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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Maan%2C+Y&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Maan%2C+Y&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Maan%2C+Y&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2412.13121">arXiv:2412.13121</a> <span> [<a href="https://arxiv.org/pdf/2412.13121">pdf</a>, <a href="https://arxiv.org/format/2412.13121">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"> Low-frequency Probes of the Persistent Radio Sources associated with Repeating FRBs </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bhusare%2C+Y">Yash Bhusare</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Kumar%2C+A">Ajay Kumar</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="2412.13121v1-abstract-short" style="display: inline;"> The discovery of Persistent Radio Sources (PRSs) associated with three repeating fast radio bursts (FRBs) has provided insight into the local environments of these FRBs. Here, we present deep radio observations of the fields surrounding three highly active repeating FRBs namely, FRB 20220912A, FRB 20240114A, and FRB 20240619D using the upgraded Giant Metrewave Radio Telescope (uGMRT) at low radio… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2412.13121v1-abstract-full').style.display = 'inline'; document.getElementById('2412.13121v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2412.13121v1-abstract-full" style="display: none;"> The discovery of Persistent Radio Sources (PRSs) associated with three repeating fast radio bursts (FRBs) has provided insight into the local environments of these FRBs. Here, we present deep radio observations of the fields surrounding three highly active repeating FRBs namely, FRB 20220912A, FRB 20240114A, and FRB 20240619D using the upgraded Giant Metrewave Radio Telescope (uGMRT) at low radio frequencies. Towards FRB~20240114A, we report the detection of compact source at 650\,MHz with a flux density of 65.6$\pm$8.1\,$渭$Jy/beam. Our measurements of the spectral index, star formation rate of the host galaxy and recently reported constraints on the physical size strongly argue for our detected source to be a persistent radio source (PRS) associated with the FRB 20240114A. For FRB~20220912A, we detect radio emission that is most likely due to star formation in the host galaxy. For FRB 20240619D, we provide upper limits on the radio emission from an associated PRS or the host galaxy. The detection of the PRS associated with FRB~20240114A is a useful addition to the PRSs known to be associated with only three other FRBs so far, and further supports the origin of the PRS in the form of magnetoionic medium surrounding the FRB sources. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2412.13121v1-abstract-full').style.display = 'none'; document.getElementById('2412.13121v1-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 December, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 4 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2411.19330">arXiv:2411.19330</a> <span> [<a href="https://arxiv.org/pdf/2411.19330">pdf</a>, <a href="https://arxiv.org/format/2411.19330">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> A direct measurement of the electron density turbulence parameter $C_1$ towards the magnetar XTE J1810-197 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Marthi%2C+V+R">Visweshwar Ram Marthi</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</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="2411.19330v2-abstract-short" style="display: inline;"> We report the first, direct measurement of the electron density turbulence parameter $C_1$, enabled by 550-750 MHz observations with the upgraded Giant Metrewave Radio Telescope. The parameter $C_1$ depends on the power law index of the wavenumber spectrum of electron density inhomogeneities in the ionized interstellar medium. Radio waves propagating through the inhomogeneous ionized medium suffer… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.19330v2-abstract-full').style.display = 'inline'; document.getElementById('2411.19330v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2411.19330v2-abstract-full" style="display: none;"> We report the first, direct measurement of the electron density turbulence parameter $C_1$, enabled by 550-750 MHz observations with the upgraded Giant Metrewave Radio Telescope. The parameter $C_1$ depends on the power law index of the wavenumber spectrum of electron density inhomogeneities in the ionized interstellar medium. Radio waves propagating through the inhomogeneous ionized medium suffer multipath propagation, as a result of which the pulsed emission from a neutron star undergoes scatter broadening. Consequently, interference between the delayed copies of the scatter-broadened electric field manifests as scintillation. We measure a scintillation bandwidth $螖谓_d=149\pm3$ Hz as well as a scatter-broadening timescale $蟿_d=1.22\pm0.09$ ms at 650 MHz towards the magnetar XTE J1810-197, using which we estimate $C_1=1.14\pm0.09$ directly from the uncertainty relation. This is also the first reported direct measurement of a scintillation bandwidth of order 100 Hz. We describe the methods employed to obtain these results and discuss their implications in general, as well as for the magnetar XTE J1810-197. We also discuss how such, effectively in-situ, measurements of $C_1$ can aid in inferring the wavenumber spectrum power law index and hence quantitatively discriminate between the various possible scattering scenarios in the ionized medium. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2411.19330v2-abstract-full').style.display = 'none'; document.getElementById('2411.19330v2-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, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 November, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 3 figures, submitted to 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/2407.05366">arXiv:2407.05366</a> <span> [<a href="https://arxiv.org/pdf/2407.05366">pdf</a>, <a href="https://arxiv.org/format/2407.05366">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> </div> <p class="title is-5 mathjax"> An activity transition in FRB 20201124A: methodological rigor, detection of frequency-dependent cessation, and a geometric magnetar model </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bilous%2C+A+V">A. V. Bilous</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Pastor-Marazuela%2C+I">I. Pastor-Marazuela</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Rajwade%2C+K+M">K. M. Rajwade</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+Y+Y">Y. Y. Wang</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="2407.05366v1-abstract-short" style="display: inline;"> We report detections of fast radio bursts (FRBs) from the repeating source FRB 20201124A with Apertif/WSRT and GMRT, and measurements of basic burst properties, especially the dispersion measure (DM) and fluence. Based on comparisons of these properties with previously published larger samples, we argue that the excess DM reported earlier for pulses with integrated signal to noise ratio… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.05366v1-abstract-full').style.display = 'inline'; document.getElementById('2407.05366v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2407.05366v1-abstract-full" style="display: none;"> We report detections of fast radio bursts (FRBs) from the repeating source FRB 20201124A with Apertif/WSRT and GMRT, and measurements of basic burst properties, especially the dispersion measure (DM) and fluence. Based on comparisons of these properties with previously published larger samples, we argue that the excess DM reported earlier for pulses with integrated signal to noise ratio $\lesssim 1000$ is due to incompletely accounting for the so-called sad trombone effect, even when using structure-maximizing DM algorithms. Our investigations of fluence distributions next lead us to advise against formal power-law fitting, especially dissuading the use of the least-square method, and we demonstrate the large biases involved. A maximum likelihood estimator (MLE) provides a much more accurate estimate of the power law and we provide accessible code for direct inclusion in future research. Our GMRT observations were fortuitously scheduled around the end of the activity cycle as recorded by FAST. We detected several bursts (one of them very strong) at 400/600 MHz, a few hours after sensitive FAST non-detections already showed the 1.3 GHz FRB emission to have ceased. After FRB 20180916B, this is a second example of a frequency-dependent activity window identified in a repeating FRB source. Since numerous efforts have so-far failed to determine a spin period for FRB 20201124A, we conjecture it to be an ultra-long period magnetar, with a period on the scale of months, and with a very wide, highly irregular duty cycle. Assuming the emission comes from closed field lines, we use radius-to-frequency mapping and polarization information from other studies to constrain the magnetospheric geometry and location of the emission region. Our initial findings are consistent with a possible connection between FRBs and crustal motion events. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2407.05366v1-abstract-full').style.display = 'none'; document.getElementById('2407.05366v1-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, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">submitted to A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.12804">arXiv:2406.12804</a> <span> [<a href="https://arxiv.org/pdf/2406.12804">pdf</a>, <a href="https://arxiv.org/format/2406.12804">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"> Varying activity and the burst properties of FRB 20240114A probed with GMRT down to 300 MHz </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kumar%2C+A">Ajay Kumar</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Bhusare%2C+Y">Yash Bhusare</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="2406.12804v2-abstract-short" style="display: inline;"> Repeating Fast Radio Bursts (FRBs) can exhibit a wide range of burst repetition rates, from none to hundreds of bursts per hour. Here, we report the detection and characteristics of 60 bursts from the recently discovered FRB 20240114A, observed with the upgraded Giant Metrewave Radio Telescope (uGMRT) in the frequency ranges 300-500MHz and 550-750 MHz. The majority of the bursts show narrow emissi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.12804v2-abstract-full').style.display = 'inline'; document.getElementById('2406.12804v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.12804v2-abstract-full" style="display: none;"> Repeating Fast Radio Bursts (FRBs) can exhibit a wide range of burst repetition rates, from none to hundreds of bursts per hour. Here, we report the detection and characteristics of 60 bursts from the recently discovered FRB 20240114A, observed with the upgraded Giant Metrewave Radio Telescope (uGMRT) in the frequency ranges 300-500MHz and 550-750 MHz. The majority of the bursts show narrow emission bandwidth with $螖谓/谓\sim$ 10\%. All of the bursts we detect are faint ($<$10 Jy ms) and thus probe the lower end of the energy distribution. We determine the rate function for FRB 20240114A at 400 MHz, and downward drift rates at 400 and 650 MHz, and discuss our measurements in the context of the repeating FRB population. We observe sudden variations in the burst activity of FRB 20240114A over time. From our data as well as the publicly available information on other observations of FRB 20240114A so far, there is an indication that FRB 20240114A potentially exhibits chromaticity in its burst activity. While the burst properties of FRB 20240114A are similar to other repeating FRBs, the frequency-dependent activity, if established, could provide crucial clues to the origin of repeating FRBs. We also place the most stringent 5$蟽$ upper limits of 600 $渭$Jy and 89 $渭$Jy on any persistent radio source (PRS) associated with FRB 20240114A at 400 MHz and 650 MHz, respectively, and compare these with the luminosity of the known PRSs associated with FRB121102A and FRB190520B. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.12804v2-abstract-full').style.display = 'none'; document.getElementById('2406.12804v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 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">13 Pages, 5 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/2406.00482">arXiv:2406.00482</a> <span> [<a href="https://arxiv.org/pdf/2406.00482">pdf</a>, <a href="https://arxiv.org/format/2406.00482">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202450953">10.1051/0004-6361/202450953 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Comprehensive analysis of the Apertif Fast Radio Burst sample: similarities with young, energetic neutron stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Pastor-Marazuela%2C+I">In茅s Pastor-Marazuela</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Bilous%2C+A">Anna Bilous</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">Liam Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L">Leon Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Petroff%2C+E">Emily Petroff</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">Dany Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">Kelley M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=Orr%C3%B9%2C+E">Emanuela Orr霉</a>, <a href="/search/astro-ph?searchtype=author&query=Sclocco%2C+A">Alessio Sclocco</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+Y">Yuyang Wang</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="2406.00482v2-abstract-short" style="display: inline;"> Understanding the origin of fast radio bursts (FRBs) has become the main science driver of recent dedicated FRB surveys. Between July 2019 and February 2022, we carried out ALERT, an FRB survey at 1370 MHz using the Apertif instrument installed at the Westerbork Synthesis Radio Telescope (WSRT). Here we report the detection of 18 new FRBs, and we study the properties of the entire 24 burst sample… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.00482v2-abstract-full').style.display = 'inline'; document.getElementById('2406.00482v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.00482v2-abstract-full" style="display: none;"> Understanding the origin of fast radio bursts (FRBs) has become the main science driver of recent dedicated FRB surveys. Between July 2019 and February 2022, we carried out ALERT, an FRB survey at 1370 MHz using the Apertif instrument installed at the Westerbork Synthesis Radio Telescope (WSRT). Here we report the detection of 18 new FRBs, and we study the properties of the entire 24 burst sample detected during the survey. For five bursts, we identify host galaxy candidates with >50% probability association. We observe an average linear polarisation fraction of $\sim$43% and an average circular polarisation fraction consistent with 0%. A third of the FRBs display multiple components. The sample next reveals a population of highly scattered bursts, which is most likely to have been produced in the immediate circumburst environment. Furthermore, two FRBs show evidence for high rotation measures, reaching |RM|>$10^3$ rad m$^{-2}$ in the source reference frames. Together, the scattering and rotation measures ALERT finds prove that a large fraction of FRBs are embedded in complex media such as star forming regions or supernova remnants. Through the discovery of the third most dispersed FRB so far, we show that one-off FRBs can emit at frequencies in excess of 6 GHz. Finally, we determine an FRB all-sky rate of $459^{+208}_{-155}$ sky$^{-1}$ day$^{-1}$ above a fluence limit of 4.1 Jy ms, and a fluence cumulative distribution with a power law index $纬=-1.23\pm0.06\pm0.2$, which is roughly consistent with the Euclidean Universe predictions. Through the high resolution in time, frequency, polarisation and localisation that ALERT featured, we were able to determine the morphological complexity, polarisation, local scattering and magnetic environment, and high-frequency luminosity of FRBs. We find all these strongly resemble those seen in young, energetic, highly magnetised neutron stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.00482v2-abstract-full').style.display = 'none'; document.getElementById('2406.00482v2-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">v1</span> submitted 1 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">40 pages (including 11 of appendix), 37 figures, 5 tables. Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 693, A279 (2025) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.09201">arXiv:2311.09201</a> <span> [<a href="https://arxiv.org/pdf/2311.09201">pdf</a>, <a href="https://arxiv.org/format/2311.09201">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div 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/10.1051/0004-6361/202348621">10.1051/0004-6361/202348621 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Topology of Pulsar Profiles (ToPP). I. Graph theory method and classification of the EPN </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">D. Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</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="2311.09201v2-abstract-short" style="display: inline;"> Some of the most important information on a radio pulsar is derived from its average pulse profile. Many early pulsar studies were necessarily based on only few such profiles. There, discrete profile components were linked to emission mechanism models for individual stars through human interpretation. For the population as a whole, profiles morphology must reflect the geometry and overall evolutio… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.09201v2-abstract-full').style.display = 'inline'; document.getElementById('2311.09201v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.09201v2-abstract-full" style="display: none;"> Some of the most important information on a radio pulsar is derived from its average pulse profile. Many early pulsar studies were necessarily based on only few such profiles. There, discrete profile components were linked to emission mechanism models for individual stars through human interpretation. For the population as a whole, profiles morphology must reflect the geometry and overall evolution of the radio emitting regions. The problem, however, is that this population is becoming too large for intensive studies of all sources individually. Moreover, connecting profiles from a large collection of pulsars rapidly becomes cumbersome. In this article, we present ToPP, the first-ever unsupervised method to sort pulsars by profile-shape similarity, using graph topology. We apply ToPP to the publicly available European Pulsar Network profile database, providing the first organised visual overview of multi-frequency profiles representing 90 individual pulsars. We find discrete evolutionary tracks, varying from simple, single component profiles at all frequencies, towards diverse mixtures of more complex profiles with frequency evolution. The profile evolution is continuous, extending out to millisecond pulsars, and does not fall in sharp classes. We interpret the profiles as a mixture of pulsar core/cone emission type, spin-down energetics, and the line-of-sight impact angle towards the magnetic axis. We show how ToPP can systematically classify sources into the Rankin empirical profile scheme. ToPP forms one of the key unsupervised methods that will be essential to explore upcoming pulsar census data such as expected by the Square Kilometer Array. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.09201v2-abstract-full').style.display = 'none'; document.getElementById('2311.09201v2-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> 16 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted to A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 687, A113 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.00693">arXiv:2309.00693</a> <span> [<a href="https://arxiv.org/pdf/2309.00693">pdf</a>, <a href="https://arxiv.org/format/2309.00693">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="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> Comparing recent PTA results on the nanohertz stochastic gravitational wave background </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=The+International+Pulsar+Timing+Array+Collaboration"> The International Pulsar Timing Array Collaboration</a>, <a href="/search/astro-ph?searchtype=author&query=Agazie%2C+G">G. Agazie</a>, <a href="/search/astro-ph?searchtype=author&query=Antoniadis%2C+J">J. Antoniadis</a>, <a href="/search/astro-ph?searchtype=author&query=Anumarlapudi%2C+A">A. Anumarlapudi</a>, <a href="/search/astro-ph?searchtype=author&query=Archibald%2C+A+M">A. M. Archibald</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+P">P. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+S">S. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Arzoumanian%2C+Z">Z. Arzoumanian</a>, <a href="/search/astro-ph?searchtype=author&query=Askew%2C+J">J. Askew</a>, <a href="/search/astro-ph?searchtype=author&query=Babak%2C+S">S. Babak</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">M. Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bailes%2C+M">M. Bailes</a>, <a href="/search/astro-ph?searchtype=author&query=Nielsen%2C+A+-+B">A. -S. Bak Nielsen</a>, <a href="/search/astro-ph?searchtype=author&query=Baker%2C+P+T">P. T. Baker</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C+G">C. G. Bassa</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">A. Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=B%C3%A9csy%2C+B">B. B茅csy</a>, <a href="/search/astro-ph?searchtype=author&query=Berthereau%2C+A">A. Berthereau</a>, <a href="/search/astro-ph?searchtype=author&query=Bhat%2C+N+D+R">N. D. R. Bhat</a>, <a href="/search/astro-ph?searchtype=author&query=Blecha%2C+L">L. Blecha</a>, <a href="/search/astro-ph?searchtype=author&query=Bonetti%2C+M">M. Bonetti</a>, <a href="/search/astro-ph?searchtype=author&query=Bortolas%2C+E">E. Bortolas</a>, <a href="/search/astro-ph?searchtype=author&query=Brazier%2C+A">A. Brazier</a>, <a href="/search/astro-ph?searchtype=author&query=Brook%2C+P+R">P. R. Brook</a>, <a href="/search/astro-ph?searchtype=author&query=Burgay%2C+M">M. Burgay</a> , et al. (220 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2309.00693v1-abstract-short" style="display: inline;"> The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTA… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.00693v1-abstract-full').style.display = 'inline'; document.getElementById('2309.00693v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.00693v1-abstract-full" style="display: none;"> The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within $1蟽$. The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we "extended" each PTA's data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the Hellings and Downs correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA's Data Release 3, which will involve not just adding in additional pulsars, but also including data from all three PTAs where any given pulsar is timed by more than as single PTA. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.00693v1-abstract-full').style.display = 'none'; document.getElementById('2309.00693v1-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 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 9 figures, submitted to ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.16227">arXiv:2306.16227</a> <span> [<a href="https://arxiv.org/pdf/2306.16227">pdf</a>, <a href="https://arxiv.org/format/2306.16227">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> The second data release from the European Pulsar Timing Array: IV. Implications for massive black holes, dark matter and the early Universe </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Antoniadis%2C+J">J. Antoniadis</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+P">P. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+S">S. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Auclair%2C+P">P. Auclair</a>, <a href="/search/astro-ph?searchtype=author&query=Babak%2C+S">S. Babak</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">M. Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Nielsen%2C+A+-+B">A. -S. Bak Nielsen</a>, <a href="/search/astro-ph?searchtype=author&query=Barausse%2C+E">E. Barausse</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C+G">C. G. Bassa</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">A. Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Berthereau%2C+A">A. Berthereau</a>, <a href="/search/astro-ph?searchtype=author&query=Bonetti%2C+M">M. Bonetti</a>, <a href="/search/astro-ph?searchtype=author&query=Bortolas%2C+E">E. Bortolas</a>, <a href="/search/astro-ph?searchtype=author&query=Brook%2C+P+R">P. R. Brook</a>, <a href="/search/astro-ph?searchtype=author&query=Burgay%2C+M">M. Burgay</a>, <a href="/search/astro-ph?searchtype=author&query=Caballero%2C+R+N">R. N. Caballero</a>, <a href="/search/astro-ph?searchtype=author&query=Caprini%2C+C">C. Caprini</a>, <a href="/search/astro-ph?searchtype=author&query=Chalumeau%2C+A">A. Chalumeau</a>, <a href="/search/astro-ph?searchtype=author&query=Champion%2C+D+J">D. J. Champion</a>, <a href="/search/astro-ph?searchtype=author&query=Chanlaridis%2C+S">S. Chanlaridis</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+S">S. Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Cognard%2C+I">I. Cognard</a>, <a href="/search/astro-ph?searchtype=author&query=Crisostomi%2C+M">M. Crisostomi</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">S. Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Deb%2C+D">D. Deb</a> , et al. (89 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.16227v2-abstract-short" style="display: inline;"> The European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases respectively, with the correlation properties of a gravitational wave background (GWB). Such signal may have its origin in a number of physical processes including a cosmic population of inspiralling sup… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.16227v2-abstract-full').style.display = 'inline'; document.getElementById('2306.16227v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.16227v2-abstract-full" style="display: none;"> The European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases respectively, with the correlation properties of a gravitational wave background (GWB). Such signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, cosmic strings and tensor mode generation by non-linear evolution of scalar perturbations in the early Universe; oscillations of the Galactic potential in the presence of ultra-light dark matter (ULDM). At the current stage of emerging evidence, it is impossible to discriminate among the different origins. Therefore, in this paper, we consider each process separately, and investigate the implications of the signal under the hypothesis that it is generated by that specific process. We find that the signal is consistent with a cosmic population of inspiralling SMBHBs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the SMBH-host galaxy scaling relations. If this origin is confirmed, this is the first direct evidence that SMBHBs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. As for early Universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. Other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. Finally, a ULDM origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of ULDM in our Galaxy. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.16227v2-abstract-full').style.display = 'none'; document.getElementById('2306.16227v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">30 pages, 23 figures, replaced to match the version published in Astronomy & Astrophysics, note the change in the numbering order in the series (now paper IV)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.16226">arXiv:2306.16226</a> <span> [<a href="https://arxiv.org/pdf/2306.16226">pdf</a>, <a href="https://arxiv.org/format/2306.16226">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</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/10.1051/0004-6361/202348568">10.1051/0004-6361/202348568 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The second data release from the European Pulsar Timing Array V. Search for continuous gravitational wave signals </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Antoniadis%2C+J">J. Antoniadis</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+P">P. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+S">S. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Babak%2C+S">S. Babak</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">M. Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Nielsen%2C+A+S+B">A. S. Bak Nielsen</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C+G">C. G. Bassa</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">A. Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Berthereau%2C+A">A. Berthereau</a>, <a href="/search/astro-ph?searchtype=author&query=Bonetti%2C+M">M. Bonetti</a>, <a href="/search/astro-ph?searchtype=author&query=Bortolas%2C+E">E. Bortolas</a>, <a href="/search/astro-ph?searchtype=author&query=Brook%2C+P+R">P. R. Brook</a>, <a href="/search/astro-ph?searchtype=author&query=Burgay%2C+M">M. Burgay</a>, <a href="/search/astro-ph?searchtype=author&query=Caballero%2C+R+N">R. N. Caballero</a>, <a href="/search/astro-ph?searchtype=author&query=Chalumeau%2C+A">A. Chalumeau</a>, <a href="/search/astro-ph?searchtype=author&query=Champion%2C+D+J">D. J. Champion</a>, <a href="/search/astro-ph?searchtype=author&query=Chanlaridis%2C+S">S. Chanlaridis</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+S">S. Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Cognard%2C+I">I. Cognard</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">S. Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Deb%2C+D">D. Deb</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">S. Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Desvignes%2C+G">G. Desvignes</a>, <a href="/search/astro-ph?searchtype=author&query=Dhanda-Batra%2C+N">N. Dhanda-Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Dwivedi%2C+C">C. Dwivedi</a> , et al. (75 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.16226v3-abstract-short" style="display: inline;"> We present the results of a search for continuous gravitational wave signals (CGWs) in the second data release (DR2) of the European Pulsar Timing Array (EPTA) collaboration. The most significant candidate event from this search has a gravitational wave frequency of 4-5 nHz. Such a signal could be generated by a supermassive black hole binary (SMBHB) in the local Universe. We present the results o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.16226v3-abstract-full').style.display = 'inline'; document.getElementById('2306.16226v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.16226v3-abstract-full" style="display: none;"> We present the results of a search for continuous gravitational wave signals (CGWs) in the second data release (DR2) of the European Pulsar Timing Array (EPTA) collaboration. The most significant candidate event from this search has a gravitational wave frequency of 4-5 nHz. Such a signal could be generated by a supermassive black hole binary (SMBHB) in the local Universe. We present the results of a follow-up analysis of this candidate using both Bayesian and frequentist methods. The Bayesian analysis gives a Bayes factor of 4 in favor of the presence of the CGW over a common uncorrelated noise process, while the frequentist analysis estimates the p-value of the candidate to be 1%, also assuming the presence of common uncorrelated red noise. However, comparing a model that includes both a CGW and a gravitational wave background (GWB) to a GWB only, the Bayes factor in favour of the CGW model is only 0.7. Therefore, we cannot conclusively determine the origin of the observed feature, but we cannot rule it out as a CGW source. We present results of simulations that demonstrate that data containing a weak gravitational wave background can be misinterpreted as data including a CGW and vice versa, providing two plausible explanations of the EPTA DR2 data. Further investigations combining data from all PTA collaborations will be needed to reveal the true origin of this feature. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.16226v3-abstract-full').style.display = 'none'; document.getElementById('2306.16226v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">13 figures, 15 pages, accepted</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 690, A118 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.16225">arXiv:2306.16225</a> <span> [<a href="https://arxiv.org/pdf/2306.16225">pdf</a>, <a href="https://arxiv.org/format/2306.16225">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div 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/10.1051/0004-6361/202346842">10.1051/0004-6361/202346842 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The second data release from the European Pulsar Timing Array II. Customised pulsar noise models for spatially correlated gravitational waves </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Antoniadis%2C+J">J. Antoniadis</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+P">P. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+S">S. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Babak%2C+S">S. Babak</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">M. Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Nielsen%2C+A+S+B">A. S. Bak Nielsen</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C+G">C. G. Bassa</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">A. Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Berthereau%2C+A">A. Berthereau</a>, <a href="/search/astro-ph?searchtype=author&query=Bonetti%2C+M">M. Bonetti</a>, <a href="/search/astro-ph?searchtype=author&query=Bortolas%2C+E">E. Bortolas</a>, <a href="/search/astro-ph?searchtype=author&query=Brook%2C+P+R">P. R. Brook</a>, <a href="/search/astro-ph?searchtype=author&query=Burgay%2C+M">M. Burgay</a>, <a href="/search/astro-ph?searchtype=author&query=Caballero%2C+R+N">R. N. Caballero</a>, <a href="/search/astro-ph?searchtype=author&query=Chalumeau%2C+A">A. Chalumeau</a>, <a href="/search/astro-ph?searchtype=author&query=Champion%2C+D+J">D. J. Champion</a>, <a href="/search/astro-ph?searchtype=author&query=Chanlaridis%2C+S">S. Chanlaridis</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+S">S. Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Cognard%2C+I">I. Cognard</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">S. Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Deb%2C+D">D. Deb</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">S. Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Desvignes%2C+G">G. Desvignes</a>, <a href="/search/astro-ph?searchtype=author&query=Dhanda-Batra%2C+N">N. Dhanda-Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Dwivedi%2C+C">C. Dwivedi</a> , et al. (73 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.16225v1-abstract-short" style="display: inline;"> The nanohertz gravitational wave background (GWB) is expected to be an aggregate signal of an ensemble of gravitational waves emitted predominantly by a large population of coalescing supermassive black hole binaries in the centres of merging galaxies. Pulsar timing arrays, ensembles of extremely stable pulsars, are the most precise experiments capable of detecting this background. However, the su… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.16225v1-abstract-full').style.display = 'inline'; document.getElementById('2306.16225v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.16225v1-abstract-full" style="display: none;"> The nanohertz gravitational wave background (GWB) is expected to be an aggregate signal of an ensemble of gravitational waves emitted predominantly by a large population of coalescing supermassive black hole binaries in the centres of merging galaxies. Pulsar timing arrays, ensembles of extremely stable pulsars, are the most precise experiments capable of detecting this background. However, the subtle imprints that the GWB induces on pulsar timing data are obscured by many sources of noise. These must be carefully characterized to increase the sensitivity to the GWB. In this paper, we present a novel technique to estimate the optimal number of frequency coefficients for modelling achromatic and chromatic noise and perform model selection. We also incorporate a new model to fit for scattering variations in the pulsar timing package temponest and created realistic simulations of the European Pulsar Timing Array (EPTA) datasets that allowed us to test the efficacy of our noise modelling algorithms. We present an in-depth analysis of the noise properties of 25 millisecond pulsars (MSPs) that form the second data release (DR2) of the EPTA and investigate the effect of incorporating low-frequency data from the Indian PTA collaboration. We use enterprise and temponest packages to compare noise models with those reported with the EPTA DR1. We find that, while in some pulsars we can successfully disentangle chromatic from achromatic noise owing to the wider frequency coverage in DR2, in others the noise models evolve in a more complicated way. We also find evidence of long-term scattering variations in PSR J1600$-$3053. Through our simulations, we identify intrinsic biases in our current noise analysis techniques and discuss their effect on GWB searches. The results presented here directly help improve sensitivity to the GWB and are already being used as part of global PTA efforts. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.16225v1-abstract-full').style.display = 'none'; document.getElementById('2306.16225v1-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 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">20 pages, 6 figures, 9 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 678, A49 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.16214">arXiv:2306.16214</a> <span> [<a href="https://arxiv.org/pdf/2306.16214">pdf</a>, <a href="https://arxiv.org/format/2306.16214">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202346844">10.1051/0004-6361/202346844 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The second data release from the European Pulsar Timing Array III. Search for gravitational wave signals </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Antoniadis%2C+J">J. Antoniadis</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+P">P. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+S">S. Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Babak%2C+S">S. Babak</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">M. Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Nielsen%2C+A+-+B">A. -S. Bak Nielsen</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C+G">C. G. Bassa</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">A. Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Berthereau%2C+A">A. Berthereau</a>, <a href="/search/astro-ph?searchtype=author&query=Bonetti%2C+M">M. Bonetti</a>, <a href="/search/astro-ph?searchtype=author&query=Bortolas%2C+E">E. Bortolas</a>, <a href="/search/astro-ph?searchtype=author&query=Brook%2C+P+R">P. R. Brook</a>, <a href="/search/astro-ph?searchtype=author&query=Burgay%2C+M">M. Burgay</a>, <a href="/search/astro-ph?searchtype=author&query=Caballero%2C+R+N">R. N. Caballero</a>, <a href="/search/astro-ph?searchtype=author&query=Chalumeau%2C+A">A. Chalumeau</a>, <a href="/search/astro-ph?searchtype=author&query=Champion%2C+D+J">D. J. Champion</a>, <a href="/search/astro-ph?searchtype=author&query=Chanlaridis%2C+S">S. Chanlaridis</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+S">S. Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Cognard%2C+I">I. Cognard</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">S. Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Deb%2C+D">D. Deb</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">S. Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Desvignes%2C+G">G. Desvignes</a>, <a href="/search/astro-ph?searchtype=author&query=Dhanda-Batra%2C+N">N. Dhanda-Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Dwivedi%2C+C">C. Dwivedi</a> , et al. (73 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2306.16214v1-abstract-short" style="display: inline;"> We present the results of the search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using the second data release of the European Pulsar Timing Array (EPTA) for 25 millisecond pulsars and a combination with the first data release of the Indian Pulsar Timing Array (InPTA). We analysed (i) the full 24.7-year EPTA data set, (ii) its 10.3-year subset based on… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.16214v1-abstract-full').style.display = 'inline'; document.getElementById('2306.16214v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.16214v1-abstract-full" style="display: none;"> We present the results of the search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using the second data release of the European Pulsar Timing Array (EPTA) for 25 millisecond pulsars and a combination with the first data release of the Indian Pulsar Timing Array (InPTA). We analysed (i) the full 24.7-year EPTA data set, (ii) its 10.3-year subset based on modern observing systems, (iii) the combination of the full data set with the first data release of the InPTA for ten commonly timed millisecond pulsars, and (iv) the combination of the 10.3-year subset with the InPTA data. These combinations allowed us to probe the contributions of instrumental noise and interstellar propagation effects. With the full data set, we find marginal evidence for a GWB, with a Bayes factor of four and a false alarm probability of $4\%$. With the 10.3-year subset, we report evidence for a GWB, with a Bayes factor of $60$ and a false alarm probability of about $0.1\%$ ($\gtrsim 3蟽$ significance). The addition of the InPTA data yields results that are broadly consistent with the EPTA-only data sets, with the benefit of better noise modelling. Analyses were performed with different data processing pipelines to test the consistency of the results from independent software packages. The inferred spectrum from the latest EPTA data from new generation observing systems is rather uncertain and in mild tension with the common signal measured in the full data set. However, if the spectral index is fixed at 13/3, the two data sets give a similar amplitude of ($2.5\pm0.7)\times10^{-15}$ at a reference frequency of $1\,{\rm yr}^{-1}$. By continuing our detection efforts as part of the International Pulsar Timing Array (IPTA), we expect to be able to improve the measurement of spatial correlations and better characterise this signal in the coming years. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.16214v1-abstract-full').style.display = 'none'; document.getElementById('2306.16214v1-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 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">21 pages, 14 figures, 4 appendix figures, accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 678, A50 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.13072">arXiv:2304.13072</a> <span> [<a href="https://arxiv.org/pdf/2304.13072">pdf</a>, <a href="https://arxiv.org/format/2304.13072">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> <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/stad3122">10.1093/mnras/stad3122 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multi-band Extension of the Wideband Timing Technique </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Paladi%2C+A+K">Avinash Kumar Paladi</a>, <a href="/search/astro-ph?searchtype=author&query=Dwivedi%2C+C">Churchil Dwivedi</a>, <a href="/search/astro-ph?searchtype=author&query=Rana%2C+P">Prerna Rana</a>, <a href="/search/astro-ph?searchtype=author&query=K%2C+N">Nobleson K</a>, <a href="/search/astro-ph?searchtype=author&query=Susobhanan%2C+A">Abhimanyu Susobhanan</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Tarafdar%2C+P">Pratik Tarafdar</a>, <a href="/search/astro-ph?searchtype=author&query=Deb%2C+D">Debabrata Deb</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+S">Swetha Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Gopakumar%2C+A">A Gopakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M A Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Batra%2C+N+D">Neelam Dhanda Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Debnath%2C+J">Jyotijwal Debnath</a>, <a href="/search/astro-ph?searchtype=author&query=Kareem%2C+F">Fazal Kareem</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+P">Paramasivan Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">Adarsh Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">Subhajit Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">Shantanu Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+Y">Yashwant Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Hisano%2C+S">Shinnosuke Hisano</a>, <a href="/search/astro-ph?searchtype=author&query=Kharbanda%2C+D">Divyansh Kharbanda</a>, <a href="/search/astro-ph?searchtype=author&query=Kikunaga%2C+T">Tomonosuke Kikunaga</a>, <a href="/search/astro-ph?searchtype=author&query=Kolhe%2C+N">Neel Kolhe</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a> , et al. (5 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="2304.13072v2-abstract-short" style="display: inline;"> The wideband timing technique enables the high-precision simultaneous estimation of pulsar Times of Arrival (ToAs) and Dispersion Measures (DMs) while effectively modeling frequency-dependent profile evolution. We present two novel independent methods that extend the standard wideband technique to handle simultaneous multi-band pulsar data incorporating profile evolution over a larger frequency sp… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.13072v2-abstract-full').style.display = 'inline'; document.getElementById('2304.13072v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.13072v2-abstract-full" style="display: none;"> The wideband timing technique enables the high-precision simultaneous estimation of pulsar Times of Arrival (ToAs) and Dispersion Measures (DMs) while effectively modeling frequency-dependent profile evolution. We present two novel independent methods that extend the standard wideband technique to handle simultaneous multi-band pulsar data incorporating profile evolution over a larger frequency span to estimate DMs and ToAs with enhanced precision. We implement the wideband likelihood using the libstempo python interface to perform wideband timing in the tempo2 framework. We present the application of these techniques to the dataset of fourteen millisecond pulsars observed simultaneously in Band 3 (300 - 500 MHz) and Band 5 (1260 - 1460 MHz) of the upgraded Giant Metrewave Radio Telescope (uGMRT) with a large band gap of 760 MHz as a part of the Indian Pulsar Timing Array (InPTA) campaign. We achieve increased ToA and DM precision and sub-microsecond root mean square post-fit timing residuals by combining simultaneous multi-band pulsar observations done in non-contiguous bands for the first time using our novel techniques. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.13072v2-abstract-full').style.display = 'none'; document.getElementById('2304.13072v2-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 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">Published 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/2303.12105">arXiv:2303.12105</a> <span> [<a href="https://arxiv.org/pdf/2303.12105">pdf</a>, <a href="https://arxiv.org/format/2303.12105">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div 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/10.1103/PhysRevD.108.023008">10.1103/PhysRevD.108.023008 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Noise analysis of the Indian Pulsar Timing Array data release I </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Srivastava%2C+A">Aman Srivastava</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">Shantanu Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Kolhe%2C+N">Neel Kolhe</a>, <a href="/search/astro-ph?searchtype=author&query=Surnis%2C+M">Mayuresh Surnis</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Susobhanan%2C+A">Abhimanyu Susobhanan</a>, <a href="/search/astro-ph?searchtype=author&query=Chalumeau%2C+A">Aur茅lien Chalumeau</a>, <a href="/search/astro-ph?searchtype=author&query=Hisano%2C+S">Shinnosuke Hisano</a>, <a href="/search/astro-ph?searchtype=author&query=K.%2C+N">Nobleson K.