X-rays. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.14631v1-abstract-full').style.display = 'none'; document.getElementById('2406.14631v1-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 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">14 pages, 6 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/2406.14630">arXiv:2406.14630</a> <span> [<a href="https://arxiv.org/pdf/2406.14630">pdf</a>, <a href="https://arxiv.org/format/2406.14630">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"> Multistructured accretion flow of Sgr A* I: Examination of a RIAF model </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Balakrishnan%2C+M">Mayura Balakrishnan</a>, <a href="/search/?searchtype=author&query=Corrales%2C+L">Lia Corrales</a>, <a href="/search/?searchtype=author&query=Markoff%2C+S">Sera Markoff</a>, <a href="/search/?searchtype=author&query=Nowak%2C+M">Michael Nowak</a>, <a href="/search/?searchtype=author&query=Haggard%2C+D">Daryl Haggard</a>, <a href="/search/?searchtype=author&query=Wang%2C+Q+D">Q. Daniel Wang</a>, <a href="/search/?searchtype=author&query=Neilsen%2C+J">Joey Neilsen</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Calder%C3%B3n%2C+D">Diego Calder贸n</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</a>, <a href="/search/?searchtype=author&query=Baganoff%2C+F">Fred Baganoff</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="2406.14630v1-abstract-short" style="display: inline;"> The extreme low-luminosity supermassive black hole Sgr A* provides a unique laboratory in which to test radiatively inefficient accretion flow (RIAF) models. Previous fits to the quiescent Chandra ACIS-S spectrum found a RIAF model with an equal inflow-outflow balance works well. In this work, we apply the RIAF model to the Chandra HETG-S spectrum obtained through the Chandra X-ray Visionary Progr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.14630v1-abstract-full').style.display = 'inline'; document.getElementById('2406.14630v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.14630v1-abstract-full" style="display: none;"> The extreme low-luminosity supermassive black hole Sgr A* provides a unique laboratory in which to test radiatively inefficient accretion flow (RIAF) models. Previous fits to the quiescent Chandra ACIS-S spectrum found a RIAF model with an equal inflow-outflow balance works well. In this work, we apply the RIAF model to the Chandra HETG-S spectrum obtained through the Chandra X-ray Visionary Program, which displays features suggestive of temperature and velocity structures within the plasma. A comprehensive forward model analysis accounting for the accretion flow geometry and HETG-S instrumental effects is required for a full interpretation of the quiescent Chandra HETG-S spectrum. We present a RIAF model that takes these effects into account. Our fits to the high-resolution gratings spectrum indicate an inflow balanced by an outflow ($s \sim 1$) alongside a temperature profile that appears shallower than what would be expected from a gravitational potential following $1/r$. The data require that the abundance of Iron relative to solar is $Z_{Fe} < 0.32 Z_\odot$ (90\% credible interval), much lower than the $2~Z_\odot$ metallicity measured in nearby late-type giants. While future missions like NewAthena will provide higher spectral resolution, source separation will continue to be a problem. Leveraging Chandra's unparalleled spatial resolution, which is not expected to be surpassed for decades, remains essential for detailed investigations of the densely populated Galactic Center in X-rays. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.14630v1-abstract-full').style.display = 'none'; document.getElementById('2406.14630v1-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 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, 5 figures, 1 table. 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/2401.00977">arXiv:2401.00977</a> <span> [<a href="https://arxiv.org/pdf/2401.00977">pdf</a>, <a href="https://arxiv.org/format/2401.00977">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/10.1093/mnras/stad3635">10.1093/mnras/stad3635 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-ray plasma flow and turbulence in the colliding winds of WR140 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Miyamoto%2C+A">Asca Miyamoto</a>, <a href="/search/?searchtype=author&query=Sugawara%2C+Y">Yasuharu Sugawara</a>, <a href="/search/?searchtype=author&query=Maeda%2C+Y">Yoshitomo Maeda</a>, <a href="/search/?searchtype=author&query=Ishida%2C+M">Manabu Ishida</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</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="2401.00977v1-abstract-short" style="display: inline;"> We analyse $\textit{XMM-Newton}$ RGS spectra of Wolf-Rayet (WR) 140, an archetype long-period eccentric WR+O colliding wind binary. We evaluate the spectra of O and Fe emission lines and find that the plasmas emitting these lines have the largest approaching velocities with the largest velocity dispersions between phases 0.935 and 0.968 where the inferior conjunction of the O star occurs. This beh… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.00977v1-abstract-full').style.display = 'inline'; document.getElementById('2401.00977v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.00977v1-abstract-full" style="display: none;"> We analyse $\textit{XMM-Newton}$ RGS spectra of Wolf-Rayet (WR) 140, an archetype long-period eccentric WR+O colliding wind binary. We evaluate the spectra of O and Fe emission lines and find that the plasmas emitting these lines have the largest approaching velocities with the largest velocity dispersions between phases 0.935 and 0.968 where the inferior conjunction of the O star occurs. This behaviour is the same as that of the Ne line-emission plasma presented in our previous paper. We perform diagnosis of electron number density $n_{\rm e}$ using He-like triplet lines of O and Ne-like Fe-L lines. The former results in a conservative upper limit of $n_{\rm e} \lesssim 10^{10}$-10$^{12}$ cm$^{-3}$ on the O line-emission site, while the latter can not impose any constraint on the Fe line-emission site because of statistical limitations. We calculate the line-of-sight velocity and its dispersion separately along the shock cone. By comparing the observed and calculated line-of-sight velocities, we update the distance of the Ne line-emission site from the stagnation point. By assuming radiative cooling of the Ne line-emission plasma using the observed temperature and the local stellar wind density, we estimate the line-emission site extends along the shock cone by at most $\pm$58 per cent (phase 0.816) of the distance from the stagnation point. In this framework, excess of the observed velocity dispersion over the calculated one is ascribed to turbulence in the hot-shocked plasma at earlier orbital phases of 0.816, 0.912, and 0.935, with the largest velocity dispersion of 340-630 km s$^{-1}$ at phase 0.912. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.00977v1-abstract-full').style.display = 'none'; document.getElementById('2401.00977v1-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> 1 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, 9 figures, Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.15948">arXiv:2311.15948</a> <span> [<a href="https://arxiv.org/pdf/2311.15948">pdf</a>, <a href="https://arxiv.org/format/2311.15948">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="Earth and Planetary Astrophysics">astro-ph.EP</span> </div> </div> <p class="title is-5 mathjax"> A First Look with JWST Aperture Masking Interferometry (AMI): Resolving Circumstellar Dust around the Wolf-Rayet Binary WR 137 beyond the Rayleigh Limit </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lau%2C+R+M">Ryan M. Lau</a>, <a href="/search/?searchtype=author&query=Hankins%2C+M+J">Matthew J. Hankins</a>, <a href="/search/?searchtype=author&query=Sanchez-Bermudez%2C+J">Joel Sanchez-Bermudez</a>, <a href="/search/?searchtype=author&query=Thatte%2C+D">Deepashri Thatte</a>, <a href="/search/?searchtype=author&query=Soulain%2C+A">Anthony Soulain</a>, <a href="/search/?searchtype=author&query=Cooper%2C+R+A">Rachel A. Cooper</a>, <a href="/search/?searchtype=author&query=Sivaramakrishnan%2C+A">Anand Sivaramakrishnan</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Greenbaum%2C+A+Z">Alexandra Z. Greenbaum</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Han%2C+Y">Yinuo Han</a>, <a href="/search/?searchtype=author&query=Jones%2C+O+C">Olivia C. Jones</a>, <a href="/search/?searchtype=author&query=Madura%2C+T">Thomas Madura</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Morris%2C+M+R">Mark R. Morris</a>, <a href="/search/?searchtype=author&query=Onaka%2C+T">Takashi Onaka</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Smith%2C+N">Nathan Smith</a>, <a href="/search/?searchtype=author&query=Tuthill%2C+P">Peter Tuthill</a>, <a href="/search/?searchtype=author&query=Volk%2C+K">Kevin Volk</a>, <a href="/search/?searchtype=author&query=Weigelt%2C+G">Gerd Weigelt</a>, <a href="/search/?searchtype=author&query=Williams%2C+P+M">Peredur M. Williams</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="2311.15948v2-abstract-short" style="display: inline;"> We present infrared aperture masking interferometry (AMI) observations of newly formed dust from the colliding winds of the massive binary system Wolf-Rayet (WR) 137 with JWST using the Near Infrared Imager and Slitless Spectrograph (NIRISS). NIRISS AMI observations of WR 137 and a point-spread-function calibrator star, HD~228337, were taken using the F380M and F480M filters in 2022 July and Augus… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.15948v2-abstract-full').style.display = 'inline'; document.getElementById('2311.15948v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.15948v2-abstract-full" style="display: none;"> We present infrared aperture masking interferometry (AMI) observations of newly formed dust from the colliding winds of the massive binary system Wolf-Rayet (WR) 137 with JWST using the Near Infrared Imager and Slitless Spectrograph (NIRISS). NIRISS AMI observations of WR 137 and a point-spread-function calibrator star, HD~228337, were taken using the F380M and F480M filters in 2022 July and August as part of the Director's Discretionary Early Release Science (DD-ERS) program 1349. Interferometric observables (squared visibilities and closure phases) from the WR 137 "interferogram" were extracted and calibrated using three independent software tools: ImPlaneIA, AMICAL, and SAMpip. The analysis of the calibrated observables yielded consistent values except for slightly discrepant closure phases measured by ImPlaneIA. Based on all three sets of calibrated observables, images were reconstructed using three independent software tools: BSMEM, IRBis, and SQUEEZE. All reconstructed image combinations generated consistent images in both F380M and F480M filters. The reconstructed images of WR 137 reveal a bright central core with a $\sim300$ mas linear filament extending to the northwest. A geometric colliding-wind model with dust production constrained to the orbital plane of the binary system and enhanced as the system approaches periapsis provided a general agreement with the interferometric observables and reconstructed images. Based on a colliding-wind dust condensation analysis, we suggest that dust formation within the orbital plane of WR 137 is induced by enhanced equatorial mass-loss from the rapidly rotating O9 companion star, whose axis of rotation is aligned with that of the orbit. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.15948v2-abstract-full').style.display = 'none'; document.getElementById('2311.15948v2-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 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">18 pages, 8 figures, Accepted for publication in ApJ. Updated plotting error in Fig. 2</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.01445">arXiv:2211.01445</a> <span> [<a href="https://arxiv.org/pdf/2211.01445">pdf</a>, <a href="https://arxiv.org/format/2211.01445">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="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> The long-term spectral changes of eta Carinae: are they caused by a dissipating occulter as indicated by CMFGEN models? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Damineli%2C+A">A. Damineli</a>, <a href="/search/?searchtype=author&query=Hillier%2C+D+J">D. J. Hillier</a>, <a href="/search/?searchtype=author&query=Navarete%2C+F">F. Navarete</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">A. F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Weigelt%2C+G">G. Weigelt</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">M. F. Corcoran</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">T. R. Gull</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">N. D. Richardson</a>, <a href="/search/?searchtype=author&query=Ho%2C+T+P">T. P. Ho</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">T. I. Madura</a>, <a href="/search/?searchtype=author&query=Espinoza-Galeas%2C+D">D. Espinoza-Galeas</a>, <a href="/search/?searchtype=author&query=Hartman%2C+H">H. Hartman</a>, <a href="/search/?searchtype=author&query=Morris%2C+P">P. Morris</a>, <a href="/search/?searchtype=author&query=Pickett%2C+C+S">C. S. Pickett</a>, <a href="/search/?searchtype=author&query=Stevens%2C+I+R">I. R. Stevens</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">C. M. P. Russell</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">K. Hamaguchi</a>, <a href="/search/?searchtype=author&query=Jablonski%2C+F+J">F. J. Jablonski</a>, <a href="/search/?searchtype=author&query=Teodoro%2C+M">M. Teodoro</a>, <a href="/search/?searchtype=author&query=McGee%2C+P">P. McGee</a>, <a href="/search/?searchtype=author&query=Cacella%2C+P">P. Cacella</a>, <a href="/search/?searchtype=author&query=Heathcote%2C+B">B. Heathcote</a>, <a href="/search/?searchtype=author&query=Harrison%2C+K">K. Harrison</a>, <a href="/search/?searchtype=author&query=Johnston%2C+M">M. Johnston</a>, <a href="/search/?searchtype=author&query=Bohlsen%2C+T">T. Bohlsen</a> , et al. (1 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="2211.01445v2-abstract-short" style="display: inline;"> Eta Carinae ($畏$\,Car) exhibits a unique set of P Cygni profiles with both broad and narrow components. Over many decades, the spectrum has changed -- there has been an increase in observed continuum fluxes and a decrease in FeII and HI emission line equivalent widths. The spectrum is evolving towards that of a P Cygni star such as P~Cygni itself and HDE~316285. The spectral evolution has been att… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.01445v2-abstract-full').style.display = 'inline'; document.getElementById('2211.01445v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.01445v2-abstract-full" style="display: none;"> Eta Carinae ($畏$\,Car) exhibits a unique set of P Cygni profiles with both broad and narrow components. Over many decades, the spectrum has changed -- there has been an increase in observed continuum fluxes and a decrease in FeII and HI emission line equivalent widths. The spectrum is evolving towards that of a P Cygni star such as P~Cygni itself and HDE~316285. The spectral evolution has been attributed to intrinsic variations such as a decrease in the mass-loss rate of the primary star or differential evolution in a latitudinal-dependent stellar wind. However intrinsic wind changes conflict with three observational results: the steady long-term bolometric luminosity; the repeating X-ray light curve over the binary period; and the constancy of the dust-scattered spectrum from the Homunculus. We extend previous work that showed a secular strengthening of P~Cygni absorptions by adding more orbital cycles to overcome temporary instabilities and by examining more atomic transitions. {\sc cmfgen} modeling of the primary wind shows that a time-decreasing mass-loss rate is not the best explanation for the observations. However, models with a `small' dissipating absorber in our line-of-site can explain both the increase in brightness and changes in the emission and P Cygni absorption profiles. If the spectral evolution is caused by the dissipating circumstellar medium, and not by intrinsic changes in the binary, the dynamical timescale to recover from the Great Eruption is much less than a century, different from previous suggestions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.01445v2-abstract-full').style.display = 'none'; document.getElementById('2211.01445v2-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 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2022. </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">71 pages, 8 figures, 4 long tables, to appear on 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/2210.06452">arXiv:2210.06452</a> <span> [<a href="https://arxiv.org/pdf/2210.06452">pdf</a>, <a href="https://arxiv.org/format/2210.06452">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="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey 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/10.1038/s41550-022-01812-x">10.1038/s41550-022-01812-x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Nested Dust Shells around the Wolf-Rayet Binary WR 140 observed with JWST </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lau%2C+R+M">Ryan M. Lau</a>, <a