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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Gurvits%2C+L&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Gurvits%2C+L&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Gurvits%2C+L&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> <li> <a href="/search/?searchtype=author&query=Gurvits%2C+L&start=100" class="pagination-link " aria-label="Page 3" aria-current="page">3 </a> </li> </ul> </nav> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2408.14965">arXiv:2408.14965</a> <span> [<a href="https://arxiv.org/pdf/2408.14965">pdf</a>, <a href="https://arxiv.org/format/2408.14965">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> </div> <p class="title is-5 mathjax"> Planetary radio interferometry and Doppler experiment as an operational component of the Jupiter Icy Moons Explorer mission </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Pallichadath%2C+V">Vidhya Pallichadath</a>, <a href="/search/astro-ph?searchtype=author&query=Dirkx%2C+D">Dominic Dirkx</a>, <a href="/search/astro-ph?searchtype=author&query=Fayolle%2C+M+S">Marie S. Fayolle</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">Sandor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Boven%2C+P">Paul Boven</a>, <a href="/search/astro-ph?searchtype=author&query=Cimo%2C+G">Giuseppe Cimo</a>, <a href="/search/astro-ph?searchtype=author&query=Fogasy%2C+J">Judit Fogasy</a>, <a href="/search/astro-ph?searchtype=author&query=Calves%2C+G+M">Guifre Molera Calves</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">Krisztina Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Said%2C+N+M+M">N. Masdiana Md Said</a>, <a href="/search/astro-ph?searchtype=author&query=Vermeersen%2C+B+L+A">Bert L. A. Vermeersen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2408.14965v1-abstract-short" style="display: inline;"> We present an overview of the operations and engineering interface for Planetary Radio Interferometry and Doppler Experiment (PRIDE) radio astronomy observations as a scientific component of the ESA s Jupiter Icy Moons Explorer (JUICE) mission, as well as other prospective planetary and space science missions. The article discusses advanced scheduling and planning methods that make it possible to… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.14965v1-abstract-full').style.display = 'inline'; document.getElementById('2408.14965v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2408.14965v1-abstract-full" style="display: none;"> We present an overview of the operations and engineering interface for Planetary Radio Interferometry and Doppler Experiment (PRIDE) radio astronomy observations as a scientific component of the ESA s Jupiter Icy Moons Explorer (JUICE) mission, as well as other prospective planetary and space science missions. The article discusses advanced scheduling and planning methods that make it possible to create observing schedules for observations of specific spacecraft in concurrence with observations of natural radio sources. In order to put this into practice and find suitable natural background calibrator sources for PRIDE of JUICE mission, we developed planning and scheduling software. The conventional scheduling software for natural celestial radio sources is not set up to include spacecraft as observation targets in the necessary control files. Therefore, difficulties already arise during observation planning. We report on the development of new and the adaptation of existing routines used in astrophysical and geodetic VLBI for satellite scheduling and planning. The analysis of the PRIDE science observations led to improved observational planning, and the mission s scheduling methodologies were studied using a systems engineering approach. In addition, we highlighted the new procedures, like finding charts for selecting calibrator radio sources over a range of frequency bands and the outcomes of those strategies for science operation planning. A simulation of the flyby of Venus during the cruise phase of the JUICE spacecraft, based on the Tudat software, is also presented, resulting in a promising opportunity to test PRIDE techniques and evaluate the improvements that PRIDE observables can make to natural bodies ephemerides. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2408.14965v1-abstract-full').style.display = 'none'; document.getElementById('2408.14965v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">34 pages</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.12917">arXiv:2406.12917</a> <span> [<a href="https://arxiv.org/pdf/2406.12917">pdf</a>, <a href="https://arxiv.org/format/2406.12917">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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1117/12.3019835">10.1117/12.3019835 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The Black Hole Explorer: Motivation and Vision </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Johnson%2C+M+D">Michael D. Johnson</a>, <a href="/search/astro-ph?searchtype=author&query=Akiyama%2C+K">Kazunori Akiyama</a>, <a href="/search/astro-ph?searchtype=author&query=Baturin%2C+R">Rebecca Baturin</a>, <a href="/search/astro-ph?searchtype=author&query=Bilyeu%2C+B">Bryan Bilyeu</a>, <a href="/search/astro-ph?searchtype=author&query=Blackburn%2C+L">Lindy Blackburn</a>, <a href="/search/astro-ph?searchtype=author&query=Boroson%2C+D">Don Boroson</a>, <a href="/search/astro-ph?searchtype=author&query=Cardenas-Avendano%2C+A">Alejandro Cardenas-Avendano</a>, <a href="/search/astro-ph?searchtype=author&query=Chael%2C+A">Andrew Chael</a>, <a href="/search/astro-ph?searchtype=author&query=Chan%2C+C">Chi-kwan Chan</a>, <a href="/search/astro-ph?searchtype=author&query=Chang%2C+D">Dominic Chang</a>, <a href="/search/astro-ph?searchtype=author&query=Cheimets%2C+P">Peter Cheimets</a>, <a href="/search/astro-ph?searchtype=author&query=Chou%2C+C">Cathy Chou</a>, <a href="/search/astro-ph?searchtype=author&query=Doeleman%2C+S+S">Sheperd S. Doeleman</a>, <a href="/search/astro-ph?searchtype=author&query=Farah%2C+J">Joseph Farah</a>, <a href="/search/astro-ph?searchtype=author&query=Galison%2C+P">Peter Galison</a>, <a href="/search/astro-ph?searchtype=author&query=Gamble%2C+R">Ronald Gamble</a>, <a href="/search/astro-ph?searchtype=author&query=Gammie%2C+C+F">Charles F. Gammie</a>, <a href="/search/astro-ph?searchtype=author&query=Gelles%2C+Z">Zachary Gelles</a>, <a href="/search/astro-ph?searchtype=author&query=Gomez%2C+J+L">Jose L. Gomez</a>, <a href="/search/astro-ph?searchtype=author&query=Gralla%2C+S+E">Samuel E. Gralla</a>, <a href="/search/astro-ph?searchtype=author&query=Grimes%2C+P">Paul Grimes</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Hadar%2C+S">Shahar Hadar</a>, <a href="/search/astro-ph?searchtype=author&query=Haworth%2C+K">Kari Haworth</a>, <a href="/search/astro-ph?searchtype=author&query=Hada%2C+K">Kazuhiro Hada</a> , et al. (43 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.12917v1-abstract-short" style="display: inline;"> We present the Black Hole Explorer (BHEX), a mission that will produce the sharpest images in the history of astronomy by extending submillimeter Very-Long-Baseline Interferometry (VLBI) to space. BHEX will discover and measure the bright and narrow "photon ring" that is predicted to exist in images of black holes, produced from light that has orbited the black hole before escaping. This discovery… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.12917v1-abstract-full').style.display = 'inline'; document.getElementById('2406.12917v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.12917v1-abstract-full" style="display: none;"> We present the Black Hole Explorer (BHEX), a mission that will produce the sharpest images in the history of astronomy by extending submillimeter Very-Long-Baseline Interferometry (VLBI) to space. BHEX will discover and measure the bright and narrow "photon ring" that is predicted to exist in images of black holes, produced from light that has orbited the black hole before escaping. This discovery will expose universal features of a black hole's spacetime that are distinct from the complex astrophysics of the emitting plasma, allowing the first direct measurements of a supermassive black hole's spin. In addition to studying the properties of the nearby supermassive black holes M87* and Sgr A*, BHEX will measure the properties of dozens of additional supermassive black holes, providing crucial insights into the processes that drive their creation and growth. BHEX will also connect these supermassive black holes to their relativistic jets, elucidating the power source for the brightest and most efficient engines in the universe. BHEX will address fundamental open questions in the physics and astrophysics of black holes that cannot be answered without submillimeter space VLBI. The mission is enabled by recent technological breakthroughs, including the development of ultra-high-speed downlink using laser communications, and it leverages billions of dollars of existing ground infrastructure. We present the motivation for BHEX, its science goals and associated requirements, and the pathway to launch within the next decade. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.12917v1-abstract-full').style.display = 'none'; document.getElementById('2406.12917v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Proceedings for SPIE Astronomical Telescopes and Instrumentation</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Proceedings Volume 13092, Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave; 130922D (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.07635">arXiv:2406.07635</a> <span> [<a href="https://arxiv.org/pdf/2406.07635">pdf</a>, <a href="https://arxiv.org/format/2406.07635">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> A gamma-ray flare from TXS 1508+572: characterizing the jet of a $z=4.31$ blazar in the early Universe </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gokus%2C+A">Andrea Gokus</a>, <a href="/search/astro-ph?searchtype=author&query=B%C3%B6ttcher%2C+M">Markus B枚ttcher</a>, <a href="/search/astro-ph?searchtype=author&query=Errando%2C+M">Manel Errando</a>, <a href="/search/astro-ph?searchtype=author&query=Kreter%2C+M">Michael Kreter</a>, <a href="/search/astro-ph?searchtype=author&query=He%C3%9Fd%C3%B6rfer%2C+J">Jonas He脽d枚rfer</a>, <a href="/search/astro-ph?searchtype=author&query=Eppel%2C+F">Florian Eppel</a>, <a href="/search/astro-ph?searchtype=author&query=Kadler%2C+M">Matthias Kadler</a>, <a href="/search/astro-ph?searchtype=author&query=Smith%2C+P+S">Paul S. Smith</a>, <a href="/search/astro-ph?searchtype=author&query=Benke%2C+P">Petra Benke</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Kraus%2C+A">Alex Kraus</a>, <a href="/search/astro-ph?searchtype=author&query=Lisakov%2C+M">Mikhail Lisakov</a>, <a href="/search/astro-ph?searchtype=author&query=McBride%2C+F">Felicia McBride</a>, <a href="/search/astro-ph?searchtype=author&query=Ros%2C+E">Eduardo Ros</a>, <a