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value="">Relevance</option></select> </span> </div> <div class="control"> <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/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/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/1612.07917">arXiv:1612.07917</a> <span> [<a href="https://arxiv.org/pdf/1612.07917">pdf</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> <p class="title is-5 mathjax"> MANTIS: The Mid-Frequency Aperture Array Transient and Intensity-Mapping System </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=Santos%2C+M">M. Santos</a>, <a href="/search/astro-ph?searchtype=author&query=Macquart%2C+J+P">J. P. Macquart</a>, <a href="/search/astro-ph?searchtype=author&query=Abdalla%2C+F">F. Abdalla</a>, <a href="/search/astro-ph?searchtype=author&query=Petroff%2C+E">E. Petroff</a>, <a href="/search/astro-ph?searchtype=author&query=Siemion%2C+A">A. Siemion</a>, <a href="/search/astro-ph?searchtype=author&query=Taylor%2C+R">R. Taylor</a>, <a href="/search/astro-ph?searchtype=author&query=Smirnov%2C+O">O. Smirnov</a>, <a href="/search/astro-ph?searchtype=author&query=Davidson%2C+D">D. Davidson</a>, <a href="/search/astro-ph?searchtype=author&query=Broderick%2C+J">J. Broderick</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=Woudt%2C+P">P. Woudt</a>, <a href="/search/astro-ph?searchtype=author&query=Garrett%2C+M+A">M. A. Garrett</a>, <a href="/search/astro-ph?searchtype=author&query=Faulkner%2C+A+J">A. J. Faulkner</a>, <a href="/search/astro-ph?searchtype=author&query=Torchinsky%2C+S+A">S. A. Torchinsky</a>, <a href="/search/astro-ph?searchtype=author&query=van+Bemmel%2C+I+M">I. M. van Bemmel</a>, <a href="/search/astro-ph?searchtype=author&query=Hessels%2C+J">J. Hessels</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="1612.07917v1-abstract-short" style="display: inline;"> The objective of this paper is to present the main characteristics of a wide-field MFAA precursor that we envisage to be built at the SKA site in South Africa. Known as MANTIS (the Mid-Frequency Aperture Array Transient and Intensity-Mapping System), this ambitious instrument will represent the next logical step towards the MFAA based SKA telescope. The goal is to use innovative aperture array tec… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1612.07917v1-abstract-full').style.display = 'inline'; document.getElementById('1612.07917v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1612.07917v1-abstract-full" style="display: none;"> The objective of this paper is to present the main characteristics of a wide-field MFAA precursor that we envisage to be built at the SKA site in South Africa. Known as MANTIS (the Mid-Frequency Aperture Array Transient and Intensity-Mapping System), this ambitious instrument will represent the next logical step towards the MFAA based SKA telescope. The goal is to use innovative aperture array technology at cm wavelengths, in order to demonstrate the feasibility of deploying huge collecting areas at modest construction and operational cost. Such a transformative step is required in order to continue the exponential progress in radio telescope performance, and to make the ambitious scale of the SKA Phase 2 a realistic near-time proposition. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1612.07917v1-abstract-full').style.display = 'none'; document.getElementById('1612.07917v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 December, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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">White paper of the MANTIS MFAA science demonstrator</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0806.0234">arXiv:0806.0234</a> <span> [<a href="https://arxiv.org/pdf/0806.0234">pdf</a>, <a href="https://arxiv.org/ps/0806.0234">ps</a>, <a href="https://arxiv.org/format/0806.0234">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.2973599">10.1063/1.2973599 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> APERTIF, a focal plane array for the WSRT </p> <p class="authors"> <span class="search-hit">Authors:</span> <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=Oosterloo%2C+T+A">T. A. Oosterloo</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=Bakker%2C+L">L. Bakker</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+der+Hulst%2C+J+M">J. M. van der Hulst</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="0806.0234v1-abstract-short" style="display: inline;"> In this paper we describe a focal plane array (FPA) prototype, based on Vivaldi elements, developed for the Westerbork Synthesis Radio Telescope (WSRT) to increase its instantaneous field of view by a factor 25 and double its current bandwidth. This prototype is the first step in a project that has the ambition to equip most of the WSRT antennas with FPAs to improve the survey speed of