href="/search/?searchtype=author&query=Hankins%2C+M+J">Matthew J. Hankins</a>, <a href="/search/?searchtype=author&query=Han%2C+Y">Yinuo Han</a>, <a href="/search/?searchtype=author&query=Argyriou%2C+I">Ioannis Argyriou</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Eldridge%2C+J+J">Jan J. Eldridge</a>, <a href="/search/?searchtype=author&query=Endo%2C+I">Izumi Endo</a>, <a href="/search/?searchtype=author&query=Fox%2C+O+D">Ori D. Fox</a>, <a href="/search/?searchtype=author&query=Marin%2C+M+G">Macarena Garcia Marin</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Jones%2C+O+C">Olivia C. Jones</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Lamberts%2C+A">Astrid Lamberts</a>, <a href="/search/?searchtype=author&query=Law%2C+D+R">David R. Law</a>, <a href="/search/?searchtype=author&query=Madura%2C+T">Thomas Madura</a>, <a href="/search/?searchtype=author&query=Marchenko%2C+S+V">Sergey V. Marchenko</a>, <a href="/search/?searchtype=author&query=Matsuhara%2C+H">Hideo Matsuhara</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Morris%2C+M+R">Mark R. Morris</a>, <a href="/search/?searchtype=author&query=Morris%2C+P+W">Patrick W. Morris</a>, <a href="/search/?searchtype=author&query=Onaka%2C+T">Takashi Onaka</a>, <a href="/search/?searchtype=author&query=Ressler%2C+M+E">Michael E. Ressler</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Sanchez-Bermudez%2C+J">Joel Sanchez-Bermudez</a> , et al. (7 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="2210.06452v1-abstract-short" style="display: inline;"> Massive colliding-wind binaries that host a Wolf-Rayet (WR) star present a potentially important source of dust and chemical enrichment in the interstellar medium (ISM). However, the chemical composition and survival of dust formed from such systems is not well understood. The carbon-rich WR (WC) binary WR~140 presents an ideal astrophysical laboratory for investigating these questions given its w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.06452v1-abstract-full').style.display = 'inline'; document.getElementById('2210.06452v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.06452v1-abstract-full" style="display: none;"> Massive colliding-wind binaries that host a Wolf-Rayet (WR) star present a potentially important source of dust and chemical enrichment in the interstellar medium (ISM). However, the chemical composition and survival of dust formed from such systems is not well understood. The carbon-rich WR (WC) binary WR~140 presents an ideal astrophysical laboratory for investigating these questions given its well-defined orbital period and predictable dust-formation episodes every 7.93 years around periastron passage. We present observations from our Early Release Science program (ERS1349) with the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) Medium-Resolution Spectrometer (MRS) and Imager that reveal the spectral and spatial signatures of nested circumstellar dust shells around WR~140. MIRI MRS spectroscopy of the second dust shell and Imager detections of over 17 shells formed throughout the past $\gtrsim130$ years confirm the survival of carbonaceous dust grains from WR~140 that are likely carriers of "unidentified infrared" (UIR)-band features at 6.4 and 7.7 $渭$m. The observations indicate that dust-forming WC binaries can enrich the ISM with organic compounds and carbonaceous dust. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.06452v1-abstract-full').style.display = 'none'; document.getElementById('2210.06452v1-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> 12 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2022. </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">Published in Nature Astronomy on Oct 12, 2022; 21 pages, 5 figures, 2 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Lau, R.M., Hankins, M.J., Han, Y. et al. Nested dust shells around the Wolf-Rayet binary WR 140 observed with JWST. Nat Astron (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2207.03457">arXiv:2207.03457</a> <span> [<a href="https://arxiv.org/pdf/2207.03457">pdf</a>, <a href="https://arxiv.org/format/2207.03457">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/10.3847/1538-4357/ac69ce">10.3847/1538-4357/ac69ce <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> NICER X-ray Observations of Eta Carinae During its Most Recent Periastron Passage </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Espinoza-Galeas%2C+D">David Espinoza-Galeas</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael Francis Corcoran</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A">Anthony Moffat</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Weigelt%2C+G">Gerd Weigelt</a>, <a href="/search/?searchtype=author&query=Hillier%2C+D+J">D. John Hillier</a>, <a href="/search/?searchtype=author&query=Damineli%2C+A">Augusto Damineli</a>, <a href="/search/?searchtype=author&query=Stevens%2C+I+R">Ian R. Stevens</a>, <a href="/search/?searchtype=author&query=Madura%2C+T">Thomas Madura</a>, <a href="/search/?searchtype=author&query=Gendreau%2C+K">Keith Gendreau</a>, <a href="/search/?searchtype=author&query=Arzoumanian%2C+Z">Zaven Arzoumanian</a>, <a href="/search/?searchtype=author&query=Navarete%2C+F">Felipe Navarete</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="2207.03457v1-abstract-short" style="display: inline;"> We report high-precision X-ray monitoring observations in the 0.4-10 keV band of the luminous, long-period colliding-wind binary Eta Carinae up to and through its most recent X-ray minimum/periastron passage in February 2020. Eta Carinae reached its observed maximum X-ray flux on 7 January 2020, at a flux level of $3.30 \times 10^{-10}$ ergs s$^{-1}$ cm$^{-2}$, followed by a rapid plunge to its ob… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.03457v1-abstract-full').style.display = 'inline'; document.getElementById('2207.03457v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2207.03457v1-abstract-full" style="display: none;"> We report high-precision X-ray monitoring observations in the 0.4-10 keV band of the luminous, long-period colliding-wind binary Eta Carinae up to and through its most recent X-ray minimum/periastron passage in February 2020. Eta Carinae reached its observed maximum X-ray flux on 7 January 2020, at a flux level of $3.30 \times 10^{-10}$ ergs s$^{-1}$ cm$^{-2}$, followed by a rapid plunge to its observed minimum flux, $0.03 \times 10^{-10}$ ergs s$^{-1}$ cm$^{-2}$ near 17 February 2020. The NICER observations show an X-ray recovery from minimum of only $\sim$16 days, the shortest X-ray minimum observed so far. We provide new constraints of the "deep" and "shallow" minimum intervals. Variations in the characteristic X-ray temperature of the hottest observed X-ray emission indicate that the apex of the wind-wind "bow shock" enters the companion's wind acceleration zone about 81 days before the start of the X-ray minimum. There is a step-like increase in column density just before the X-ray minimum, probably associated with the presence of dense clumps near the shock apex. During recovery and after, the column density shows a smooth decline, which agrees with previous $N_{H}$ measurements made by SWIFT at the same orbital phase, indicating that changes in mass-loss rate are only a few percent over the two cycles. Finally, we use the variations in the X-ray flux of the outer ejecta seen by NICER to derive a kinetic X-ray luminosity of the ejecta of $\sim 10^{41}$ ergs s$^{-1}$ near the time of the "Great Eruption'. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.03457v1-abstract-full').style.display = 'none'; document.getElementById('2207.03457v1-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 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.15116">arXiv:2205.15116</a> <span> [<a href="https://arxiv.org/pdf/2205.15116">pdf</a>, <a href="https://arxiv.org/format/2205.15116">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> </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/ac74c2">10.3847/1538-4357/ac74c2 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Eta Carinae: an evolving view of the central binary, its interacting winds and its foreground ejecta </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Hillier%2C+D+J">D. John Hillier</a>, <a href="/search/?searchtype=author&query=Hartman%2C+H">Henrik Hartman</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Damineli%2C+A">Augusto Damineli</a>, <a href="/search/?searchtype=author&query=Espinoza-Galeas%2C+D">David Espinoza-Galeas</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Navarete%2C+F">Felipe Navarete</a>, <a href="/search/?searchtype=author&query=Nielsen%2C+K">Krister Nielsen</a>, <a href="/search/?searchtype=author&query=Madura%2C+T">Thomas Madura</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Morris%2C+P">Patrick Morris</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Stevens%2C+I+R">Ian R. Stevens</a>, <a href="/search/?searchtype=author&query=Weigelt%2C+G">Gerd Weigelt</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="2205.15116v1-abstract-short" style="display: inline;"> FUV spectra of Eta Car, recorded across two decades with HST/STIS, document multiple changes in resonant lines caused by dissipating extinction in our line of sight. The FUV flux has increased nearly ten-fold which has led to increased ionization of the multiple shells within the Homunculus and photo-destruction of molecular hydrogen. Comparison of observed resonant line profiles with CMFGEN model… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.15116v1-abstract-full').style.display = 'inline'; document.getElementById('2205.15116v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.15116v1-abstract-full" style="display: none;"> FUV spectra of Eta Car, recorded across two decades with HST/STIS, document multiple changes in resonant lines caused by dissipating extinction in our line of sight. The FUV flux has increased nearly ten-fold which has led to increased ionization of the multiple shells within the Homunculus and photo-destruction of molecular hydrogen. Comparison of observed resonant line profiles with CMFGEN model profiles allows separation of wind-wind collision and shell absorptions from the primary wind, P Cygni profiles.The dissipating occulter preferentially obscured the central binary and interacting winds relative to the very extended primary wind. We are now able to monitor changes in the colliding winds with orbital phase. High velocity transient absorptions occurred across the most recent periastron passage, indicating acceleration of the primary wind by the secondary wind which leads to a downstream, high velocity bowshock that is newly generated every orbital period. There is no evidence of changes in the properties of the binary winds. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.15116v1-abstract-full').style.display = 'none'; document.getElementById('2205.15116v1-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 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </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">36 pages, 22 figures, accepted 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/2109.10350">arXiv:2109.10350</a> <span> [<a href="https://arxiv.org/pdf/2109.10350">pdf</a>, <a href="https://arxiv.org/format/2109.10350">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/10.3847/1538-4357/ac2430">10.3847/1538-4357/ac2430 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Competitive X-ray and Optical Cooling in the Collisionless Shocks of WR 140 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Pollock%2C+A+M+T">A. M. T. Pollock</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">M. F. Corcoran</a>, <a href="/search/?searchtype=author&query=Stevens%2C+I+R">I. R. Stevens</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">C. M. P. Russell</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">K. Hamaguchi</a>, <a href="/search/?searchtype=author&query=Williams%2C+P+M">P. M. Williams</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">A. F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Weigelt%2C+G">G. Weigelt</a>, <a href="/search/?searchtype=author&query=Shenavrin%2C+V">V. Shenavrin</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">N. D. Richardson</a>, <a href="/search/?searchtype=author&query=Espinoza%2C+D">D. Espinoza</a>, <a href="/search/?searchtype=author&query=Drake%2C+S+A">S. A. Drake</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="2109.10350v1-abstract-short" style="display: inline;"> WR 140 is a long-period, highly eccentric Wolf-Rayet star binary system with exceptionally well-determined orbital and stellar parameters. Bright, variable X-ray emission is generated in shocks produced by the collision of the winds of the WC7pd+O5.5fc component stars. We discuss the variations in the context of the colliding-wind model using broad-band spectrometry from the RXTE, SWIFT, and NICER… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.10350v1-abstract-full').style.display = 'inline'; document.getElementById('2109.10350v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.10350v1-abstract-full" style="display: none;"> WR 140 is a long-period, highly eccentric Wolf-Rayet star binary system with exceptionally well-determined orbital and stellar parameters. Bright, variable X-ray emission is generated in shocks produced by the collision of the winds of the WC7pd+O5.5fc component stars. We discuss the variations in the context of the colliding-wind model using broad-band spectrometry from the RXTE, SWIFT, and NICER observatories obtained over 20 years and nearly 1000 observations through 3 consecutive 7.94-year orbits including 3 periastron passages. The X-ray luminosity varies as expected with the inverse of the stellar separation over most of the orbit: departures near periastron are produced when cooling shifts to excess optical emission in CIII $\lambda5696$ in particular. We use X-ray absorption to estimate mass-loss rates for both stars and to constrain the system morphology. The absorption maximum coincides closely with inferior conjunction of the WC star and provides evidence of the ion-reflection mechanism that underlies the formation of collisionless shocks governed by magnetic fields probably generated by the Weibel instability. Comparisons with K-band emission and HeI $位$10830 absorption show that both are correlated after periastron with the asymmetric X-ray absorption. Dust appears within a few days of periastron suggesting formation within shocked gas near the stagnation point. X-ray flares seen in $畏$ Carinae have not occurred in WR 140, suggesting the absence of large-scale wind inhomogeneities. Relatively constant soft emission revealed during the X-ray minimum is probably not from recombining plasma entrained in outflowing shocked gas. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.10350v1-abstract-full').style.display = 'none'; document.getElementById('2109.10350v1-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 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2021. </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">52 pages, 17+1 figures, Accepted for publication in The Astrophysical Journal 23 August 2021</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2102.09445">arXiv:2102.09445</a> <span> [<a href="https://arxiv.org/pdf/2102.09445">pdf</a>, <a href="https://arxiv.org/ps/2102.09445">ps</a>, <a href="https://arxiv.org/format/2102.09445">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> </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/10.1093/mnras/stab508">10.1093/mnras/stab508 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Conditions in the WR 140 wind-collision region revealed by the 1.083-micron He I line profile </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Williams%2C+P+M">Peredur M. Williams</a>, <a href="/search/?searchtype=author&query=Varricatt%2C+W+P">Watson P. Varricatt</a>, <a href="/search/?searchtype=author&query=Chen%C3%A9%2C+A">Andr茅-Nicolas Chen茅</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Ted R. Gull</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Pollock%2C+A+M+T">Andrew M. T. Pollock</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Sander%2C+A+A+C">Andreas A. C. Sander</a>, <a href="/search/?searchtype=author&query=Stevens%2C+I+R">Ian R. Stevens</a>, <a href="/search/?searchtype=author&query=Weigelt%2C+G">Gerd Weigelt</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="2102.09445v1-abstract-short" style="display: inline;"> We present spectroscopy of the P~Cygni profile of the 1.083-micron He I line in the WC7 + O5 colliding-wind binary (CWB) WR 140 (HD 193793), observed in 2008, before its periastron passage in 2009, and in 2016-17, spanning the subsequent periastron passage. Both absorption and emission components showed strong variations. The variation of the absorption component as the O5 star was occulted by the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.09445v1-abstract-full').style.display = 'inline'; document.getElementById('2102.09445v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2102.09445v1-abstract-full" style="display: none;"> We present spectroscopy of the P~Cygni profile of the 1.083-micron He I line in the WC7 + O5 colliding-wind binary (CWB) WR 140 (HD 193793), observed in 2008, before its periastron passage in 2009, and in 2016-17, spanning the subsequent periastron passage. Both absorption and emission components showed strong variations. The variation of the absorption component as the O5 star was occulted by the wind-collision region (WCR) sets a tight constraint on its geometry. While the sightline to the O5 star traversed the WCR, the strength and breadth of the absorption component varied significantly on time-scales of days. An emission sub-peak was observed on all our profiles. The variation of its radial velocity with orbital phase was shown to be consistent with formation in the WCR as it swung round the stars in their orbit. Modelling the profile gave a measure of the extent of the sub-peak forming region. In the phase range 0.93-0.99, the flux in the sub-peak increased steadily, approximately inversely proportionally to the stellar separation, indicating that the shocked gas in the WCR where the line was formed was adiabatic. After periastron, the sub-peak flux was anomalously strong and varied rapidly, suggesting formation in clumps down-stream in the WCR. For most of the time, its flux exceeded the 2-10-keV X-ray emission, showing it to be a significant coolant of the shocked wind. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.09445v1-abstract-full').style.display = 'none'; document.getElementById('2102.09445v1-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 February, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2021. </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, 14 figures, accepted for publication in the MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2005.05404">arXiv:2005.05404</a> <span> [<a href="https://arxiv.org/pdf/2005.05404">pdf</a>, <a href="https://arxiv.org/format/2005.05404">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 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/10.1093/mnras/staa1352">10.1093/mnras/staa1352 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VVV Infrared Variability Catalog (VIVA-I) </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lopes%2C+C+E+F">C. E. Ferreira Lopes</a>, <a href="/search/?searchtype=author&query=Cross%2C+N+J+G">N. J. G. Cross</a>, <a href="/search/?searchtype=author&query=Catelan%2C+M">M. Catelan</a>, <a href="/search/?searchtype=author&query=Minniti%2C+D">D. Minniti</a>, <a href="/search/?searchtype=author&query=Hempel%2C+M">M. Hempel</a>, <a href="/search/?searchtype=author&query=Lucas%2C+P+W">P. W. Lucas</a>, <a href="/search/?searchtype=author&query=Angeloni%2C+R">R. Angeloni</a>, <a href="/search/?searchtype=author&query=Jablonsky%2C+F">F. Jablonsky</a>, <a href="/search/?searchtype=author&query=Braga%2C+V+F">V. F. Braga</a>, <a href="/search/?searchtype=author&query=Leao%2C+I+C">I. C. Leao</a>, <a href="/search/?searchtype=author&query=Herpich%2C+F+R">F. R. Herpich</a>, <a href="/search/?searchtype=author&query=Alonso-Garcia%2C+J">J. Alonso-Garcia</a>, <a href="/search/?searchtype=author&query=Papageorgiou%2C+A">A. Papageorgiou</a>, <a href="/search/?searchtype=author&query=Pichara%2C+K">K. Pichara</a>, <a href="/search/?searchtype=author&query=Saito%2C+R+K">R. K. Saito</a>, <a href="/search/?searchtype=author&query=Bradley%2C+A">A. Bradley</a>, <a href="/search/?searchtype=author&query=Beamin%2C+J+C">J. C. Beamin</a>, <a href="/search/?searchtype=author&query=Cortes%2C+C">C. Cortes</a>, <a href="/search/?searchtype=author&query=De+Medeiros%2C+J+R">J. R. De Medeiros</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher. M. P. Russell</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="2005.05404v1-abstract-short" style="display: inline;"> Thanks to the VISTA Variables in the Via Lactea (VVV) ESO Public Survey it is now possible to explore a large number of objects in those regions. This paper addresses the variability analysis of all VVV point sources having more than 10 observations in VVVDR4 using a novel approach. In total, the near-IR light curves of 288,378,769 sources were analysed using methods developed in the New Insight I… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.05404v1-abstract-full').style.display = 'inline'; document.getElementById('2005.05404v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2005.05404v1-abstract-full" style="display: none;"> Thanks to the VISTA Variables in the Via Lactea (VVV) ESO Public Survey it is now possible to explore a large number of objects in those regions. This paper addresses the variability analysis of all VVV point sources having more than 10 observations in VVVDR4 using a novel approach. In total, the near-IR light curves of 288,378,769 sources were analysed using methods developed in the New Insight Into Time Series Analysis project. As a result, we present a complete sample having 44, 998, 752 variable star candidates (VVV-CVSC), which include accurate individual coordinates, near-IR magnitudes (ZYJHKs), extinctions A(Ks), variability indices, periods, amplitudes, among other parameters to assess the science. Unfortunately, a side effect of having a highly complete sample, is also having a high level of contamination by non-variable (contamination ratio of non-variables to variables is slightly over 10:1). To deal with this, we also provide some flags and parameters that can be used by the community to de-crease the number of variable candidates without heavily decreasing the completeness of the sample. In particular, we cross-identified 339,601 of our sources with Simbad and AAVSO databases, which provide us with information for these objects at other wavelegths. This sub-sample constitutes a unique resource to study the corresponding near-IR variability of known sources as well as to assess the IR variability related with X-ray and Gamma-Ray sources. On the other hand, the other 99.5% sources in our sample constitutes a number of potentially new objects with variability information for the heavily crowded and reddened regions of the Galactic Plane and Bulge. The present results also provide an important queryable resource to perform variability analysis and to characterize ongoing and future surveys like TESS and LSST. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.05404v1-abstract-full').style.display = 'none'; document.getElementById('2005.05404v1-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> 11 May, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2020. </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">27 pages, 14 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/1912.12344">arXiv:1912.12344</a> <span> [<a href="https://arxiv.org/pdf/1912.12344">pdf</a>, <a href="https://arxiv.org/format/1912.12344">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/10.1093/mnras/stz3624">10.1093/mnras/stz3624 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Colliding Winds in and around the Stellar Group IRS 13E at the Galactic Center </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Wang%2C+Q+D">Q. Daniel Wang</a>, <a href="/search/?searchtype=author&query=Li%2C+J">Jun Li</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</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="1912.12344v1-abstract-short" style="display: inline;"> IRS~13E is an enigmatic compact group of massive stars located in projection only 3.6 arcseconds away from Sgr A*. This group has been suggested to be bounded by an intermediate-mass black hole (IMBH). We present a multi-wavelength study of the group and its interplay with the environment. Based on Chandra observations, we find the X-ray spectrum of IRS~13E can be well characterized by an opticall… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.12344v1-abstract-full').style.display = 'inline'; document.getElementById('1912.12344v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.12344v1-abstract-full" style="display: none;"> IRS~13E is an enigmatic compact group of massive stars located in projection only 3.6 arcseconds away from Sgr A*. This group has been suggested to be bounded by an intermediate-mass black hole (IMBH). We present a multi-wavelength study of the group and its interplay with the environment. Based on Chandra observations, we find the X-ray spectrum of IRS~13E can be well characterized by an optically thin thermal plasma. The emission peaks between two strongly mass-losing Wolf-Rayet stars of the group. These properties can be reasonably well reproduced by simulated colliding winds of these two stars. However, this scenario under-predicts the X-ray intensity in outer regions. The residual emission likely results from the ram-pressure confinement of the IRS~13E group wind by the ambient medium and is apparently associated with a shell-like warm gas structure seen in Pa-alpha and in ALMA observations. These latter observations also show strongly peaked thermal emission with unusually large velocity spread between the two stars. These results indicate that the group is colliding with the bar of the dense cool gas mini-spiral around Sgr A*. The extended X-ray morphology of IRS~13E and its association with the bar further suggest that the group is physically much farther away than the projected distance from Sgr A*. The presence of an IMBH, while favorable to keep the stars bound together, is not necessary to explain the observed stellar and gas properties of IRS~13E. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.12344v1-abstract-full').style.display = 'none'; document.getElementById('1912.12344v1-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 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </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, accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1910.06976">arXiv:1910.06976</a> <span> [<a href="https://arxiv.org/pdf/1910.06976">pdf</a>, <a href="https://arxiv.org/format/1910.06976">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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/ab5e81">10.3847/2041-8213/ab5e81 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Stellar winds pump the heart of the Milky Way </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Calder%C3%B3n%2C+D">Diego Calder贸n</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</a>, <a href="/search/?searchtype=author&query=Schartmann%2C+M">Marc Schartmann</a>, <a href="/search/?searchtype=author&query=Burkert%2C+A">Andreas Burkert</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</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="1910.06976v2-abstract-short" style="display: inline;"> The central super-massive black hole of the Milky Way, Sgr A*, accretes at a very low rate making it a very underluminous galactic nucleus. Despite the tens of Wolf-Rayet stars present within the inner parsec supplying ${\sim}10^{-3}\rm\ M_{\odot}\ yr^{-1}$ in stellar winds, only a negligible fraction of this material ($<10^{-4}$) ends up being accreted onto Sgr A*. The recent discovery of cold ga… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.06976v2-abstract-full').style.display = 'inline'; document.getElementById('1910.06976v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1910.06976v2-abstract-full" style="display: none;"> The central super-massive black hole of the Milky Way, Sgr A*, accretes at a very low rate making it a very underluminous galactic nucleus. Despite the tens of Wolf-Rayet stars present within the inner parsec supplying ${\sim}10^{-3}\rm\ M_{\odot}\ yr^{-1}$ in stellar winds, only a negligible fraction of this material ($<10^{-4}$) ends up being accreted onto Sgr A*. The recent discovery of cold gas (${\sim}10^4\rm\ K$) in its vicinity raised questions about how such material could settle in the hostile (${\sim}10^7\rm\ K$) environment near Sgr A*. In this work we show that the system of mass-losing stars blowing winds can naturally account for both the hot, inefficient accretion flow, as well as the formation of a cold disk-like structure. We run hydrodynamical simulations using the grid-based code Ramses starting as early in the past as possible to observe the state of the system at the present time. Our results show that the system reaches a quasi-steady state in about ${\sim}500\rm\ yr$ with material being captured at a rate of ${\sim}10^{-6}\rm\ M_{\odot}\ yr^{-1}$ at scales of ${\sim}10^{-4}\rm\ pc$, consistent with the observations and previous models. However, on longer timescales ($\gtrsim3000\rm\ yr$) the material accumulates close to the black hole in the form of a disk. Considering the duration of the Wolf-Rayet phase (${\sim}10^5\rm\ yr$), we conclude that this scenario likely has already happened, and could be responsible for the more active past of Sgr A*, and/or its current outflow. We argue that the hypothesis of the mass-losing stars being the main regulator of the activity of the black hole deserves further consideration. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.06976v2-abstract-full').style.display = 'none'; document.getElementById('1910.06976v2-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 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 October, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2019. </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">6 pages and 5 figures. 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/1906.04181">arXiv:1906.04181</a> <span> [<a href="https://arxiv.org/pdf/1906.04181">pdf</a>, <a href="https://arxiv.org/format/1906.04181">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link 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/10.1093/mnras/staa090">10.1093/mnras/staa090 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> 3D simulations of clump formation in stellar wind collisions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Calder%C3%B3n%2C+D">Diego Calder贸n</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</a>, <a href="/search/?searchtype=author&query=Schartmann%2C+M">Marc Schartmann</a>, <a href="/search/?searchtype=author&query=Burkert%2C+A">Andreas Burkert</a>, <a href="/search/?searchtype=author&query=Prieto%2C+J">Joaqu铆n Prieto</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</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="1906.04181v2-abstract-short" style="display: inline;"> The inner parsec of our Galaxy contains tens of Wolf-Rayet stars whose powerful outflows are constantly interacting while filling the region with hot, diffuse plasma. Theoretical models have shown that, in some cases, the collision of stellar winds can generate cold, dense material in the form of clumps. However, their formation process and properties are not well understood yet. In this work we p… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.04181v2-abstract-full').style.display = 'inline'; document.getElementById('1906.04181v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.04181v2-abstract-full" style="display: none;"> The inner parsec of our Galaxy contains tens of Wolf-Rayet stars whose powerful outflows are constantly interacting while filling the region with hot, diffuse plasma. Theoretical models have shown that, in some cases, the collision of stellar winds can generate cold, dense material in the form of clumps. However, their formation process and properties are not well understood yet. In this work we present, for the first time, a statistical study of the clump formation process in unstable wind collisions. We study systems with dense outflows (${\sim}10^{-5}\rm\ M_{\odot}\ yr^{-1}$), wind speeds of $500$-$1500\rm\ km\ s^{-1}$, and stellar separations of ${\sim}20$-$200\rm\ au$. We develop 3D high resolution hydrodynamical simulations of stellar wind collisions with the adaptive-mesh refinement grid-based code Ramses. We aim to characterise the initial properties of clumps that form through hydrodynamic instabilities, mostly via the non-linear thin shell instability (NTSI). Our results confirm that more massive clumps are formed in systems whose winds are close to the transition between the radiative and adiabatic regimes. Increasing either the wind speed or the degree of asymmetry increases the dispersion of the clump mass and ejection speed distributions. Nevertheless, the most massive clumps are very light (${\sim}10^{-3}$-$10^{-2}\rm\ M_{\oplus}$), about three orders of magnitude less massive than theoretical upper limits. Applying these results to the Galactic Centre we find that clumps formed through the NTSI should not be heavy enough either to affect the thermodynamic state of the region or to survive for long enough to fall onto the central super-massive black hole. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.04181v2-abstract-full').style.display = 'none'; document.getElementById('1906.04181v2-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, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 June, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2019. </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, 20 Figures, 2 Tables. Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1904.09219">arXiv:1904.09219</a> <span> [<a href="https://arxiv.org/pdf/1904.09219">pdf</a>, <a href="https://arxiv.org/ps/1904.09219">ps</a>, <a href="https://arxiv.org/format/1904.09219">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/10.1038/s41550-018-0505-1">10.1038/s41550-018-0505-1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Non-thermal X-rays from Colliding Wind Shock Acceleration in the Massive Binary Eta Carinae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Pittard%2C+J+M">Julian M. Pittard</a>, <a href="/search/?searchtype=author&query=Sharma%2C+N">Neetika Sharma</a>, <a href="/search/?searchtype=author&query=Takahashi%2C+H">Hiromitsu Takahashi</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Grefenstette%2C+B+W">Brian W. Grefenstette</a>, <a href="/search/?searchtype=author&query=Wik%2C+D+R">Daniel R. Wik</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</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="1904.09219v1-abstract-short" style="display: inline;"> Cosmic-ray acceleration has been a long-standing mystery and despite more than a century of study, we still do not have a complete census of acceleration mechanisms. The collision of strong stellar winds in massive binary systems creates powerful shocks, which have been expected to produce high-energy cosmic-rays through Fermi acceleration at the shock interface. The accelerated particles should c… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.09219v1-abstract-full').style.display = 'inline'; document.getElementById('1904.09219v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1904.09219v1-abstract-full" style="display: none;"> Cosmic-ray acceleration has been a long-standing mystery and despite more than a century of study, we still do not have a complete census of acceleration mechanisms. The collision of strong stellar winds in massive binary systems creates powerful shocks, which have been expected to produce high-energy cosmic-rays through Fermi acceleration at the shock interface. The accelerated particles should collide with stellar photons or ambient material, producing non-thermal emission observable in X-rays and gamma-rays. The supermassive binary star eta Carinae drives the strongest colliding wind shock in the solar neighborhood. Observations with non-focusing high-energy observatories indicate a high energy source near eta Carinae, but have been unable to conclusively identify eta Carinae as the source because of their relatively poor angular resolution. Here we present the first direct focussing observations of the non-thermal source in the extremely hard X-ray band, which is found to be spatially coincident with the star within several arc-seconds. These observations show that the source of non-thermal X-rays varies with the orbital phase of the binary, and that the photon index of the emission is similar to that derived through analysis of the gamma-ray spectrum. This is conclusive evidence that the high-energy emission indeed originates from non-thermal particles accelerated at colliding wind shocks. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1904.09219v1-abstract-full').style.display = 'none'; document.getElementById('1904.09219v1-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 April, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2019. </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">36 pages, 7 figures, 2 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Astronomy 2 (2018) 731-736 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1707.08159">arXiv:1707.08159</a> <span> [<a href="https://arxiv.org/pdf/1707.08159">pdf</a>, <a href="https://arxiv.org/format/1707.08159">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/10.1017/S1743921317003131">10.1017/S1743921317003131 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Modelling the thermal X-ray emission around the Galactic centre from colliding Wolf-Rayet winds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Wang%2C+Q+D">Q. Daniel Wang</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</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="1707.08159v1-abstract-short" style="display: inline;"> We compute the thermal X-ray emission from hydrodynamic simulations of the 30 Wolf-Rayet (WR) stars orbiting within a parsec of Sgr A$^*$, with the aim of interpreting the Chandra X-ray observations of this region. The model well reproduces the spectral shape of the observations, indicating that the shocked WR winds are the dominant source of this thermal emission. The model X-ray flux is tied to… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1707.08159v1-abstract-full').style.display = 'inline'; document.getElementById('1707.08159v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1707.08159v1-abstract-full" style="display: none;"> We compute the thermal X-ray emission from hydrodynamic simulations of the 30 Wolf-Rayet (WR) stars orbiting within a parsec of Sgr A$^*$, with the aim of interpreting the Chandra X-ray observations of this region. The model well reproduces the spectral shape of the observations, indicating that the shocked WR winds are the dominant source of this thermal emission. The model X-ray flux is tied to the strength of the Sgr A$^*$ outflow, which clears out hot gas from the vicinity of Sgr A$^*$. A moderate outflow best fits the present-day observations, even though this supermassive black hole (SMBH) outflow ended $\sim$100 yr ago. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1707.08159v1-abstract-full').style.display = 'none'; document.getElementById('1707.08159v1-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 July, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2017. </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">1 page, 1 figure; to appear in Proceedings of IAU Symposium 329, "The Lives and Death-Throes of Massive Stars"</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1707.06954">arXiv:1707.06954</a> <span> [<a href="https://arxiv.org/pdf/1707.06954">pdf</a>, <a href="https://arxiv.org/format/1707.06954">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</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/10.1017/S1743921317003180">10.1017/S1743921317003180 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> 360-degree videos: a new visualization technique for astrophysical simulations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</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="1707.06954v1-abstract-short" style="display: inline;"> 360-degree videos are a new type of movie that renders over all 4$蟺$ steradian. Video sharing sites such as YouTube now allow this unique content to be shared via virtual reality (VR) goggles, hand-held smartphones/tablets, and computers. Creating 360$^\circ$ videos from astrophysical simulations is not only a new way to view these simulations as you are immersed in them, but is also a way to crea… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1707.06954v1-abstract-full').style.display = 'inline'; document.getElementById('1707.06954v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1707.06954v1-abstract-full" style="display: none;"> 360-degree videos are a new type of movie that renders over all 4$蟺$ steradian. Video sharing sites such as YouTube now allow this unique content to be shared via virtual reality (VR) goggles, hand-held smartphones/tablets, and computers. Creating 360$^\circ$ videos from astrophysical simulations is not only a new way to view these simulations as you are immersed in them, but is also a way to create engaging content for outreach to the public. We present what we believe is the first 360$^\circ$ video of an astrophysical simulation: a hydrodynamics calculation of the central parsec of the Galactic centre. We also describe how to create such movies, and briefly comment on what new science can be extracted from astrophysical simulations using 360$^\circ$ videos. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1707.06954v1-abstract-full').style.display = 'none'; document.getElementById('1707.06954v1-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 July, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2017. </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">3 pages, 2 figures; to appear in Proceedings of IAU Symposium 329, "The Lives and Death-Throes of Massive Stars"</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1707.03390">arXiv:1707.03390</a> <span> [<a href="https://arxiv.org/pdf/1707.03390">pdf</a>, <a href="https://arxiv.org/ps/1707.03390">ps</a>, <a href="https://arxiv.org/format/1707.03390">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> </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/10.1093/mnras/stx1731">10.1093/mnras/stx1731 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The variability of the BRITE-est Wolf-Rayet binary, $纬^2$ Velorum I. Photometric and spectroscopic evidence for colliding winds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=St-Jean%2C+L">Lucas St-Jean</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/?searchtype=author&query=St-Louis%2C+N">Nicole St-Louis</a>, <a href="/search/?searchtype=author&query=Shenar%2C+T">Tomer Shenar</a>, <a href="/search/?searchtype=author&query=Pablo%2C+H">Herbert Pablo</a>, <a href="/search/?searchtype=author&query=Hill%2C+G+M">Grant M. Hill</a>, <a href="/search/?searchtype=author&query=Ramiaramanantsoa%2C+T">Tahina Ramiaramanantsoa</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M">Michael Corcoran</a>, <a href="/search/?searchtype=author&query=Hamuguchi%2C+K">Kenji Hamuguchi</a>, <a href="/search/?searchtype=author&query=Eversberg%2C+T">Thomas Eversberg</a>, <a href="/search/?searchtype=author&query=Miszalski%2C+B">Brent Miszalski</a>, <a href="/search/?searchtype=author&query=Chen%C3%A9%2C+A">Andr茅-Nicolas Chen茅</a>, <a href="/search/?searchtype=author&query=Waldron%2C+W">Wayne Waldron</a>, <a href="/search/?searchtype=author&query=Kotze%2C+E+J">Enrico J. Kotze</a>, <a href="/search/?searchtype=author&query=Kotze%2C+M+M">Marissa M. Kotze</a>, <a href="/search/?searchtype=author&query=Luckas%2C+P">Paul Luckas</a>, <a href="/search/?searchtype=author&query=Cacella%2C+P">Paulo Cacella</a>, <a href="/search/?searchtype=author&query=Heathcote%2C+B">Bernard Heathcote</a>, <a href="/search/?searchtype=author&query=Powles%2C+J">Jonathan Powles</a>, <a href="/search/?searchtype=author&query=Bohlsen%2C+T">Terry Bohlsen</a>, <a href="/search/?searchtype=author&query=Locke%2C+M">Malcolm Locke</a>, <a href="/search/?searchtype=author&query=Handler%2C+G">Gerald Handler</a>, <a href="/search/?searchtype=author&query=Kuschnig%2C+R">Rainer Kuschnig</a> , et al. (4 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="1707.03390v1-abstract-short" style="display: inline;"> We report on the first multi-color precision light curve of the bright Wolf-Rayet binary $纬^2$ Velorum, obtained over six months with the nanosatellites in the BRITE- Constellation fleet. In parallel, we obtained 488 high-resolution optical spectra of the system. In this first report on the datasets, we revise the spectroscopic orbit and report on the bulk properties of the colliding winds. We fin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1707.03390v1-abstract-full').style.display = 'inline'; document.getElementById('1707.03390v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1707.03390v1-abstract-full" style="display: none;"> We report on the first multi-color precision light curve of the bright Wolf-Rayet binary $纬^2$ Velorum, obtained over six months with the nanosatellites in the BRITE- Constellation fleet. In parallel, we obtained 488 high-resolution optical spectra of the system. In this first report on the datasets, we revise the spectroscopic orbit and report on the bulk properties of the colliding winds. We find a dependence of both the light curve and excess emission properties that scales with the inverse of the binary separation. When analyzing the spectroscopic properties in combination with the photometry, we find that the phase dependence is caused only by excess emission in the lines, and not from a changing continuum. We also detect a narrow, high-velocity absorption component from the He I $位$5876 transition, which appears twice in the orbit. We calculate smoothed-particle hydrodynamical simulations of the colliding winds and can accurately associate the absorption from He I to the leading and trailing arms of the wind shock cone passing tangentially through our line of sight. The simulations also explain the general strength and kinematics of the emission excess observed in wind lines such as C III $位$5696 of the system. These results represent the first in a series of investigations into the winds and properties of $纬^2$ Velorum through multi-technique and multi-wavelength observational campaigns. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1707.03390v1-abstract-full').style.display = 'none'; document.getElementById('1707.03390v1-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> 11 July, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2017. </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, 14 figures, additional measurements to be included in online dataset. Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1610.02146">arXiv:1610.02146</a> <span> [<a href="https://arxiv.org/pdf/1610.02146">pdf</a>, <a href="https://arxiv.org/format/1610.02146">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/10.1017/S1743921316012308">10.1017/S1743921316012308 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Modelling the thermal X-ray emission around the Galactic centre from colliding Wolf-Rayet winds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Wang%2C+Q+D">Q. Daniel Wang</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</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="1610.02146v1-abstract-short" style="display: inline;"> The Galactic centre is a hotbed of astrophysical activity, with the injection of wind material from $\sim$30 massive Wolf-Rayet (WR) stars orbiting within 12" of the super-massive black hole (SMBH) playing an important role. Hydrodynamic simulations of such colliding and accreting winds produce a complex density and temperature structure of cold wind material shocking with the ambient medium, crea… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.02146v1-abstract-full').style.display = 'inline'; document.getElementById('1610.02146v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1610.02146v1-abstract-full" style="display: none;"> The Galactic centre is a hotbed of astrophysical activity, with the injection of wind material from $\sim$30 massive Wolf-Rayet (WR) stars orbiting within 12" of the super-massive black hole (SMBH) playing an important role. Hydrodynamic simulations of such colliding and accreting winds produce a complex density and temperature structure of cold wind material shocking with the ambient medium, creating a large reservoir of hot, X-ray-emitting gas. This work aims to confront the 3Ms of Chandra X-ray Visionary Program (XVP) observations of this diffuse emission by computing the X-ray emission from these hydrodynamic simulations of the colliding WR winds, amid exploring a variety of SMBH feedback mechanisms. The major success of the model is that it reproduces the spectral shape from the 2"--5" ring around the SMBH, where most of the stellar wind material that is ultimately captured by Sgr A* is shock-heated and thermalised. This naturally explains that the hot gas comes from colliding WR winds, and that the wind speeds of these stars are in general well constrained. The flux level of these spectra, as well as 12"$\times$12" images of 4--9 keV, show the X-ray flux is tied to the SMBH feedback strength; stronger feedback clears out more hot gas, thereby decreasing the thermal X-ray emission. The model in which Sgr A* produced an intermediate-strength outflow during the last few centuries best matches the observations to within about 10%, showing SMBH feedback is required to interpret the X-ray emission in this region. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.02146v1-abstract-full').style.display = 'none'; document.getElementById('1610.02146v1-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 October, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2016. </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">4 pages, 3 figures, to appear in "Proceedings of IAU Symposium 322: The Multi-Messenger Astrophysics of the Galactic Centre," Steve Longmore, Geoff Bicknell and Roland Crocker, eds</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1608.01374">arXiv:1608.01374</a> <span> [<a href="https://arxiv.org/pdf/1608.01374">pdf</a>, <a href="https://arxiv.org/ps/1608.01374">ps</a>, <a href="https://arxiv.org/format/1608.01374">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/10.3847/0004-637X/832/2/140">10.3847/0004-637X/832/2/140 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Discovery of Rapidly Moving Partial X-ray Absorbers within gamma Cassiopeiae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">K. Hamaguchi</a>, <a href="/search/?searchtype=author&query=Oskinova%2C+L">L. Oskinova</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">C. M. P. Russell</a>, <a href="/search/?searchtype=author&query=Petre%2C+R">R. Petre</a>, <a href="/search/?searchtype=author&query=Enoto%2C+T">T. Enoto</a>, <a href="/search/?searchtype=author&query=Morihana%2C+K">K. Morihana</a>, <a href="/search/?searchtype=author&query=Ishida%2C+M">M. Ishida</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="1608.01374v1-abstract-short" style="display: inline;"> Gamma Cassiopeiae is an enigmatic Be star with unusually strong hard X-ray emission. The Suzaku observatory detected six rapid X-ray spectral hardening events called "softness dips" in a ~100 ksec duration observation in 2011. All the softness dip events show symmetric softness ratio variations, and some of them have flat bottoms apparently due to saturation. The softness dip spectra are best desc… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1608.01374v1-abstract-full').style.display = 'inline'; document.getElementById('1608.01374v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1608.01374v1-abstract-full" style="display: none;"> Gamma Cassiopeiae is an enigmatic Be star with unusually strong hard X-ray emission. The Suzaku observatory detected six rapid X-ray spectral hardening events called "softness dips" in a ~100 ksec duration observation in 2011. All the softness dip events show symmetric softness ratio variations, and some of them have flat bottoms apparently due to saturation. The softness dip spectra are best described by either ~40% or ~70% partial covering absorption to kT ~12 keV plasma emission by matter with a neutral hydrogen column density of ~2-8e21 cm-2, while the spectrum outside of these dips is almost free of absorption. This result suggests the presence of two distinct X-ray emitting spots in the gamma Cas system, perhaps on a white dwarf companion with dipole mass accretion. The partial covering absorbers may be blobs in the Be stellar wind, the Be disk, or rotating around the white dwarf companion. Weak correlations of the softness ratios to the hard X-ray flux suggest the presence of stable plasmas at kT ~0.9 and 5 keV, which may originate from the Be or white dwarf winds. The formation of a Be star and white dwarf binary system requires mass transfer between two stars; gamma Cas may have experienced such activity in the past. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1608.01374v1-abstract-full').style.display = 'none'; document.getElementById('1608.01374v1-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 August, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2016. </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, 5 figures, accepted for publication in 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/1607.01562">arXiv:1607.01562</a> <span> [<a href="https://arxiv.org/pdf/1607.01562">pdf</a>, <a href="https://arxiv.org/format/1607.01562">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/10.1093/mnras/stw2584">10.1093/mnras/stw2584 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Modelling the thermal X-ray emission around the Galactic Centre from colliding Wolf-Rayet winds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Wang%2C+Q+D">Q. Daniel Wang</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</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="1607.01562v3-abstract-short" style="display: inline;"> The Galactic Centre is a hotbed of astrophysical activity, with the injection of wind material from $\sim$30 massive Wolf-Rayet (WR) stars orbiting within 12 arcsec of the supermassive black hole (SMBH) playing an important role. Hydrodynamic simulations of such colliding and accreting winds produce a complex density and temperature structure of cold wind material shocking with the ambient medium,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1607.01562v3-abstract-full').style.display = 'inline'; document.getElementById('1607.01562v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1607.01562v3-abstract-full" style="display: none;"> The Galactic Centre is a hotbed of astrophysical activity, with the injection of wind material from $\sim$30 massive Wolf-Rayet (WR) stars orbiting within 12 arcsec of the supermassive black hole (SMBH) playing an important role. Hydrodynamic simulations of such colliding and accreting winds produce a complex density and temperature structure of cold wind material shocking with the ambient medium, creating a large reservoir of hot, X-ray-emitting gas. This work aims to confront the 3 Ms of Chandra X-ray Visionary Program observations of this diffuse emission by computing the X-ray emission from these hydrodynamic simulations of the colliding WR winds, amid exploring a variety of SMBH feedback mechanisms. The major success of the model is that it reproduces the spectral shape from the 2-5 arcsec ring around the SMBH, where most of the stellar wind material that is ultimately captured by Sgr A* is shock-heated and thermalised. This naturally explains that the hot gas comes from colliding WR winds, and that the wind speeds of these stars are, in general, well constrained. The flux level of these spectra, as well as 12 $\times$ 12-arcsec$^2$ images of 4-9 keV, shows that the X-ray flux is tied to the SMBH feedback strength; stronger feedback clears out more hot gas, thereby decreasing the thermal X-ray emission. The model in which Sgr A* produced an intermediate-strength outflow during the last few centuries best matches the observations to within about 10 per cent, showing that SMBH feedback is required to interpret the X-ray emission in this region. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1607.01562v3-abstract-full').style.display = 'none'; document.getElementById('1607.01562v3-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> 1 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 July, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2016. </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, 8 figures, published in MNRAS</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2017, MNRAS, 464, 4958-4965 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1606.03655">arXiv:1606.03655</a> <span> [<a href="https://arxiv.org/pdf/1606.03655">pdf</a>, <a href="https://arxiv.org/ps/1606.03655">ps</a>, <a href="https://arxiv.org/format/1606.03655">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> </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/10.1093/mnras/stw1415">10.1093/mnras/stw1415 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> To $v_\infty$ and beyond! The He I absorption variability across the 2014.6 periastron passage of $畏$ Carinae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</a>, <a href="/search/?searchtype=author&query=St-Jean%2C+L">Lucas St-Jean</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Damineli%2C+A">Augusto Damineli</a>, <a href="/search/?searchtype=author&query=Teodoro%2C+M">Mairan Teodoro</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Walter%2C+F+M">Frederick M. Walter</a>, <a href="/search/?searchtype=author&query=Clementel%2C+N">Nicola Clementel</a>, <a href="/search/?searchtype=author&query=Groh%2C+J+H">Jos茅 H. Groh</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Hillier%2C+D+J">D. John Hillier</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="1606.03655v1-abstract-short" style="display: inline;"> We have monitored the massive binary star $畏$ Carinae with the CTIO/SMARTS 1.5~m telescope and CHIRON spectrograph from the previous apastron passage of the system through the recent 2014.6 periastron passage. Our monitoring has resulted in a large, homogeneous data set with an unprecedented time-sampling, spectral resolving power, and signal-to-noise. This allowed us to investigate temporal varia… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1606.03655v1-abstract-full').style.display = 'inline'; document.getElementById('1606.03655v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1606.03655v1-abstract-full" style="display: none;"> We have monitored the massive binary star $畏$ Carinae with the CTIO/SMARTS 1.5~m telescope and CHIRON spectrograph from the previous apastron passage of the system through the recent 2014.6 periastron passage. Our monitoring has resulted in a large, homogeneous data set with an unprecedented time-sampling, spectral resolving power, and signal-to-noise. This allowed us to investigate temporal variability previously unexplored in the system and discover a kinematic structure in the P Cygni absorption troughs of neutral helium wind lines. The features observed occurred prior to the periastron passage and are seen as we look through the trailing arm of the wind-wind collision shock cone. We show that the bulk of the variability is repeatable across the last five periastron passages, and that the absorption occurs in the inner 230 AU of the system. In addition, we found an additional, high-velocity absorption component super-imposed on the P Cygni absorption troughs that has been previously un-observed in these lines, but which bears resemblance to the observations of the He~I $位$10830 脜 feature across previous cycles. Through a comparison of the current smoothed particle hydrodynamical simulations, we show that the observed variations are likely caused by instabilities in the wind-wind collision region in our line-of-sight, coupled with stochastic variability related to clumping in the winds. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1606.03655v1-abstract-full').style.display = 'none'; document.getElementById('1606.03655v1-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> 11 June, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2016. </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 to MNRAS, 28 pages including 14 figures and a 9 page appendix</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.01629">arXiv:1603.01629</a> <span> [<a href="https://arxiv.org/pdf/1603.01629">pdf</a>, <a href="https://arxiv.org/format/1603.01629">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="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/10.1093/mnras/stw339">10.1093/mnras/stw339 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Modelling the Central Constant Emission X-ray component of eta Carinae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">Stanley P. Owocki</a>, <a href="/search/?searchtype=author&query=Hillier%2C+D+J">D. John Hillier</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="1603.01629v1-abstract-short" style="display: inline;"> The X-ray emission of $畏$ Carinae shows multiple features at various spatial and temporal scales. The central constant emission (CCE) component is centred on the binary and arises from spatial scales much smaller than the bipolar Homunculus nebula, but likely larger than the central wind--wind collision region between the stars as it does not vary over the $\sim$2-3 month X-ray minimum when it can… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.01629v1-abstract-full').style.display = 'inline'; document.getElementById('1603.01629v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.01629v1-abstract-full" style="display: none;"> The X-ray emission of $畏$ Carinae shows multiple features at various spatial and temporal scales. The central constant emission (CCE) component is centred on the binary and arises from spatial scales much smaller than the bipolar Homunculus nebula, but likely larger than the central wind--wind collision region between the stars as it does not vary over the $\sim$2-3 month X-ray minimum when it can be observed. Using large-scale 3D smoothed particle hydrodynamics (SPH) simulations, we model both the colliding-wind region between the stars, and the region where the secondary wind collides with primary wind ejected from the previous periastron passage. The simulations extend out to one hundred semimajor axes and make two limiting assumptions (strong coupling and no coupling) about the influence of the primary radiation field on the secondary wind. We perform 3D radiative transfer calculations on the SPH output to synthesize the X-ray emission, with the aim of reproducing the CCE spectrum. For the preferred primary mass-loss rate $\dot{M}_A\approx8.5\times10^{-4}$ M$_\odot$ yr$^{-1}$, the model spectra well reproduce the observation as the strong- and no-coupling spectra bound the CCE observation for longitude of periastron $蠅\approx252^\circ$, and bound/converge on the observation for $蠅\approx90^\circ$. This suggests that $畏$ Carinae has moderate coupling between the primary radiation and secondary wind, that both the region between the stars and the comoving collision on the backside of the secondary generate the CCE, and that the CCE cannot place constraints on the binary's line of sight. We also discuss comparisons with common X-ray fitting parameters. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.01629v1-abstract-full').style.display = 'none'; document.getElementById('1603.01629v1-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 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2016. </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, 15 figures, accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1602.01148">arXiv:1602.01148</a> <span> [<a href="https://arxiv.org/pdf/1602.01148">pdf</a>, <a href="https://arxiv.org/ps/1602.01148">ps</a>, <a href="https://arxiv.org/format/1602.01148">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="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/10.3847/0004-637X/817/1/23">10.3847/0004-637X/817/1/23 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Eta Carinae's Thermal X-ray Tail Measured with XMM-Newton and NuSTAR </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Takahashi%2C+H">Hiromitsu Takahashi</a>, <a href="/search/?searchtype=author&query=Grefenstette%2C+B+W">Brian W. Grefenstette</a>, <a href="/search/?searchtype=author&query=Yuasa%2C+T">Takayuki Yuasa</a>, <a href="/search/?searchtype=author&query=Stuhlinger%2C+M">Martin Stuhlinger</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Sharma%2C+N">Neetika Sharma</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Groh%2C+J">Jose Groh</a>, <a href="/search/?searchtype=author&query=Pittard%2C+J+M">Julian M. Pittard</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S">Stanley Owocki</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="1602.01148v1-abstract-short" style="display: inline;"> The evolved, massive highly eccentric binary system, eta Carinae, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission associated with eta Car extending up to ~50 k… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.01148v1-abstract-full').style.display = 'inline'; document.getElementById('1602.01148v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1602.01148v1-abstract-full" style="display: none;"> The evolved, massive highly eccentric binary system, eta Carinae, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission associated with eta Car extending up to ~50 keV for the first time. The NuSTAR spectrum above 10 keV can be fit with the bremsstrahlung tail from a kT ~6 keV plasma. This temperature is Delta kT ~2 keV higher than those measured from the iron K emission line complex, if the shocked gas is in collisional ionization equilibrium. This result may suggest that the companion star's pre-shock wind velocity is underestimated. The NuSTAR observation near the X-ray minimum state showed a gradual decline in the X-ray emission by 40% at energies above 5 keV in a day, the largest rate of change of the X-ray flux yet observed in individual eta Car observations. The column density to the hardest emission component, NH ~1e24 cm-2, marked one of the highest values ever observed for eta Car, strongly suggesting increased obscuration of the wind-wind colliding X-ray emission by the thick primary stellar wind prior to superior conjunction. Neither observation detected the power-law component in the extremely hard band that INTEGRAL and Suzaku observed prior to 2011. If the non-detection by NuSTAR is caused by absorption, the power-law source must be small and located very near the WWC apex. Alternatively, it may be that the power-law source is not related to either eta Car or the GeV gamma-ray source. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.01148v1-abstract-full').style.display = 'none'; document.getElementById('1602.01148v1-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 February, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2016. </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">24 pages, 6 figures, 2 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, 817:23, 2016 January 20 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1511.01150">arXiv:1511.01150</a> <span> [<a href="https://arxiv.org/pdf/1511.01150">pdf</a>, <a href="https://arxiv.org/format/1511.01150">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"> Hydrodynamic and radiative transfer modeling of X-ray emission from colliding WR winds: WR 140 & the Galactic center </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Cuadra%2C+J">Jorge Cuadra</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">Stanley P. Owocki</a>, <a href="/search/?searchtype=author&query=Wang%2C+Q+D">Q. Daniel Wang</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Sugawara%2C+Y">Yasuharu Sugawara</a>, <a href="/search/?searchtype=author&query=Pollock%2C+A+M+T">Andrew M. T. Pollock</a>, <a href="/search/?searchtype=author&query=Kallman%2C+T+R">Timothy R. Kallman</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="1511.01150v1-abstract-short" style="display: inline;"> Colliding Wolf-Rayet (WR) winds produce thermal X-ray emission widely observed by X-ray telescopes. In wide WR+O binaries, such as WR 140, the X-ray flux is tied to the orbital phase, and is a direct probe of the winds' properties. In the Galactic center, $\sim$30 WRs orbit the super massive black hole (SMBH) within $\sim$10", leading to a smorgasbord of wind-wind collisions. To model the X-ray em… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1511.01150v1-abstract-full').style.display = 'inline'; document.getElementById('1511.01150v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1511.01150v1-abstract-full" style="display: none;"> Colliding Wolf-Rayet (WR) winds produce thermal X-ray emission widely observed by X-ray telescopes. In wide WR+O binaries, such as WR 140, the X-ray flux is tied to the orbital phase, and is a direct probe of the winds' properties. In the Galactic center, $\sim$30 WRs orbit the super massive black hole (SMBH) within $\sim$10", leading to a smorgasbord of wind-wind collisions. To model the X-ray emission of WR 140 and the Galactic center, we perform 3D hydrodynamic simulations to trace the complex gaseous flows, and then carry out 3D radiative transfer calculations to compute the variable X-ray spectra. The model WR 140 RXTE light curve matches the data well for all phases except the X-ray minimum associated with periastron, while the model spectra agree with the RXTE hardness ratio and the shape of the Suzaku observations throughout the orbit. The Galactic center model of the Chandra flux and spectral shape match well in the region r$<$3", but the model flux falls off too rapidly beyond this radius. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1511.01150v1-abstract-full').style.display = 'none'; document.getElementById('1511.01150v1-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 November, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2015. </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">3 pages, 5 figures, to appear in the proceedings of the "International Workshop on Wolf-Rayet Stars", eds. W.-R. Hamann, A. Sander, and H. Todt</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1507.07961">arXiv:1507.07961</a> <span> [<a href="https://arxiv.org/pdf/1507.07961">pdf</a>, <a href="https://arxiv.org/format/1507.07961">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="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> The X-ray Lightcurve of the Supermassive star eta Carinae, 1996--2014 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">M. F. Corcoran</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">K. Hamaguchi</a>, <a href="/search/?searchtype=author&query=Liburd%2C+J+K">J. K. Liburd</a>, <a href="/search/?searchtype=author&query=Morris%2C+D">D. Morris</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">T. R. Gull</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">T. I. Madura</a>, <a href="/search/?searchtype=author&query=Teodoro%2C+M">M. Teodoro</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">A. F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">N. D. Richardson</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">C. M. P. Russell</a>, <a href="/search/?searchtype=author&query=Pollock%2C+A+M+T">A. M. T. Pollock</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">S. P. Owocki</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="1507.07961v1-abstract-short" style="display: inline;"> Eta Carinae is the nearest example of a supermassive, superluminous, unstable star. Mass loss from the system is critical in shaping its circumstellar medium and in determining its ultimate fate. Eta Car currently loses mass via a dense, slow stellar wind and possesses one of the largest mass loss rates known. It is prone to episodes of extreme mass ejection via eruptions from some as-yet unspecif… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1507.07961v1-abstract-full').style.display = 'inline'; document.getElementById('1507.07961v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1507.07961v1-abstract-full" style="display: none;"> Eta Carinae is the nearest example of a supermassive, superluminous, unstable star. Mass loss from the system is critical in shaping its circumstellar medium and in determining its ultimate fate. Eta Car currently loses mass via a dense, slow stellar wind and possesses one of the largest mass loss rates known. It is prone to episodes of extreme mass ejection via eruptions from some as-yet unspecified cause; the best examples of this are the large-scale eruptions which occurred in 19th century. Eta Car is a colliding wind binary in which strong variations in X-ray emission and in other wavebands are driven by the violent collision of the wind of eta Car-A and the fast, less dense wind of an otherwise hidden companion star. X-ray variations are the simplest diagnostic we have to study the wind-wind collision and allow us to measure the state of the stellar mass loss from both stars. We present the X-ray lightcurve over the last 20 years from ROSAT observations and monitoring with the Rossi X-ray Timing Explorer and the X-ray Telescope on the Swift satellite. We compare and contrast the behavior of the X-ray emission from the system over that timespan, including surprising variations during the 2014 X-ray minimum. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1507.07961v1-abstract-full').style.display = 'none'; document.getElementById('1507.07961v1-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> 28 July, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2015. </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">International Workshop on Wolf-Rayet Stars, Potsdam, Germany, 1 - 5 June 2015</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1507.05101">arXiv:1507.05101</a> <span> [<a href="https://arxiv.org/pdf/1507.05101">pdf</a>, <a href="https://arxiv.org/format/1507.05101">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="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/10.1088/0004-637X/809/2/132">10.1088/0004-637X/809/2/132 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Coordinated X-ray and Optical Campaign on the Nearest Massive Eclipsing Binary, Delta Ori Aa: I. Overview of the X-ray Spectrum </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">M. F. Corcoran</a>, <a href="/search/?searchtype=author&query=Nichols%2C+J+S">J. S. Nichols</a>, <a href="/search/?searchtype=author&query=Pablo%2C+H">H. Pablo</a>, <a href="/search/?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/?searchtype=author&query=Pollock%2C+A+M+T">A. M. T. Pollock</a>, <a href="/search/?searchtype=author&query=Waldron%2C+W+L">W. L. Waldron</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">A. F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">N. D. Richardson</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">C. M. P. Russell</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">K. Hamaguchi</a>, <a href="/search/?searchtype=author&query=Huenemoerder%2C+D+P">D. P. Huenemoerder</a>, <a href="/search/?searchtype=author&query=Oskinova%2C+L">L. Oskinova</a>, <a href="/search/?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/?searchtype=author&query=Naze%2C+Y">Y. Naze</a>, <a href="/search/?searchtype=author&query=Ignace%2C+R">R. Ignace</a>, <a href="/search/?searchtype=author&query=Evans%2C+N+R">N. R. Evans</a>, <a href="/search/?searchtype=author&query=Lomax%2C+J+R">J. R. Lomax</a>, <a href="/search/?searchtype=author&query=Hoffman%2C+J+L">J. L. Hoffman</a>, <a href="/search/?searchtype=author&query=Gayley%2C+K">K. Gayley</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">S. P. Owocki</a>, <a href="/search/?searchtype=author&query=Leutenegger%2C+M">M. Leutenegger</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">T. R. Gull</a>, <a href="/search/?searchtype=author&query=Hole%2C+K+T">K. T. Hole</a>, <a href="/search/?searchtype=author&query=Lauer%2C+J">J. Lauer</a>, <a href="/search/?searchtype=author&query=Iping%2C+R+C">R. C. Iping</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="1507.05101v2-abstract-short" style="display: inline;"> We present an overview of four phase-constrained Chandra HETGS X-ray observations of Delta Ori A. Delta Ori A is actually a triple system which includes the nearest massive eclipsing spectroscopic binary, Delta Ori Aa, the only such object which can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, Delta Ori Aa2, has a much lower X-ray luminosity than the br… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1507.05101v2-abstract-full').style.display = 'inline'; document.getElementById('1507.05101v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1507.05101v2-abstract-full" style="display: none;"> We present an overview of four phase-constrained Chandra HETGS X-ray observations of Delta Ori A. Delta Ori A is actually a triple system which includes the nearest massive eclipsing spectroscopic binary, Delta Ori Aa, the only such object which can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, Delta Ori Aa2, has a much lower X-ray luminosity than the brighter primary, Delta Ori A provides a unique system with which to test the spatial distribution of the X-ray emitting gas around Delta Ori Aa1 via occultation by the photosphere of and wind cavity around the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ksec and covering nearly the entire binary orbit. Companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities simultaneous with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectrum. We find that the X-ray emission is dominated by embedded wind shock emission from star Aa1, with little contribution from the tertiary star Ab or the shocked gas produced by the collision of the wind of Aa1 against the surface of Aa2. We find a similar temperature distribution to previous X-ray spectrum analyses. We also show that the line half-widths are about $0.3-0.5\times$ the terminal velocity of the wind of star Aa1. We find a strong anti-correlation between line widths and the line excitation energy, which suggests that longer-wavelength, lower-temperature lines form farther out in the wind. Our analysis also indicates that the ratio of the intensities of the strong and weak lines of \ion{Fe}{17} and \ion{Ne}{10} are inconsistent with model predictions, which may be an effect of resonance scattering <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1507.05101v2-abstract-full').style.display = 'none'; document.getElementById('1507.05101v2-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 July, 2015; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 July, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2015. </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 ApJ; revised according to ApJ proof</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJ, 809, 132 (15p,2015) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1507.04972">arXiv:1507.04972</a> <span> [<a href="https://arxiv.org/pdf/1507.04972">pdf</a>, <a href="https://arxiv.org/ps/1507.04972">ps</a>, <a href="https://arxiv.org/format/1507.04972">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/10.1088/0004-637X/809/2/133">10.1088/0004-637X/809/2/133 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Coordinated X-ray and Optical Campaign of the Nearby Massive Binary $未$ Orionis Aa: II. X-ray Variability </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Nichols%2C+J+S">J. S. Nichols</a>, <a href="/search/?searchtype=author&query=Huenemoerder%2C+D+P">D. P. Huenemoerder</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">M. F. Corcoran</a>, <a href="/search/?searchtype=author&query=Waldron%2C+W">W. Waldron</a>, <a href="/search/?searchtype=author&query=Naz%C3%A9%2C+Y">Y. Naz茅</a>, <a href="/search/?searchtype=author&query=Pollock%2C+A+M+T">A. M. T. Pollock</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">A. F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Lauer%2C+J">J. Lauer</a>, <a href="/search/?searchtype=author&query=Shenar%2C+T">T. Shenar</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">C. M. P. Russell</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">N. D. Richardson</a>, <a href="/search/?searchtype=author&query=Pablo%2C+H">H. Pablo</a>, <a href="/search/?searchtype=author&query=Evans%2C+N+R">N R. Evans</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">K. Hamaguchi</a>, <a href="/search/?searchtype=author&query=Gull%2C+T">T. Gull</a>, <a href="/search/?searchtype=author&query=Hamann%2C+W+R">W. R. Hamann</a>, <a href="/search/?searchtype=author&query=Oskinova%2C+L">L. Oskinova</a>, <a href="/search/?searchtype=author&query=Ignace%2C+R">R. Ignace</a>, <a href="/search/?searchtype=author&query=Hoffman%2C+J+L">Jennifer L. Hoffman</a>, <a href="/search/?searchtype=author&query=Hole%2C+K+T">K. T. Hole</a>, <a href="/search/?searchtype=author&query=Lomax%2C+J+R">J. R. Lomax</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="1507.04972v1-abstract-short" style="display: inline;"> We present time-resolved and phase-resolved variability studies of an extensive X-ray high-resolution spectral dataset of the $未$ Orionis Aa binary system. The four observations, obtained with Chandra ACIS HETGS, have a total exposure time of ~479 ks and provide nearly complete binary phase coverage. Variability of the total X-ray flux in the range 5-25 $脜$ is confirmed, with maximum amplitude of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1507.04972v1-abstract-full').style.display = 'inline'; document.getElementById('1507.04972v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1507.04972v1-abstract-full" style="display: none;"> We present time-resolved and phase-resolved variability studies of an extensive X-ray high-resolution spectral dataset of the $未$ Orionis Aa binary system. The four observations, obtained with Chandra ACIS HETGS, have a total exposure time of ~479 ks and provide nearly complete binary phase coverage. Variability of the total X-ray flux in the range 5-25 $脜$ is confirmed, with maximum amplitude of about +/-15% within a single ~125 ks observation. Periods of 4.76d and 2.04d are found in the total X-ray flux, as well as an apparent overall increase in flux level throughout the 9-day observational campaign. Using 40 ks contiguous spectra derived from the original observations, we investigate variability of emission line parameters and ratios. Several emission lines are shown to be variable, including S XV, Si XIII, and Ne IX. For the first time, variations of the X-ray emission line widths as a function of the binary phase are found in a binary system, with the smallest widths at phase=0.0 when the secondary $未$ Orionis Aa2 is at inferior conjunction. Using 3D hydrodynamic modeling of the interacting winds, we relate the emission line width variability to the presence of a wind cavity created by a wind-wind collision, which is effectively void of embedded wind shocks and is carved out of the X-ray-producing primary wind, thus producing phase-locked X-ray variability. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1507.04972v1-abstract-full').style.display = 'none'; document.getElementById('1507.04972v1-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, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2015. </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">36 pages, 14 Tables, 19 Figures, accepted by ApJ, one of 4 related papers to be published together</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJ, 809, 133 (21p,2015) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1504.08002">arXiv:1504.08002</a> <span> [<a href="https://arxiv.org/pdf/1504.08002">pdf</a>, <a href="https://arxiv.org/ps/1504.08002">ps</a>, <a href="https://arxiv.org/format/1504.08002">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="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/10.1088/0004-637X/809/2/134">10.1088/0004-637X/809/2/134 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, delta Orionis Aa: III. Analysis of Optical Photometric MOST and Spectroscopic (Ground Based) Variations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Pablo%2C+H">Herbert Pablo</a>, <a href="/search/?searchtype=author&query=Richardson%2C+N+D">Noel D. Richardson</a>, <a href="/search/?searchtype=author&query=Moffat%2C+A+F+J">Anthony F. J. Moffat</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M">Michael Corcoran</a>, <a href="/search/?searchtype=author&query=Shenar%2C+T">Tomer Shenar</a>, <a href="/search/?searchtype=author&query=Benvenuto%2C+O">Omar Benvenuto</a>, <a href="/search/?searchtype=author&query=Fuller%2C+J">Jim Fuller</a>, <a href="/search/?searchtype=author&query=Naze%2C+Y">Yael Naze</a>, <a href="/search/?searchtype=author&query=Hoffman%2C+J+L">Jennifer L. Hoffman</a>, <a href="/search/?searchtype=author&query=Miroshnichenko%2C+A">Anatoly Miroshnichenko</a>, <a href="/search/?searchtype=author&query=Apellaniz%2C+J+M">Jesus Maiz Apellaniz</a>, <a href="/search/?searchtype=author&query=Evans%2C+N">Nancy Evans</a>, <a href="/search/?searchtype=author&query=Eversberg%2C+T">Thomas Eversberg</a>, <a href="/search/?searchtype=author&query=Gayley%2C+K">Ken Gayley</a>, <a href="/search/?searchtype=author&query=Gull%2C+T">Ted Gull</a>, <a href="/search/?searchtype=author&query=Hamaguch%2C+K">Kenji Hamaguch</a>, <a href="/search/?searchtype=author&query=Hamann%2C+W">Wolf-Rainer Hamann</a>, <a href="/search/?searchtype=author&query=Henrichs%2C+H">Huib Henrichs</a>, <a href="/search/?searchtype=author&query=Hole%2C+T">Tabetha Hole</a>, <a href="/search/?searchtype=author&query=Ignace%2C+R">Richard Ignace</a>, <a href="/search/?searchtype=author&query=Iping%2C+R">Rosina Iping</a>, <a href="/search/?searchtype=author&query=Lauer%2C+J">Jennifer Lauer</a>, <a href="/search/?searchtype=author&query=Leutenegger%2C+M">Maurice Leutenegger</a>, <a href="/search/?searchtype=author&query=Lomax%2C+J">Jamie Lomax</a>, <a href="/search/?searchtype=author&query=Nichols%2C+J">Joy Nichols</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="1504.08002v1-abstract-short" style="display: inline;"> We report on both high-precision photometry from the MOST space telescope and ground-based spectroscopy of the triple system delta Ori A consisting of a binary O9.5II+early-B (Aa1 and Aa2) with P = 5.7d, and a more distant tertiary (O9 IV P > 400 yrs). This data was collected in concert with X-ray spectroscopy from the Chandra X-ray Observatory. Thanks to continuous coverage for 3 weeks, the MOST… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1504.08002v1-abstract-full').style.display = 'inline'; document.getElementById('1504.08002v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1504.08002v1-abstract-full" style="display: none;"> We report on both high-precision photometry from the MOST space telescope and ground-based spectroscopy of the triple system delta Ori A consisting of a binary O9.5II+early-B (Aa1 and Aa2) with P = 5.7d, and a more distant tertiary (O9 IV P > 400 yrs). This data was collected in concert with X-ray spectroscopy from the Chandra X-ray Observatory. Thanks to continuous coverage for 3 weeks, the MOST light curve reveals clear eclipses between Aa1 and Aa2 for the first time in non-phased data. From the spectroscopy we have a well constrained radial velocity curve of Aa1. While we are unable to recover radial velocity variations of the secondary star, we are able to constrain several fundamental parameters of this system and determine an approximate mass of the primary using apsidal motion. We also detected second order modulations at 12 separate frequencies with spacings indicative of tidally influenced oscillations. These spacings have never been seen in a massive binary, making this system one of only a handful of such binaries which show evidence for tidally induced pulsations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1504.08002v1-abstract-full').style.display = 'none'; document.getElementById('1504.08002v1-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 April, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2015. </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 to Apj. Part of a 4 paper series. 