href="/search/astro-ph?searchtype=author&query=R%C3%B6sch%2C+F">Florian R枚sch</a>, <a href="/search/astro-ph?searchtype=author&query=Wilms%2C+J">J枚rn Wilms</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.07635v2-abstract-short" style="display: inline;"> Blazars can be detected from very large distances due to their high luminosity. However, the detection of $纬$-ray emission of blazars beyond $z=3$ has only been confirmed for a small number of sources. Such observations probe the growth of supermassive black holes close to the peak of star formation in the history of galaxy evolution. As a result from a continuous monitoring of a sample of 80… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.07635v2-abstract-full').style.display = 'inline'; document.getElementById('2406.07635v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.07635v2-abstract-full" style="display: none;"> Blazars can be detected from very large distances due to their high luminosity. However, the detection of $纬$-ray emission of blazars beyond $z=3$ has only been confirmed for a small number of sources. Such observations probe the growth of supermassive black holes close to the peak of star formation in the history of galaxy evolution. As a result from a continuous monitoring of a sample of 80 $z>3$ blazars with Fermi-LAT, we present the first detection of a $纬$-ray flare from the $z=4.31$ blazar TXS 1508+572. This source showed high $纬$-ray activity from February to August 2022, reaching a peak luminosity comparable to the most luminous flares ever detected with Fermi -LAT. We conducted a multiwavelength observing campaign involving XMM-Newton, Swift, the Effelsberg 100-m radio telescope and the Very Long Baseline Array. In addition, we make use of the monitoring programs by the Zwicky Transient Facility and NEOWISE at optical and infrared wavelengths, respectively. We find that the source is particularly variable in the infrared band on daily time scales. The spectral energy distribution collected during our campaign is well described by a one-zone leptonic model, with the $纬$-ray flare originating from an increase of external Compton emission as a result of a fresh injection of accelerated electrons. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.07635v2-abstract-full').style.display = 'none'; document.getElementById('2406.07635v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 8 figures; accepted by ApJ on July 30 - Initial version on arXiv is the submitted one</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2406.03135">arXiv:2406.03135</a> <span> [<a href="https://arxiv.org/pdf/2406.03135">pdf</a>, <a href="https://arxiv.org/format/2406.03135">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/10.1051/0004-6361/202450153">10.1051/0004-6361/202450153 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Very-long-baseline interferometry study of the flaring blazar TXS 1508+572 in the early Universe </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Benke%2C+P">P. Benke</a>, <a href="/search/astro-ph?searchtype=author&query=Gokus%2C+A">A. Gokus</a>, <a href="/search/astro-ph?searchtype=author&query=Lisakov%2C+M">M. Lisakov</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Eppel%2C+F">F. Eppel</a>, <a href="/search/astro-ph?searchtype=author&query=He%C3%9Fd%C3%B6rfer%2C+J">J. He脽d枚rfer</a>, <a href="/search/astro-ph?searchtype=author&query=Kadler%2C+M">M. Kadler</a>, <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+Y">Y. Y. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=Ros%2C+E">E. Ros</a>, <a href="/search/astro-ph?searchtype=author&query=R%C3%B6sch%2C+F">F. R枚sch</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2406.03135v3-abstract-short" style="display: inline;"> High-redshift blazars provide valuable input to studies of the evolution of active galactic nuclei (AGN) jets and provide constraints on cosmological models. Detections at high energies ($0.1<\mathrm{E}<100$ GeV) of these distant sources are rare, but when they exhibit bright gamma-ray flares, we are able to study them. However, contemporaneous multi-wavelength observations of high-redshift object… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.03135v3-abstract-full').style.display = 'inline'; document.getElementById('2406.03135v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2406.03135v3-abstract-full" style="display: none;"> High-redshift blazars provide valuable input to studies of the evolution of active galactic nuclei (AGN) jets and provide constraints on cosmological models. Detections at high energies ($0.1<\mathrm{E}<100$ GeV) of these distant sources are rare, but when they exhibit bright gamma-ray flares, we are able to study them. However, contemporaneous multi-wavelength observations of high-redshift objects ($z>4$) during their different periods of activity have not been carried out so far. An excellent opportunity for such a study arose when the blazar TXS 1508+572 ($z=4.31$) exhibited a $纬$-ray flare in 2022 February in the $0.1-300$ GeV range with a flux 25 times brighter than the one reported in the in the fourth catalog of the \textit{Fermi} Large Area Telescope. Our goal is to monitor the morphological changes, spectral index and opacity variations that could be associated with the preceding $纬$-ray flare in TXS 1508+572 to find the origin of the high-energy emission in this source. We also plan to compare the source characteristics in the radio band to the blazars in the local Universe ($z<0.1$). In addition, we aim to collect quasi-simultaneous data to our multi-wavelength observations of the object, making TXS 1508+572 the first blazar in the early Universe ($z>4$) with contemporaneous multi-frequency data available in its high state. In order to study the parsec-scale structure of the source, we performed three epochs of very-long-baseline interferometry (VLBI) follow-up observations with the Very Long Baseline Array (VLBA) supplemented with the Effelsberg 100-m Telescope at 15, 22, and 43 GHz, which corresponds to 80, 117, and 228 GHz in the rest frame of TXS 1508+572. In addition, one 86 GHz (456 GHz) measurement was performed by the VLBA and the Green Bank Telescope during the first epoch. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2406.03135v3-abstract-full').style.display = 'none'; document.getElementById('2406.03135v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 August, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 5 June, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 689, A43 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.00562">arXiv:2405.00562</a> <span> [<a href="https://arxiv.org/pdf/2405.00562">pdf</a>, <a href="https://arxiv.org/format/2405.00562">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</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/10.1016/j.icarus.2024.116101">10.1016/j.icarus.2024.116101 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Contribution of PRIDE VLBI products to the joint JUICE-Europa Clipper moons' ephemerides solution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fayolle%2C+M+S">Marie S. Fayolle</a>, <a href="/search/astro-ph?searchtype=author&query=Dirkx%2C+D">Dominic Dirkx</a>, <a href="/search/astro-ph?searchtype=author&query=Cimo%2C+G">Giuseppe Cimo</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Lainey%2C+V">Valery Lainey</a>, <a href="/search/astro-ph?searchtype=author&query=Visser%2C+P+N+A+M">Pieter N. A. M. Visser</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.00562v1-abstract-short" style="display: inline;"> In the coming decade, JUICE and Europa Clipper radio-science will yield the most accurate estimation to date of the Galilean moons' physical parameters and ephemerides. JUICE's PRIDE (Planetary Radio Interferometry and Doppler Experiment) will help achieve such a solution by providing VLBI (Very Long Baseline Interferometry) observations of the spacecraft's lateral position, complementing nominal… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.00562v1-abstract-full').style.display = 'inline'; document.getElementById('2405.00562v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.00562v1-abstract-full" style="display: none;"> In the coming decade, JUICE and Europa Clipper radio-science will yield the most accurate estimation to date of the Galilean moons' physical parameters and ephemerides. JUICE's PRIDE (Planetary Radio Interferometry and Doppler Experiment) will help achieve such a solution by providing VLBI (Very Long Baseline Interferometry) observations of the spacecraft's lateral position, complementing nominal radio-science measurements. We quantify how PRIDE VLBI can contribute to the moons' ephemerides determination, in terms of attainable solution improvement and validation opportunities. To this end, we simulated both single- and dual-spacecraft VLBI, exploiting the potential simultaneous tracking of JUICE and Europa Clipper. We considered various tracking and data quality scenarios, and compared the formal uncertainties obtained with and without VLBI. This was performed for both global and local (i.e., per-flyby) estimations of the moons' states, as achieving a global solution first requires proceeding arc-per-arc. We showed that both single- and dual-spacecraft VLBI only bring limited improvement to the global state estimation, but significantly contribute to the moons' normal points (i.e., local states at flyby times), most notably in the out-of-plane direction. Additionally, we designed a validation plan exploiting PRIDE VLBI to progressively validate the classical radio-science solution. By improving the local state estimations and offering various validation opportunities, PRIDE will be invaluable in overcoming possible dynamical modelling challenges. It can therefore play a key role in reconstructing a global solution for the Galilean moons' dynamics with the uncertainty levels promised by JUICE-Europa Clipper analyses. This, in turn, is critical to the accurate characterisation of tidal dissipation in the Jovian system, holding the key to the long-term evolution of the Galilean moons. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.00562v1-abstract-full').style.display = 'none'; document.getElementById('2405.00562v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 1 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2402.09908">arXiv:2402.09908</a> <span> [<a href="https://arxiv.org/pdf/2402.09908">pdf</a>, <a href="https://arxiv.org/format/2402.09908">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> </div> <p class="title is-5 mathjax"> Proper motion of the radio jets in two blazars at redshift above 3 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Krezinger%2C+M">Mate Krezinger</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">Sandor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">Krisztina Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Gabanyi%2C+K+E">Krisztina E. Gabanyi</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">Tao An</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Yingkang Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Titov%2C+O">Oleg Titov</a>, <a href="/search/astro-ph?searchtype=author&query=Melnikov%2C+A">Alexey Melnikov</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</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="2402.09908v1-abstract-short" style="display: inline;"> There is still a limited number of high-redshift ($z>3$) active galactic nuclei (AGN) whose jet kinematics have been studied with very long baseline interferometry (VLBI). Without a dedicated proper motion survey, regularly conducted astrometric VLBI observations of bright radio-emitting AGN with sensitive arrays can be utilized to follow changes in the jets, by means of high-resolution imaging an… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.09908v1-abstract-full').style.display = 'inline'; document.getElementById('2402.09908v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2402.09908v1-abstract-full" style="display: none;"> There is still a limited number of high-redshift ($z>3$) active galactic nuclei (AGN) whose jet kinematics have been studied with very long baseline interferometry (VLBI). Without a dedicated proper motion survey, regularly conducted astrometric VLBI observations of bright radio-emitting AGN with sensitive arrays can be utilized to follow changes in the jets, by means of high-resolution imaging and brightness distribution modeling. Here we present a first-time VLBI jet kinematic study of NVSS~J080518$+$614423 ($z = 3.033$) and NVSS~J165844$-$073918 ($z = 3.742$), two flat-spectrum radio quasars that display milliarcsecond-scale jet morphology. Archival astrometric observations carried out mainly with the Very Long Baseline Array, supplemented by recent data taken with the European VLBI Network, allowed us to monitor changes in their radio structure in the $7.6-8.6$~GHz frequency band, covering almost two decades. By identifying individual jet components at each epoch, we were able to determine the apparent proper motion for multiple features in both sources. Apparent superluminal motions range between $(1-14)\,c$, and are found to be consistent with studies of other high-redshift AGN targets. Using the physical parameters derived from the brightness distribution modeling, we estimate the Doppler-boosting factors ($未\approx 11.2$ and $未\approx 2.7$), the Lorentz factors ($螕\approx 7.4$ and $螕\approx 36.6$) and the jet viewing angles ($胃\approx 4\fdg4$ and $胃\approx 8\fdg0$), for NVSS~J080518$+$614423 and NVSS~J165844$-$073918, respectively. The data revealed a stationary jet component with negligible apparent proper motion in NVSS~J165844$-$073918. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2402.09908v1-abstract-full').style.display = 'none'; document.getElementById('2402.09908v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Supplementary tables can also be found at the end of the main tex file</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.09096">arXiv:2401.09096</a> <span> [<a href="https://arxiv.org/pdf/2401.09096">pdf</a>, <a href="https://arxiv.org/ps/2401.09096">ps</a>, <a href="https://arxiv.org/format/2401.09096">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </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/10.30970/jps.28.1902">10.30970/jps.28.1902 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On the Possibility of Detecting a Global Signal in the Line of the Hyperfine Structure of Hydrogen from the Dark Ages </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Konovalenko%2C+O">Olexandr Konovalenko</a>, <a href="/search/astro-ph?searchtype=author&query=Zakharenko%2C+V">Vyacheslav Zakharenko</a>, <a href="/search/astro-ph?searchtype=author&query=Novosyadlyj%2C+B">Bohdan Novosyadlyj</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Stepkin%2C+S">Sergiy Stepkin</a>, <a href="/search/astro-ph?searchtype=author&query=Vasylkivskyi%2C+Y">Yevhen Vasylkivskyi</a>, <a href="/search/astro-ph?searchtype=author&query=Tokarsky%2C+P">Petro Tokarsky</a>, <a href="/search/astro-ph?searchtype=author&query=Ulyanov%2C+O">Oleg Ulyanov</a>, <a href="/search/astro-ph?searchtype=author&query=Stanislavsky%2C+O">Olexandr Stanislavsky</a>, <a href="/search/astro-ph?searchtype=author&query=Bubnov%2C+I">Igor Bubnov</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.09096v2-abstract-short" style="display: inline;"> We analyze the possibilities of detecting a signal in the hydrogen 21~cm line, which was formed in the early Universe during the the Dark Ages cosmological epoch, using the Ukrainian radio telescopes UTR-2 and GURT of the National Academy of Sciences of Ukraine. As a result of cosmological expansion, this line is shifted to the decameter range of wavelengths ($位_{obs}\approx18$ m,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.09096v2-abstract-full').style.display = 'inline'; document.getElementById('2401.09096v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.09096v2-abstract-full" style="display: none;"> We analyze the possibilities of detecting a signal in the hydrogen 21~cm line, which was formed in the early Universe during the the Dark Ages cosmological epoch, using the Ukrainian radio telescopes UTR-2 and GURT of the National Academy of Sciences of Ukraine. As a result of cosmological expansion, this line is shifted to the decameter range of wavelengths ($位_{obs}\approx18$ m, $谓_{obs}\approx16$ MHz) and is in the band of operational frequencies of these telescopes. The brightness temperature of the predicted sky-averaged global signal ranges from $\sim-0.08$ to $\sim0.02$ K, depending on the cosmological model. Such a faint signal is a challenge even for the world's largest radio telescope in the decameter wavelength range, UTR-2, since the signal level of the foreground synchrotron radiation of the Galaxy at these wavelengths is 20000--40000~K. The paper highlights the peculiarities of spectroscopy at the decameter waves, interfering factors of natural and instrumental origin and the ways of eliminating them in order to reliably detect the signal in the 21~cm line, which can become an important source of information both about the environment in which the first stars and galaxies were born, and about the nature of dark matter particles and the magnitude of primordial magnetic fields. It was concluded that the detection of such a signal using the most sensitive radio telescopes at the decameter wavelength range is possible (with the signal integration over the frequency band of 25~MHz), the detection time will be $\sim50$~days) and can be implemented in the coming years of peace in Ukraine. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.09096v2-abstract-full').style.display = 'none'; document.getElementById('2401.09096v2-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 February, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 16 figures; v1 - Ukrainian text, v2 - English text</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Journal of Physical Studies, V. 28, No.1, id. 1902, 2024 (in Ukrainian) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.15765">arXiv:2312.15765</a> <span> [<a href="https://arxiv.org/pdf/2312.15765">pdf</a>, <a href="https://arxiv.org/ps/2312.15765">ps</a>, <a href="https://arxiv.org/format/2312.15765">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202348602">10.1051/0004-6361/202348602 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Milliarcsecond-scale radio structure of the most distant BL Lac object candidate at redshift 6.57 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S. Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Y. Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">K. Perger</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">T. An</a>, <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">K. 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Hwang%2C+C+-">C. -Y. Hwang</a>, <a href="/search/astro-ph?searchtype=author&query=Koptelova%2C+E">E. Koptelova</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Z. Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Fogasy%2C+J">J. Fogasy</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.15765v1-abstract-short" style="display: inline;"> The existence of accreting supermassive black holes up to billions of solar masses at early cosmological epochs (in the context of this work, redshifts z>=6) requires very fast growth rates which is challenging to explain. The presence of a relativistic jet can be a direct indication of activity and accretion status in active galactic nuclei (AGN), constraining the radiative properties of these ex… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.15765v1-abstract-full').style.display = 'inline'; document.getElementById('2312.15765v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.15765v1-abstract-full" style="display: none;"> The existence of accreting supermassive black holes up to billions of solar masses at early cosmological epochs (in the context of this work, redshifts z>=6) requires very fast growth rates which is challenging to explain. The presence of a relativistic jet can be a direct indication of activity and accretion status in active galactic nuclei (AGN), constraining the radiative properties of these extreme objects. However, known jetted AGN beyond z~6 are still very rare. The radio-emitting AGN J2331+1129 has recently been claimed as a candidate BL Lac object at redshift z=6.57, based on its synchrotron-dominated emission spectrum and the lack of ultraviolet/optical emission lines. It is a promising candidate for the highest-redshift blazar known to date. The aim of the observations described here was to support or refute the blazar classification of this peculiar source. We performed high-resolution radio interferometric imaging observations of J2331+1129 using the Very Long Baseline Array at 1.6 and 4.9 GHz in 2022 Feb. The images revealed a compact but slightly resolved, flat-spectrum core feature at both frequencies, indicating that the total radio emission is produced by a compact jet and originates from within a central 10-pc scale region. While these are consistent with the radio properties of a BL Lac object, the inferred brightness temperatures are at least an order of magnitude lower than expected from a Doppler-boosted radio jet, leaving the high-redshift BL Lac identification still an open question. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.15765v1-abstract-full').style.display = 'none'; document.getElementById('2312.15765v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 1 figure, accepted for publication in Astronomy & Astrophysics as a Letter to the Editor</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astronomy and Astrophysics, Vol. 681, L12 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.08643">arXiv:2312.08643</a> <span> [<a href="https://arxiv.org/pdf/2312.08643">pdf</a>, <a href="https://arxiv.org/format/2312.08643">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/10.1051/0004-6361/202347157">10.1051/0004-6361/202347157 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Unveiling the Bent Jet Structure and Polarization of OJ 287 at 1.7 GHz with Space VLBI </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Cho%2C+I">Ilje Cho</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez%2C+J+L">Jos茅 L. G贸mez</a>, <a href="/search/astro-ph?searchtype=author&query=Lico%2C+R">Rocco Lico</a>, <a href="/search/astro-ph?searchtype=author&query=Zhao%2C+G">Guang-Yao Zhao</a>, <a href="/search/astro-ph?searchtype=author&query=Traianou%2C+E">Efthalia Traianou</a>, <a href="/search/astro-ph?searchtype=author&query=Dahale%2C+R">Rohan Dahale</a>, <a href="/search/astro-ph?searchtype=author&query=Fuentes%2C+A">Antonio Fuentes</a>, <a href="/search/astro-ph?searchtype=author&query=Toscano%2C+T">Teresa Toscano</a>, <a href="/search/astro-ph?searchtype=author&query=Foschi%2C+M">Marianna Foschi</a>, <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+Y">Yuri Y. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=Lobanov%2C+A">Andrei Lobanov</a>, <a href="/search/astro-ph?searchtype=author&query=Pushkarev%2C+A+B">Alexander B. Pushkarev</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+J">Jae-Young Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Lisakov%2C+M">Mikhail Lisakov</a>, <a href="/search/astro-ph?searchtype=author&query=Voitsik%2C+P">Petr Voitsik</a>, <a href="/search/astro-ph?searchtype=author&query=Myserlis%2C+I">Ioannis Myserlis</a>, <a href="/search/astro-ph?searchtype=author&query=P%C3%B6tzl%2C+F">Felix P枚tzl</a>, <a href="/search/astro-ph?searchtype=author&query=Ros%2C+E">Eduardo Ros</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.08643v2-abstract-short" style="display: inline;"> We present total intensity and linear polarization images of OJ287 at 1.68GHz, obtained through space-based VLBI observations with RadioAstron on April 16, 2016. The observations were conducted using a ground array consisting of the VLBA and the EVN. Ground-space fringes were detected with a maximum projected baseline length of 5.6 Earth's diameter, resulting in an angular resolution of 530 uas. W… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.08643v2-abstract-full').style.display = 'inline'; document.getElementById('2312.08643v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.08643v2-abstract-full" style="display: none;"> We present total intensity and linear polarization images of OJ287 at 1.68GHz, obtained through space-based VLBI observations with RadioAstron on April 16, 2016. The observations were conducted using a ground array consisting of the VLBA and the EVN. Ground-space fringes were detected with a maximum projected baseline length of 5.6 Earth's diameter, resulting in an angular resolution of 530 uas. With this unprecedented resolution at such a low frequency, the progressively bending jet structure of OJ287 has been resolved up to 10 pc of the projected distance from the radio core. In comparison with close-in-time VLBI observations at 15, 43, 86 GHz from MOJAVE and VLBA-BU-BLAZAR monitoring projects, we obtain the spectral index map showing the opaque core and optically thin jet components. The optically thick core has a brightness temperature of 10$^{13}$ K, and is further resolved into two sub-components at higher frequencies labeled C1 and C2. These sub-components exhibit a transition from optically thick to thin, with a SSA turnover frequency estimated to be 33 and 11.5 GHz, and a turnover flux density 4 and 0.7 Jy, respectively. Assuming a Doppler boosting factor of 10, the SSA values provide the estimate of the magnetic field strengths from SSA of 3.4 G for C1 and 1.0 G for C2. The magnetic field strengths assuming equipartition arguments are also estimated as 2.6 G and 1.6 G, respectively. The integrated degree of linear polarization is found to be approximately 2.5 %, with the electric vector position angle being well aligned with the local jet direction at the core region. This alignment suggests a predominant toroidal magnetic field, which is in agreement with the jet formation model that requires a helical magnetic field anchored to either the black hole ergosphere or the accretion disk. Further downstream, the jet seems to be predominantly threaded by a poloidal magnetic field. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.08643v2-abstract-full').style.display = 'none'; document.getElementById('2312.08643v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 11 figures, 3 tables</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 2024, 683, A248 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2312.02130">arXiv:2312.02130</a> <span> [<a href="https://arxiv.org/pdf/2312.02130">pdf</a>, <a href="https://arxiv.org/format/2312.02130">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Theory">hep-th</span> </div> </div> <p class="title is-5 mathjax"> Fundamental Physics Opportunities with the Next-Generation Event Horizon Telescope </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Ayzenberg%2C+D">Dimitry Ayzenberg</a>, <a href="/search/astro-ph?searchtype=author&query=Blackburn%2C+L">Lindy Blackburn</a>, <a href="/search/astro-ph?searchtype=author&query=Brito%2C+R">Richard Brito</a>, <a href="/search/astro-ph?searchtype=author&query=Britzen%2C+S">Silke Britzen</a>, <a href="/search/astro-ph?searchtype=author&query=Broderick%2C+A+E">Avery E. Broderick</a>, <a href="/search/astro-ph?searchtype=author&query=Carballo-Rubio%2C+R">Ra煤l Carballo-Rubio</a>, <a href="/search/astro-ph?searchtype=author&query=Cardoso%2C+V">Vitor Cardoso</a>, <a href="/search/astro-ph?searchtype=author&query=Chael%2C+A">Andrew Chael</a>, <a href="/search/astro-ph?searchtype=author&query=Chatterjee%2C+K">Koushik Chatterjee</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+Y">Yifan Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Cunha%2C+P+V+P">Pedro V. P. Cunha</a>, <a href="/search/astro-ph?searchtype=author&query=Davoudiasl%2C+H">Hooman Davoudiasl</a>, <a href="/search/astro-ph?searchtype=author&query=Denton%2C+P+B">Peter B. Denton</a>, <a href="/search/astro-ph?searchtype=author&query=Doeleman%2C+S+S">Sheperd S. Doeleman</a>, <a href="/search/astro-ph?searchtype=author&query=Eichhorn%2C+A">Astrid Eichhorn</a>, <a href="/search/astro-ph?searchtype=author&query=Eubanks%2C+M">Marshall Eubanks</a>, <a href="/search/astro-ph?searchtype=author&query=Fang%2C+Y">Yun Fang</a>, <a href="/search/astro-ph?searchtype=author&query=Foschi%2C+A">Arianna Foschi</a>, <a href="/search/astro-ph?searchtype=author&query=Fromm%2C+C+M">Christian M. Fromm</a>, <a href="/search/astro-ph?searchtype=author&query=Galison%2C+P">Peter Galison</a>, <a href="/search/astro-ph?searchtype=author&query=Ghosh%2C+S+G">Sushant G. Ghosh</a>, <a href="/search/astro-ph?searchtype=author&query=Gold%2C+R">Roman Gold</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Hadar%2C+S">Shahar Hadar</a>, <a href="/search/astro-ph?searchtype=author&query=Held%2C+A">Aaron Held</a> , et al. (23 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2312.02130v1-abstract-short" style="display: inline;"> The Event Horizon Telescope (EHT) Collaboration recently published the first images of the supermassive black holes in the cores of the Messier 87 and Milky Way galaxies. These observations have provided a new means to study supermassive black holes and probe physical processes occurring in the strong-field regime. We review the prospects of future observations and theoretical studies of supermass… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.02130v1-abstract-full').style.display = 'inline'; document.getElementById('2312.02130v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2312.02130v1-abstract-full" style="display: none;"> The Event Horizon Telescope (EHT) Collaboration recently published the first images of the supermassive black holes in the cores of the Messier 87 and Milky Way galaxies. These observations have provided a new means to study supermassive black holes and probe physical processes occurring in the strong-field regime. We review the prospects of future observations and theoretical studies of supermassive black hole systems with the next-generation Event Horizon Telescope (ngEHT), which will greatly enhance the capabilities of the existing EHT array. These enhancements will open up several previously inaccessible avenues of investigation, thereby providing important new insights into the properties of supermassive black holes and their environments. This review describes the current state of knowledge for five key science cases, summarising the unique challenges and opportunities for fundamental physics investigations that the ngEHT will enable. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2312.02130v1-abstract-full').style.display = 'none'; document.getElementById('2312.02130v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">To be submitted to journal. Comments are welcome</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.04376">arXiv:2311.04376</a> <span> [<a href="https://arxiv.org/pdf/2311.04376">pdf</a>, <a href="https://arxiv.org/format/2311.04376">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-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/10.1007/s11214-023-01026-1">10.1007/s11214-023-01026-1 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Planetary Radio Interferometry and Doppler Experiment (PRIDE) of the JUICE mission </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Cimo%2C+G">Giuseppe Cimo</a>, <a href="/search/astro-ph?searchtype=author&query=Dirkx%2C+D">Dominic Dirkx</a>, <a href="/search/astro-ph?searchtype=author&query=Pallichadath%2C+V">Vidhya Pallichadath</a>, <a href="/search/astro-ph?searchtype=author&query=Akins%2C+A">Alexander Akins</a>, <a href="/search/astro-ph?searchtype=author&query=Altobelli%2C+N">Nicolas Altobelli</a>, <a href="/search/astro-ph?searchtype=author&query=Bocanegra-Bahamon%2C+T+M">Tatiana M. Bocanegra-Bahamon</a>, <a href="/search/astro-ph?searchtype=author&query=Cazaux%2C+S+M">Stephanie M. Cazaux</a>, <a href="/search/astro-ph?searchtype=author&query=Charlot%2C+P">Patrick Charlot</a>, <a href="/search/astro-ph?searchtype=author&query=Duev%2C+D+A">Dmitry A. Duev</a>, <a href="/search/astro-ph?searchtype=author&query=Fayolle%2C+M+S">Marie S. Fayolle</a>, <a href="/search/astro-ph?searchtype=author&query=Fogasy%2C+J">Judit Fogasy</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">Sandor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Lainey%2C+V">Valery Lainey</a>, <a href="/search/astro-ph?searchtype=author&query=Calves%2C+G+M">Guifre Molera Calves</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">Krisztina Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Pogrebenko%2C+S+V">Sergey V. Pogrebenko</a>, <a href="/search/astro-ph?searchtype=author&query=Said%2C+N+M+M">N. Masdiana Md Said</a>, <a href="/search/astro-ph?searchtype=author&query=Vallat%2C+C">Claire Vallat</a>, <a href="/search/astro-ph?searchtype=author&query=Vermeersen%2C+B+L+A">Bert