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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <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/2306.03710">arXiv:2306.03710</a> <span> [<a href="https://arxiv.org/pdf/2306.03710">pdf</a>, <a href="https://arxiv.org/format/2306.03710">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/10.1051/0004-6361/202346618">10.1051/0004-6361/202346618 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Apertif 1.4 GHz continuum observations of the Bo枚tes field and their combined view with LOFAR </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=Offringa%2C+A+R">A. R. Offringa</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=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=de+Blok%2C+W+J+G">W. J. G. de Blok</a>, <a href="/search/astro-ph?searchtype=author&query=Bozkurt%2C+A">A. Bozkurt</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=Gunst%2C+A+W">A. W. Gunst</a>, <a href="/search/astro-ph?searchtype=author&query=Holties%2C+H+A">H. A. Holties</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=Oostrum%2C+L+C">L. C. Oostrum</a>, <a href="/search/astro-ph?searchtype=author&query=Vohl%2C+D">D. Vohl</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=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="2306.03710v1-abstract-short" style="display: inline;"> We present a new image of a 26.5 square degree region in the Bo枚tes constellation obtained at 1.4 GHz using the Aperture Tile in Focus (Apertif) system on the Westerbork Synthesis Radio Telescope. We use a newly developed processing pipeline which includes direction-dependent self-calibration which provides a significant improvement of the quality of the images compared to those released as part o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.03710v1-abstract-full').style.display = 'inline'; document.getElementById('2306.03710v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.03710v1-abstract-full" style="display: none;"> We present a new image of a 26.5 square degree region in the Bo枚tes constellation obtained at 1.4 GHz using the Aperture Tile in Focus (Apertif) system on the Westerbork Synthesis Radio Telescope. We use a newly developed processing pipeline which includes direction-dependent self-calibration which provides a significant improvement of the quality of the images compared to those released as part of the Apertif first data release. For the Bo枚tes region, we mosaic 187 Apertif images and extract a source catalog. The mosaic image has an angular resolution of 27${\times}$11.5 arcseconds and a median background noise of 40 $渭$Jy/beam. The catalog has 8994 sources and is complete down to the 0.3 mJy level. We combine the Apertif image with LOFAR images of the Bo枚tes field at 54 and 150 MHz to study spectral properties of the sources. We find a spectral flattening towards low flux density sources. Using the spectral index limits from Apertif non-detections we derive that up to 9 percent of the sources have ultra-steep spectra with a slope steeper than -1.2. Steepening of the spectral index with increasing redshift is also seen in the data showing a different dependency for the low-frequency spectral index and the high frequency one. This can be explained by a population of sources having concave radio spectra with a turnover frequency around the LOFAR band. Additionally, we discuss cases of individual extended sources with an interesting resolved spectral structure. With the improved pipeline, we aim to continue processing data from the Apertif wide-area surveys and release the improved 1.4 GHz images of several famous fields. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.03710v1-abstract-full').style.display = 'none'; document.getElementById('2306.03710v1-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, 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 pages, 9 figures; to be published in A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 676, A37 (2023) </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/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/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/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/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/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/1801.04834">arXiv:1801.04834</a> <span> [<a href="https://arxiv.org/pdf/1801.04834">pdf</a>, <a href="https://arxiv.org/format/1801.04834">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.2018.04.006">10.1016/j.ascom.2018.04.006 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Cobalt: A GPU-based correlator and beamformer for LOFAR </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Broekema%2C+P+C">P. Chris Broekema</a>, <a href="/search/astro-ph?searchtype=author&query=Mol%2C+J+J+D">J. Jan David Mol</a>, <a href="/search/astro-ph?searchtype=author&query=Nijboer%2C+R">Ronald Nijboer</a>, <a href="/search/astro-ph?searchtype=author&query=van+Amesfoort%2C+A+S">Alexander S. van Amesfoort</a>, <a href="/search/astro-ph?searchtype=author&query=Brentjens%2C+M+A">Michiel A. Brentjens</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=Klijn%2C+W+F+A">Wouter F. A. Klijn</a>, <a href="/search/astro-ph?searchtype=author&query=Romein%2C+J+W">John W. Romein</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="1801.04834v3-abstract-short" style="display: inline;"> For low-frequency radio astronomy, software correlation and beamforming on general purpose hardware is a viable alternative to custom designed hardware. LOFAR, a new-generation radio telescope centered in the Netherlands with international stations in Germany, France, Ireland, Latvia, Poland, Sweden