the teles… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0806.0234v1-abstract-full').style.display = 'inline'; document.getElementById('0806.0234v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0806.0234v1-abstract-full" style="display: none;"> In this paper we describe a focal plane array (FPA) prototype, based on Vivaldi elements, developed for the Westerbork Synthesis Radio Telescope (WSRT) to increase its instantaneous field of view by a factor 25 and double its current bandwidth. This prototype is the first step in a project that has the ambition to equip most of the WSRT antennas with FPAs to improve the survey speed of the telescope. Examples of scientific applications are surveys of the northern sky in polarised continuum and HI emission, and efficient searches for pulsars and transients. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0806.0234v1-abstract-full').style.display = 'none'; document.getElementById('0806.0234v1-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 June, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 6 figures. Presented at "The Evolution of Galaxies through the Neutral Hydrogen Window", Feb 1-3, 2008, Arecibo Observatory, Puerto Rico. High resolution versions of figures available in jpg-format</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0802.4151">arXiv:0802.4151</a> <span> [<a href="https://arxiv.org/pdf/0802.4151">pdf</a>, <a href="https://arxiv.org/ps/0802.4151">ps</a>, <a href="https://arxiv.org/format/0802.4151">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.nima.2008.02.092">10.1016/j.nima.2008.02.092 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Amplitude calibration of a digital radio antenna array for measuring cosmic ray air showers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nehls%2C+S">S. Nehls</a>, <a href="/search/astro-ph?searchtype=author&query=Hakenjos%2C+A">A. Hakenjos</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=Bluemer%2C+J">J. Bluemer</a>, <a href="/search/astro-ph?searchtype=author&query=Bozdog%2C+H">H. Bozdog</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=Falcke%2C+H">H. Falcke</a>, <a href="/search/astro-ph?searchtype=author&query=Haungs%2C+A">A. Haungs</a>, <a href="/search/astro-ph?searchtype=author&query=Horneffer%2C+A">A. Horneffer</a>, <a href="/search/astro-ph?searchtype=author&query=Huege%2C+T">T. Huege</a>, <a href="/search/astro-ph?searchtype=author&query=Isar%2C+P+G">P. G. Isar</a>, <a href="/search/astro-ph?searchtype=author&query=Kroemer%2C+O">O. Kroemer</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="0802.4151v1-abstract-short" style="display: inline;"> Radio pulses are emitted during the development of air showers, where air showers are generated by ultra-high energy cosmic rays entering the Earth's atmosphere. These nanosecond short pulses are presently investigated by various experiments for the purpose of using them as a new detection technique for cosmic particles. For an array of 30 digital radio antennas (LOPES experiment) an absolute am… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0802.4151v1-abstract-full').style.display = 'inline'; document.getElementById('0802.4151v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0802.4151v1-abstract-full" style="display: none;"> Radio pulses are emitted during the development of air showers, where air showers are generated by ultra-high energy cosmic rays entering the Earth's atmosphere. These nanosecond short pulses are presently investigated by various experiments for the purpose of using them as a new detection technique for cosmic particles. For an array of 30 digital radio antennas (LOPES experiment) an absolute amplitude calibration of the radio antennas including the full electronic chain of the data acquisition system is performed, in order to estimate absolute values of the electric field strength for these short radio pulses. This is mandatory, because the measured radio signals in the MHz frequency range have to be compared with theoretical estimates and with predictions from Monte Carlo simulations to reconstruct features of the primary cosmic particle. A commercial reference radio emitter is used to estimate frequency dependent correction factors for each single antenna of the radio antenna array. The expected received power is related to the power recorded by the full electronic chain. Systematic uncertainties due to different environmental conditions and the described calibration procedure are of order 20%. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0802.4151v1-abstract-full').style.display = 'none'; document.getElementById('0802.4151v1-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 February, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Article accepted by Nuclear Instruments and Methods in Physics Research, A (NIM A)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nucl.Instrum.Meth.A589:350-361,2008 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0610652">arXiv:astro-ph/0610652</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0610652">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0610652">ps</a>, <a href="https://arxiv.org/format/astro-ph/0610652">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S174392130701112X">10.1017/S174392130701112X <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A very brief description of LOFAR - the Low Frequency Array </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Falcke%2C+H">H. Falcke</a>, <a href="/search/astro-ph?searchtype=author&query=van+Haarlem%2C+M+P">M. P. van Haarlem</a>, <a href="/search/astro-ph?searchtype=author&query=de+Bruyn%2C+A+G">A. G. de Bruyn</a>, <a href="/search/astro-ph?searchtype=author&query=Braun%2C+R">R. Braun</a>, <a href="/search/astro-ph?searchtype=author&query=R%C3%B6ttgering%2C+H+J+A">H. J. A. R枚ttgering</a>, <a href="/search/astro-ph?searchtype=author&query=Stappers%2C+B">B. Stappers</a>, <a href="/search/astro-ph?searchtype=author&query=Boland%2C+W+H+W+M">W. H. W. M. Boland</a>, <a href="/search/astro-ph?searchtype=author&query=Butcher%2C+H+R">H. R. Butcher</a>, <a href="/search/astro-ph?searchtype=author&query=de+Geus%2C+E+J">E. J. de Geus</a>, <a href="/search/astro-ph?searchtype=author&query=Koopmans%2C+L">L. Koopmans</a>, <a href="/search/astro-ph?searchtype=author&query=Fender%2C+R">R. Fender</a>, <a href="/search/astro-ph?searchtype=author&query=Kuijpers%2C+J">J. Kuijpers</a>, <a href="/search/astro-ph?searchtype=author&query=Miley%2C+G+K">G. K. Miley</a>, <a href="/search/astro-ph?searchtype=author&query=Schilizzi%2C+R+T">R. T. Schilizzi</a>, <a href="/search/astro-ph?searchtype=author&query=Vogt%2C+C">C. Vogt</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=Wise%2C+M">M. Wise</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=Hamaker%2C+J+P">J. P. Hamaker</a>, <a href="/search/astro-ph?searchtype=author&query=Noordam%2C+J+E">J. E. Noordam</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T">T. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=B%C3%A4hren%2C+L">L. B盲hren</a>, <a href="/search/astro-ph?searchtype=author&query=Brentjens%2C+M+A">M. A. Brentjens</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=Bregman%2C+J+D">J. D. Bregman</a> , et al. (6 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0610652v1-abstract-short" style="display: inline;"> LOFAR (Low Frequency Array) is an innovative radio telescope optimized for the frequency range 30-240 MHz. The telescope is realized as a phased aperture array without any moving parts. Digital beam forming allows the telescope to point to any part of the sky within a second. Transient buffering makes retrospective imaging of explosive short-term events possible. The scientific focus of LOFAR wi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0610652v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0610652v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0610652v1-abstract-full" style="display: none;"> LOFAR (Low Frequency Array) is an innovative radio telescope optimized for the frequency range 30-240 MHz. The telescope is realized as a phased aperture array without any moving parts. Digital beam forming allows the telescope to point to any part of the sky within a second. Transient buffering makes retrospective imaging of explosive short-term events possible. The scientific focus of LOFAR will initially be on four key science projects (KSPs): 1) detection of the formation of the very first stars and galaxies in the universe during the so-called epoch of reionization by measuring the power spectrum of the neutral hydrogen 21-cm line (Shaver et al. 1999) on the ~5' scale; 2) low-frequency surveys of the sky with of order $10^8$ expected new sources; 3) all-sky monitoring and detection of transient radio sources such as gamma-ray bursts, x-ray binaries, and exo-planets (Farrell et al. 2004); and 4) radio detection of ultra-high energy cosmic rays and neutrinos (Falcke & Gorham 2003) allowing for the first time access to particles beyond 10^21 eV (Scholten et al. 2006). Apart from the KSPs open access for smaller projects is also planned. Here we give a brief description of the telescope. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0610652v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0610652v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 October, 2006; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2006. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">2 pages, IAU GA 2006, Highlights of Astronomy, Volume 14, K.A. van der Hucht, ed</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0610596">arXiv:astro-ph/0610596</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0610596">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0610596">ps</a>, <a href="https://arxiv.org/format/astro-ph/0610596">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> </div> <p class="title is-5 mathjax"> LOFAR - Opening up a new window on the Universe </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Rottgering%2C+H+J+A">H. J. A. Rottgering</a>, <a href="/search/astro-ph?searchtype=author&query=Braun%2C+R">R. Braun</a>, <a href="/search/astro-ph?searchtype=author&query=Barthel%2C+P+D">P. D. Barthel</a>, <a href="/search/astro-ph?searchtype=author&query=van+Haarlem%2C+M+P">M. P. van Haarlem</a>, <a href="/search/astro-ph?searchtype=author&query=Miley%2C+G+K">G. K. Miley</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">R. Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Snellen%2C+I">I. Snellen</a>, <a href="/search/astro-ph?searchtype=author&query=Falcke%2C+H">H. Falcke</a>, <a href="/search/astro-ph?searchtype=author&query=de+Bruyn%2C+A+G">A. G. de Bruyn</a>, <a href="/search/astro-ph?searchtype=author&query=Stappers%2C+R+B">R. B. Stappers</a>, <a href="/search/astro-ph?searchtype=author&query=Boland%2C+W+H+W+M">W. H. W. M. Boland</a>, <a href="/search/astro-ph?searchtype=author&query=Butcher%2C+H+R">H. R. Butcher</a>, <a href="/search/astro-ph?searchtype=author&query=de+Geus%2C+E+J">E. J. de Geus</a>, <a href="/search/astro-ph?searchtype=author&query=Koopmans%2C+L">L. Koopmans</a>, <a href="/search/astro-ph?searchtype=author&query=Fender%2C+R">R. Fender</a>, <a href="/search/astro-ph?searchtype=author&query=Kuijpers%2C+J">J. Kuijpers</a>, <a href="/search/astro-ph?searchtype=author&query=Schilizzi%2C+R+T">R. T. Schilizzi</a>, <a href="/search/astro-ph?searchtype=author&query=Vogt%2C+C">C. Vogt</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=Wise%2C+M">M. Wise</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=Hamaker%2C+J+P">J. P. Hamaker</a>, <a href="/search/astro-ph?searchtype=author&query=Noordam%2C+J+E">J. E. Noordam</a>, <a href="/search/astro-ph?searchtype=author&query=Oosterloo%2C+T">T. Oosterloo</a>, <a href="/search/astro-ph?searchtype=author&query=Bahren%2C+L">L. Bahren</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="astro-ph/0610596v2-abstract-short" style="display: inline;"> LOFAR, the Low Frequency Array, is a next-generation radio telescope that is being built in Northern Europe and expected to be fully operational at the end of this decade. It will operate at frequencies from 15 to 240 MHz (corresponding to wavelengths of 20 to 1.2 m). Its superb sensitivity, high angular resolution, large field of view and flexible spectroscopic capabilities will represent a dra… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0610596v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0610596v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0610596v2-abstract-full" style="display: none;"> LOFAR, the Low Frequency Array, is a next-generation radio telescope that is being built in Northern Europe and expected to be fully operational at the end of this decade. It will operate at frequencies from 15 to 240 MHz (corresponding to wavelengths of 20 to 1.2 m). Its superb sensitivity, high angular resolution, large field of view and flexible spectroscopic capabilities will represent a dramatic improvement over previous facilities at these wavelengths. As such, LOFAR will carry out a broad range of fundamental astrophysical studies. The design of LOFAR has been driven by four fundamental astrophysical applications: (i) The Epoch of Reionisation, (ii) Extragalactic Surveys and their exploitation to study the formation and evolution of clusters, galaxies and black holes, (iii) Transient Sources and their association with high energy objects such as gamma ray bursts, and (iv) Cosmic Ray showers and their exploitation to study the origin of ultra-high energy cosmic rays. In this conference the foreseen LOFAR work on the epoch of reionisation has been covered by de Bruyn and on cosmic ray showers by Falcke. During this contribution we will first present the LOFAR project with an emphasis on the challenges faced when carrying out sensitive imaging at low radio frequencies. Subsequently, we will discuss LOFAR's capabilities to survey the low-frequency radio sky. Main aims for the planned surveys are studies of z>6 radio galaxies, diffuse emission associated with distant clusters and starbursting galaxies at z>2. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0610596v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0610596v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 January, 2007; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 October, 2006; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2006. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 5 figures, to appear in the proceedings of the conference "Cosmology, galaxy formation and astroparticle physics on the 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