L. A. Vermeersen</a>, <a href="/search/astro-ph?searchtype=author&query=Visser%2C+P+N+A+M">Pieter N. A. M. Visser</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+K">Kuo-Nung Wang</a>, <a href="/search/astro-ph?searchtype=author&query=Willner%2C+K">Konrad Willner</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.04376v2-abstract-short" style="display: inline;"> Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a multi-purpose experimental technique aimed at enhancing the science return of planetary missions. The technique exploits the science payload and spacecraft service systems without requiring a dedicated onboard instrumentation or imposing on the existing instrumentation any special for PRIDE requirements. PRIDE is based on the near-… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.04376v2-abstract-full').style.display = 'inline'; document.getElementById('2311.04376v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.04376v2-abstract-full" style="display: none;"> Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a multi-purpose experimental technique aimed at enhancing the science return of planetary missions. The technique exploits the science payload and spacecraft service systems without requiring a dedicated onboard instrumentation or imposing on the existing instrumentation any special for PRIDE requirements. PRIDE is based on the near-field phase-referencing Very Long Baseline Interferometry (VLBI) and evaluation of the Doppler shift of the radio signal transmitted by spacecraft by observing it with multiple Earth-based radio telescopes. The methodology of PRIDE has been developed initially at the Joint Institute for VLBI ERIC (JIVE) for tracking the ESA's Huygens Probe during its descent in the atmosphere of Titan in 2005. From that point on, the technique has been demonstrated for various planetary and other space science missions. The estimates of lateral position of the target spacecraft are done using the phase-referencing VLBI technique. Together with radial Doppler estimates, these observables can be used for a variety of applications, including improving the knowledge of the spacecraft state vector. The PRIDE measurements can be applied to a broad scope of research fields including studies of atmospheres through the use of radio occultations, the improvement of planetary and satellite ephemerides, as well as gravity field parameters and other geodetic properties of interest, and estimations of interplanetary plasma properties. This paper presents the implementation of PRIDE as a component of the ESA's Jupiter Icy Moons Explorer (JUICE) mission. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.04376v2-abstract-full').style.display = 'none'; document.getElementById('2311.04376v2-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 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">JUICE collection, Space Science Reviews, 2023, 219:79</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Space Science Reviews (2023) 219:79 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.01861">arXiv:2311.01861</a> <span> [<a href="https://arxiv.org/pdf/2311.01861">pdf</a>, <a href="https://arxiv.org/format/2311.01861">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41550-023-02105-7">10.1038/s41550-023-02105-7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Filamentary structures as the origin of blazar jet radio variability </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fuentes%2C+A">Antonio Fuentes</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez%2C+J+L">Jos茅 L. G贸mez</a>, <a href="/search/astro-ph?searchtype=author&query=Mart%C3%AD%2C+J+M">Jos茅 M. Mart铆</a>, <a href="/search/astro-ph?searchtype=author&query=Perucho%2C+M">Manel Perucho</a>, <a href="/search/astro-ph?searchtype=author&query=Zhao%2C+G">Guang-Yao Zhao</a>, <a href="/search/astro-ph?searchtype=author&query=Lico%2C+R">Rocco Lico</a>, <a href="/search/astro-ph?searchtype=author&query=Lobanov%2C+A+P">Andrei P. Lobanov</a>, <a href="/search/astro-ph?searchtype=author&query=Bruni%2C+G">Gabriele Bruni</a>, <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+Y">Yuri Y. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=Chael%2C+A">Andrew Chael</a>, <a href="/search/astro-ph?searchtype=author&query=Akiyama%2C+K">Kazunori Akiyama</a>, <a href="/search/astro-ph?searchtype=author&query=Bouman%2C+K+L">Katherine L. Bouman</a>, <a href="/search/astro-ph?searchtype=author&query=Sun%2C+H">He Sun</a>, <a href="/search/astro-ph?searchtype=author&query=Cho%2C+I">Ilje Cho</a>, <a href="/search/astro-ph?searchtype=author&query=Traianou%2C+E">Efthalia Traianou</a>, <a href="/search/astro-ph?searchtype=author&query=Toscano%2C+T">Teresa Toscano</a>, <a href="/search/astro-ph?searchtype=author&query=Dahale%2C+R">Rohan Dahale</a>, <a href="/search/astro-ph?searchtype=author&query=Foschi%2C+M">Marianna Foschi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S">Svetlana Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Kim%2C+J">Jae-Young Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Mizuno%2C+Y">Yosuke Mizuno</a>, <a href="/search/astro-ph?searchtype=author&query=Ros%2C+E">Eduardo Ros</a>, <a href="/search/astro-ph?searchtype=author&query=Savolainen%2C+T">Tuomas Savolainen</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2311.01861v1-abstract-short" style="display: inline;"> Supermassive black holes at the centre of active galactic nuclei power some of the most luminous objects in the Universe. Typically, very long baseline interferometric (VLBI) observations of blazars have revealed only funnel-like morphologies with little information of the ejected plasma internal structure, or lacked the sufficient dynamic range to reconstruct the extended jet emission. Here we sh… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.01861v1-abstract-full').style.display = 'inline'; document.getElementById('2311.01861v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.01861v1-abstract-full" style="display: none;"> Supermassive black holes at the centre of active galactic nuclei power some of the most luminous objects in the Universe. Typically, very long baseline interferometric (VLBI) observations of blazars have revealed only funnel-like morphologies with little information of the ejected plasma internal structure, or lacked the sufficient dynamic range to reconstruct the extended jet emission. Here we show microarcsecond-scale angular resolution images of the blazar 3C 279 obtained at 22 GHz with the space VLBI mission RadioAstron, which allowed us to resolve the jet transversely and reveal several filaments produced by plasma instabilities in a kinetically dominated flow. Our high angular resolution and dynamic range image suggests that emission features traveling down the jet may manifest as a result of differential Doppler-boosting within the filaments, as opposed to the standard shock-in-jet model invoked to explain blazar jet radio variability. Moreover, we infer that the filaments in 3C 279 are possibly threaded by a helical magnetic field rotating clockwise, as seen in the direction of the flow motion, with an intrinsic helix pitch angle of ~45 degrees in a jet with a Lorentz factor of ~13 at the time of observation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.01861v1-abstract-full').style.display = 'none'; document.getElementById('2311.01861v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 7 figures. Initial version of an article published in Nature Astronomy</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Astronomy 7 (2023) 1359 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.17127">arXiv:2309.17127</a> <span> [<a href="https://arxiv.org/pdf/2309.17127">pdf</a>, <a href="https://arxiv.org/format/2309.17127">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="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.actaastro.2023.09.035">10.1016/j.actaastro.2023.09.035 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Orbital configurations of spaceborne interferometers for studying photon rings of supermassive black holes </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Hudson%2C+B">Ben Hudson</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Wielgus%2C+M">Maciek Wielgus</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+L">Lei Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Zheng%2C+W">Weimin Zheng</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="2309.17127v2-abstract-short" style="display: inline;"> Recent advances in technology coupled with the progress of observational radio astronomy methods resulted in achieving a major milestone of astrophysics - a direct image of the shadow of a supermassive black hole, taken by the Earth-based Event Horizon Telescope (EHT). The EHT was able to achieve a resolution of $\sim$20 $渭$as, enabling it to resolve the shadows of the black holes in the centres o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.17127v2-abstract-full').style.display = 'inline'; document.getElementById('2309.17127v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.17127v2-abstract-full" style="display: none;"> Recent advances in technology coupled with the progress of observational radio astronomy methods resulted in achieving a major milestone of astrophysics - a direct image of the shadow of a supermassive black hole, taken by the Earth-based Event Horizon Telescope (EHT). The EHT was able to achieve a resolution of $\sim$20 $渭$as, enabling it to resolve the shadows of the black holes in the centres of two celestial objects: the supergiant elliptical galaxy M87 and the Milky Way Galaxy. The EHT results mark the start of a new round of development of next generation Very Long Baseline Interferometers (VLBI) which will be able to operate at millimetre and sub-millimetre wavelengths. The inclusion of baselines exceeding the diameter of the Earth and observation at as short a wavelength as possible is imperative for further development of high resolution astronomical observations. This can be achieved by a spaceborne VLBI system. We consider the preliminary mission design of such a system, specifically focused on the detection and analysis of photon rings, an intrinsic feature of supermassive black holes. Optimised Earth, Sun-Earth L2 and Earth-Moon L2 orbit configurations for the space interferometer system are presented, all of which provide an order of magnitude improvement in resolution compared to the EHT. Such a space-borne interferometer would be able to conduct a comprehensive survey of supermassive black holes in active galactic nuclei and enable uniquely robust and accurate tests of strong gravity, through detection of the photon ring features. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.17127v2-abstract-full').style.display = 'none'; document.getElementById('2309.17127v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 29 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Acta Astronautica. 