</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+S">Swetha Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Kharbanda%2C+D">Divyansh Kharbanda</a>, <a href="/search/astro-ph?searchtype=author&query=Singha%2C+J">Jaikhomba Singha</a>, <a href="/search/astro-ph?searchtype=author&query=Tarafdar%2C+P">Pratik Tarafdar</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+P">P Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">Adarsh Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">Subhajit Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Dey%2C+L">Lankeswar Dey</a>, <a href="/search/astro-ph?searchtype=author&query=Dwivedi%2C+C">Churchil Dwivedi</a>, <a href="/search/astro-ph?searchtype=author&query=Girgaonkar%2C+R">Raghav Girgaonkar</a>, <a href="/search/astro-ph?searchtype=author&query=Gopakumar%2C+A">A. Gopakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+Y">Yashwant Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Kikunaga%2C+T">Tomonosuke Kikunaga</a>, <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M. A. Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+K">Kuo Liu</a> , et al. (6 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="2303.12105v2-abstract-short" style="display: inline;"> The Indian Pulsar Timing Array (InPTA) collaboration has recently made its first official data release (DR1) for a sample of 14 pulsars using 3.5 years of uGMRT observations. We present the results of single-pulsar noise analysis for each of these 14 pulsars using the InPTA DR1. For this purpose, we consider white noise, achromatic red noise, dispersion measure (DM) variations, and scattering vari… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.12105v2-abstract-full').style.display = 'inline'; document.getElementById('2303.12105v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2303.12105v2-abstract-full" style="display: none;"> The Indian Pulsar Timing Array (InPTA) collaboration has recently made its first official data release (DR1) for a sample of 14 pulsars using 3.5 years of uGMRT observations. We present the results of single-pulsar noise analysis for each of these 14 pulsars using the InPTA DR1. For this purpose, we consider white noise, achromatic red noise, dispersion measure (DM) variations, and scattering variations in our analysis. We apply Bayesian model selection to obtain the preferred noise models among these for each pulsar. For PSR J1600$-$3053, we find no evidence of DM and scattering variations, while for PSR J1909$-$3744, we find no significant scattering variations. Properties vary dramatically among pulsars. For example, we find a strong chromatic noise with chromatic index $\sim$ 2.9 for PSR J1939+2134, indicating the possibility of a scattering index that doesn't agree with that expected for a Kolmogorov scattering medium consistent with similar results for millisecond pulsars in past studies. Despite the relatively short time baseline, the noise models broadly agree with the other PTAs and provide, at the same time, well-constrained DM and scattering variations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2303.12105v2-abstract-full').style.display = 'none'; document.getElementById('2303.12105v2-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> 16 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in PRD, 30 pages, 17 figures, 4 tables</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.01562">arXiv:2301.01562</a> <span> [<a href="https://arxiv.org/pdf/2301.01562">pdf</a>, <a href="https://arxiv.org/format/2301.01562">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/10.1051/0004-6361/202245022">10.1051/0004-6361/202245022 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> An interference detection strategy for Apertif based on AOFlagger 3 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Offringa%2C+A+R">A. R. Offringa</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A">A. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T+A">T. A. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">H. D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C+G">C. G. Bassa</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+L">D. L. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Blok%2C+W+J+G">W. J. G. Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Orr%C3%BA%2C+E">E. Orr煤</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">D. Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=Ziemke%2C+J">J. Ziemke</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="2301.01562v1-abstract-short" style="display: inline;"> Context. Apertif is a multi-beam receiver system for the Westerbork Synthesis Radio Telescope that operates at 1.1-1.5 GHz, which overlaps with various radio services, resulting in contamination of astronomical signals with radio-frequency interference (RFI). Aims. We analyze approaches to mitigate Apertif interference and design an automated detection procedure for its imaging mode. Using this ap… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.01562v1-abstract-full').style.display = 'inline'; document.getElementById('2301.01562v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.01562v1-abstract-full" style="display: none;"> Context. Apertif is a multi-beam receiver system for the Westerbork Synthesis Radio Telescope that operates at 1.1-1.5 GHz, which overlaps with various radio services, resulting in contamination of astronomical signals with radio-frequency interference (RFI). Aims. We analyze approaches to mitigate Apertif interference and design an automated detection procedure for its imaging mode. Using this approach, we present long-term RFI detection results of over 300 Apertif observations. Methods. Our approach is based on the AOFlagger detection approach. We introduce several new features, including ways to deal with ranges of invalid data (e.g. caused by shadowing) in both the SumThreshold and scale-invariant rank operator steps; pre-calibration bandpass calibration; auto-correlation flagging; and HI flagging avoidance. These methods are implemented in a new framework that uses the Lua language for scripting, which is new in AOFlagger version 3. Results. Our approach removes RFI fully automatically, and is robust and effective enough for further calibration and (continuum) imaging of these data. Analysis of 304 observations show an average of 11.1% of lost data due to RFI with a large spread. We observe 14.6% RFI in auto-correlations. Computationally, AOFlagger achieves a throughput of 370 MB/s on a single computing node. Compared to published machine learning results, the method is one to two orders of magnitude faster. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.01562v1-abstract-full').style.display = 'none'; document.getElementById('2301.01562v1-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 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 10 figures. Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 670, A166 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2208.05348">arXiv:2208.05348</a> <span> [<a href="https://arxiv.org/pdf/2208.05348">pdf</a>, <a href="https://arxiv.org/format/2208.05348">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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202244007">10.1051/0004-6361/202244007 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> First release of Apertif imaging survey data </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">Elizabeth A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Denes%2C+H">H. Denes</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A">A. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+M">D. M. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">R. Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T+A">T. A. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Orru%2C+E">E. Orru</a>, <a href="/search/astro-ph?searchtype=author&query=Schulz%2C+R">R. Schulz</a>, <a href="/search/astro-ph?searchtype=author&query=van+Amesfoort%2C+A+S">A. S. van Amesfoort</a>, <a href="/search/astro-ph?searchtype=author&query=Berger%2C+A">A. Berger</a>, <a href="/search/astro-ph?searchtype=author&query=Boersma%2C+O+M">O. M. Boersma</a>, <a href="/search/astro-ph?searchtype=author&query=Bouwhuis%2C+M">M. Bouwhuis</a>, <a href="/search/astro-ph?searchtype=author&query=Brink%2C+R+v+d">R. van den Brink</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">L. Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=van+Diepen%2C+G+N+J">G. N. J. van Diepen</a>, <a href="/search/astro-ph?searchtype=author&query=Dijkema%2C+T+J">T. J. Dijkema</a>, <a href="/search/astro-ph?searchtype=author&query=Ebbendorf%2C+N">N. Ebbendorf</a> , et al. (34 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="2208.05348v2-abstract-short" style="display: inline;"> (Abridged) Apertif is a phased-array feed system for WSRT, providing forty instantaneous beams over 300 MHz of bandwidth. A dedicated survey program started on 1 July 2019, with the last observations taken on 28 February 2022. We describe the release of data products from the first year of survey operations, through 30 June 2020. We focus on defining quality control metrics for the processed data… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.05348v2-abstract-full').style.display = 'inline'; document.getElementById('2208.05348v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2208.05348v2-abstract-full" style="display: none;"> (Abridged) Apertif is a phased-array feed system for WSRT, providing forty instantaneous beams over 300 MHz of bandwidth. A dedicated survey program started on 1 July 2019, with the last observations taken on 28 February 2022. We describe the release of data products from the first year of survey operations, through 30 June 2020. We focus on defining quality control metrics for the processed data products. The Apertif imaging pipeline, Apercal, automatically produces non-primary beam corrected continuum images, polarization images and cubes, and uncleaned spectral line and dirty beam cubes for each beam of an Apertif imaging observation. For this release, processed data products are considered on a beam-by-beam basis within an observation. We validate the continuum images by using metrics that identify deviations from Gaussian noise in the residual images. If the continuum image passes validation, we release all processed data products for a given beam. We apply further validation to the polarization and line data products. We release all raw observational data from the first year of survey observations, for a total of 221 observations of 160 independent target fields, covering approximately one thousand square degrees of sky. Images and cubes are released on a per beam basis, and 3374 beams are released. The median noise in the continuum images is 41.4 uJy/bm, with a slightly lower median noise of 36.9 uJy/bm in the Stokes V polarization image. The median angular resolution is 11.6"/sin(Dec). The median noise for all line cubes, with a spectral resolution of 36.6 kHz, is 1.6 mJy/bm, corresponding to a 3-sigma HI column density sensitivity of 1.8 x 10^20 atoms cm^-2 over 20 km/s (for a median angular resolution of 24" x 15"). We also provide primary beam images for each individual Apertif compound beam. The data are made accessible using a Virtual Observatory interface. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.05348v2-abstract-full').style.display = 'none'; document.getElementById('2208.05348v2-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 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 10 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">Accepted for publication in A&A, updated Figure 1</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 667, A38 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2208.05342">arXiv:2208.05342</a> <span> [<a href="https://arxiv.org/pdf/2208.05342">pdf</a>, <a href="https://arxiv.org/format/2208.05342">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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202244008">10.1051/0004-6361/202244008 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Continuum source catalog for the first APERTIF data release </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A+M">A. M. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T+A">T. A. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">R. Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Mancini%2C+M">M. Mancini</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">H. D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+M">D. M. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Berger%2C+A">A. Berger</a>, <a href="/search/astro-ph?searchtype=author&query=Brink%2C+R+v+d">R. van den Brink</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">L. Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Mika%2C+A">A'. Mika</a>, <a href="/search/astro-ph?searchtype=author&query=Norden%2C+M+J">M. J. Norden</a>, <a href="/search/astro-ph?searchtype=author&query=Offringa%2C+A+R">A. R. Offringa</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Schuur%2C+D">D. van der Schuur</a> , et al. (3 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="2208.05342v1-abstract-short" style="display: inline;"> The first data release of Apertif survey contains 3074 radio continuum images covering a thousand square degrees of the sky. The observations were performed during August 2019 to July 2020. The continuum images were produced at a central frequency 1355 MHz with the bandwidth of $\sim$150 MHz and angular resolution reaching 10". In this work we introduce and apply a new method to obtain a primary b… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.05342v1-abstract-full').style.display = 'inline'; document.getElementById('2208.05342v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2208.05342v1-abstract-full" style="display: none;"> The first data release of Apertif survey contains 3074 radio continuum images covering a thousand square degrees of the sky. The observations were performed during August 2019 to July 2020. The continuum images were produced at a central frequency 1355 MHz with the bandwidth of $\sim$150 MHz and angular resolution reaching 10". In this work we introduce and apply a new method to obtain a primary beam model using a machine learning approach, Gaussian process regression. The primary beam models obtained with this method are published along with the data products for the first Apertif data release. We apply the method to the continuum images, mosaic them and extract the source catalog. The catalog contains 249672 radio sources many of which are detected for the first time at these frequencies. We cross-match the coordinates with the NVSS, LOFAR/DR1/value-added and LOFAR/DR2 catalogs resulting in 44523, 22825 and 152824 common sources respectively. The first sample provides a unique opportunity to detect long term transient sources which have significantly changed their flux density for the last 25 years. The second and the third ones combined together provide information about spectral properties of the sources as well as the redshift estimates. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2208.05342v1-abstract-full').style.display = 'none'; document.getElementById('2208.05342v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">12 pages, 9 figures; accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 667, A39 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2207.06461">arXiv:2207.06461</a> <span> [<a href="https://arxiv.org/pdf/2207.06461">pdf</a>, <a href="https://arxiv.org/format/2207.06461">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <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/10.1007/s12036-022-09869-w">10.1007/s12036-022-09869-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Nanohertz Gravitational Wave Astronomy during the SKA Era: An InPTA perspective </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Gopakumar%2C+A">Achamveedu Gopakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Pandian%2C+A">Arul Pandian</a>, <a href="/search/astro-ph?searchtype=author&query=Prabu%2C+T">Thiagaraj Prabu</a>, <a href="/search/astro-ph?searchtype=author&query=Dey%2C+L">Lankeswar Dey</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">Shantanu Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Tarafdar%2C+P">Pratik Tarafdar</a>, <a href="/search/astro-ph?searchtype=author&query=Rana%2C+P">Prerna Rana</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Batra%2C+N+D">Neelam Dhanda Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Girgaonkar%2C+R">Raghav Girgaonkar</a>, <a href="/search/astro-ph?searchtype=author&query=Agarwal%2C+N">Nikita Agarwal</a>, <a href="/search/astro-ph?searchtype=author&query=Arumugam%2C+P">Paramasivan Arumugam</a>, <a href="/search/astro-ph?searchtype=author&query=Banik%2C+S">Sarmistha Banik</a>, <a href="/search/astro-ph?searchtype=author&query=Basu%2C+A">Avishek Basu</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">Adarsh Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">Subhajit Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+Y">Yashwant Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Hisano%2C+S">Shinnosuke Hisano</a>, <a href="/search/astro-ph?searchtype=author&query=Kato%2C+R">Ryo Kato</a>, <a href="/search/astro-ph?searchtype=author&query=Kharbanda%2C+D">Divyansh Kharbanda</a>, <a href="/search/astro-ph?searchtype=author&query=Kikunaga%2C+T">Tomonosuke Kikunaga</a>, <a href="/search/astro-ph?searchtype=author&query=Kolhe%2C+N">Neel Kolhe</a>, <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M. A. Krishnakumar</a> , et al. (12 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2207.06461v1-abstract-short" style="display: inline;"> Decades long monitoring of millisecond pulsars, which exhibit highly stable rotational periods, in pulsar timing array experiments is on the threshold of discovering nanohertz stochastic gravitational wave background. This paper describes the Indian Pulsar timing array (InPTA) experiment, which employs the upgraded Giant Metrewave Radio Telescope (uGMRT) for timing an ensemble of millisecond pulsa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.06461v1-abstract-full').style.display = 'inline'; document.getElementById('2207.06461v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2207.06461v1-abstract-full" style="display: none;"> Decades long monitoring of millisecond pulsars, which exhibit highly stable rotational periods, in pulsar timing array experiments is on the threshold of discovering nanohertz stochastic gravitational wave background. This paper describes the Indian Pulsar timing array (InPTA) experiment, which employs the upgraded Giant Metrewave Radio Telescope (uGMRT) for timing an ensemble of millisecond pulsars for this purpose. We highlight InPTA's observation strategies and analysis methods, which are relevant for a future PTA experiment with the more sensitive Square Kilometer Array (SKA) telescope. We show that the unique multi-sub-array multi-band wide-bandwidth frequency coverage of the InPTA provides Dispersion Measure estimates with unprecedented precision for PTA pulsars, e.g., ~ 2 x 10{-5} pc-cm{-3} for PSR J1909-3744. Configuring the SKA-low and SKA-mid as two and four sub-arrays respectively, it is shown that comparable precision is achievable, using observation strategies similar to those pursued by the InPTA, for a larger sample of 62 pulsars requiring about 26 and 7 hours per epoch for the SKA-mid and the SKA-low telescopes respectively. We also review the ongoing efforts to develop PTA-relevant general relativistic constructs that will be required to search for nanohertz gravitational waves from isolated super-massive black hole binary systems like blazar OJ 287. These efforts should be relevant to pursue persistent multi-messenger gravitational wave astronomy during the forthcoming era of the SKA telescope, the Thirty Meter Telescope, and the next-generation Event Horizon Telescope. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.06461v1-abstract-full').style.display = 'none'; document.getElementById('2207.06461v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">Accepted for publication in Journal of Astronomy and Astrophysics for Special Issue on Indian Participation in the SKA (Editors : Abhirup Datta, Nirupam Roy, Preeti Kharb and Tirthankar Roy Choudhury)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2206.09289">arXiv:2206.09289</a> <span> [<a href="https://arxiv.org/pdf/2206.09289">pdf</a>, <a href="https://arxiv.org/format/2206.09289">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> <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/10.1017/pasa.2022.46">10.1017/pasa.2022.46 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Indian Pulsar Timing Array: First data release </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Tarafdar%2C+P">Pratik Tarafdar</a>, <a href="/search/astro-ph?searchtype=author&query=K.%2C+N">Nobleson K.</a>, <a href="/search/astro-ph?searchtype=author&query=Rana%2C+P">Prerna Rana</a>, <a href="/search/astro-ph?searchtype=author&query=Singha%2C+J">Jaikhomba Singha</a>, <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M. A. Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Paladi%2C+A+K">Avinash Kumar Paladi</a>, <a href="/search/astro-ph?searchtype=author&query=Kolhe%2C+N">Neel Kolhe</a>, <a href="/search/astro-ph?searchtype=author&query=Batra%2C+N+D">Neelam Dhanda Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Agarwal%2C+N">Nikita Agarwal</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">Adarsh Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">Subhajit Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">Shantanu Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Dey%2C+L">Lankeswar Dey</a>, <a href="/search/astro-ph?searchtype=author&query=Hisano%2C+S">Shinnosuke Hisano</a>, <a href="/search/astro-ph?searchtype=author&query=Ingale%2C+P">Prathamesh Ingale</a>, <a href="/search/astro-ph?searchtype=author&query=Kato%2C+R">Ryo Kato</a>, <a href="/search/astro-ph?searchtype=author&query=Kharbanda%2C+D">Divyansh Kharbanda</a>, <a href="/search/astro-ph?searchtype=author&query=Kikunaga%2C+T">Tomonosuke Kikunaga</a>, <a href="/search/astro-ph?searchtype=author&query=Marmat%2C+P">Piyush Marmat</a>, <a href="/search/astro-ph?searchtype=author&query=Pandian%2C+B+A">B. Arul Pandian</a>, <a href="/search/astro-ph?searchtype=author&query=Prabu%2C+T">T. Prabu</a>, <a href="/search/astro-ph?searchtype=author&query=Srivastava%2C+A">Aman Srivastava</a>, <a href="/search/astro-ph?searchtype=author&query=Surnis%2C+M">Mayuresh Surnis</a>, <a href="/search/astro-ph?searchtype=author&query=Susarla%2C+S+C">Sai Chaitanya Susarla</a> , et al. (13 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="2206.09289v3-abstract-short" style="display: inline;"> We present the pulse arrival times and high-precision dispersion measure estimates for 14 millisecond pulsars observed simultaneously in the 300-500 MHz and 1260-1460 MHz frequency bands using the upgraded Giant Metrewave Radio Telescope (uGMRT). The data spans over a baseline of 3.5 years (2018-2021), and is the first official data release made available by the Indian Pulsar Timing Array collabor… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.09289v3-abstract-full').style.display = 'inline'; document.getElementById('2206.09289v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2206.09289v3-abstract-full" style="display: none;"> We present the pulse arrival times and high-precision dispersion measure estimates for 14 millisecond pulsars observed simultaneously in the 300-500 MHz and 1260-1460 MHz frequency bands using the upgraded Giant Metrewave Radio Telescope (uGMRT). The data spans over a baseline of 3.5 years (2018-2021), and is the first official data release made available by the Indian Pulsar Timing Array collaboration. This data release presents a unique opportunity for investigating the interstellar medium effects at low radio frequencies and their impact on the timing precision of pulsar timing array experiments. In addition to the dispersion measure time series and pulse arrival times obtained using both narrowband and wideband timing techniques, we also present the dispersion measure structure function analysis for selected pulsars. Our ongoing investigations regarding the frequency dependence of dispersion measures have been discussed. Based on the preliminary analysis for five millisecond pulsars, we do not find any conclusive evidence of chromaticity in dispersion measures. Data from regular simultaneous two-frequency observations are presented for the first time in this work. This distinctive feature leads us to the highest precision dispersion measure estimates obtained so far for a subset of our sample. Simultaneous multi-band uGMRT observations in Band 3 and Band 5 are crucial for high-precision dispersion measure estimation and for the prospect of expanding the overall frequency coverage upon the combination of data from the various Pulsar Timing Array consortia in the near future. Parts of the data presented in this work are expected to be incorporated into the upcoming third data release of the International Pulsar Timing Array. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.09289v3-abstract-full').style.display = 'none'; document.getElementById('2206.09289v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 June, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">23 pages, 21 figures, 3 tables. Published in PASA</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Publications of the Astronomical Society of Australia, Volume 39, 2022, e053 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2206.02382">arXiv:2206.02382</a> <span> [<a href="https://arxiv.org/pdf/2206.02382">pdf</a>, <a href="https://arxiv.org/format/2206.02382">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ac75e2">10.3847/1538-4357/ac75e2 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> MeerKAT observations of the reversing drifting subpulses in PSR J1750-3503 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Szary%2C+A">Andrzej Szary</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Wright%2C+G">Geoff Wright</a>, <a href="/search/astro-ph?searchtype=author&query=Weltevrede%2C+P">Patrick Weltevrede</a>, <a href="/search/astro-ph?searchtype=author&query=Agar%2C+C+H">Crispin H. Agar</a>, <a href="/search/astro-ph?searchtype=author&query=Tiburzi%2C+C">Caterina Tiburzi</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Keith%2C+M+J">Michael J. Keith</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="2206.02382v1-abstract-short" style="display: inline;"> We present an analysis of the subpulse drift in PSR J1750-3503, which is characterized by abrupt transitions of drift direction. As the pulsar does not exhibit other mode changes or clear nulling, it is an ideal candidate system for studying the phenomenon of drift direction change. For $\sim 80\%$ of the time the subpulses are characterized by positive drift - from early to later longitudes - whi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.02382v1-abstract-full').style.display = 'inline'; document.getElementById('2206.02382v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2206.02382v1-abstract-full" style="display: none;"> We present an analysis of the subpulse drift in PSR J1750-3503, which is characterized by abrupt transitions of drift direction. As the pulsar does not exhibit other mode changes or clear nulling, it is an ideal candidate system for studying the phenomenon of drift direction change. For $\sim 80\%$ of the time the subpulses are characterized by positive drift - from early to later longitudes - while the drift direction is negative in the other $\sim 20\%$. The subpulse separation for single pulses with positive drift, $P_2=(18.8\pm 0.1)^{\circ}$, is higher then for single pulses with negative drift, $P_2=(17.5\pm 0.2)^{\circ}$. When the drift is stable, the measured repetition time of the drift pattern is $P_3^{\rm obs}=(43.5 \pm 0.4) P$, where $P$ is pulsar period. We show that the observed data can be reproduced by a carousel models with subpulse rotation around the magnetic axis using purely dipolar configuration of surface magnetic field. The observed drift characteristics can be modeled assuming that the actual repetition time $P_3<2P$, such that we observe its aliased value. A small variation in $P_3$, of the order of $6\%$ (or less assuming higher alias orders), is enough to reproduce the characteristic drift direction changes we observe. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.02382v1-abstract-full').style.display = 'none'; document.getElementById('2206.02382v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 June, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">14 pages, 11 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/2205.12362">arXiv:2205.12362</a> <span> [<a href="https://arxiv.org/pdf/2205.12362">pdf</a>, <a href="https://arxiv.org/format/2205.12362">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div 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/10.1051/0004-6361/202244107">10.1051/0004-6361/202244107 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Apertif Radio Transient System (ARTS): Design, Commissioning, Data Release, and Detection of the first 5 Fast Radio Bursts </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Kooistra%2C+E">Eric Kooistra</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L">Leon Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">Liam Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Hargreaves%2C+J+E">J. E. Hargreaves</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Pastor-Marazuela%2C+I">In茅s Pastor-Marazuela</a>, <a href="/search/astro-ph?searchtype=author&query=Petroff%2C+E">Emily Petroff</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Schuur%2C+D">Daniel van der Schuur</a>, <a href="/search/astro-ph?searchtype=author&query=Sclocco%2C+A">Alessio Sclocco</a>, <a href="/search/astro-ph?searchtype=author&query=Straal%2C+S+M">Samayra M. Straal</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">Dany Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnholds%2C+S+J">Stefan J. Wijnholds</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">Elizabeth A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">Bj枚rn Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Attema%2C+J">Jisk Attema</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C">Cees Bassa</a>, <a href="/search/astro-ph?searchtype=author&query=Bast%2C+J+E">Jeanette E. Bast</a>, <a href="/search/astro-ph?searchtype=author&query=Bilous%2C+A">Anna Bilous</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Boersma%2C+O+M">Oliver M. Boersma</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">Wim A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">Arthur H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">Sieds Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">Helga D茅nes</a> , et al. (27 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="2205.12362v2-abstract-short" style="display: inline;"> Fast Radio Bursts must be powered by uniquely energetic emission mechanisms. This requirement has eliminated a number of possible source types, but several remain. Identifying the physical nature of Fast Radio Burst (FRB) emitters arguably requires good localisation of more detections, and broadband studies enabled by real-time alerting. We here present the Apertif Radio Transient System (ARTS), a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.12362v2-abstract-full').style.display = 'inline'; document.getElementById('2205.12362v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.12362v2-abstract-full" style="display: none;"> Fast Radio Bursts must be powered by uniquely energetic emission mechanisms. This requirement has eliminated a number of possible source types, but several remain. Identifying the physical nature of Fast Radio Burst (FRB) emitters arguably requires good localisation of more detections, and broadband studies enabled by real-time alerting. We here present the Apertif Radio Transient System (ARTS), a supercomputing radio-telescope instrument that performs real-time FRB detection and localisation on the Westerbork Synthesis Radio Telescope (WSRT) interferometer. It reaches coherent-addition sensitivity over the entire field of the view of the primary dish beam. After commissioning results verified the system performed as planned, we initiated the Apertif FRB survey (ALERT). Over the first 5 weeks we observed at design sensitivity in 2019, we detected 5 new FRBs, and interferometrically localised each of these to 0.4--10 sq. arcmin. All detections are broad band and very narrow, of order 1 ms duration, and unscattered. Dispersion measures are generally high. Only through the very high time and frequency resolution of ARTS are these hard-to-find FRBs detected, producing an unbiased view of the intrinsic population properties. Most localisation regions are small enough to rule out the presence of associated persistent radio sources. Three FRBs cut through the halos of M31 and M33. We demonstrate that Apertif can localise one-off FRBs with an accuracy that maps magneto-ionic material along well-defined lines of sight. The rate of 1 every ~7 days next ensures a considerable number of new sources are detected for such study. The combination of detection rate and localisation accuracy exemplified by the 5 first ARTS FRBs thus marks a new phase in which a growing number of bursts can be used to probe our Universe. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.12362v2-abstract-full').style.display = 'none'; document.getElementById('2205.12362v2-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 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 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">Accepted version</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 672, A117 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.09662">arXiv:2205.09662</a> <span> [<a href="https://arxiv.org/pdf/2205.09662">pdf</a>, <a href="https://arxiv.org/format/2205.09662">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/10.1051/0004-6361/202244045">10.1051/0004-6361/202244045 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Characterising the Apertif primary beam response </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">H. D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A">A. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">R. Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T+A">T. A. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Ivashina%2C+M+V">M. V. Ivashina</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">B. Hut</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+M">D. M. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Mika%2C+%C3%81">脕. Mika</a>, <a href="/search/astro-ph?searchtype=author&query=Norden%2C+M+J">M. J. Norden</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Pisano%2C+D+J">D. J. Pisano</a>, <a href="/search/astro-ph?searchtype=author&query=Smits%2C+R">R. Smits</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Brink%2C+R+v+d">R. van den Brink</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Schuur%2C+D">D. van der Schuur</a> , et al. (5 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="2205.09662v2-abstract-short" style="display: inline;"> Context. Phased Array Feeds (PAFs) are multi element receivers in the focal plane of a telescope that make it possible to form simultaneously multiple beams on the sky by combining the complex gains of the individual antenna elements. Recently the Westerbork Synthesis Radio Telescope (WSRT) was upgraded with PAF receivers and carried out several observing programs including two imaging surveys and… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.09662v2-abstract-full').style.display = 'inline'; document.getElementById('2205.09662v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.09662v2-abstract-full" style="display: none;"> Context. Phased Array Feeds (PAFs) are multi element receivers in the focal plane of a telescope that make it possible to form simultaneously multiple beams on the sky by combining the complex gains of the individual antenna elements. Recently the Westerbork Synthesis Radio Telescope (WSRT) was upgraded with PAF receivers and carried out several observing programs including two imaging surveys and a time domain survey. The Apertif imaging surveys use a configuration, where 40 partially overlapping compound beams (CBs) are simultaneously formed on the sky and arranged in an approximately rectangular shape. Aims. This manuscript aims to characterise the response of the 40 Apertif CBs to create frequency-resolved, I, XX and YY polarization empirical beam shapes. The measured CB maps can be used for image deconvolution, primary beam correction and mosaicing of Apertif imaging data. Methods. We use drift scan measurements to measure the response of each of the 40 CBs of Apertif. We derive beam maps for all individual beams in I, XX and YY polarisation in 10 or 18 frequency bins over the same bandwidth as the Apertif imaging surveys. We sample the main lobe of the beams and the side lobes up to a radius of 0.6 degrees from the beam centres. In addition, we derive beam maps for each individual WSRT dish as well. Results. We present the frequency and time dependence of the beam shapes and sizes. We compare the compound beam shapes derived with the drift scan method to beam shapes derived with an independent method using a Gaussian Process Regression comparison between the Apertif continuum images and the NRAO VLA Sky Survey (NVSS) catalogue. We find a good agreement between the beam shapes derived with the two independent methods. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.09662v2-abstract-full').style.display = 'none'; document.getElementById('2205.09662v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 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">Accepted for publication by A&A, 14 pages, 15 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 667, A40 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2203.16925">arXiv:2203.16925</a> <span> [<a href="https://arxiv.org/pdf/2203.16925">pdf</a>, <a href="https://arxiv.org/format/2203.16925">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="Cosmology and Nongalactic Astrophysics">astro-ph.CO</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/10.1051/0004-6361/202243201">10.1051/0004-6361/202243201 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Apertif science verification campaign - Characteristics of polarised radio sources </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Berger%2C+A">A. Berger</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">H. D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Schulz%2C+R">R. Schulz</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">L. Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">B. Hut</a>, <a href="/search/astro-ph?searchtype=author&query=Ivashina%2C+M+V">M. V. Ivashina</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Mika%2C+A">A. Mika</a>, <a href="/search/astro-ph?searchtype=author&query=Mulder%2C+H">H. Mulder</a>, <a href="/search/astro-ph?searchtype=author&query=Norden%2C+M+J">M. J. Norden</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Orr%C3%BA%2C+E">E. Orr煤</a>, <a href="/search/astro-ph?searchtype=author&query=Ruiter%2C+M">M. Ruiter</a>, <a href="/search/astro-ph?searchtype=author&query=Smits%2C+R">R. Smits</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Vermaas%2C+N+J">N. J. Vermaas</a> , et al. (2 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="2203.16925v1-abstract-short" style="display: inline;"> We analyse five early science datasets from the APERture Tile in Focus (Apertif) phased array feed system to verify the polarisation capabilities of Apertif in view of future larger data releases. We aim to characterise the source population of the polarised sky in the L-Band using polarised source information in combination with IR and optical data. We use automatic routines to generate full fiel… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.16925v1-abstract-full').style.display = 'inline'; document.getElementById('2203.16925v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2203.16925v1-abstract-full" style="display: none;"> We analyse five early science datasets from the APERture Tile in Focus (Apertif) phased array feed system to verify the polarisation capabilities of Apertif in view of future larger data releases. We aim to characterise the source population of the polarised sky in the L-Band using polarised source information in combination with IR and optical data. We use automatic routines to generate full field-of-view Q- and U-cubes and perform RM-Synthesis, source finding, and cross-matching with published radio, optical, and IR data to generate polarised source catalogues. SED-fitting routines were used to determine photometric redshifts, star-formation rates, and galaxy masses. IR colour information was used to classify sources as AGN or star-forming-dominated and early- or late-type. We surveyed an area of 56deg$^2$ and detected 1357 polarised source components in 1170 sources. The fraction of polarised sources is 10.57% with a median fractional polarisation of 4.70$\pm$0.14%. We confirmed the reliability of the Apertif measurements by comparing them with polarised cross-identified NVSS sources. Average RMs of the individual fields lie within the error of the best Milky Way foreground measurements. All of our polarised sources were found to be dominated by AGN activity in the radio regime with most of them being radio-loud (79%) and of the FRII class (87%). The host galaxies of our polarised source sample are dominated by intermediate disc and star-forming disc galaxies. The contribution of star formation to the radio emission is on the order of a few percent for $\approx$10% of the polarised sources while for $\approx$90% it is completely dominated by the AGN. We do not see any change in fractional polarisation for different star-formation rates of the AGN host galaxies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2203.16925v1-abstract-full').style.display = 'none'; document.getElementById('2203.16925v1-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 March, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">24 pages, 21 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 663, A103 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.08002">arXiv:2202.08002</a> <span> [<a href="https://arxiv.org/pdf/2202.08002">pdf</a>, <a href="https://arxiv.org/format/2202.08002">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202243339">10.1051/0004-6361/202243339 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A fast radio burst with sub-millisecond quasi-periodic structure </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Pastor-Marazuela%2C+I">In茅s Pastor-Marazuela</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Bilous%2C+A">Anna Bilous</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">Liam Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L">Leon Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Petroff%2C+E">Emily Petroff</a>, <a href="/search/astro-ph?searchtype=author&query=Straal%2C+S">Samayra Straal</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">Dany Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Attema%2C+J">Jisk Attema</a>, <a href="/search/astro-ph?searchtype=author&query=Boersma%2C+O+M">Oliver M. Boersma</a>, <a href="/search/astro-ph?searchtype=author&query=Brink%2C+R+v+d">R. van den Brink</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">H. D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">B. Hut</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A">A. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. Marcel Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+M">D. M. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Mika%2C+%C3%81">脕. Mika</a> , et al. (9 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="2202.08002v1-abstract-short" style="display: inline;"> Fast radio bursts (FRBs) are extragalactic radio transients of extraordinary luminosity. Studying the diverse temporal and spectral behaviour recently observed in a number of FRBs may help determine the nature of the entire class. For example, a fast spinning or highly magnetised neutron star might generate the rotation-powered acceleration required to explain the bright emission. Periodic, sub-se… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.08002v1-abstract-full').style.display = 'inline'; document.getElementById('2202.08002v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.08002v1-abstract-full" style="display: none;"> Fast radio bursts (FRBs) are extragalactic radio transients of extraordinary luminosity. Studying the diverse temporal and spectral behaviour recently observed in a number of FRBs may help determine the nature of the entire class. For example, a fast spinning or highly magnetised neutron star might generate the rotation-powered acceleration required to explain the bright emission. Periodic, sub-second components, suggesting such rotation, were recently reported in one FRB, and potentially in two more. Here we report the discovery of FRB 20201020A with Apertif, an FRB showing five components regularly spaced by 0.415 ms. This sub-millisecond structure in FRB 20201020A carries important clues about the progenitor of this FRB specifically, and potentially about that of FRBs in general. We thus contrast its features to the predictions of the main FRB source models. We perform a timing analysis of the FRB 20201020A components to determine the significance of the periodicity. We compare these against the timing properties of the previously reported CHIME FRBs with sub-second quasi-periodic components, and against two Apertif bursts from repeating FRB 20180916B that show complex time-frequency structure. We find the periodicity of FRB 20201020A to be marginally significant at 2.5$蟽$. Its repeating subcomponents cannot be explained as a pulsar rotation since the required spin rate of over 2 kHz exceeds the limits set by typical neutron star equations of state and observations. The fast periodicity is also in conflict with a compact object merger scenario. These quasi-periodic components could, however, be caused by equidistant emitting regions in the magnetosphere of a magnetar. The sub-millisecond spacing of the components in FRB 20201020A, the smallest observed so far in a one-off FRB, may rule out both neutron-star rotation and binary mergers as the direct source of quasi-periodic FRBs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.08002v1-abstract-full').style.display = 'none'; document.getElementById('2202.08002v1-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> 16 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">13 pages, 6 figures, 3 tables, supplementary material. Submitted to A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 678, A149 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.13006">arXiv:2201.13006</a> <span> [<a href="https://arxiv.org/pdf/2201.13006">pdf</a>, <a href="https://arxiv.org/format/2201.13006">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ac68f1">10.3847/1538-4357/ac68f1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Magnetar XTE J1810-197: Spectro-temporal evolution of average radio emission </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Surnis%2C+M+P">Mayuresh P. Surnis</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</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="2201.13006v2-abstract-short" style="display: inline;"> We present the long-term spectro-temporal evolution of the average radio emission properties of the magnetar XTE J1810-197 (PSR J1809-1943) following its most recent outburst in late 2018. We report the results from two and a half years of monitoring campaign with the upgraded Giant Metrewave Radio Telescope carried out over the frequency range of 300 - 1450 MHz. Our observations show intriguing t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.13006v2-abstract-full').style.display = 'inline'; document.getElementById('2201.13006v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.13006v2-abstract-full" style="display: none;"> We present the long-term spectro-temporal evolution of the average radio emission properties of the magnetar XTE J1810-197 (PSR J1809-1943) following its most recent outburst in late 2018. We report the results from two and a half years of monitoring campaign with the upgraded Giant Metrewave Radio Telescope carried out over the frequency range of 300 - 1450 MHz. Our observations show intriguing time variability in the average profile width, flux density, spectral index and the broadband spectral shape. While the average profile width appears to gradually decrease at later epochs, the flux density shows multiple episodes of radio re-brightening over the course of our monitoring. Our systematic monitoring observations reveal that the radio spectrum has steepened over time, resulting in evolution from a magnetar-like to a more pulsar-like spectrum. A more detailed analysis reveals that the radio spectrum has a turnover, and this turnover shifts towards lower frequencies with time. We present the details of our analysis leading to these results, and discuss our findings in the context of magnetar radio emission mechanisms as well as potential manifestations of the intervening medium. We also briefly discuss whether an evolving spectral turnover could be an ubiquitous property of radio magnetars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.13006v2-abstract-full').style.display = 'none'; document.getElementById('2201.13006v2-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 