11 figures, 4 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJ, 809, 134 (11p,2015) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1410.6171">arXiv:1410.6171</a> <span> [<a href="https://arxiv.org/pdf/1410.6171">pdf</a>, <a href="https://arxiv.org/ps/1410.6171">ps</a>, <a href="https://arxiv.org/format/1410.6171">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/10.1088/0004-637X/795/2/119">10.1088/0004-637X/795/2/119 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Suzaku Monitoring of Hard X-ray Emission from Eta Carinae over a Single Binary Orbital Cycle </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Takahashi%2C+H">Hiromitsu Takahashi</a>, <a href="/search/?searchtype=author&query=Yuasa%2C+T">Takayuki Yuasa</a>, <a href="/search/?searchtype=author&query=Ishida%2C+M">Manabu Ishida</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Pittard%2C+J+M">Julian M. Pittard</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</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="1410.6171v1-abstract-short" style="display: inline;"> The Suzaku X-ray observatory monitored the supermassive binary system Eta Carinae 10 times during the whole 5.5 year orbital cycle between 2005-2011. This series of observations presents the first long-term monitoring of this enigmatic system in the extremely hard X-ray band between 15-40 keV. During most of the orbit, the 15-25 keV emission varied similarly to the 2-10 keV emission, indicating an… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1410.6171v1-abstract-full').style.display = 'inline'; document.getElementById('1410.6171v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1410.6171v1-abstract-full" style="display: none;"> The Suzaku X-ray observatory monitored the supermassive binary system Eta Carinae 10 times during the whole 5.5 year orbital cycle between 2005-2011. This series of observations presents the first long-term monitoring of this enigmatic system in the extremely hard X-ray band between 15-40 keV. During most of the orbit, the 15-25 keV emission varied similarly to the 2-10 keV emission, indicating an origin in the hard energy tail of the kT ~4 keV wind-wind collision (WWC) plasma. However, the 15-25 keV emission declined only by a factor of 3 around periastron when the 2-10 keV emission dropped by two orders of magnitude due probably to an eclipse of the WWC plasma. The observed minimum in the 15-25 keV emission occurred after the 2-10 keV flux had already recovered by a factor of ~3. This may mean that the WWC activity was strong, but hidden behind the thick primary stellar wind during the eclipse. The 25-40 keV flux was rather constant through the orbital cycle, at the level measured with INTEGRAL in 2004. This result may suggest a connection of this flux component to the gamma-ray source detected in this field. The Helium-like Fe Kalpha line complex at ~6.7 keV became strongly distorted toward periastron as seen in the previous cycle. The 5-9 keV spectra can be reproduced well with a two-component spectral model, which includes plasma in collision equilibrium (CE) and a plasma in non-equilibrium ionization (NEI) with tau ~1e11 cm-3 s-1. The NEI plasma increases in importance toward periastron. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1410.6171v1-abstract-full').style.display = 'none'; document.getElementById('1410.6171v1-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 October, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2014. </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, 6 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophysical Journal, 2014, 795, 119 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1410.6117">arXiv:1410.6117</a> <span> [<a href="https://arxiv.org/pdf/1410.6117">pdf</a>, <a href="https://arxiv.org/ps/1410.6117">ps</a>, <a href="https://arxiv.org/format/1410.6117">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> </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/10.1051/0004-6361/201424468">10.1051/0004-6361/201424468 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> V444 Cyg X-ray and polarimetric variability: Radiative and Coriolis forces shape the wind collision region </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Lomax%2C+J+R">Jamie R. Lomax</a>, <a href="/search/?searchtype=author&query=Naze%2C+Y">Yael Naze</a>, <a href="/search/?searchtype=author&query=Hoffman%2C+J+L">Jennifer L. Hoffman</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=De+Becker%2C+M">Michael De Becker</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Davidson%2C+J+W">James W. Davidson</a>, <a href="/search/?searchtype=author&query=Neilson%2C+H+R">Hilding R. Neilson</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S">Stan Owocki</a>, <a href="/search/?searchtype=author&query=Pittard%2C+J+M">Julian M. Pittard</a>, <a href="/search/?searchtype=author&query=Pollock%2C+A+M+T">Andy M. T. Pollock</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="1410.6117v1-abstract-short" style="display: inline;"> We present results from a study of the eclipsing, colliding-wind binary V444 Cyg that uses a combination of X-ray and optical spectropolarimetric methods to describe the 3-D nature of the shock and wind structure within the system. We have created the most complete X-ray light curve of V444 Cyg to date using 40 ksec of new data from Swift, and 200 ksec of new and archived XMM-Newton observations.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1410.6117v1-abstract-full').style.display = 'inline'; document.getElementById('1410.6117v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1410.6117v1-abstract-full" style="display: none;"> We present results from a study of the eclipsing, colliding-wind binary V444 Cyg that uses a combination of X-ray and optical spectropolarimetric methods to describe the 3-D nature of the shock and wind structure within the system. We have created the most complete X-ray light curve of V444 Cyg to date using 40 ksec of new data from Swift, and 200 ksec of new and archived XMM-Newton observations. In addition, we have characterized the intrinsic, polarimetric phase-dependent behavior of the strongest optical emission lines using data obtained with the University of Wisconsin's Half-Wave Spectropolarimeter. We have detected evidence of the Coriolis distortion of the wind-wind collision in the X-ray regime, which manifests itself through asymmetric behavior around the eclipses in the system's X-ray light curves. The large opening angle of the X-ray emitting region, as well as its location (i.e. the WN wind does not collide with the O star, but rather its wind) are evidence of radiative braking/inhibition occurring within the system. Additionally, the polarimetric results show evidence of the cavity the wind-wind collision region carves out of the Wolf-Rayet star's wind. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1410.6117v1-abstract-full').style.display = 'none'; document.getElementById('1410.6117v1-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 October, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2014. </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, 14 figures, accepted 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 573, A43 (2015) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1405.4808">arXiv:1405.4808</a> <span> [<a href="https://arxiv.org/pdf/1405.4808">pdf</a>, <a href="https://arxiv.org/ps/1405.4808">ps</a>, <a href="https://arxiv.org/format/1405.4808">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"> 3D Dynamical Modeling of Wind Accretion in Cyg X-3 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Okazaki%2C+A+T">Atsuo T. Okazaki</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</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="1405.4808v1-abstract-short" style="display: inline;"> Cyg X-3 is a high mass X-ray binary consisting of a Wolf-Rayet star and a compact object in a very short orbital period of 4.8h. The only confirmed microquasar with high energy gamma-ray emission, Cyg X-3 provides a unique opportunity to study the relationship between the accretion power and the power in high energy emission. Because of a compact orbit and a slow Wolf-Rayet wind, the flow structur… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1405.4808v1-abstract-full').style.display = 'inline'; document.getElementById('1405.4808v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1405.4808v1-abstract-full" style="display: none;"> Cyg X-3 is a high mass X-ray binary consisting of a Wolf-Rayet star and a compact object in a very short orbital period of 4.8h. The only confirmed microquasar with high energy gamma-ray emission, Cyg X-3 provides a unique opportunity to study the relationship between the accretion power and the power in high energy emission. Because of a compact orbit and a slow Wolf-Rayet wind, the flow structure around the compact object is thought to be strongly affected by the orbital motion, details of which can be obtained only by numerical simulations. In this paper, we report on the results from 3D hydrodynamic simulations of the wind accretion in Cyg X-3. For simplicity we adopt an anti-gravity-like force that emulates the radiative acceleration consistent with the beta-velocity wind. Due to the rapid orbital motion, the flow around the compact object has large density gradients. As a result, the accretion rate onto the compact object is significantly lower than that of the Bondi-Hoyle-Lyttleton rate. We also calculate the model X-ray light curve. Although it roughly agrees with the observed light curve, more detailed modeling is needed for detailed comparison. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1405.4808v1-abstract-full').style.display = 'none'; document.getElementById('1405.4808v1-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 May, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2014. </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">2 pages, 2 figures, Proceedings from "Suzaku-Maxi 2014: Expanding the Frontiers of the X-ray Universe"</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1405.4803">arXiv:1405.4803</a> <span> [<a href="https://arxiv.org/pdf/1405.4803">pdf</a>, <a href="https://arxiv.org/format/1405.4803">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"> 3D Hydrodynamic & Radiative Transfer Models of X-ray Emission from Colliding Wind Binaries </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Okazaki%2C+A+T">Atsuo T. Okazaki</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">Stanley P. Owocki</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Sugawara%2C+Y">Yasuharu Sugawara</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="1405.4803v1-abstract-short" style="display: inline;"> Colliding wind binaries (CWBs) are unique laboratories for X-ray astrophysics. The massive stars in these systems possess powerful stellar winds with speeds up to $\sim$3000 km s$^{-1}$, and their collision leads to hot plasma (up to $\sim10^8$K) that emit thermal X-rays (up to $\sim$10 keV). Many X-ray telescopes have observed CWBs, including Suzaku, and our work aims to model these X-ray observa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1405.4803v1-abstract-full').style.display = 'inline'; document.getElementById('1405.4803v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1405.4803v1-abstract-full" style="display: none;"> Colliding wind binaries (CWBs) are unique laboratories for X-ray astrophysics. The massive stars in these systems possess powerful stellar winds with speeds up to $\sim$3000 km s$^{-1}$, and their collision leads to hot plasma (up to $\sim10^8$K) that emit thermal X-rays (up to $\sim$10 keV). Many X-ray telescopes have observed CWBs, including Suzaku, and our work aims to model these X-ray observations. We use 3D smoothed particle hydrodynamics (SPH) to model the wind-wind interaction, and then perform 3D radiative transfer to compute the emergent X-ray flux, which is folded through X-ray telescopes' response functions to compare directly with observations. In these proceedings, we present our models of Suzaku observations of the multi-year-period, highly eccentric systems $畏$ Carinae and WR 140. The models reproduce the observations well away from periastron passage, but only $畏$ Carinae's X-ray spectrum is reproduced at periastron; the WR 140 model produces too much flux during this more complicated phase. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1405.4803v1-abstract-full').style.display = 'none'; document.getElementById('1405.4803v1-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 May, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2014. </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">2 pages, 3 figures, Proceedings from "Suzaku-MAXI 2014: Expanding the Frontiers of the X-ray Universe"</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1310.0487">arXiv:1310.0487</a> <span> [<a href="https://arxiv.org/pdf/1310.0487">pdf</a>, <a href="https://arxiv.org/ps/1310.0487">ps</a>, <a href="https://arxiv.org/format/1310.0487">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> </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/10.1093/mnras/stt1871">10.1093/mnras/stt1871 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraints on decreases in Eta Carinae's mass loss from 3D hydrodynamic simulations of its binary colliding winds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Okazaki%2C+A+T">Atsuo T. Okazaki</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">Stanley P. Owocki</a>, <a href="/search/?searchtype=author&query=Groh%2C+J+H">Jose H. Groh</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Hamaguchi%2C+K">Kenji Hamaguchi</a>, <a href="/search/?searchtype=author&query=Teodoro%2C+M">Mairan Teodoro</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="1310.0487v1-abstract-short" style="display: inline;"> Recent work suggests that the mass-loss rate of the primary star (Eta A) in the massive colliding wind binary Eta Carinae dropped by a factor of 2-3 between 1999 and 2010. We present results from large- (r=1545au) and small- (r=155au) domain, 3D smoothed particle hydrodynamic (SPH) simulations of Eta Car's colliding winds for 3 Eta A mass-loss rates (2.4, 4.8, and 8.5 x 10^-4 M_sun/yr), investigat… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.0487v1-abstract-full').style.display = 'inline'; document.getElementById('1310.0487v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1310.0487v1-abstract-full" style="display: none;"> Recent work suggests that the mass-loss rate of the primary star (Eta A) in the massive colliding wind binary Eta Carinae dropped by a factor of 2-3 between 1999 and 2010. We present results from large- (r=1545au) and small- (r=155au) domain, 3D smoothed particle hydrodynamic (SPH) simulations of Eta Car's colliding winds for 3 Eta A mass-loss rates (2.4, 4.8, and 8.5 x 10^-4 M_sun/yr), investigating the effects on the dynamics of the binary wind-wind collision (WWC). These simulations include orbital motion, optically thin radiative cooling, and radiative forces. We find that Eta A's mass-loss rate greatly affects the time-dependent hydrodynamics at all spatial scales investigated. The simulations also show that the post-shock wind of the companion star (Eta B) switches from the adiabatic to the radiative-cooling regime during periastron passage. The SPH simulations together with 1D radiative transfer models of Eta A's spectra reveal that a factor of 2 or more drop in Eta A's mass-loss rate should lead to substantial changes in numerous multiwavelength observables. Recent observations are not fully consistent with the model predictions, indicating that any drop in Eta A's mass-loss rate was likely by a factor < 2 and occurred after 2004. We speculate that most of the recent observed changes in Eta Car are due to a small increase in the WWC opening angle that produces significant effects because our line-of-sight to the system lies close to the dense walls of the WWC zone. A modest decrease in Eta A's mass-loss rate may be responsible, but changes in the wind/stellar parameters of Eta B cannot yet be fully ruled out. We suggest observations during Eta Car's next periastron in 2014 to further test for decreases in Eta A's mass-loss rate. If Eta A's mass-loss rate is declining and continues to do so, the 2014 X-ray minimum should be even shorter than that of 2009. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1310.0487v1-abstract-full').style.display = 'none'; document.getElementById('1310.0487v1-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> 1 October, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2013. </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">38 pages, 25 figures, 1 table. Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1111.2226">arXiv:1111.2226</a> <span> [<a href="https://arxiv.org/pdf/1111.2226">pdf</a>, <a href="https://arxiv.org/ps/1111.2226">ps</a>, <a href="https://arxiv.org/format/1111.2226">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> </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/10.1111/j.1365-2966.2011.20165.x">10.1111/j.1365-2966.2011.20165.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Constraining the Absolute Orientation of Eta Carinae's Binary Orbit: A 3-D Dynamical Model for the Broad [Fe III] Emission </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</a>, <a href="/search/?searchtype=author&query=Gull%2C+T+R">Theodore R. Gull</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">Stanley P. Owocki</a>, <a href="/search/?searchtype=author&query=Groh%2C+J+H">Jose H. Groh</a>, <a href="/search/?searchtype=author&query=Okazaki%2C+A+T">Atsuo T. Okazaki</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</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="1111.2226v1-abstract-short" style="display: inline;"> We present a three-dimensional (3-D) dynamical model for the broad [Fe III] emission observed in Eta Carinae using the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS). This model is based on full 3-D Smoothed Particle Hydrodynamics (SPH) simulations of Eta Car's binary colliding winds. Radiative transfer codes are used to generate synthetic spectro-images of [Fe III] emissio… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1111.2226v1-abstract-full').style.display = 'inline'; document.getElementById('1111.2226v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1111.2226v1-abstract-full" style="display: none;"> We present a three-dimensional (3-D) dynamical model for the broad [Fe III] emission observed in Eta Carinae using the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS). This model is based on full 3-D Smoothed Particle Hydrodynamics (SPH) simulations of Eta Car's binary colliding winds. Radiative transfer codes are used to generate synthetic spectro-images of [Fe III] emission line structures at various observed orbital phases and STIS slit position angles (PAs). Through a parameter study that varies the orbital inclination i, the PA 胃 that the orbital plane projection of the line-of-sight makes with the apastron side of the semi-major axis, and the PA on the sky of the orbital axis, we are able, for the first time, to tightly constrain the absolute 3-D orientation of the binary orbit. To simultaneously reproduce the blue-shifted emission arcs observed at orbital phase 0.976, STIS slit PA = +38 degrees, and the temporal variations in emission seen at negative slit PAs, the binary needs to have an i \approx 130 to 145 degrees, 胃 \approx -15 to +30 degrees, and an orbital axis projected on the sky at a PA \approx 302 to 327 degrees east of north. This represents a system with an orbital axis that is closely aligned with the inferred polar axis of the Homunculus nebula, in 3-D. The companion star, Eta B, thus orbits clockwise on the sky and is on the observer's side of the system at apastron. This orientation has important implications for theories for the formation of the Homunculus and helps lay the groundwork for orbital modeling to determine the stellar masses. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1111.2226v1-abstract-full').style.display = 'none'; document.getElementById('1111.2226v1-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 November, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2011. </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, 12 color figures, plus 2 online-only appendices (available in the /anc folder of the Source directory). Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1111.0100">arXiv:1111.0100</a> <span> [<a href="https://arxiv.org/pdf/1111.0100">pdf</a>, <a href="https://arxiv.org/format/1111.0100">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> </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/10.1017/S1743921311011641">10.1017/S1743921311011641 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> X-ray Modeling of 畏 Carinae and WR140 from SPH Simulations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">Stanley P. Owocki</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Okazaki%2C+A+T">Atsuo T. Okazaki</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</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="1111.0100v1-abstract-short" style="display: inline;"> The colliding wind binary (CWB) systems 畏 Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these X-ray light curves and spectra, we apply 3D hydrodynamic simulations of the wind-wind collision using smoothed particle hydrodynamics (SPH),… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1111.0100v1-abstract-full').style.display = 'inline'; document.getElementById('1111.0100v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1111.0100v1-abstract-full" style="display: none;"> The colliding wind binary (CWB) systems 畏 Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these X-ray light curves and spectra, we apply 3D hydrodynamic simulations of the wind-wind collision using smoothed particle hydrodynamics (SPH), with the recent improvements of radiative cooling and the acceleration of the stellar winds according to a 尾 law. For both systems, the 2-10 keV RXTE light curves are well-reproduced in absolute units for most phases, but the light curve dips associated with the periastron passages are not well matched. In WR140, the dip is too weak, and in 畏 Carinae, the large difference in wind speeds of the two stars leads to a hot, post-periastron bubble that produces excess emission toward the end of the X-ray minimum. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1111.0100v1-abstract-full').style.display = 'none'; document.getElementById('1111.0100v1-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 October, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2011. </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">3 pages, 3 figures, to appear in "Four Decades of Research on Massive Stars: A Scientific Meeting in Honour of Anthony F. J. Moffatt", eds. L. Drissen, C. Robert, and N. St-Louis, ASP Conference Series</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1110.1692">arXiv:1110.1692</a> <span> [<a href="https://arxiv.org/pdf/1110.1692">pdf</a>, <a href="https://arxiv.org/format/1110.1692">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> </div> </div> <p class="title is-5 mathjax"> X-ray Modeling of 畏 Carinae and WR140 from SPH Simulations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</a>, <a href="/search/?searchtype=author&query=Okazaki%2C+A+T">Atsuo T. Okazaki</a>, <a href="/search/?searchtype=author&query=Madura%2C+T+I">Thomas I. Madura</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">Stanley P. Owocki</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="1110.1692v1-abstract-short" style="display: inline;"> The colliding wind binary (CWB) systems 畏 Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these RXTE X-ray light curves, we model the wind-wind collision using 3D smoothed particle hydrodynamics (SPH) simulations. Adiabatic simulations… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1110.1692v1-abstract-full').style.display = 'inline'; document.getElementById('1110.1692v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1110.1692v1-abstract-full" style="display: none;"> The colliding wind binary (CWB) systems 畏 Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these RXTE X-ray light curves, we model the wind-wind collision using 3D smoothed particle hydrodynamics (SPH) simulations. Adiabatic simulations that account for the absorption of X-rays from an assumed point source at the apex of the wind-collision shock cone by the distorted winds can closely match the observed 2-10keV RXTE light curves of both 畏 Car and WR140. This point-source model can also explain the early recovery of 畏 Car's X-ray light curve from the 2009.0 minimum by a factor of 2-4 reduction in the mass loss rate of 畏 Car. Our more recent models relax the point-source approximation and account for the spatially extended emission along the wind-wind interaction shock front. For WR140, the computed X-ray light curve again matches the RXTE observations quite well. But for 畏 Car, a hot, post-periastron bubble leads to an emission level that does not match the extended X-ray minimum observed by RXTE. Initial results from incorporating radiative cooling and radiatively-driven wind acceleration via a new anti-gravity approach into the SPH code are also discussed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1110.1692v1-abstract-full').style.display = 'none'; document.getElementById('1110.1692v1-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 October, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2011. </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, 3 figures, Proceedings of the 39th Li茅ge Astrophysical Colloquium, held in Li猫ge 12-16 July 2010, edited by G. Rauw, M. De Becker, Y. Naz茅, J.-M. Vreux, P. Williams</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2011BSRSL..80..719R </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0803.3977">arXiv:0803.3977</a> <span> [<a href="https://arxiv.org/pdf/0803.3977">pdf</a>, <a href="https://arxiv.org/ps/0803.3977">ps</a>, <a href="https://arxiv.org/format/0803.3977">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</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/10.1017/S1743921308020413">10.1017/S1743921308020413 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> 3-D SPH simulations of colliding winds in eta Carinae </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Okazaki%2C+A+T">Atsuo T. Okazaki</a>, <a href="/search/?searchtype=author&query=Owocki%2C+S+P">Stanley P. Owocki</a>, <a href="/search/?searchtype=author&query=Russell%2C+C+M+P">Christopher M. P. Russell</a>, <a href="/search/?searchtype=author&query=Corcoran%2C+M+F">Michael F. Corcoran</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="0803.3977v1-abstract-short" style="display: inline;"> We study colliding winds in the superluminous binary eta Carinae by performing three-dimensional, Smoothed Particle Hydrodynamics (SPH) simulations. For simplicity, we assume both winds to be isothermal. We also assume that wind particles coast without any net external forces. We find that the lower density, faster wind from the secondary carves out a spiral cavity in the higher density, slower… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.3977v1-abstract-full').style.display = 'inline'; document.getElementById('0803.3977v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0803.3977v1-abstract-full" style="display: none;"> We study colliding winds in the superluminous binary eta Carinae by performing three-dimensional, Smoothed Particle Hydrodynamics (SPH) simulations. For simplicity, we assume both winds to be isothermal. We also assume that wind particles coast without any net external forces. We find that the lower density, faster wind from the secondary carves out a spiral cavity in the higher density, slower wind from the primary. Because of the phase-dependent orbital motion, the cavity is very thin on the periastron side, whereas it occupies a large volume on the apastron side. The model X-ray light curve using the simulated density structure fits very well with the observed light curve for a viewing angle of i=54 degrees and phi=36 degrees, where i is the inclination angle and phi is the azimuth from apastron. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.3977v1-abstract-full').style.display = 'none'; document.getElementById('0803.3977v1-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 March, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2008. </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">6 pages, 3 figures, To be published in Proceedings of IAU Symposium 250: Massive Stars as Cosmic Engines, held in Kauai, Hawaii, USA, Dec 2007, edited by F. Bresolin, P.A. Crowther & J. Puls (Cambridge University Press)</span> </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/about">About</a></li> <li><a href="https://info.arxiv.org/help">Help</a></li> </ul> </div> <div class="column"> <ul class="nav-spaced"> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>contact arXiv</title><desc>Click here to contact arXiv</desc><path d="M502.3 190.8c3.9-3.1 9.7-.2 9.7 4.7V400c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V195.6c0-5 5.7-7.8 9.7-4.7 22.4 17.4 52.1 39.5 154.1 113.6 21.1 15.4 56.7 47.8 92.2 47.6 35.7.3 72-32.8 92.3-47.6 102-74.1 131.6-96.3 154-113.7zM256 320c23.2.4 56.6-29.2 73.4-41.4 132.7-96.3 142.8-104.7 173.4-128.7 5.8-4.5 9.2-11.5 9.2-18.9v-19c0-26.5-21.5-48-48-48H48C21.5 64 0 85.5 0 112v19c0 7.4 3.4 14.3 9.2 18.9 30.6 23.9 40.7 32.4 173.4 128.7 16.8 12.2 50.2 41.8 73.4 41.4z"/></svg> <a href="https://info.arxiv.org/help/contact.html"> Contact</a> </li> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>subscribe to arXiv mailings</title><desc>Click here to subscribe</desc><path d="M476 3.2L12.5 270.6c-18.1 10.4-15.8 35.6 2.2 43.2L121 358.4l287.3-253.2c5.5-4.9 13.3 2.6 8.6 8.3L176 407v80.5c0 23.6 28.5 32.9 42.5 15.8L282 426l124.6 52.2c14.2 6 30.4-2.9 33-18.2l72-432C515 7.8 493.3-6.8 476 3.2z"/></svg> <a href="https://info.arxiv.org/help/subscribe"> Subscribe</a> </li> </ul> </div> </div> </div>   <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/help/license/index.html">Copyright</a></li> <li><a href="https://info.arxiv.org/help/policies/privacy_policy.html">Privacy Policy</a></li> </ul> </div> <div class="column sorry-app-links"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/help/web_accessibility.html">Web Accessibility Assistance</a></li> <li> <p class="help"> <a class="a11y-main-link" href="https://status.arxiv.org" target="_blank">arXiv Operational Status <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 512" class="icon filter-dark_grey" role="presentation"><path d="M224.3 273l-136 136c-9.4 9.4-24.6 9.4-33.9 0l-22.6-22.6c-9.4-9.4-9.4-24.6 0-33.9l96.4-96.4-96.4-96.4c-9.4-9.4-9.4-24.6 0-33.9L54.3 103c9.4-9.4 24.6-9.4 33.9 0l136 136c9.5 9.4 9.5 24.6.1 34z"/></svg></a><br> Get status notifications via <a class="is-link" href="https://subscribe.sorryapp.com/24846f03/email/new" target="_blank"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><path d="M502.3 190.8c3.9-3.1 9.7-.2 9.7 4.7V400c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V195.6c0-5 5.7-7.8 9.7-4.7 22.4 17.4 52.1 39.5 154.1 113.6 21.1 15.4 56.7 47.8 92.2 47.6 35.7.3 72-32.8 92.3-47.6 102-74.1 131.6-96.3 154-113.7zM256 320c23.2.4 56.6-29.2 73.4-41.4 132.7-96.3 142.8-104.7 173.4-128.7 5.8-4.5 9.2-11.5 9.2-18.9v-19c0-26.5-21.5-48-48-48H48C21.5 64 0 85.5 0 112v19c0 7.4 3.4 14.3 9.2 18.9 30.6 23.9 40.7 32.4 173.4 128.7 16.8 12.2 50.2 41.8 73.4 41.4z"/></svg>email</a> or <a class="is-link" href="https://subscribe.sorryapp.com/24846f03/slack/new" target="_blank"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512" class="icon filter-black" role="presentation"><path d="M94.12 315.1c0 25.9-21.16 47.06-47.06 47.06S0 341 0 315.1c0-25.9 21.16-47.06 47.06-47.06h47.06v47.06zm23.72 0c0-25.9 21.16-47.06 47.06-47.06s47.06 21.16 47.06 47.06v117.84c0 25.9-21.16 47.06-47.06 47.06s-47.06-21.16-47.06-47.06V315.1zm47.06-188.98c-25.9 0-47.06-21.16-47.06-47.06S139 32 164.9 32s47.06 21.16 47.06 47.06v47.06H164.9zm0 23.72c25.9 0 47.06 21.16 47.06 47.06s-21.16 47.06-47.06 47.06H47.06C21.16 243.96 0 222.8 0 196.9s21.16-47.06 47.06-47.06H164.9zm188.98 47.06c0-25.9 21.16-47.06 47.06-47.06 25.9 0 47.06 21.16 47.06 47.06s-21.16 47.06-47.06 47.06h-47.06V196.9zm-23.72 0c0 25.9-21.16 47.06-47.06 47.06-25.9 0-47.06-21.16-47.06-47.06V79.06c0-25.9 21.16-47.06 47.06-47.06 25.9 0 47.06 21.16 47.06 47.06V196.9zM283.1 385.88c25.9 0 47.06 21.16 47.06 47.06 0 25.9-21.16 47.06-47.06 47.06-25.9 0-47.06-21.16-47.06-47.06v-47.06h47.06zm0-23.72c-25.9 0-47.06-21.16-47.06-47.06 0-25.9 21.16-47.06 47.06-47.06h117.84c25.9 0 47.06 21.16 47.06 47.06 0 25.9-21.16 47.06-47.06 47.06H283.1z"/></svg>slack</a> </p> </li> </ul> </div> </div> </div>  </div> </footer> <script src="https://static.arxiv.org/static/base/1.0.0a5/js/member_acknowledgement.js"></script> </body> </html>

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