and the UK, has successfully used software real-time processors based on IBM Blue Gene technology s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.04834v3-abstract-full').style.display = 'inline'; document.getElementById('1801.04834v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1801.04834v3-abstract-full" style="display: none;"> For low-frequency radio astronomy, software correlation and beamforming on general purpose hardware is a viable alternative to custom designed hardware. LOFAR, a new-generation radio telescope centered in the Netherlands with international stations in Germany, France, Ireland, Latvia, Poland, Sweden and the UK, has successfully used software real-time processors based on IBM Blue Gene technology since 2004. Since then, developments in technology have allowed us to build a system based on commercial off-the-shelf components that combines the same capabilities with lower operational cost. In this paper we describe the design and implementation of a GPU-based correlator and beamformer with the same capabilities as the Blue Gene based systems. We focus on the design approach taken, and show the challenges faced in selecting an appropriate system. The design, implementation and verification of the software system shows the value of a modern test-driven development approach. Operational experience, based on three years of operations, demonstrates that a general purpose system is a good alternative to the previous supercomputer-based system or custom-designed hardware. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.04834v3-abstract-full').style.display = 'none'; document.getElementById('1801.04834v3-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 April, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 January, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astronomy and Computing, Volume 23, April 2018, Pages 180-192 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.01594">arXiv:1603.01594</a> <span> [<a href="https://arxiv.org/pdf/1603.01594">pdf</a>, <a href="https://arxiv.org/format/1603.01594">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="High Energy Physics - Experiment">hep-ex</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/nature16976">10.1038/nature16976 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A large light-mass component of cosmic rays at 10^{17} - 10^{17.5} eV from radio observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Buitink%2C+S">S. Buitink</a>, <a href="/search/astro-ph?searchtype=author&query=Corstanje%2C+A">A. Corstanje</a>, <a href="/search/astro-ph?searchtype=author&query=Falcke%2C+H">H. Falcke</a>, <a href="/search/astro-ph?searchtype=author&query=H%C3%B6randel%2C+J+R">J. R. H枚randel</a>, <a href="/search/astro-ph?searchtype=author&query=Huege%2C+T">T. Huege</a>, <a href="/search/astro-ph?searchtype=author&query=Nelles%2C+A">A. Nelles</a>, <a href="/search/astro-ph?searchtype=author&query=Rachen%2C+J+P">J. P. Rachen</a>, <a href="/search/astro-ph?searchtype=author&query=Rossetto%2C+L">L. Rossetto</a>, <a href="/search/astro-ph?searchtype=author&query=Schellart%2C+P+.">P . Schellart</a>, <a href="/search/astro-ph?searchtype=author&query=Scholten%2C+O">O. Scholten</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=Thoudam%2C+S">S. Thoudam</a>, <a href="/search/astro-ph?searchtype=author&query=Trinh%2C+T+N+G">T. N. G. Trinh</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J">J. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Asgekar%2C+A">A. Asgekar</a>, <a href="/search/astro-ph?searchtype=author&query=Avruch%2C+I+M">I. M. Avruch</a>, <a href="/search/astro-ph?searchtype=author&query=Bell%2C+M+E">M. E. Bell</a>, <a href="/search/astro-ph?searchtype=author&query=Bentum%2C+M+J">M. J. Bentum</a>, <a href="/search/astro-ph?searchtype=author&query=Bernardi%2C+G">G. Bernardi</a>, <a href="/search/astro-ph?searchtype=author&query=Best%2C+P">P. Best</a>, <a href="/search/astro-ph?searchtype=author&query=Bonafede%2C+A">A. Bonafede</a>, <a href="/search/astro-ph?searchtype=author&query=Breitling%2C+F">F. Breitling</a>, <a href="/search/astro-ph?searchtype=author&query=Broderick%2C+J+W">J. W. Broderick</a>, <a href="/search/astro-ph?searchtype=author&query=Brouw%2C+W+N">W. N. Brouw</a>, <a href="/search/astro-ph?searchtype=author&query=Br%C3%BCggen%2C+M">M. Br眉ggen</a> , et al. (79 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1603.01594v2-abstract-short" style="display: inline;"> Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10^{17} eV and 10^{18} eV are essential to understand whether this energy range is dominated by Galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.01594v2-abstract-full').style.display = 'inline'; document.getElementById('1603.01594v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.01594v2-abstract-full" style="display: none;"> Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10^{17} eV and 10^{18} eV are essential to understand whether this energy range is dominated by Galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate cascades of secondary particles (air showers) in the atmosphere and their masses are inferred from measurements of the atmospheric depth of the shower maximum, Xmax, or the composition of shower particles reaching the ground. Current measurements suffer from either low precision, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique, suitable for determination of Xmax with a duty cycle of in principle nearly 100%. The radiation is generated by the separation of relativistic charged particles in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean precision of 16 g/cm^2 between 10^{17}-10^{17.5} eV. Because of the high resolution in $Xmax we can determine the mass spectrum and find a mixed composition, containing a light mass fraction of ~80%. Unless the extragalactic component becomes significant already below 10^{17.5} eV, our measurements indicate an additional Galactic component dominating at this energy range. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.01594v2-abstract-full').style.display = 'none'; document.getElementById('1603.01594v2-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 May, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">35 pages, 11 figures, updated version: Pierre Auger Observatory data ICRC 2015 added to Fig 2</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature 531, 70 (2016) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1204.3864">arXiv:1204.3864</a> <span> [<a href="https://arxiv.org/pdf/1204.3864">pdf</a>, <a href="https://arxiv.org/ps/1204.3864">ps</a>, <a href="https://arxiv.org/format/1204.3864">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/10.1051/0004-6361/201218970">10.1051/0004-6361/201218970 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Wide-band Simultaneous Observations of Pulsars: Disentangling Dispersion Measure and Profile Variations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hassall%2C+T+E">T. E. Hassall</a>, <a href="/search/astro-ph?searchtype=author&query=Stappers%2C+B+W">B. W. Stappers</a>, <a href="/search/astro-ph?searchtype=author&query=Hessels%2C+J+W+T">J. W. T. Hessels</a>, <a href="/search/astro-ph?searchtype=author&query=Kramer%2C+M">M. Kramer</a>, <a href="/search/astro-ph?searchtype=author&query=Alexov%2C+A">A. Alexov</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+K">K. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Coenen%2C+T">T. Coenen</a>, <a href="/search/astro-ph?searchtype=author&query=Karastergiou%2C+A">A. Karastergiou</a>, <a href="/search/astro-ph?searchtype=author&query=Keane%2C+E+F">E. F. Keane</a>, <a href="/search/astro-ph?searchtype=author&query=Kondratiev%2C+V+I">V. I. Kondratiev</a>, <a href="/search/astro-ph?searchtype=author&query=Lazaridis%2C+K">K. Lazaridis</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=Noutsos%2C+A">A. Noutsos</a>, <a href="/search/astro-ph?searchtype=author&query=Serylak%2C+M">M. Serylak</a>, <a href="/search/astro-ph?searchtype=author&query=Sobey%2C+C">C. Sobey</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=Weltevrede%2C+P">P. Weltevrede</a>, <a href="/search/astro-ph?searchtype=author&query=Zagkouris%2C+K">K. Zagkouris</a>, <a href="/search/astro-ph?searchtype=author&query=Fender%2C+R">R. Fender</a>, <a href="/search/astro-ph?searchtype=author&query=Wijers%2C+R+A+M+J">R. A. M. J. Wijers</a>, <a href="/search/astro-ph?searchtype=author&query=Bahren%2C+L">L. Bahren</a>, <a href="/search/astro-ph?searchtype=author&query=Bell%2C+M+E">M. E. Bell</a>, <a href="/search/astro-ph?searchtype=author&query=Broderick%2C+J+W">J. W. Broderick</a>, <a href="/search/astro-ph?searchtype=author&query=Corbel%2C+S">S. Corbel</a>, <a href="/search/astro-ph?searchtype=author&query=Daw%2C+E+J">E. J. Daw</a> , et al. (69 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="1204.3864v2-abstract-short" style="display: inline;"> Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since the late 1960s. We performed wide-band simultaneous observations of four pulsars with LOFAR (at 40-190 MHz), the 76-m Lovell Telescope (at 1400 MHz) and the Effelsberg 100-m Telescope (at 8000 MHz) to test the accuracy of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1204.3864v2-abstract-full').style.display = 'inline'; document.getElementById('1204.3864v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1204.3864v2-abstract-full" style="display: none;"> Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since the late 1960s. We performed wide-band simultaneous observations of four pulsars with LOFAR (at 40-190 MHz), the 76-m Lovell Telescope (at 1400 MHz) and the Effelsberg 100-m Telescope (at 8000 MHz) to test the accuracy of the dispersion law over a broad frequency range. In this paper we present the results of these observations which show that the dispersion law is accurate to better than 1 part in 100000 across our observing band. We use this fact to constrain some of the properties of the ISM along the line-of-sight and use the lack of any aberration or retardation effects to determine upper limits on emission heights in the pulsar magnetosphere. We also discuss the effect of pulse profile evolution on our observations, and the implications that it could have for precision pulsar timing projects such as the detection of gravitational waves with pulsar timing arrays. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1204.3864v2-abstract-full').style.display = 'none'; document.getElementById('1204.3864v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 May, 2012; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 April, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2012. </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, 14 Figures, Accepted for publication in Astronomy & Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A Volume 543, July 2012 </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/about">About</a></li> <li><a href="https://info.arxiv.org/help">Help</a></li> </ul> </div> <div class="column"> <ul class="nav-spaced"> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>contact arXiv</title><desc>Click here to contact arXiv</desc><path d="M502.3 190.8c3.9-3.1 9.7-.2 9.7 4.7V400c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V195.6c0-5 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