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 31 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">12 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/2112.06908">arXiv:2112.06908</a> <span> [<a href="https://arxiv.org/pdf/2112.06908">pdf</a>, <a href="https://arxiv.org/format/2112.06908">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> <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/stac532">10.1093/mnras/stac532 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Low-frequency wideband timing of InPTA pulsars observed with the uGMRT </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nobleson%2C+K">K Nobleson</a>, <a href="/search/astro-ph?searchtype=author&query=Agarwal%2C+N">Nikita Agarwal</a>, <a href="/search/astro-ph?searchtype=author&query=Girgaonkar%2C+R">Raghav Girgaonkar</a>, <a href="/search/astro-ph?searchtype=author&query=Pandian%2C+A">Arul Pandian</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M A Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Susobhanan%2C+A">Abhimanyu Susobhanan</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">Shantanu Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Prabu%2C+T">T Prabu</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">Adarsh Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Pennucci%2C+T+T">Timothy T Pennucci</a>, <a href="/search/astro-ph?searchtype=author&query=Banik%2C+S">Sarmistha Banik</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Batra%2C+N+D">Neelam Dhanda Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Choudhary%2C+A">Arpita Choudhary</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">Subhajit Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Dey%2C+L">Lankeswar Dey</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+Y">Yashwant Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Hisano%2C+S">Shinnosuke Hisano</a>, <a href="/search/astro-ph?searchtype=author&query=Kato%2C+R">Ryo Kato</a>, <a href="/search/astro-ph?searchtype=author&query=Kharbanda%2C+D">Divyansh Kharbanda</a>, <a href="/search/astro-ph?searchtype=author&query=Kikunaga%2C+T">Tomonosuke Kikunaga</a>, <a href="/search/astro-ph?searchtype=author&query=Kolhe%2C+N">Neel Kolhe</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Marmat%2C+P">Piyush Marmat</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="2112.06908v3-abstract-short" style="display: inline;"> High-precision measurements of the pulsar dispersion measure (DM) are possible using telescopes with low-frequency wideband receivers. We present an initial study of the application of the wideband timing technique, which can simultaneously measure the pulsar times of arrival (ToAs) and DMs, for a set of five pulsars observed with the upgraded Giant Metrewave Radio Telescope (uGMRT) as part of the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.06908v3-abstract-full').style.display = 'inline'; document.getElementById('2112.06908v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.06908v3-abstract-full" style="display: none;"> High-precision measurements of the pulsar dispersion measure (DM) are possible using telescopes with low-frequency wideband receivers. We present an initial study of the application of the wideband timing technique, which can simultaneously measure the pulsar times of arrival (ToAs) and DMs, for a set of five pulsars observed with the upgraded Giant Metrewave Radio Telescope (uGMRT) as part of the Indian Pulsar Timing Array (InPTA) campaign. We have used the observations with the 300-500 MHz band of the uGMRT for this purpose. We obtain high precision in DM measurements with precisions of the order 10^{-6}cm^{-3}pc. The ToAs obtained have sub-渭s precision and the root-mean-square of the post-fit ToA residuals are in the sub-渭s range. We find that the uncertainties in the DMs and ToAs obtained with this wideband technique, applied to low-frequency data, are consistent with the results obtained with traditional pulsar timing techniques and comparable to high-frequency results from other PTAs. This work opens up an interesting possibility of using low-frequency wideband observations for precision pulsar timing and gravitational wave detection with similar precision as high-frequency observations used conventionally. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.06908v3-abstract-full').style.display = 'none'; document.getElementById('2112.06908v3-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> 23 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">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/2112.03722">arXiv:2112.03722</a> <span> [<a href="https://arxiv.org/pdf/2112.03722">pdf</a>, <a href="https://arxiv.org/format/2112.03722">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/10.1016/j.ascom.2021.100514">10.1016/j.ascom.2021.100514 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Apercal -- The Apertif Calibration Pipeline </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Schulz%2C+R">R. Schulz</a>, <a href="/search/astro-ph?searchtype=author&query=Dijkema%2C+T+J">T. J. Dijkema</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Offringa%2C+A+R">A. R. Offringa</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A">A. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Frank%2C+B+S">B. S. Frank</a>, <a href="/search/astro-ph?searchtype=author&query=Vilchez%2C+N+P+E">N. P. E. Vilchez</a>, <a href="/search/astro-ph?searchtype=author&query=Verstappen%2C+J">J. Verstappen</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+K">E. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Denes%2C+H">H. Denes</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D">D. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">R. Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T">T. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Pisano%2C+D+-">D. -J. Pisano</a>, <a href="/search/astro-ph?searchtype=author&query=Ivashina%2C+M+V">M. V. Ivashina</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L+D">L. D. Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a> , et al. (11 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="2112.03722v1-abstract-short" style="display: inline;"> Apertif (APERture Tile In Focus) is one of the Square Kilometre Array (SKA) pathfinder facilities. The Apertif project is an upgrade to the 50-year-old Westerbork Synthesis Radio Telescope (WSRT) using phased-array feed technology. The new receivers create 40 individual beams on the sky, achieving an instantaneous sky coverage of 6.5 square degrees. The primary goal of the Apertif Imaging Survey i… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.03722v1-abstract-full').style.display = 'inline'; document.getElementById('2112.03722v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.03722v1-abstract-full" style="display: none;"> Apertif (APERture Tile In Focus) is one of the Square Kilometre Array (SKA) pathfinder facilities. The Apertif project is an upgrade to the 50-year-old Westerbork Synthesis Radio Telescope (WSRT) using phased-array feed technology. The new receivers create 40 individual beams on the sky, achieving an instantaneous sky coverage of 6.5 square degrees. The primary goal of the Apertif Imaging Survey is to perform a wide survey of 3500 square degrees (AWES) and a medium deep survey of 350 square degrees (AMES) of neutral atomic hydrogen (up to a redshift of 0.26), radio continuum emission and polarisation. Each survey pointing yields 4.6 TB of correlated data. The goal of Apercal is to process this data and fully automatically generate science ready data products for the astronomical community while keeping up with the survey observations. We make use of common astronomical software packages in combination with Python based routines and parallelisation. We use an object oriented module-based approach to ensure easy adaptation of the pipeline. A Jupyter notebook based framework allows user interaction and execution of individual modules as well as a full automatic processing of a complete survey observation. If nothing interrupts processing, we are able to reduce a single pointing survey observation on our five node cluster with 24 physical cores and 256 GB of memory each within 24h keeping up with the speed of the surveys. The quality of the generated images is sufficient for scientific usage for 44 % of the recorded data products with single images reaching dynamic ranges of several thousands. Future improvements will increase this percentage to over 80 %. Our design allowed development of the pipeline in parallel to the commissioning of the Apertif system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.03722v1-abstract-full').style.display = 'none'; document.getElementById('2112.03722v1-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 December, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astronomy and Computing 38 (2022) 100514 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2109.14234">arXiv:2109.14234</a> <span> [<a href="https://arxiv.org/pdf/2109.14234">pdf</a>, <a href="https://arxiv.org/format/2109.14234">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/10.1051/0004-6361/202141739">10.1051/0004-6361/202141739 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Apertif, Phased Array Feeds for the Westerbork Synthesis Radio Telescope </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T+A">T. A. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Verheijen%2C+M+A+W">M. A. W. Verheijen</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Braun%2C+R">R. Braun</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=Holties%2C+H">H. Holties</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">B. Hut</a>, <a href="/search/astro-ph?searchtype=author&query=Kooistra%2C+E">E. Kooistra</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">R. Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Orr%C3%BA%2C+E">E. Orr煤</a>, <a href="/search/astro-ph?searchtype=author&query=Ruiter%2C+M">M. Ruiter</a>, <a href="/search/astro-ph?searchtype=author&query=Schoenmakers%2C+A+P">A. P. Schoenmakers</a>, <a href="/search/astro-ph?searchtype=author&query=Vermaas%2C+N+J">N. J. Vermaas</a>, <a href="/search/astro-ph?searchtype=author&query=Wijnholds%2C+S+J">S. J. Wijnholds</a>, <a href="/search/astro-ph?searchtype=author&query=van+Amesfoort%2C+A+S">A. S. van Amesfoort</a>, <a href="/search/astro-ph?searchtype=author&query=Arts%2C+M+J">M. J. Arts</a>, <a href="/search/astro-ph?searchtype=author&query=Attema%2C+J+J">J. J. Attema</a>, <a href="/search/astro-ph?searchtype=author&query=Bakker%2C+L">L. Bakker</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C+G">C. G. Bassa</a> , et al. (65 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="2109.14234v2-abstract-short" style="display: inline;"> We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of the Westerbork Synthesis Radio Telescope which has transformed this telescope into a high-sensitivity, wide field-of-view L-band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams can be formed on the sky simultaneously, significantly increasing the s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.14234v2-abstract-full').style.display = 'inline'; document.getElementById('2109.14234v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.14234v2-abstract-full" style="display: none;"> We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of the Westerbork Synthesis Radio Telescope which has transformed this telescope into a high-sensitivity, wide field-of-view L-band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams can be formed on the sky simultaneously, significantly increasing the survey speed of the telescope. With this upgraded instrument, an imaging survey covering an area of 2300 deg2 is being performed which will deliver both continuum and spectral line data sets, of which the first data has been publicly released. In addition, a time domain transient and pulsar survey covering 15,000 deg2 is in progress. An overview of the Apertif science drivers, hardware and software of the upgraded telescope is presented, along with its key performance characteristics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.14234v2-abstract-full').style.display = 'none'; document.getElementById('2109.14234v2-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 September, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 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">29 pages, 42 figures, accepted for publication by 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 658, A146 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2109.08500">arXiv:2109.08500</a> <span> [<a href="https://arxiv.org/pdf/2109.08500">pdf</a>, <a href="https://arxiv.org/format/2109.08500">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202142242">10.1051/0004-6361/202142242 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Dual-frequency single-pulse study of PSR B0950+08 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bilous%2C+A+V">A. V. Bilous</a>, <a href="/search/astro-ph?searchtype=author&query=Griessmeier%2C+J+M">J. M. Griessmeier</a>, <a href="/search/astro-ph?searchtype=author&query=Pennucci%2C+T">T. Pennucci</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+Z">Z. Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Bondonneau%2C+L">L. Bondonneau</a>, <a href="/search/astro-ph?searchtype=author&query=Kondratiev%2C+V">V. Kondratiev</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">L. Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Petroff%2C+E">E. Petroff</a>, <a href="/search/astro-ph?searchtype=author&query=Verbiest%2C+J+P+W">J. P. W. Verbiest</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">D. Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=McKee%2C+J+W">J. W. McKee</a>, <a href="/search/astro-ph?searchtype=author&query=Shaifullah%2C+G">G. Shaifullah</a>, <a href="/search/astro-ph?searchtype=author&query=Theureau%2C+G">G. Theureau</a>, <a href="/search/astro-ph?searchtype=author&query=Ulyanov%2C+O+M">O. M. Ulyanov</a>, <a href="/search/astro-ph?searchtype=author&query=Cecconi%2C+B">B. Cecconi</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H">A. H. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Corbel%2C+S">S. Corbel</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=Denes%2C+H">H. Denes</a>, <a href="/search/astro-ph?searchtype=author&query=Girard%2C+J+N">J. N. Girard</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">B. Hut</a>, <a href="/search/astro-ph?searchtype=author&query=Ivashina%2C+M">M. Ivashina</a> , et al. (11 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="2109.08500v2-abstract-short" style="display: inline;"> PSR B0950+08 is a bright non-recycled pulsar whose single-pulse fluence variability is reportedly large. Based on observations at two widely separated frequencies, 55 MHz (NenuFAR) and 1.4 GHz (Westerbork Synthesis Radio Telescope), we review the properties of these single pulses. We conclude that they are more similar to ordinary pulses of radio emission than to a special kind of short and bright… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.08500v2-abstract-full').style.display = 'inline'; document.getElementById('2109.08500v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2109.08500v2-abstract-full" style="display: none;"> PSR B0950+08 is a bright non-recycled pulsar whose single-pulse fluence variability is reportedly large. Based on observations at two widely separated frequencies, 55 MHz (NenuFAR) and 1.4 GHz (Westerbork Synthesis Radio Telescope), we review the properties of these single pulses. We conclude that they are more similar to ordinary pulses of radio emission than to a special kind of short and bright Giant Pulses, observed from only a handful of pulsars. We argue that temporal variation of properties of interstellar medium along the line of sight to this nearby pulsar, namely the fluctuating size of decorrelation bandwidth of diffractive scintillation makes important contribution to observed single-pulse fluence variability. We further present interesting structures in the low-frequency single-pulse spectra that resemble the "sad trombones" seen in Fast Radio Bursts (FRBs); although for PSR B0950+08 the upward frequency drift is also routinely present. We explain these spectral features with radius-to-frequency mapping, similar to the model developed by Wang et al. (2019) for FRBs. Finally, we speculate that microsecond-scale fluence variability of the general pulsar population remains poorly known, and that its further study may bring important clues about the nature of FRBs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2109.08500v2-abstract-full').style.display = 'none'; document.getElementById('2109.08500v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 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">Accepted by A&A. This version includes a number of minor corrections, including corrected FRB luminosities on the time-luminosity phase-space plot for radio pulses from neutron stars and repeating FRBs</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 658, A143 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2107.04607">arXiv:2107.04607</a> <span> [<a href="https://arxiv.org/pdf/2107.04607">pdf</a>, <a href="https://arxiv.org/format/2107.04607">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/mnrasl/slab098">10.1093/mnrasl/slab098 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Evidence for profile changes in PSR J1713+0747 using the uGMRT </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Singha%2C+J">Jaikhomba Singha</a>, <a href="/search/astro-ph?searchtype=author&query=Surnis%2C+M+P">Mayuresh P Surnis</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Tarafdar%2C+P">Pratik Tarafdar</a>, <a href="/search/astro-ph?searchtype=author&query=Rana%2C+P">Prerna Rana</a>, <a href="/search/astro-ph?searchtype=author&query=Susobhanan%2C+A">Abhimanyu Susobhanan</a>, <a href="/search/astro-ph?searchtype=author&query=Girgaonkar%2C+R">Raghav Girgaonkar</a>, <a href="/search/astro-ph?searchtype=author&query=Kolhe%2C+N">Neel Kolhe</a>, <a href="/search/astro-ph?searchtype=author&query=Agarwal%2C+N">Nikita Agarwal</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">Shantanu Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Prabu%2C+T">T Prabu</a>, <a href="/search/astro-ph?searchtype=author&query=Bathula%2C+A">Adarsh Bathula</a>, <a href="/search/astro-ph?searchtype=author&query=Dandapat%2C+S">Subhajit Dandapat</a>, <a href="/search/astro-ph?searchtype=author&query=Dey%2C+L">Lankeswar Dey</a>, <a href="/search/astro-ph?searchtype=author&query=Hisano%2C+S">Shinnosuke Hisano</a>, <a href="/search/astro-ph?searchtype=author&query=Kato%2C+R">Ryo Kato</a>, <a href="/search/astro-ph?searchtype=author&query=Kharbanda%2C+D">Divyansh Kharbanda</a>, <a href="/search/astro-ph?searchtype=author&query=Kikunaga%2C+T">Tomonosuke Kikunaga</a>, <a href="/search/astro-ph?searchtype=author&query=Marmat%2C+P">Piyush Marmat</a>, <a href="/search/astro-ph?searchtype=author&query=Susarla%2C+S+C">Sai Chaitanya Susarla</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Batra%2C+N+D">Neelam Dhanda Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Choudhury%2C+A">Arpita Choudhury</a>, <a href="/search/astro-ph?searchtype=author&query=Gopakumar%2C+A">A Gopakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+Y">Yashwant Gupta</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="2107.04607v2-abstract-short" style="display: inline;"> PSR J1713+0747 is one of the most precisely timed pulsars in the international pulsar timing array experiment. This pulsar showed an abrupt profile shape change between April 16, 2021 (MJD 59320) and April 17, 2021 (MJD 59321). In this paper, we report the results from multi-frequency observations of this pulsar carried out with the upgraded Giant Metrewave Radio Telescope (uGMRT) before and after… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.04607v2-abstract-full').style.display = 'inline'; document.getElementById('2107.04607v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2107.04607v2-abstract-full" style="display: none;"> PSR J1713+0747 is one of the most precisely timed pulsars in the international pulsar timing array experiment. This pulsar showed an abrupt profile shape change between April 16, 2021 (MJD 59320) and April 17, 2021 (MJD 59321). In this paper, we report the results from multi-frequency observations of this pulsar carried out with the upgraded Giant Metrewave Radio Telescope (uGMRT) before and after the event. We demonstrate the profile change seen in Band 5 (1260 MHz - 1460 MHz) and Band 3 (300 MHz - 500 MHz). The timing analysis of this pulsar shows a disturbance accompanying this profile change followed by a recovery with a timescale of $\sim 159$ days. Our data suggest that a model with chromatic index as a free parameter is preferred over models with combinations of achromaticity with DM bump or scattering bump. We determine the frequency dependence to be $\sim谓^{+1.34}$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2107.04607v2-abstract-full').style.display = 'none'; document.getElementById('2107.04607v2-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> 16 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">Accepted for publication in MNRAS-Letters</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2104.04280">arXiv:2104.04280</a> <span> [<a href="https://arxiv.org/pdf/2104.04280">pdf</a>, <a href="https://arxiv.org/format/2104.04280">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202140578">10.1051/0004-6361/202140578 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A search for radio emission from double-neutron star merger GW190425 using Apertif </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Boersma%2C+O">Oliv茅r Boersma</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">Elizabeth A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">Bj枚rn Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A">Alexander Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T">Tom Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Brink%2C+R+v+d">R. van den Brink</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">L. Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">H. D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">B. Hut</a>, <a href="/search/astro-ph?searchtype=author&query=Ivashina%2C+M">M. Ivashina</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+M">D. M. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Mika%2C+%C3%81">脕. Mika</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Mulder%2C+H">H. Mulder</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Ruiter%2C+M">M. Ruiter</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Schuur%2C+D">D. van der Schuur</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="2104.04280v1-abstract-short" style="display: inline;"> Detection of the electromagnetic emission from coalescing binary neutron stars (BNS) is important for understanding the merger and afterglow. We present a search for a radio counterpart to the gravitational-wave source GW190425, a BNS merger, using Apertif on the Westerbork Synthesis Radio Telescope (WSRT). We observe a field of high probability in the associated localisation region for 3 epochs a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.04280v1-abstract-full').style.display = 'inline'; document.getElementById('2104.04280v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2104.04280v1-abstract-full" style="display: none;"> Detection of the electromagnetic emission from coalescing binary neutron stars (BNS) is important for understanding the merger and afterglow. We present a search for a radio counterpart to the gravitational-wave source GW190425, a BNS merger, using Apertif on the Westerbork Synthesis Radio Telescope (WSRT). We observe a field of high probability in the associated localisation region for 3 epochs at 68, 90 and 109 days post merger. We identify all sources that exhibit flux variations consistent with the expected afterglow emission of GW190425. We also look for possible transients. These are sources which are only present in one epoch. In addition, we quantify our ability to search for radio afterglows in fourth and future observing runs of the gravitational-wave detector network using Monte Carlo simulations. We found 25 afterglow candidates based on their variability. None of these could be associated with a possible host galaxy at the luminosity distance of GW190425. We also found 55 transient afterglow candidates that were only detected in one epoch. All turned out to be image artefacts. In the fourth observing run, we predict that up to three afterglows will be detectable by Apertif. While we did not find a source related to the afterglow emission of GW190425, the search validates our methods for future searches of radio afterglows. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2104.04280v1-abstract-full').style.display = 'none'; document.getElementById('2104.04280v1-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 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">11 pages, 7 figures, accepted for publication</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 650, A131 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.05818">arXiv:2101.05818</a> <span> [<a href="https://arxiv.org/pdf/2101.05818">pdf</a>, <a href="https://arxiv.org/ps/2101.05818">ps</a>, <a href="https://arxiv.org/format/2101.05818">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/10.1051/0004-6361/202040019">10.1051/0004-6361/202040019 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Apertif view of the OH Megamaser IRAS 10597+5926: OH 18 cm satellite lines in wide-area HI surveys </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">Kelley M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=Roberts%2C+H">H. Roberts</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">H. D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Darling%2C+J">J. Darling</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A">A. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+M">D. M. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">Raffaella Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T+A">T. A. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Schulz%2C+R">R. Schulz</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=Ivashina%2C+M">M. Ivashina</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. Marcel Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Mika%2C+%C3%81">脕. Mika</a>, <a href="/search/astro-ph?searchtype=author&query=Mulder%2C+H">H. Mulder</a>, <a href="/search/astro-ph?searchtype=author&query=Norden%2C+M+J">M. J. Norden</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Ruiter%2C+M">M. Ruiter</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</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="2101.05818v1-abstract-short" style="display: inline;"> We present the serendipitous detection of the two main OH maser lines at 1667 and 1665 MHz associated with IRAS 10597+5926 at z = 0.19612 in the untargeted Apertif Wide-area Extragalactic Survey (AWES), and the subsequent measurement of the OH 1612 MHz satellite line in the same source. With a total OH luminosity of log(L/L_Sun) = 3.90 +/- 0.03, IRAS 10597+5926 is the fourth brightest OH megamaser… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.05818v1-abstract-full').style.display = 'inline'; document.getElementById('2101.05818v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.05818v1-abstract-full" style="display: none;"> We present the serendipitous detection of the two main OH maser lines at 1667 and 1665 MHz associated with IRAS 10597+5926 at z = 0.19612 in the untargeted Apertif Wide-area Extragalactic Survey (AWES), and the subsequent measurement of the OH 1612 MHz satellite line in the same source. With a total OH luminosity of log(L/L_Sun) = 3.90 +/- 0.03, IRAS 10597+5926 is the fourth brightest OH megamaser (OHM) known. We measure a lower limit for the 1667/1612 ratio of R_1612 > 45.9 which is the highest limiting ratio measured for the 1612 MHz OH satellite line to date. OH satellite line measurements provide a potentially valuable constraint by which to compare detailed models of OH maser pumping mechanisms. Optical imaging shows the galaxy is likely a late-stage merger. Based on published infrared and far ultraviolet fluxes, we find that the galaxy is an ultra luminous infrared galaxy (ULIRG) with log(L_TIR/L_Sun) = 12.24, undergoing a star burst with an estimated star formation rate of 179 +/- 40 M_Sun/yr. These host galaxy properties are consistent with the physical conditions responsible for very bright OHM emission. Finally, we provide an update on the predicted number of OH masers that may be found in AWES, and estimate the total number of OH masers that will be detected in each of the individual main and satellite OH 18 cm lines. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.05818v1-abstract-full').style.display = 'none'; document.getElementById('2101.05818v1-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> 14 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">9 pages, 4 figures. Accepted for publication in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 647, A193 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.05334">arXiv:2101.05334</a> <span> [<a href="https://arxiv.org/pdf/2101.05334">pdf</a>, <a href="https://arxiv.org/format/2101.05334">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202140340">10.1051/0004-6361/202140340 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> High Precision Measurements of Interstellar Dispersion Measure with the upgraded GMRT </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M. A. Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Manoharan%2C+P+K">P. K. Manoharan</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Girgaonkar%2C+R">Raghav Girgaonkar</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">Shantanu Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Nobleson%2C+K">K. Nobleson</a>, <a href="/search/astro-ph?searchtype=author&query=Dey%2C+L">Lankeswar Dey</a>, <a href="/search/astro-ph?searchtype=author&query=Susobhanan%2C+A">Abhimanyu Susobhanan</a>, <a href="/search/astro-ph?searchtype=author&query=Susarla%2C+S+C">Sai Chaitanya Susarla</a>, <a href="/search/astro-ph?searchtype=author&query=Surnis%2C+M+P">Mayuresh P. Surnis</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Gopakumar%2C+A">A. Gopakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Basu%2C+A">Avishek Basu</a>, <a href="/search/astro-ph?searchtype=author&query=Batra%2C+N+D">Neelam Dhanda Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Choudhary%2C+A">Arpita Choudhary</a>, <a href="/search/astro-ph?searchtype=author&query=De%2C+K">Kishalay De</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+Y">Yashwant Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Naidu%2C+A+K">Arun Kumar Naidu</a>, <a href="/search/astro-ph?searchtype=author&query=Pathak%2C+D">Dhruv Pathak</a>, <a href="/search/astro-ph?searchtype=author&query=Singha%2C+J">Jaikhomba Singha</a>, <a href="/search/astro-ph?searchtype=author&query=Prabu%2C+T">T. Prabu</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="2101.05334v4-abstract-short" style="display: inline;"> Pulsar radio emission undergoes dispersion due to the presence of free electrons in the interstellar medium (ISM). The dispersive delay in the arrival time of pulsar signal changes over time due to the varying ISM electron column density along the line of sight. Correcting for this delay accurately is crucial for the detection of nanohertz gravitational waves using Pulsar Timing Arrays. In this wo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.05334v4-abstract-full').style.display = 'inline'; document.getElementById('2101.05334v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.05334v4-abstract-full" style="display: none;"> Pulsar radio emission undergoes dispersion due to the presence of free electrons in the interstellar medium (ISM). The dispersive delay in the arrival time of pulsar signal changes over time due to the varying ISM electron column density along the line of sight. Correcting for this delay accurately is crucial for the detection of nanohertz gravitational waves using Pulsar Timing Arrays. In this work, we present in-band and inter-band DM estimates of four pulsars observed with uGMRT over the timescale of a year using two different template alignment methods. The DMs obtained using both these methods show only subtle differences for PSR 1713+0747 and J1909$-$3744. A considerable offset is seen in the DM of PSR J1939+2134 and J2145$-$0750 between the two methods. This could be due to the presence of scattering in the former and profile evolution in the latter. We find that both methods are useful but could have a systematic offset between the DMs obtained. Irrespective of the template alignment methods followed, the precision on the DMs obtained is about $10^{-3}$ pc cm$^{-3}$ using only BAND3 and $10^{-4}$ pc cm$^{-3}$ after combining data from BAND3 and BAND5 of the uGMRT. In a particular result, we have detected a DM excess of about $5\times10^{-3}$ pc cm$^{-3}$ on 24 February 2019 for PSR J2145$-$0750. This excess appears to be due to the interaction region created by fast solar wind from a coronal hole and a coronal mass ejection (CME) observed from the Sun on that epoch. A detailed analysis of this interesting event is presented. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.05334v4-abstract-full').style.display = 'none'; document.getElementById('2101.05334v4-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 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 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">11 pages, 6 figures, 2 tables. Accepted by 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 651, A5 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2012.11630">arXiv:2012.11630</a> <span> [<a href="https://arxiv.org/pdf/2012.11630">pdf</a>, <a href="https://arxiv.org/ps/2012.11630">ps</a>, <a href="https://arxiv.org/format/2012.11630">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div 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/10.1051/0004-6361/202040164">10.1051/0004-6361/202040164 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Fourier domain excision of periodic radio frequency interference </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">Dany Vohl</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="2012.11630v2-abstract-short" style="display: inline;"> The discovery and study of pulsars and Fast Radio Bursts (FRBs) in time-domain radio data is often hampered by radio frequency interference (RFI). Some of this terrestrial RFI is impulsive and bright, and relatively easy to identify and remove. Other anthropogenic signals, however, are weaker yet periodic, and their persistence can drown out astrophysical signals. Here we show that Fourier-domain… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.11630v2-abstract-full').style.display = 'inline'; document.getElementById('2012.11630v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2012.11630v2-abstract-full" style="display: none;"> The discovery and study of pulsars and Fast Radio Bursts (FRBs) in time-domain radio data is often hampered by radio frequency interference (RFI). Some of this terrestrial RFI is impulsive and bright, and relatively easy to identify and remove. Other anthropogenic signals, however, are weaker yet periodic, and their persistence can drown out astrophysical signals. Here we show that Fourier-domain excision of periodic RFI is an effective and powerful step in detecting weak cosmic signals. We find that applying the method significantly increases the signal-to-noise ratio of transient as well as periodic pulsar signals. In live studies, we detected single pulses from pulsars and FRBs that would otherwise have remained buried in background noise. We show the method has no negative effects on pulsar pulse shape and that it enhances timing campaigns. We demonstrate the method on real-life data from a number of large radio telescopes, and conclude that Fourier-domain RFI excision increases the effective sensitivity to astrophysical sources by a significant fraction which can be even larger than an order of magnitude in case of strong RFI. An accelerated implementation of the method runs on standard time-domain radio data formats and is publicly available. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.11630v2-abstract-full').style.display = 'none'; document.getElementById('2012.11630v2-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 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 December, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">9 pages, 8 figures, accepted for publication in A&A. The associated software is available at https://github.com/ymaan4/RFIClean</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 650, A80 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2012.08348">arXiv:2012.08348</a> <span> [<a href="https://arxiv.org/pdf/2012.08348">pdf</a>, <a href="https://arxiv.org/format/2012.08348">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/10.1038/s41586-021-03724-8">10.1038/s41586-021-03724-8 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Chromatic periodic activity down to 120 MHz in a Fast Radio Burst </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Pastor-Marazuela%2C+I">In茅s Pastor-Marazuela</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">Liam Connor</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=ter+Veen%2C+S">Sander ter Veen</a>, <a href="/search/astro-ph?searchtype=author&query=Bilous%2C+A">Anna Bilous</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L">Leon Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Petroff%2C+E">Emily Petroff</a>, <a href="/search/astro-ph?searchtype=author&query=Straal%2C+S">Samayra Straal</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">Dany Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=Attema%2C+J">Jisk Attema</a>, <a href="/search/astro-ph?searchtype=author&query=Boersma%2C+O+M">Oliver M. Boersma</a>, <a href="/search/astro-ph?searchtype=author&query=Kooistra%2C+E">Eric Kooistra</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Schuur%2C+D">Daniel van der Schuur</a>, <a href="/search/astro-ph?searchtype=author&query=Sclocco%2C+A">Alessio Sclocco</a>, <a href="/search/astro-ph?searchtype=author&query=Smits%2C+R">Roy Smits</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">Elizabeth A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">Bj枚rn Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">Willem J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">Arthur H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">Sieds Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">Helga D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">Kelley M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+T">Thijs van der Hulst</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">Boudewijn Hut</a> , et al. (12 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2012.08348v1-abstract-short" style="display: inline;"> Fast radio bursts (FRBs) are extragalactic astrophysical transients whose brightness requires emitters that are highly energetic, yet compact enough to produce the short, millisecond-duration bursts. FRBs have thus far been detected between 300 MHz and 8 GHz, but lower-frequency emission has remained elusive. A subset of FRBs is known to repeat, and one of those sources, FRB 20180916B, does so wit… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.08348v1-abstract-full').style.display = 'inline'; document.getElementById('2012.08348v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2012.08348v1-abstract-full" style="display: none;"> Fast radio bursts (FRBs) are extragalactic astrophysical transients whose brightness requires emitters that are highly energetic, yet compact enough to produce the short, millisecond-duration bursts. FRBs have thus far been detected between 300 MHz and 8 GHz, but lower-frequency emission has remained elusive. A subset of FRBs is known to repeat, and one of those sources, FRB 20180916B, does so with a 16.3 day activity period. Using simultaneous Apertif and LOFAR data, we show that FRB 20180916B emits down to 120 MHz, and that its activity window is both narrower and earlier at higher frequencies. Binary wind interaction models predict a narrower periodic activity window at lower frequencies, which is the opposite of our observations. Our detections establish that low-frequency FRB emission can escape the local medium. For bursts of the same fluence, FRB 20180916B is more active below 200 MHz than at 1.4 GHz. Combining our results with previous upper-limits on the all-sky FRB rate at 150 MHz, we find that there are 3-450 FRBs/sky/day above 50 Jy ms at 90% confidence. We are able to rule out the scenario in which companion winds cause FRB periodicity. We also demonstrate that some FRBs live in clean environments that do not absorb or scatter low-frequency radiation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2012.08348v1-abstract-full').style.display = 'none'; document.getElementById('2012.08348v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 December, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">50 pages, 14 figures, 3 tables, submitted</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2011.08239">arXiv:2011.08239</a> <span> [<a href="https://arxiv.org/pdf/2011.08239">pdf</a>, <a href="https://arxiv.org/format/2011.08239">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/10.1051/0004-6361/202039102">10.1051/0004-6361/202039102 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">R. Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T+A">T. A. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Brienza%2C+M">M. Brienza</a>, <a href="/search/astro-ph?searchtype=author&query=Jurlin%2C+N">N. Jurlin</a>, <a href="/search/astro-ph?searchtype=author&query=Prandoni%2C+I">I. Prandoni</a>, <a href="/search/astro-ph?searchtype=author&query=Orru%27%2C+E">E. Orru'</a>, <a href="/search/astro-ph?searchtype=author&query=Shabala%2C+S+S">S. S. Shabala</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Best%2C+P+N">P. N. Best</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=de+Gasperin%2C+F">F. de Gasperin</a>, <a href="/search/astro-ph?searchtype=author&query=Denes%2C+H">H. Denes</a>, <a href="/search/astro-ph?searchtype=author&query=Hardcastle%2C+M">M. Hardcastle</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">B. Hut</a>, <a href="/search/astro-ph?searchtype=author&query=Kondapally%2C+R">R. Kondapally</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A+M">A. M. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+M">D. M. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Maccagni%2C+F+M">F. M. Maccagni</a>, <a href="/search/astro-ph?searchtype=author&query=Mingo%2C+B">B. Mingo</a> , et al. (14 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="2011.08239v1-abstract-short" style="display: inline;"> Supermassive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei is crucial for understanding the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.08239v1-abstract-full').style.display = 'inline'; document.getElementById('2011.08239v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2011.08239v1-abstract-full" style="display: none;"> Supermassive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei is crucial for understanding the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination of images at 1400 MHz produced by Apertif, the new phased-array feed receiver installed on the Westerbork Synthesis Radio Telescope, and images at 150 MHz provided by LOFAR, we have derived resolved spectral index images (at a resolution of ~15 arcsec) for all the sources within ~6 deg^2 area of the Lockman Hole region. We were able to select 15 extended radio sources with emission (partly or entirely) characterised by extremely steep spectral indices (steeper than 1.2). These objects represent radio sources in the remnant or the restarted phases of their life cycle. Our findings suggest this cycle to be relatively fast. They also show a variety of properties relevant for modelling the evolution of radio galaxies. For example, the restarted activity can occur while the remnant structure from a previous phase of activity is still visible. This provides constraints on the duration of the 'off' (dying) phase. In extended remnants with ultra-steep spectra at low frequencies, the activity likely stopped a few hundred megayears ago, and they correspond to the older tail of the age distribution of radio galaxies, in agreement with simulations of radio source evolution. We find remnant radio sources with a variety of structures (from double-lobed to amorphous), suggesting different types of progenitors. The present work sets the stage for exploiting low-frequency spectral index studies of extended sources by taking advantage of the large areas common to the LOFAR and the Apertif surveys. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2011.08239v1-abstract-full').style.display = 'none'; document.getElementById('2011.08239v1-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> 16 November, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">Accepted for publication in A&A. This paper is part of the 1st data release of the LoTSS Deep Fields. 17 pages, 10 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/2008.07945">arXiv:2008.07945</a> <span> [<a href="https://arxiv.org/pdf/2008.07945">pdf</a>, <a href="https://arxiv.org/format/2008.07945">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 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/10.1051/0004-6361/202038378">10.1051/0004-6361/202038378 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Extreme intra-hour variability of the radio source J1402+5347 discovered with Apertif </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T+A">T. A. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Vedantham%2C+H+K">H. K. Vedantham</a>, <a href="/search/astro-ph?searchtype=author&query=Kutkin%2C+A+M">A. M. Kutkin</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=De%27nes%2C+H">H. De'nes</a>, <a href="/search/astro-ph?searchtype=author&query=Hess%2C+K+M">K. M. Hess</a>, <a href="/search/astro-ph?searchtype=author&query=Hut%2C+B">B. Hut</a>, <a href="/search/astro-ph?searchtype=author&query=Loose%2C+G+M">G. M. Loose</a>, <a href="/search/astro-ph?searchtype=author&query=Lucero%2C+D+M">D. M. Lucero</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">R. Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Moss%2C+V+A">V. A. Moss</a>, <a href="/search/astro-ph?searchtype=author&query=Mulder%2C+H">H. Mulder</a>, <a href="/search/astro-ph?searchtype=author&query=Norden%2C+M+J">M. J. Norden</a>, <a href="/search/astro-ph?searchtype=author&query=Offringa%2C+A+R">A. R. Offringa</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Orru%60%2C+E">E. Orru`</a>, <a href="/search/astro-ph?searchtype=author&query=Ruiter%2C+M">M. Ruiter</a>, <a href="/search/astro-ph?searchtype=author&query=Schulz%2C+R">R. Schulz</a>, <a href="/search/astro-ph?searchtype=author&query=Brink%2C+R+H+v+d">R. H. van den Brink</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Hulst%2C+J+M">J. M. van der Hulst</a> , et al. (5 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="2008.07945v1-abstract-short" style="display: inline;"> The propagation of radio waves from distant compact radio sources through turbulent interstellar plasma in our Galaxy causes these sources to twinkle, a phenomenon called interstellar scintillation. Such scintillations are a unique probe of the micro-arcsecond structure of radio sources as well as of the sub-AU-scale structure of the Galactic interstellar medium. Weak scintillations (i.e. an inten… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2008.07945v1-abstract-full').style.display = 'inline'; document.getElementById('2008.07945v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2008.07945v1-abstract-full" style="display: none;"> The propagation of radio waves from distant compact radio sources through turbulent interstellar plasma in our Galaxy causes these sources to twinkle, a phenomenon called interstellar scintillation. Such scintillations are a unique probe of the micro-arcsecond structure of radio sources as well as of the sub-AU-scale structure of the Galactic interstellar medium. Weak scintillations (i.e. an intensity modulation of a few percent) on timescales of a few days or longer are commonly seen at centimetre wavelengths and are thought to result from the line-of-sight integrated turbulence in the interstellar plasma of the Milky Way. So far, only three sources were known that show more extreme variations, with modulations at the level of some dozen percent on timescales shorter than an hour. This requires propagation through nearby (d <~10 pc) anomalously dense (n_e ~10^2 cm^-3) plasma clouds. Here we report the discovery with Apertif of a source (J1402+5347) showing extreme (~50%) and rapid variations on a timescale of just 6.5 minutes in the decimetre band (1.4 GHz). The spatial scintillation pattern is highly anisotropic, with a semi-minor axis of about 20,000 km. The canonical theory of refractive scintillation constrains the scattering plasma to be within the Oort cloud. The sightline to J1402+5347, however, passes unusually close to the B3 star Alkaid (eta UMa) at a distance of 32 pc. If the scintillations are associated with Alkaid, then the angular size of J1402+5347 along the minor axis of the scintels must be smaller than ~10 micro arcsec yielding an apparent brightness temperature for an isotropic source of >~ 10^ 14K. } <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2008.07945v1-abstract-full').style.display = 'none'; document.getElementById('2008.07945v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 August, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">Accepted for Astronomy and Astrophysics Letters</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.02930">arXiv:2007.02930</a> <span> [<a href="https://arxiv.org/pdf/2007.02930">pdf</a>, <a href="https://arxiv.org/format/2007.02930">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> <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/10.1017/pasa.2021.12">10.1017/pasa.2021.12 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> pinta: The uGMRT Data Processing Pipeline for the Indian Pulsar Timing Array </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Susobhanan%2C+A">Abhimanyu Susobhanan</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Prabu%2C+T">T. Prabu</a>, <a href="/search/astro-ph?searchtype=author&query=Desai%2C+S">Shantanu Desai</a>, <a href="/search/astro-ph?searchtype=author&query=Nobleson%2C+K">K. Nobleson</a>, <a href="/search/astro-ph?searchtype=author&query=Susarla%2C+S+C">Sai Chaitanya Susarla</a>, <a href="/search/astro-ph?searchtype=author&query=Girgaonkar%2C+R">Raghav Girgaonkar</a>, <a href="/search/astro-ph?searchtype=author&query=Dey%2C+L">Lankeswar Dey</a>, <a href="/search/astro-ph?searchtype=author&query=Batra%2C+N+D">Neelam Dhanda Batra</a>, <a href="/search/astro-ph?searchtype=author&query=Gupta%2C+Y">Yashwant Gupta</a>, <a href="/search/astro-ph?searchtype=author&query=Gopakumar%2C+A">A. Gopakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Basu%2C+A">Avishek Basu</a>, <a href="/search/astro-ph?searchtype=author&query=Bethapudi%2C+S">Suryarao Bethapudi</a>, <a href="/search/astro-ph?searchtype=author&query=Choudhary%2C+A">Arpita Choudhary</a>, <a href="/search/astro-ph?searchtype=author&query=De%2C+K">Kishalay De</a>, <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M. A. Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Manoharan%2C+P+K">P. K. Manoharan</a>, <a href="/search/astro-ph?searchtype=author&query=Naidu%2C+A+K">Arun Kumar Naidu</a>, <a href="/search/astro-ph?searchtype=author&query=Pathak%2C+D">Dhruv Pathak</a>, <a href="/search/astro-ph?searchtype=author&query=Singha%2C+J">Jaikhomba Singha</a>, <a href="/search/astro-ph?searchtype=author&query=Surnis%2C+M+P">Mayuresh P. Surnis</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="2007.02930v5-abstract-short" style="display: inline;"> We introduce pinta, a pipeline for reducing the upgraded Giant Metre-wave Radio Telescope (uGMRT) raw pulsar timing data, developed for the Indian Pulsar Timing Array experiment. We provide a detailed description of the workflow and usage of pinta, as well as its computational performance and RFI mitigation characteristics. We also discuss a novel and independent determination of the relative time… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.02930v5-abstract-full').style.display = 'inline'; document.getElementById('2007.02930v5-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.02930v5-abstract-full" style="display: none;"> We introduce pinta, a pipeline for reducing the upgraded Giant Metre-wave Radio Telescope (uGMRT) raw pulsar timing data, developed for the Indian Pulsar Timing Array experiment. We provide a detailed description of the workflow and usage of pinta, as well as its computational performance and RFI mitigation characteristics. We also discuss a novel and independent determination of the relative time offsets between the different back-end modes of uGMRT and the interpretation of the uGMRT observation frequency settings, and their agreement with results obtained from engineering tests. Further, we demonstrate the capability of pinta to generate data products which can produce high-precision TOAs using PSR J1909-3744 as an example. These results are crucial for performing precision pulsar timing with the uGMRT. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.02930v5-abstract-full').style.display = 'none'; document.getElementById('2007.02930v5-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> 16 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 6 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Publications of the Astronomical Society of Australia, 38, E017 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2005.14366">arXiv:2005.14366</a> <span> [<a href="https://arxiv.org/pdf/2005.14366">pdf</a>, <a href="https://arxiv.org/format/2005.14366">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> <span class="tag is-small is-grey 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/10.1017/pasa.2020.19">10.1017/pasa.2020.19 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The MeerKAT Telescope as a Pulsar Facility: System verification and early science results from MeerTime </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bailes%2C+M">M. Bailes</a>, <a href="/search/astro-ph?searchtype=author&query=Jameson%2C+A">A. Jameson</a>, <a href="/search/astro-ph?searchtype=author&query=Abbate%2C+F">F. Abbate</a>, <a href="/search/astro-ph?searchtype=author&query=Barr%2C+E+D">E. D. Barr</a>, <a href="/search/astro-ph?searchtype=author&query=Bhat%2C+N+D+R">N. D. R. Bhat</a>, <a href="/search/astro-ph?searchtype=author&query=Bondonneau%2C+L">L. Bondonneau</a>, <a href="/search/astro-ph?searchtype=author&query=Burgay%2C+M">M. Burgay</a>, <a href="/search/astro-ph?searchtype=author&query=Buchner%2C+S+J">S. J. Buchner</a>, <a href="/search/astro-ph?searchtype=author&query=Camilo%2C+F">F. Camilo</a>, <a href="/search/astro-ph?searchtype=author&query=Champion%2C+D+J">D. J. Champion</a>, <a href="/search/astro-ph?searchtype=author&query=Cognard%2C+I">I. Cognard</a>, <a href="/search/astro-ph?searchtype=author&query=Demorest%2C+P+B">P. B. Demorest</a>, <a href="/search/astro-ph?searchtype=author&query=Freire%2C+P+C+C">P. C. C. Freire</a>, <a href="/search/astro-ph?searchtype=author&query=Gautam%2C+T">T. Gautam</a>, <a href="/search/astro-ph?searchtype=author&query=Geyer%2C+M">M. Geyer</a>, <a href="/search/astro-ph?searchtype=author&query=Griessmeier%2C+J+M">J. M. Griessmeier</a>, <a href="/search/astro-ph?searchtype=author&query=Guillemot%2C+L">L. Guillemot</a>, <a href="/search/astro-ph?searchtype=author&query=Hu%2C+H">H. Hu</a>, <a href="/search/astro-ph?searchtype=author&query=Jankowski%2C+F">F. Jankowski</a>, <a href="/search/astro-ph?searchtype=author&query=Johnston%2C+S">S. Johnston</a>, <a href="/search/astro-ph?searchtype=author&query=Karastergiou%2C+A">A. Karastergiou</a>, <a href="/search/astro-ph?searchtype=author&query=Karuppusamy%2C+R">R. Karuppusamy</a>, <a href="/search/astro-ph?searchtype=author&query=Kaur%2C+D">D. Kaur</a>, <a href="/search/astro-ph?searchtype=author&query=Keith%2C+M+J">M. J. Keith</a>, <a href="/search/astro-ph?searchtype=author&query=Kramer%2C+M">M. Kramer</a> , et al. (50 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="2005.14366v1-abstract-short" style="display: inline;"> We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for the newly-commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. MeerKAT is a high-gain (~2.8 K/Jy) low-system temperature (~18 K at 20cm) radio array that currently operates from 580-1670 MHz and can produce tied-array beams suitable for pulsar observations. This paper pres… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.14366v1-abstract-full').style.display = 'inline'; document.getElementById('2005.14366v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2005.14366v1-abstract-full" style="display: none;"> We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for the newly-commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. MeerKAT is a high-gain (~2.8 K/Jy) low-system temperature (~18 K at 20cm) radio array that currently operates from 580-1670 MHz and can produce tied-array beams suitable for pulsar observations. This paper presents results from the MeerTime Large Survey Project and commissioning tests with PTUSE. Highlights include observations of the double pulsar J0737-3039A, pulse profiles from 34 millisecond pulsars from a single 2.5h observation of the Globular cluster Terzan 5, the rotation measure of Ter5O, a 420-sigma giant pulse from the Large Magellanic Cloud pulsar PSR J0540-6919, and nulling identified in the slow pulsar PSR J0633-2015. One of the key design specifications for MeerKAT was absolute timing errors of less than 5 ns using their novel precise time system. Our timing of two bright millisecond pulsars confirm that MeerKAT delivers exceptional timing. PSR J2241-5236 exhibits a jitter limit of <4 ns per hour whilst timing of PSR J1909-3744 over almost 11 months yields an rms residual of 66 ns with only 4 min integrations. Our results confirm that the MeerKAT is an exceptional pulsar telescope. The array can be split into four separate sub-arrays to time over 1000 pulsars per day and the future deployment of S-band (1750-3500 MHz) receivers will further enhance its capabilities. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.14366v1-abstract-full').style.display = 'none'; document.getElementById('2005.14366v1-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 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">20 pages, 16 Figures, 4 Tables, accepted for publication in PASA</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2005.05643">arXiv:2005.05643</a> <span> [<a href="https://arxiv.org/pdf/2005.05643">pdf</a>, <a href="https://arxiv.org/format/2005.05643">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ab9226">10.3847/1538-4357/ab9226 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Single pulse modeling and the bi-drifting subpulses of radio pulsar B1839-04 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Szary%2C+A">Andrzej Szary</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Weltevrede%2C+P">Patrick Weltevrede</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</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="2005.05643v1-abstract-short" style="display: inline;"> We study the bi-drifting pulsar B1839-04, where the observed subpulse drift direction in the two leading pulse components is opposite from that in the two trailing components. Such diametrically opposed apparent motions challenge our understanding of an underlying structure. We find that for the geometry spanned by the observer and the pulsar magnetic and rotation axes, the observed bi-drifting in… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.05643v1-abstract-full').style.display = 'inline'; document.getElementById('2005.05643v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2005.05643v1-abstract-full" style="display: none;"> We study the bi-drifting pulsar B1839-04, where the observed subpulse drift direction in the two leading pulse components is opposite from that in the two trailing components. Such diametrically opposed apparent motions challenge our understanding of an underlying structure. We find that for the geometry spanned by the observer and the pulsar magnetic and rotation axes, the observed bi-drifting in B1839-04 can be reproduced assuming a non-dipolar configuration of the surface magnetic field. Acceptable solutions are found to either have relatively weak $(\sim 10^{12} \,{\rm G})$ or strong $(\sim 10^{14} \,{\rm G})$ surface magnetic fields. Our single pulse modeling shows that a global electric potential variation at the polar cap that leads to a solid-body-like rotation of spark forming regions is favorable in reproducing the observed drift characteristics. This variation of the potential additionally ensures that the variability is identical in all pulse components resulting in the observed phase locking of subpulses. Thorough and more general studies of pulsar geometry show that a low ratio of impact factor to opening angle $(尾/ 蟻)$ increases the likelihood of bi-drifting to be observed. We thus conclude that bi-drifting is visible when our line of sight crosses close to the magnetic pole. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.05643v1-abstract-full').style.display = 'none'; document.getElementById('2005.05643v1-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 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">15 pages, 14 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/2002.01399">arXiv:2002.01399</a> <span> [<a href="https://arxiv.org/pdf/2002.01399">pdf</a>, <a href="https://arxiv.org/format/2002.01399">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/staa3009">10.1093/mnras/staa3009 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A bright, high rotation-measure FRB that skewers the M33 halo </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">Liam Connor</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Petroff%2C+E">E. Petroff</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Attema%2C+J+J">J. J. Attema</a>, <a href="/search/astro-ph?searchtype=author&query=Bast%2C+J+E">J. E. Bast</a>, <a href="/search/astro-ph?searchtype=author&query=Boersma%2C+O+M">O. M. Boersma</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%A9nes%2C+H">H. D茅nes</a>, <a href="/search/astro-ph?searchtype=author&query=Gardenier%2C+D+W">D. W. Gardenier</a>, <a href="/search/astro-ph?searchtype=author&query=Hargreaves%2C+J+E">J. E. Hargreaves</a>, <a href="/search/astro-ph?searchtype=author&query=Kooistra%2C+E">E. Kooistra</a>, <a href="/search/astro-ph?searchtype=author&query=Pastor-Marazuela%2C+I">I. Pastor-Marazuela</a>, <a href="/search/astro-ph?searchtype=author&query=Schulz%2C+R">R. Schulz</a>, <a href="/search/astro-ph?searchtype=author&query=Sclocco%2C+A">A. Sclocco</a>, <a href="/search/astro-ph?searchtype=author&query=Smits%2C+R">R. Smits</a>, <a href="/search/astro-ph?searchtype=author&query=Straal%2C+S+M">S. M. Straal</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Schuur%2C+D">D. van der Schuur</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">Dany Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a> , et al. (15 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="2002.01399v2-abstract-short" style="display: inline;"> We report the detection of a bright fast radio burst, FRB\,191108, with Apertif on the Westerbork Synthesis Radio Telescope (WSRT). The interferometer allows us to localise the FRB to a narrow $5\arcsec\times7\arcmin$ ellipse by employing both multibeam information within the Apertif phased-array feed (PAF) beam pattern, and across different tied-array beams. The resulting sight line passes close… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.01399v2-abstract-full').style.display = 'inline'; document.getElementById('2002.01399v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2002.01399v2-abstract-full" style="display: none;"> We report the detection of a bright fast radio burst, FRB\,191108, with Apertif on the Westerbork Synthesis Radio Telescope (WSRT). The interferometer allows us to localise the FRB to a narrow $5\arcsec\times7\arcmin$ ellipse by employing both multibeam information within the Apertif phased-array feed (PAF) beam pattern, and across different tied-array beams. The resulting sight line passes close to Local Group galaxy M33, with an impact parameter of only 18\,kpc with respect to the core. It also traverses the much larger circumgalactic medium of M31, the Andromeda Galaxy. We find that the shared plasma of the Local Group galaxies could contribute $\sim$10\% of its dispersion measure of 588\,pc\,cm$^{-3}$. FRB\,191108 has a Faraday rotation measure of +474\,$\pm\,3$\,rad\,m$^{-2}$, which is too large to be explained by either the Milky Way or the intergalactic medium. Based on the more moderate RMs of other extragalactic sources that traverse the halo of M33, we conclude that the dense magnetised plasma resides in the host galaxy. The FRB exhibits frequency structure on two scales, one that is consistent with quenched Galactic scintillation and broader spectral structure with $螖谓\approx40$\,MHz. If the latter is due to scattering in the shared M33/M31 CGM, our results constrain the Local Group plasma environment. We found no accompanying persistent radio sources in the Apertif imaging survey data. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.01399v2-abstract-full').style.display = 'none'; document.getElementById('2002.01399v2-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 September, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2020. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.12217">arXiv:1912.12217</a> <span> [<a href="https://arxiv.org/pdf/1912.12217">pdf</a>, <a href="https://arxiv.org/format/1912.12217">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201937422">10.1051/0004-6361/201937422 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Repeating fast radio bursts with WSRT/Apertif </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Connor%2C+L">L. Connor</a>, <a href="/search/astro-ph?searchtype=author&query=Petroff%2C+E">E. Petroff</a>, <a href="/search/astro-ph?searchtype=author&query=Attema%2C+J+J">J. J. Attema</a>, <a href="/search/astro-ph?searchtype=author&query=Bast%2C+J+E">J. E. Bast</a>, <a href="/search/astro-ph?searchtype=author&query=Gardenier%2C+D+W">D. W. Gardenier</a>, <a href="/search/astro-ph?searchtype=author&query=Hargreaves%2C+J+E">J. E. Hargreaves</a>, <a href="/search/astro-ph?searchtype=author&query=Kooistra%2C+E">E. Kooistra</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Schuur%2C+D">D. van der Schuur</a>, <a href="/search/astro-ph?searchtype=author&query=Sclocco%2C+A">A. Sclocco</a>, <a href="/search/astro-ph?searchtype=author&query=Smits%2C+R">R. Smits</a>, <a href="/search/astro-ph?searchtype=author&query=Straal%2C+S+M">S. M. Straal</a>, <a href="/search/astro-ph?searchtype=author&query=ter+Veen%2C+S">S. ter Veen</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">D. Vohl</a>, <a href="/search/astro-ph?searchtype=author&query=Adams%2C+E+A+K">E. A. K. Adams</a>, <a href="/search/astro-ph?searchtype=author&query=Adebahr%2C+B">B. Adebahr</a>, <a href="/search/astro-ph?searchtype=author&query=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Brink%2C+R+H+v+d">R. H. van den Brink</a>, <a href="/search/astro-ph?searchtype=author&query=van+Cappellen%2C+W+A">W. A. van Cappellen</a>, <a href="/search/astro-ph?searchtype=author&query=Coolen%2C+A+H+W+M">A. H. W. M. Coolen</a>, <a href="/search/astro-ph?searchtype=author&query=Damstra%2C+S">S. Damstra</a>, <a href="/search/astro-ph?searchtype=author&query=van+Diepen%2C+G+N+J">G. N. J. van Diepen</a>, <a href="/search/astro-ph?searchtype=author&query=Frank%2C+B+S">B. S. Frank</a> , et al. (18 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="1912.12217v2-abstract-short" style="display: inline;"> Repeating fast radio bursts (FRBs) present excellent opportunities to identify FRB progenitors and host environments, as well as decipher the underlying emission mechanism. Detailed studies of repeating FRBs might also hold clues to the origin of FRBs as a population. We aim to detect the first two repeating FRBs: FRB 121102 (R1) and FRB 180814.J0422+73 (R2), and characterise their repeat statisti… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.12217v2-abstract-full').style.display = 'inline'; document.getElementById('1912.12217v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.12217v2-abstract-full" style="display: none;"> Repeating fast radio bursts (FRBs) present excellent opportunities to identify FRB progenitors and host environments, as well as decipher the underlying emission mechanism. Detailed studies of repeating FRBs might also hold clues to the origin of FRBs as a population. We aim to detect the first two repeating FRBs: FRB 121102 (R1) and FRB 180814.J0422+73 (R2), and characterise their repeat statistics. We also want to significantly improve the sky localisation of R2. We use the Westerbork Synthesis Radio Telescope to conduct extensive follow-up of these two repeating FRBs. The new phased-array feed system, Apertif, allows covering the entire sky position uncertainty of R2 with fine spatial resolution in one pointing. We characterise the energy distribution and the clustering of detected R1 bursts. We detected 30 bursts from R1. Our measurements indicate a dispersion measure of 563.5(2) pc cm$^{-3}$, suggesting a significant increase in DM over the past few years. We place an upper limit of 8% on the linear polarisation fraction of the brightest burst. We did not detect any bursts from R2. A single power-law might not fit the R1 burst energy distribution across the full energy range or widely separated detections. Our observations provide improved constraints on the clustering of R1 bursts. Our stringent upper limits on the linear polarisation fraction imply a significant depolarisation, either intrinsic to the emission mechanism or caused by the intervening medium, at 1400 MHz that is not observed at higher frequencies. The non-detection of any bursts from R2 implies either a highly clustered nature of the bursts, a steep spectral index, or a combination of both. Alternatively, R2 has turned off completely, either permanently or for an extended period of time. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.12217v2-abstract-full').style.display = 'none'; document.getElementById('1912.12217v2-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 January, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 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">11 pages, 7 figures, submitted to A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 635, A61 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.11534">arXiv:1909.11534</a> <span> [<a href="https://arxiv.org/pdf/1909.11534">pdf</a>, <a href="https://arxiv.org/format/1909.11534">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/staa146">10.1093/mnras/staa146 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A search for pulsars in subdwarf B binary systems and discovery of giant-pulse emitting PSR J0533-4524 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">J. van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Coenen%2C+T">T. Coenen</a>, <a href="/search/astro-ph?searchtype=author&query=Ishwara-Chandra%2C+C+H">C. H. Ishwara-Chandra</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="1909.11534v2-abstract-short" style="display: inline;"> Binary millisecond pulsars (MSPs) provide several opportunities for research of fundamental physics. However, finding them can be challenging. Several subdwarf B (sdB) binary systems with possible neutron star companions have been identified, allowing us to perform a targeted search for MSPs within these systems. Six sdBs with companions in the neutron star mass range, as determined from their opt… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.11534v2-abstract-full').style.display = 'inline'; document.getElementById('1909.11534v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.11534v2-abstract-full" style="display: none;"> Binary millisecond pulsars (MSPs) provide several opportunities for research of fundamental physics. However, finding them can be challenging. Several subdwarf B (sdB) binary systems with possible neutron star companions have been identified, allowing us to perform a targeted search for MSPs within these systems. Six sdBs with companions in the neutron star mass range, as determined from their optical light curves, were observed with the Green Bank and Westerbork radio telescopes. The data were searched for periodic signals as well as single pulses. No radio pulsations from sdB systems were detected, down to an average sensitivity limit of 0.11 mJy. We did, however, discover a pulsar in the field of sdB HE0532-4503. Follow-up observations with the Giant Metrewave Radio Telescope showed that this pulsar, J0533-4524, is not spatially coincident with the sdB system. The pulsar has a relatively low magnetic field but still emits giant pulses. We place an upper limit of three to the number of radio pulsars in the six sdB systems. The non-detections may be explained by a combination of the MSP beaming fraction, luminosity, and a recycling fraction <0.5. Alternatively, the assumption of co-rotation between the MSP and sdB may break down, which implies the systems are more edge-on than previously thought. This would shift the predicted companion masses into the white dwarf range. It would also explain the relative lack of edge-on sdB systems with massive companions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.11534v2-abstract-full').style.display = 'none'; document.getElementById('1909.11534v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 January, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">12 pages, 8 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/1908.04304">arXiv:1908.04304</a> <span> [<a href="https://arxiv.org/pdf/1908.04304">pdf</a>, <a href="https://arxiv.org/ps/1908.04304">ps</a>, <a href="https://arxiv.org/format/1908.04304">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/2041-8213/ab3a47">10.3847/2041-8213/ab3a47 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Distinct properties of the radio burst emission from the magnetar XTE J1810-197 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Surnis%2C+M+P">Mayuresh P. Surnis</a>, <a href="/search/astro-ph?searchtype=author&query=Bagchi%2C+M">Manjari Bagchi</a>, <a href="/search/astro-ph?searchtype=author&query=Manoharan%2C+P+K">P. K. Manoharan</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="1908.04304v2-abstract-short" style="display: inline;"> XTE J1810-197 (PSR J1809-1943) was the first ever magnetar which was found to emit transient radio emission. It has recently undergone another radio and high-energy outburst. This is only the second radio outburst that has been observed from this source. We observed J1810-197 soon after its recent radio outburst at low radio frequencies using the Giant Metrewave Radio Telescope. We present the 650… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.04304v2-abstract-full').style.display = 'inline'; document.getElementById('1908.04304v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1908.04304v2-abstract-full" style="display: none;"> XTE J1810-197 (PSR J1809-1943) was the first ever magnetar which was found to emit transient radio emission. It has recently undergone another radio and high-energy outburst. This is only the second radio outburst that has been observed from this source. We observed J1810-197 soon after its recent radio outburst at low radio frequencies using the Giant Metrewave Radio Telescope. We present the 650 MHz flux density evolution of the source in the early phases of the outburst, and its radio spectrum down to frequencies as low as 300 MHz. The magnetar also exhibits radio emission in the form of strong, narrow bursts. We show that the bursts have a characteristic intrinsic width of the order of 0.5-0.7 ms, and discuss their properties in the context of giant pulses and giant micropulses from other pulsars. We also show that the bursts exhibit spectral structures which cannot be explained by interstellar propagation effects. These structures might indicate a phenomenological link with the repeating fast radio bursts which also show interesting, more detailed frequency structures. While the spectral structures are particularly noticeable in the early phases of the outburst, these seem to be less prominent as well as less frequent in the later phases, suggesting an evolution of the underlying cause of these spectral structures. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.04304v2-abstract-full').style.display = 'none'; document.getElementById('1908.04304v2-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 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 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">A few minor changes in the previous version; consistent with the published article</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJL, 2019, vol. 882, L9 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1906.07156">arXiv:1906.07156</a> <span> [<a href="https://arxiv.org/pdf/1906.07156">pdf</a>, <a href="https://arxiv.org/format/1906.07156">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201935662">10.1051/0004-6361/201935662 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the origin of the off-pulse emission from the pulsars B0525+21 and B2045-16 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Marcote%2C+B">B. Marcote</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Y. Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Z. Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Keimpema%2C+A">A. Keimpema</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="1906.07156v1-abstract-short" style="display: inline;"> Pulsars typically exhibit radio emission in the form of narrow pulses originated from confined regions of their magnetospheres. A potential presence of magnetospherically originated emission outside this region, the so-called off-pulse emission, would challenge the existing theories. Detection of significant off-pulse emission has been reported so far from only two pulsars, B0525+21 and B2045-16,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.07156v1-abstract-full').style.display = 'inline'; document.getElementById('1906.07156v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1906.07156v1-abstract-full" style="display: none;"> Pulsars typically exhibit radio emission in the form of narrow pulses originated from confined regions of their magnetospheres. A potential presence of magnetospherically originated emission outside this region, the so-called off-pulse emission, would challenge the existing theories. Detection of significant off-pulse emission has been reported so far from only two pulsars, B0525+21 and B2045-16, at 325 and 610 MHz. However, the nature of this newly uncovered off-pulse emission remains unclear. To probe its origin we conducted very high resolution radio observations of B0525+21 and B2045-16 with the European VLBI Network (EVN) at 1.39 GHz. Whereas the pulsed emission is detected at a level consistent with previous observations, we report absence of any off-pulse emission above $42$ and $96\ \mathrm{渭Jy\ beam^{-1}}$ (three times the rms noise levels) for B0525+21 and B2045-16, respectively. Our stringent upper limits imply the off-pulse emission to be less than $0.4$ and $0.3\%$ of the period-averaged pulsed flux density, i.e., much fainter than the previously suggested values of $1$-$10\%$. Since the EVN data are most sensitive to extremely compact angular scales, our results suggest a non-magnetospheric origin for the previously reported off-pulse emission. Presence of extended emission that is resolved out on these milliarcsecond scales still remains plausible. In this case, we constrain the emission to arise from structures with sizes of $\sim (0.61$-$19) \times 10^3\ \mathrm{au}$ for B0525+21 and $\sim (0.48$-$8.3) \times 10^3\ \mathrm{au}$ for B2045-16. These constraints might indicate that the two pulsars are accompanied by compact bow-shock pulsar wind nebulae. Future observations probing intermediate angular scales ($\sim 0.1$-$5\ \mathrm{arcsec}$) will help in clarifying the actual origin of the off-pulse emission. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1906.07156v1-abstract-full').style.display = 'none'; document.getElementById('1906.07156v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 June, 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">6 pages, 4 figures, accepted for publication as a Letter in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 627, L2 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.01651">arXiv:1905.01651</a> <span> [<a href="https://arxiv.org/pdf/1905.01651">pdf</a>, <a href="https://arxiv.org/ps/1905.01651">ps</a>, <a href="https://arxiv.org/format/1905.01651">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ab20c5">10.3847/1538-4357/ab20c5 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multi-frequency scatter broadening evolution of pulsars - II. Scatter broadening of nearby pulsars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M. A. Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Manoharan%2C+P+K">P. K. Manoharan</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="1905.01651v1-abstract-short" style="display: inline;"> We present multi-frequency scatter broadening evolution of 29 pulsars observed with the LOw Frequency ARray (LOFAR) and Long Wavelength Array (LWA). We conducted new observations using LOFAR Low Band Antennae (LBA) as well as utilized the archival data from LOFAR and LWA. This study has increased the total of all multi-frequency or wide-band scattering measurements up to a dispersion measure (DM)… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.01651v1-abstract-full').style.display = 'inline'; document.getElementById('1905.01651v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.01651v1-abstract-full" style="display: none;"> We present multi-frequency scatter broadening evolution of 29 pulsars observed with the LOw Frequency ARray (LOFAR) and Long Wavelength Array (LWA). We conducted new observations using LOFAR Low Band Antennae (LBA) as well as utilized the archival data from LOFAR and LWA. This study has increased the total of all multi-frequency or wide-band scattering measurements up to a dispersion measure (DM) of 150~pc\,cm$^{-3}$ by 60\%. The scatter broadening timescale ($蟿_{sc}$) measurements at different frequencies are often combined by scaling them to a common reference frequency of 1\,GHz. Using our data, we show that the $蟿_{sc}$--DM variations are best fitted for reference frequencies close to 200--300\,MHz, and scaling to higher or lower frequencies results in significantly more scatter in data. We suggest that this effect might indicate a frequency dependence of the scatter broadening scaling index ($伪$). However, a selection bias due to our chosen observing frequencies can not be ruled out with the current data set. Our data did not favour any particular model of the DM -- $蟿_{sc}$ relations, and we do not see a statistically significant break at the low DM range in this relation. The turbulence spectral index ($尾$) is found to be steeper than that is expected from a Kolmogorov spectrum. This indicates that the local ISM turbulence may have a low wave-number cutoff or presence of large scale inhomogeneities in the line of sight to some of the reported pulsars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.01651v1-abstract-full').style.display = 'none'; document.getElementById('1905.01651v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">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/1812.01010">arXiv:1812.01010</a> <span> [<a href="https://arxiv.org/pdf/1812.01010">pdf</a>, <a href="https://arxiv.org/ps/1812.01010">ps</a>, <a href="https://arxiv.org/format/1812.01010">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/aaf41c">10.3847/1538-4357/aaf41c <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Expected imprints of the carousel in multi-frequency pulsar observations and new evidence for multi-altitude emission </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</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="1812.01010v1-abstract-short" style="display: inline;"> Subpulse modulation has been regarded as one of the most insightful and intriguing aspects of pulsar radio emission. This phenomenon is generally explained by the presence of a carousel of sparks in the polar acceleration gap region that rotates around the magnetic axis due to the E$\times$B drift. While there have been extensive single pulse studies, geometric signatures of the underlying carouse… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.01010v1-abstract-full').style.display = 'inline'; document.getElementById('1812.01010v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1812.01010v1-abstract-full" style="display: none;"> Subpulse modulation has been regarded as one of the most insightful and intriguing aspects of pulsar radio emission. This phenomenon is generally explained by the presence of a carousel of sparks in the polar acceleration gap region that rotates around the magnetic axis due to the E$\times$B drift. While there have been extensive single pulse studies, geometric signatures of the underlying carousel, or lack thereof, in simultaneous multi-frequency observations have remained largely unexplored. This work presents a theoretical account of such expected signatures, particularly that of a geometry induced phase-offset in subpulse modulation, including various formulae that can be readily applied to observations. A notable result is a method to resolve aliasing in the measured subpulse modulation period without relying on knowledge of the viewing geometry parameters. It is also shown in detail that the geometry induced phase-offset enables critical tests of various observed phenomena as well as proposed hypotheses, e.g., multi-altitude emission, magnetic field twisting, pseudo-nulls, etc., in addition to that of the carousel model itself. Finally, a detailed analysis of a 327 MHz pulse-sequence of PSR B1237+25 is presented as a case study to test the single-frequency multi-altitude emission scenario. The analysis provides a firm evidence of inner and outer conal components of this pulsar to have originated from the same carousel of subbeams and emitted at different heights. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1812.01010v1-abstract-full').style.display = 'none'; document.getElementById('1812.01010v1-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 December, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1807.08363">arXiv:1807.08363</a> <span> [<a href="https://arxiv.org/pdf/1807.08363">pdf</a>, <a href="https://arxiv.org/ps/1807.08363">ps</a>, <a href="https://arxiv.org/format/1807.08363">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/aad4ad">10.3847/1538-4357/aad4ad <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Search for Pulsars in Steep Spectrum Radio Sources </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Bassa%2C+C">Cees Bassa</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</a>, <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M. A. Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</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="1807.08363v1-abstract-short" style="display: inline;"> We report on a time-domain search for pulsars in 44 steep spectrum radio sources originally identified from recent imaging surveys. The time-domain search was conducted at 327 MHz using the Ooty radio telescope, and utilized a semi-coherent dedispersion scheme retaining the sensitivity even for sub-millisecond periods up to reasonably high dispersion measures. No new pulsars were found. We discuss… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.08363v1-abstract-full').style.display = 'inline'; document.getElementById('1807.08363v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1807.08363v1-abstract-full" style="display: none;"> We report on a time-domain search for pulsars in 44 steep spectrum radio sources originally identified from recent imaging surveys. The time-domain search was conducted at 327 MHz using the Ooty radio telescope, and utilized a semi-coherent dedispersion scheme retaining the sensitivity even for sub-millisecond periods up to reasonably high dispersion measures. No new pulsars were found. We discuss the nature of these steep spectrum sources and argue that majority of the sources in our sample should either be pulsars or a new category of Galactic sources. Several possibilities that could hinder detection of these sources as pulsars, including anomalously high scattering or alignment of the rotation and magnetic axes, are discussed in detail, and we suggest unconventional search methods to further probe these possibilities. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.08363v1-abstract-full').style.display = 'none'; document.getElementById('1807.08363v1-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, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in ApJ</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1712.04219">arXiv:1712.04219</a> <span> [<a href="https://arxiv.org/pdf/1712.04219">pdf</a>, <a href="https://arxiv.org/ps/1712.04219">ps</a>, <a href="https://arxiv.org/format/1712.04219">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/S1743921317009474">10.1017/S1743921317009474 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Exploiting simultaneous multi-frequency observations to probe polar-cap processes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</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="1712.04219v1-abstract-short" style="display: inline;"> Sub-pulse drifting has been regarded as one of the most insightful aspects of the pulsar radio emission. The phenomenon is generally explained with a system of emission sub-beams rotating around the magnetic axis, originating from a carousel of sparks near the pulsar surface (the carousel model). Since the observed radio emission at different frequencies is generated at different altitudes in the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.04219v1-abstract-full').style.display = 'inline'; document.getElementById('1712.04219v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1712.04219v1-abstract-full" style="display: none;"> Sub-pulse drifting has been regarded as one of the most insightful aspects of the pulsar radio emission. The phenomenon is generally explained with a system of emission sub-beams rotating around the magnetic axis, originating from a carousel of sparks near the pulsar surface (the carousel model). Since the observed radio emission at different frequencies is generated at different altitudes in the pulsar magnetosphere, corresponding sampling of the carousel on the polar cap differs slightly in magnetic latitude. When this aspect is considered, it is shown here that the carousel model predicts important observable effects in multi-frequency or wide-band observations. Also presented here are brief mentions of how this aspect can be exploited to probe the electrodynamics in the polar cap by estimating various physical quantities, and correctly interpret various carousel related phenomena, in addition to test the carousel model itself. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1712.04219v1-abstract-full').style.display = 'none'; document.getElementById('1712.04219v1-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 December, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">2 pages, 1 figure, Proceedings IAU Symposium No. 337 Pulsar Astrophysics - The Next 50 Years</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1709.06104">arXiv:1709.06104</a> <span> [<a href="https://arxiv.org/pdf/1709.06104">pdf</a>, <a href="https://arxiv.org/ps/1709.06104">ps</a>, <a href="https://arxiv.org/format/1709.06104">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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy 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/10.23919/URSIGASS.2017.8105320">10.23919/URSIGASS.2017.8105320 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Real-time searches for fast transients with Apertif and LOFAR </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=van+Leeuwen%2C+J">Joeri van Leeuwen</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="1709.06104v1-abstract-short" style="display: inline;"> With the installation of a new phased array system called Apertif, the instantaneous field of view of the Westerbork Synthesis Radio Telescope (WSRT) has increased to 8.7$\,$deg$^2$. This system has turned the WSRT in to an highly effective telescope to conduct Fast Radio Burst (FRB) and pulsar surveys. To exploit this advantage, an advanced and real-time backend, called the Apertif Radio Transien… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1709.06104v1-abstract-full').style.display = 'inline'; document.getElementById('1709.06104v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1709.06104v1-abstract-full" style="display: none;"> With the installation of a new phased array system called Apertif, the instantaneous field of view of the Westerbork Synthesis Radio Telescope (WSRT) has increased to 8.7$\,$deg$^2$. This system has turned the WSRT in to an highly effective telescope to conduct Fast Radio Burst (FRB) and pulsar surveys. To exploit this advantage, an advanced and real-time backend, called the Apertif Radio Transient System (ARTS), is being developed and commissioned at the WSRT. In addition to the real-time detection of FRBs, ARTS will localize the events to about 1/2600 of the field of view --- essential information for identifying the nature of FRBs. ARTS will also trigger real-time follow up with LOFAR of newly detected FRBs, to achieve localization at arcsecond precision. We review the upcoming time-domain surveys with Apertif, and present the current status of the ongoing commissioning of the time domain capabilities of Apertif. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1709.06104v1-abstract-full').style.display = 'none'; document.getElementById('1709.06104v1-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 September, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">4 pages, 2 figures; to appear in proceedings of URSI GASS 2017</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1706.08613">arXiv:1706.08613</a> <span> [<a href="https://arxiv.org/pdf/1706.08613">pdf</a>, <a href="https://arxiv.org/ps/1706.08613">ps</a>, <a href="https://arxiv.org/format/1706.08613">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/stx1615">10.1093/mnras/stx1615 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Detection of radio emission from the gamma-ray pulsar J1732-3131 at 327 MHz </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Maan%2C+Y">Yogesh Maan</a>, <a href="/search/astro-ph?searchtype=author&query=Krishnakumar%2C+M+A">M. A. Krishnakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Naidu%2C+A+K">Arun K. Naidu</a>, <a href="/search/astro-ph?searchtype=author&query=Roy%2C+S">Subhashis Roy</a>, <a href="/search/astro-ph?searchtype=author&query=Joshi%2C+B+C">Bhal Chandra Joshi</a>, <a href="/search/astro-ph?searchtype=author&query=Kerr%2C+M">Matthew Kerr</a>, <a href="/search/astro-ph?searchtype=author&query=Manoharan%2C+P+K">P. K. Manoharan</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="1706.08613v1-abstract-short" style="display: inline;"> Although originally discovered as a radio-quiet gamma-ray pulsar, J1732-3131 has exhibited intriguing detections at decameter wavelengths. We report an extensive follow-up of the pulsar at 327 MHz with the Ooty radio telescope. Using the previously observed radio characteristics, and with an effective integration time of 60 hrs, we present a detection of the pulsar at a confidence level of 99.82%.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1706.08613v1-abstract-full').style.display = 'inline'; document.getElementById('1706.08613v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1706.08613v1-abstract-full" style="display: none;"> Although originally discovered as a radio-quiet gamma-ray pulsar, J1732-3131 has exhibited intriguing detections at decameter wavelengths. We report an extensive follow-up of the pulsar at 327 MHz with the Ooty radio telescope. Using the previously observed radio characteristics, and with an effective integration time of 60 hrs, we present a detection of the pulsar at a confidence level of 99.82%. The 327 MHz mean flux density is estimated to be 0.5-0.8 mJy, which establishes the pulsar to be a steep spectrum source and one of the least-luminous pulsars known to date. We also phase-aligned the radio and gamma-ray profiles of the pulsar, and measured the phase-offset between the main peaks in the two profiles to be 0.24$\pm$0.06. We discuss the observed phase-offset in the context of various trends exhibited by the radio-loud gamma-ray pulsar population, and suggest that the gamma-ray emission from J1732-3131 is best explained by outer magnetosphere models. Details of our analysis leading to the pulsar detection, and measurements of various parameters and their implications relevant to the pulsar's emission mechanism are presented. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1706.08613v1-abstract-full').style.display = 'none'; document.getElementById('1706.08613v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 June, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">8 pages, 6 figures; Accepted for publication in MNRAS</span> </p> </li> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Maan%2C+Y&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Maan%2C+Y&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Maan%2C+Y&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> </ul> </nav> <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 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