40 pages, 13 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.06779">arXiv:2308.06779</a> <span> [<a href="https://arxiv.org/pdf/2308.06779">pdf</a>, <a href="https://arxiv.org/format/2308.06779">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</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/10.1016/j.pss.2022.105531">10.1016/j.pss.2022.105531 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Decoupled and coupled moons' ephemerides estimation strategies -- Application to the JUICE mission </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fayolle%2C+M">M. Fayolle</a>, <a href="/search/astro-ph?searchtype=author&query=Dirkx%2C+D">D. Dirkx</a>, <a href="/search/astro-ph?searchtype=author&query=Lainey%2C+V">V. Lainey</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Visser%2C+P+N+A+M">P. N. A. M. Visser</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="2308.06779v1-abstract-short" style="display: inline;"> When reconstructing natural satellites' ephemerides from space missions' tracking data, the dynamics of the spacecraft and natural bodies are often solved for separately, in a decoupled manner. Alternatively, the ephemeris generation and spacecraft orbit determination can be performed concurrently. This method directly maps the available data set to the estimated parameters' covariances while full… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.06779v1-abstract-full').style.display = 'inline'; document.getElementById('2308.06779v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.06779v1-abstract-full" style="display: none;"> When reconstructing natural satellites' ephemerides from space missions' tracking data, the dynamics of the spacecraft and natural bodies are often solved for separately, in a decoupled manner. Alternatively, the ephemeris generation and spacecraft orbit determination can be performed concurrently. This method directly maps the available data set to the estimated parameters' covariances while fully accounting for all dynamical couplings. It thus provides a statistically consistent solution to the estimation problem, whereas this is not directly ensured with the decoupled strategy. For the Galilean moons in particular, the JUICE mission provides a unique opportunity for ephemerides improvement. For such a dynamically coupled problem, choosing between the two strategies will be influential. This paper provides a detailed, explicit formulation for the coupled approach, before comparing the performances of the two state estimation methods for the JUICE test case. To this end, we used both decoupled and coupled models on simulated JUICE radiometric data. We compared the resulting covariances for the Galilean moons' states, and showed that the decoupled approach yields slightly lower formal errors for the moons' tangential positions. On the other hand, the coupled model can reduce the state uncertainties by more than one order of magnitude in the radial direction. It also proved more sensitive to the dynamical coupling between Io, Europa and Ganymede, allowing the solutions for the first two moons to fully benefit from JUICE orbital phase around Ganymede. However, many issues remain to be solved before a concurrent estimation strategy can be successfully applied to reconstruct the moons' dynamics over long timescales. Nonetheless, our analysis highlights promising ephemerides improvements and thus motivates future efforts to reach a coupled state solution for the Galilean moons. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.06779v1-abstract-full').style.display = 'none'; document.getElementById('2308.06779v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Planetary and Space Science 219 (2022): 105531 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2307.15961">arXiv:2307.15961</a> <span> [<a href="https://arxiv.org/pdf/2307.15961">pdf</a>, <a href="https://arxiv.org/format/2307.15961">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</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/10.1051/0004-6361/202347019">10.1051/0004-6361/202347019 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Spacecraft VLBI tracking to enhance stellar occultations astrometry of planetary satellites </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fayolle%2C+M">M. Fayolle</a>, <a href="/search/astro-ph?searchtype=author&query=Lainey%2C+V">V. Lainey</a>, <a href="/search/astro-ph?searchtype=author&query=Dirkx%2C+D">D. Dirkx</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Cimo%2C+G">G. Cimo</a>, <a href="/search/astro-ph?searchtype=author&query=Bolton%2C+S+J">S. J. Bolton</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="2307.15961v1-abstract-short" style="display: inline;"> Stellar occultations currently provide the most accurate ground-based measurements of the positions of natural satellites (down to a few kilometres for the Galilean moons). However, when using these observations in the calculation of satellite ephemerides, the uncertainty in the planetary ephemerides dominates the error budget of the occultation. We quantify the local refinement in the central pla… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.15961v1-abstract-full').style.display = 'inline'; document.getElementById('2307.15961v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2307.15961v1-abstract-full" style="display: none;"> Stellar occultations currently provide the most accurate ground-based measurements of the positions of natural satellites (down to a few kilometres for the Galilean moons). However, when using these observations in the calculation of satellite ephemerides, the uncertainty in the planetary ephemerides dominates the error budget of the occultation. We quantify the local refinement in the central planet's position achievable by performing Very Long Baseline Interferometry (VLBI) tracking of an in-system spacecraft temporally close to an occultation. We demonstrate the potential of using VLBI to enhance the science return of stellar occultations for satellite ephemerides. We identified the most promising observation and tracking opportunities offered by the Juno spacecraft around Jupiter as perfect test cases, for which we ran simulations of our VLBI experiment. VLBI tracking at Juno's perijove close to a stellar occultation locally (in time) reduces the uncertainty in Jupiter's angular position in the sky to 250-400 m. This represents up to an order of magnitude improvement with respect to current solutions and is lower than the stellar occultation error, thus allowing the moon ephemeris solution to fully benefit from the observation. Our simulations showed that the proposed tracking and observation experiment can efficiently use synergies between ground- and space-based observations to enhance the science return on both ends. The reduced error budget for stellar occultations indeed helps to improve the moons' ephemerides, which in turn benefit planetary missions and their science products, such as the recently launched JUICE and upcoming Europa Clipper missions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.15961v1-abstract-full').style.display = 'none'; document.getElementById('2307.15961v1-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 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2307.13435">arXiv:2307.13435</a> <span> [<a href="https://arxiv.org/pdf/2307.13435">pdf</a>, <a href="https://arxiv.org/format/2307.13435">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</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/10.1088/1361-6382/ace609">10.1088/1361-6382/ace609 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gravitational redshift test of EEP with RA from near Earth to the distance of the Moon </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Nunes%2C+N+V">N. V. Nunes</a>, <a href="/search/astro-ph?searchtype=author&query=Bartel%2C+N">N. Bartel</a>, <a href="/search/astro-ph?searchtype=author&query=Belonenko%2C+A">A. Belonenko</a>, <a href="/search/astro-ph?searchtype=author&query=Manucharyan%2C+G+D">G. D. Manucharyan</a>, <a href="/search/astro-ph?searchtype=author&query=Popov%2C+S+M">S. M. Popov</a>, <a href="/search/astro-ph?searchtype=author&query=Rudenko%2C+V+N">V. N. Rudenko</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Cim%C3%B2%2C+G">G. Cim貌</a>, <a href="/search/astro-ph?searchtype=author&query=Calv%C3%A9s%2C+G+M">G. Molera Calv茅s</a>, <a href="/search/astro-ph?searchtype=author&query=Zakhvatkin%2C+M+V">M. V. Zakhvatkin</a>, <a href="/search/astro-ph?searchtype=author&query=Bietenholz%2C+M+F">M. F. Bietenholz</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="2307.13435v1-abstract-short" style="display: inline;"> The Einstein Equivalence Principle (EEP) is a cornerstone of general relativity and predicts the existence of gravitational redshift. We report on new results of measuring this shift with RadioAstron (RA), a space VLBI spacecraft launched into an evolving high eccentricity orbit around Earth with geocentric distances reaching 353,000 km. The spacecraft and ground tracking stations at Pushchino, Ru… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.13435v1-abstract-full').style.display = 'inline'; document.getElementById('2307.13435v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2307.13435v1-abstract-full" style="display: none;"> The Einstein Equivalence Principle (EEP) is a cornerstone of general relativity and predicts the existence of gravitational redshift. We report on new results of measuring this shift with RadioAstron (RA), a space VLBI spacecraft launched into an evolving high eccentricity orbit around Earth with geocentric distances reaching 353,000 km. The spacecraft and ground tracking stations at Pushchino, Russia, and Green Bank, USA, were each equipped with a hydrogen maser frequency standard allowing a possible violation of the predicted gravitational redshift, in the form of a violation parameter $\varepsilon$, to be measured. By alternating between RadioAstron's frequency referencing modes during dedicated sessions between 2015 and 2017, the recorded downlink frequencies can essentially be corrected for the non-relativistic Doppler shift. We report on an analysis using the Doppler-tracking frequency measurements made during these sessions and find $\varepsilon = (2.1 \pm 3.3)\times10^{-4}$. We also discuss prospects for measuring $\varepsilon$ with a significantly smaller uncertainty using instead the time-domain recordings of the spacecraft signals and envision how $10^{-7}$ might be possible for a future space VLBI mission. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2307.13435v1-abstract-full').style.display = 'none'; document.getElementById('2307.13435v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 July, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 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">Nelson V Nunes et al 2023 Class. Quantum Grav. in press https://doi.org/10.1088/1361-6382/ace609</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.17647">arXiv:2306.17647</a> <span> [<a href="https://arxiv.org/pdf/2306.17647">pdf</a>, <a href="https://arxiv.org/format/2306.17647">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/10.1109/HISTELCON56357.2023.10365962">10.1109/HISTELCON56357.2023.10365962 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Brief History of Space VLBI </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</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="2306.17647v1-abstract-short" style="display: inline;"> Space Very Long Baseline Interferometry is a radio astronomy technique distinguished by a record-high angular resolution reaching single-digit microseconds of arc. The paper provides a brief account of the history of developments of this technique over the period 1960s-2020s. </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.17647v1-abstract-full" style="display: none;"> Space Very Long Baseline Interferometry is a radio astronomy technique distinguished by a record-high angular resolution reaching single-digit microseconds of arc. The paper provides a brief account of the history of developments of this technique over the period 1960s-2020s. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.17647v1-abstract-full').style.display = 'none'; document.getElementById('2306.17647v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">To appear in the Proceedings of the IEEE "History of Electrotechnology Conference", Florence, Italy, 2023. arXiv admin note: substantial text overlap with arXiv:1810.01230</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A Brief History of Space VLBI," 2023 8th IEEE History of Electrotechnology Conference (HISTELCON), Florence, Italy, 2023, pp. 171-174 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2306.17632">arXiv:2306.17632</a> <span> [<a href="https://arxiv.org/pdf/2306.17632">pdf</a>, <a href="https://arxiv.org/format/2306.17632">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202346904">10.1051/0004-6361/202346904 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> From binary to singular: the AGN PSO J334.2028+1.4075 under the high-resolution scope </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Benke%2C+P">P. Benke</a>, <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">K. 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S. Frey</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">T. An</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Kun%2C+E">E. Kun</a>, <a href="/search/astro-ph?searchtype=author&query=Mohan%2C+P">P. Mohan</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Z. Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Ros%2C+E">E. Ros</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="2306.17632v1-abstract-short" style="display: inline;"> PSO J334.2028+1.4075 (PSO J334) is a luminous quasar located at redshift z=2.06. The source gained attention when periodic flux density variations were discovered in its optical light curve. These variations were initially interpreted as the variability due to the orbital motion of a supermassive black hole binary (SMBHB) residing in a single circumbinary accretion disk. However, subsequent multiw… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.17632v1-abstract-full').style.display = 'inline'; document.getElementById('2306.17632v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2306.17632v1-abstract-full" style="display: none;"> PSO J334.2028+1.4075 (PSO J334) is a luminous quasar located at redshift z=2.06. The source gained attention when periodic flux density variations were discovered in its optical light curve. These variations were initially interpreted as the variability due to the orbital motion of a supermassive black hole binary (SMBHB) residing in a single circumbinary accretion disk. However, subsequent multiwavelength observations provided evidence against the binary hypothesis as no optical periodicity was found on extended time baselines. On the other hand, detailed radio analysis with the Karl G. Jansky Very Large Array (VLA) and the Very Long Baseline Array (VLBA) revealed a lobe-dominated quasar at kpc scales, and possibly a precessing jet, which could retain PSO J334 as a binary SMBH candidate. We aim to study both the large- and small-scale radio structures in PSO J334 to provide additional evidence for or against the binary scenario. We observed the source at 1.7 GHz with the European Very Long Baseline Interferometry Network (EVN), and at 1.5 and 6.2 GHz with the VLA, at frequencies that complement the previous radio interferometric study. Our images reveal a single component at parsec scales slightly resolved in the southeast-northwest direction and a lobe-dominated quasar at kiloparsec scales with a complex structure. The source morphology and polarization in our VLA maps suggest that the jet is interacting with dense clumps of the ambient medium. While we also observe a misalignment between the inner jet and the outer lobes, we suggest that this is due to the restarted nature of the radio jet activity and the possible presence of a warped accretion disk rather than due to the perturbing effects of a companion SMBH. Our analysis suggests that PSO J334 is most likely a jetted AGN with a single SMBH, and there is no clear evidence of a binary SMBH system in its central engine. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2306.17632v1-abstract-full').style.display = 'none'; document.getElementById('2306.17632v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 June, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 677, A1 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.10229">arXiv:2304.10229</a> <span> [<a href="https://arxiv.org/pdf/2304.10229">pdf</a>, <a href="https://arxiv.org/format/2304.10229">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</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/10.1007/s11214-023-00996-6">10.1007/s11214-023-00996-6 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Jupiter Science Enabled by ESA's Jupiter Icy Moons Explorer </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Fletcher%2C+L+N">Leigh N. Fletcher</a>, <a href="/search/astro-ph?searchtype=author&query=Cavali%C3%A9%2C+T">Thibault Cavali茅</a>, <a href="/search/astro-ph?searchtype=author&query=Grassi%2C+D">Davide Grassi</a>, <a href="/search/astro-ph?searchtype=author&query=Hueso%2C+R">Ricardo Hueso</a>, <a href="/search/astro-ph?searchtype=author&query=Lara%2C+L+M">Luisa M. Lara</a>, <a href="/search/astro-ph?searchtype=author&query=Kaspi%2C+Y">Yohai Kaspi</a>, <a href="/search/astro-ph?searchtype=author&query=Galanti%2C+E">Eli Galanti</a>, <a href="/search/astro-ph?searchtype=author&query=Greathouse%2C+T+K">Thomas K. Greathouse</a>, <a href="/search/astro-ph?searchtype=author&query=Molyneux%2C+P+M">Philippa M. Molyneux</a>, <a href="/search/astro-ph?searchtype=author&query=Galand%2C+M">Marina Galand</a>, <a href="/search/astro-ph?searchtype=author&query=Vallat%2C+C">Claire Vallat</a>, <a href="/search/astro-ph?searchtype=author&query=Witasse%2C+O">Olivier Witasse</a>, <a href="/search/astro-ph?searchtype=author&query=Lorente%2C+R">Rosario Lorente</a>, <a href="/search/astro-ph?searchtype=author&query=Hartogh%2C+P">Paul Hartogh</a>, <a href="/search/astro-ph?searchtype=author&query=Poulet%2C+F">Fran莽ois Poulet</a>, <a href="/search/astro-ph?searchtype=author&query=Langevin%2C+Y">Yves Langevin</a>, <a href="/search/astro-ph?searchtype=author&query=Palumbo%2C+P">Pasquale Palumbo</a>, <a href="/search/astro-ph?searchtype=author&query=Gladstone%2C+G+R">G. Randall Gladstone</a>, <a href="/search/astro-ph?searchtype=author&query=Retherford%2C+K+D">Kurt D. Retherford</a>, <a href="/search/astro-ph?searchtype=author&query=Dougherty%2C+M+K">Michele K. Dougherty</a>, <a href="/search/astro-ph?searchtype=author&query=Wahlund%2C+J">Jan-Erik Wahlund</a>, <a href="/search/astro-ph?searchtype=author&query=Barabash%2C+S">Stas Barabash</a>, <a href="/search/astro-ph?searchtype=author&query=Iess%2C+L">Luciano Iess</a>, <a href="/search/astro-ph?searchtype=author&query=Bruzzone%2C+L">Lorenzo Bruzzone</a>, <a href="/search/astro-ph?searchtype=author&query=Hussmann%2C+H">Hauke Hussmann</a> , et al. (25 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2304.10229v4-abstract-short" style="display: inline;"> ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and spa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.10229v4-abstract-full').style.display = 'inline'; document.getElementById('2304.10229v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.10229v4-abstract-full" style="display: none;"> ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared spectroscopy (0.49-5.56 $渭$m), and sub-millimetre sounding (near 530-625\,GHz and 1067-1275\,GHz). This is coupled to radio, stellar, and solar occultation opportunities to explore the atmosphere at high vertical resolution; and radio and plasma wave measurements of electric discharges in the Jovian atmosphere and auroras. Cross-disciplinary scientific investigations enable JUICE to explore coupling processes in giant planet atmospheres, to show how the atmosphere is connected to (i) the deep circulation and composition of the hydrogen-dominated interior; and (ii) to the currents and charged particle environments of the external magnetosphere. JUICE will provide a comprehensive characterisation of the atmosphere and auroras of this archetypal giant planet. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.10229v4-abstract-full').style.display = 'none'; document.getElementById('2304.10229v4-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 October, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 20 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">83 pages, 24 figures, accepted to Space Science Reviews special issue on ESA's JUICE mission</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Space Sci Rev. 2023; 219(7): 53 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.09816">arXiv:2304.09816</a> <span> [<a href="https://arxiv.org/pdf/2304.09816">pdf</a>, <a href="https://arxiv.org/format/2304.09816">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/accf17">10.3847/1538-4357/accf17 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> RadioAstron Space VLBI Imaging of the jet in M87: I. Detection of high brightness temperature at 22 GHz </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kim%2C+J">Jae-Young Kim</a>, <a href="/search/astro-ph?searchtype=author&query=Savolainen%2C+T">Tuomas Savolainen</a>, <a href="/search/astro-ph?searchtype=author&query=Voitsik%2C+P">Petr Voitsik</a>, <a href="/search/astro-ph?searchtype=author&query=Kravchenko%2C+E+V">Evgeniya V. Kravchenko</a>, <a href="/search/astro-ph?searchtype=author&query=Lisakov%2C+M+M">Mikhail M. Lisakov</a>, <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+Y">Yuri Y. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=M%C3%BCller%2C+H">Hendrik M眉ller</a>, <a href="/search/astro-ph?searchtype=author&query=Lobanov%2C+A+P">Andrei P. Lobanov</a>, <a href="/search/astro-ph?searchtype=author&query=Sokolovsky%2C+K+V">Kirill V. Sokolovsky</a>, <a href="/search/astro-ph?searchtype=author&query=Bruni%2C+G">Gabriele Bruni</a>, <a href="/search/astro-ph?searchtype=author&query=Edwards%2C+P+G">Philip G. Edwards</a>, <a href="/search/astro-ph?searchtype=author&query=Reynolds%2C+C">Cormac Reynolds</a>, <a href="/search/astro-ph?searchtype=author&query=Bach%2C+U">Uwe Bach</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Krichbaum%2C+T+P">Thomas P. Krichbaum</a>, <a href="/search/astro-ph?searchtype=author&query=Hada%2C+K">Kazuhiro Hada</a>, <a href="/search/astro-ph?searchtype=author&query=Giroletti%2C+M">Marcello Giroletti</a>, <a href="/search/astro-ph?searchtype=author&query=Orienti%2C+M">Monica Orienti</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J+M">James M. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Lee%2C+S">Sang-Sung Lee</a>, <a href="/search/astro-ph?searchtype=author&query=Sohn%2C+B+W">Bong Won Sohn</a>, <a href="/search/astro-ph?searchtype=author&query=Zensus%2C+J+A">J. Anton Zensus</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="2304.09816v1-abstract-short" style="display: inline;"> We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in Feb 2014 at 22 GHz with 21 ground stations, reaching projected $(u,v)$-spacings up to $\sim11\,$G$位$. The imaging experiment was complemented by snapshot RadioAstron data of M87 obtained duri… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.09816v1-abstract-full').style.display = 'inline'; document.getElementById('2304.09816v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.09816v1-abstract-full" style="display: none;"> We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in Feb 2014 at 22 GHz with 21 ground stations, reaching projected $(u,v)$-spacings up to $\sim11\,$G$位$. The imaging experiment was complemented by snapshot RadioAstron data of M87 obtained during 2013--2016 from the AGN Survey Key Science Program. Their longest baselines extend up to $\sim25\,$G$位$. For all these measurements, fringes are detected only up to $\sim$2.8 Earth Diameter or $\sim$3 G$位$ baseline lengths, resulting in a new image with angular resolution of $\sim150\,渭$as or $\sim20$ Schwarzschild radii spatial resolution. The new image not only shows edge-brightened jet and counterjet structures down to submilliarcsecond scales but also clearly resolves the VLBI core region. While the overall size of the core is comparable to those reported in the literature, the ground-space fringe detection and slightly super-resolved RadioAstron image suggest the presence of substructures in the nucleus, whose minimum brightness temperature exceeds $T_{\rm B, min}\sim10^{12}\,$K. It is challenging to explain the origin of this record-high $T_{\rm B, min}$ value for M87 by pure Doppler boosting effect with a simple conical jet geometry and known jet speed. Therefore, this can be evidence for more extreme Doppler boosting due to a blazar-like small jet viewing angle or highly efficient particle acceleration processes occurring already at the base of the outflow. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.09816v1-abstract-full').style.display = 'none'; document.getElementById('2304.09816v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">27 pages, 13 figures, accepted for publication in ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJ 952 (2023) 34 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.12957">arXiv:2302.12957</a> <span> [<a href="https://arxiv.org/pdf/2302.12957">pdf</a>, <a href="https://arxiv.org/format/2302.12957">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-3881/aca964">10.3847/1538-3881/aca964 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Astrometric Apparent Motion of High-redshift Radio Sources </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Titov%2C+O">Oleg Titov</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">Sandor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Melnikov%2C+A">Alexei Melnikov</a>, <a href="/search/astro-ph?searchtype=author&query=Shu%2C+F">Fengchun Shu</a>, <a href="/search/astro-ph?searchtype=author&query=Xia%2C+B">Bo Xia</a>, <a href="/search/astro-ph?searchtype=author&query=Gonzalez%2C+J">Javier Gonzalez</a>, <a href="/search/astro-ph?searchtype=author&query=Tercero%2C+B">Belen Tercero</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L">Leonid Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=de+Witt%2C+A">Aletha de Witt</a>, <a href="/search/astro-ph?searchtype=author&query=McCallum%2C+J">Jamie McCallum</a>, <a href="/search/astro-ph?searchtype=author&query=Kharinov%2C+M">Mikhail Kharinov</a>, <a href="/search/astro-ph?searchtype=author&query=Zimovsky%2C+V">Vladimir Zimovsky</a>, <a href="/search/astro-ph?searchtype=author&query=Krezinger%2C+M">Mate Krezinger</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="2302.12957v1-abstract-short" style="display: inline;"> Radio-loud quasars at high redshift (z > 4) are rare objects in the Universe and rarely observed with Very Long Baseline Interferometry (VLBI). But some of them have flux density sufficiently high for monitoring of their apparent position. The instability of the astrometric positions could be linked to the astrophysical process in the jetted active galactic nuclei in the early Universe. Regular ob… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.12957v1-abstract-full').style.display = 'inline'; document.getElementById('2302.12957v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.12957v1-abstract-full" style="display: none;"> Radio-loud quasars at high redshift (z > 4) are rare objects in the Universe and rarely observed with Very Long Baseline Interferometry (VLBI). But some of them have flux density sufficiently high for monitoring of their apparent position. The instability of the astrometric positions could be linked to the astrophysical process in the jetted active galactic nuclei in the early Universe. Regular observations of the high-redshift quasars are used for estimating their apparent proper motion over several years. We have undertaken regular VLBI observations of several high-redshift quasars at 2.3 GHz (S band) and 8.4 GHz (X band) with a network of five radio telescopes: 40-m Yebes (Spain), 25-m Sheshan (China), and three 32-m telescopes of the Quasar VLBI Network (Russia) -- Svetloe, Zelenchukskaya, and Badary. Additional facilities joined this network occasionally. The sources have also been observed in three sessions with the European VLBI Network (EVN) in 2018--2019 and one Long Baseline Array (LBA) experiment in 2018. In addition, several experiments conducted with the Very Long Baseline Array (VLBA) in 2017--2018were used to improve the time sampling and the statistics. Based on these 37 astrometric VLBI experiments between 2017 and 2021, we estimated the apparent proper motions of four quasars: 0901+697, 1428+422, 1508+572, and 2101+600. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.12957v1-abstract-full').style.display = 'none'; document.getElementById('2302.12957v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astronomical Journal, Vol. 165, id. 69 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.06214">arXiv:2302.06214</a> <span> [<a href="https://arxiv.org/pdf/2302.06214">pdf</a>, <a href="https://arxiv.org/format/2302.06214">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stad493">10.1093/mnras/stad493 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Intermediate-mass black holes: finding of episodic, large-scale and powerful jet activity in a dwarf galaxy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Yang%2C+J">Jun Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Liao%2C+M">Mai Liao</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+X">Xiang Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Cui%2C+L">Lang Cui</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+X">Xiaolong Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+W">Wen Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Varenius%2C+E">Eskil Varenius</a>, <a href="/search/astro-ph?searchtype=author&query=Conway%2C+J+E">John E. Conway</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+R">Rurong Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Chang%2C+N">Ning Chang</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="2302.06214v1-abstract-short" style="display: inline;"> Dwarf galaxies are characterised by a very low luminosity and low mass. Because of significant accretion and ejection activity of massive black holes, some dwarf galaxies also host low-luminosity active galactic nuclei (AGNs). In a few dwarf AGNs, very long baseline interferometry (VLBI) observations have found faint non-thermal radio emission. SDSS J090613.77+561015.2 is a dwarf AGN owning an int… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.06214v1-abstract-full').style.display = 'inline'; document.getElementById('2302.06214v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.06214v1-abstract-full" style="display: none;"> Dwarf galaxies are characterised by a very low luminosity and low mass. Because of significant accretion and ejection activity of massive black holes, some dwarf galaxies also host low-luminosity active galactic nuclei (AGNs). In a few dwarf AGNs, very long baseline interferometry (VLBI) observations have found faint non-thermal radio emission. SDSS J090613.77+561015.2 is a dwarf AGN owning an intermediate-mass black hole (IMBH) with a mass of $M_{BH} = 3.6^{+5.9}_{-2.3} \times 10^5 M_{sun}$ and showing a rarely-seen two-component radio structure in its radio nucleus. To further probe their nature, i.e. the IMBH jet activity, we performed additional deep observations with the European VLBI Network (EVN) at 1.66 GHz and 4.99 GHz. We find the more diffuse emission regions and structure details. These new EVN imaging results allow us to reveal a two-sided jet morphology with a size up to about 150 mas (projected length $\sim$140 pc) and a radio luminosity of about $3\times10^{38}$ erg s$^{-1}$. The peak feature has an optically thin radio spectrum and thus more likely represents a relatively young ejecta instead of a jet base. The EVN study on SDSS J090613.77+561015.2 demonstrates the existence of episodic, relatively large-scale and powerful IMBH jet activity in dwarf AGNs. Moreover, we collected a small sample of VLBI-detected dwarf AGNs and investigated their connections with normal AGNs. We notice that these radio sources in the dwarf AGNs tend to have steep spectra and small linear sizes, and possibly represent ejecta from scaled-down episodic jet activity. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.06214v1-abstract-full').style.display = 'none'; document.getElementById('2302.06214v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in MRNAS, 10 pages, 6 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Monthly Notices of the Royal Astronomical Society, Vol. 520, pp. 5964-5973 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.12283">arXiv:2301.12283</a> <span> [<a href="https://arxiv.org/pdf/2301.12283">pdf</a>, <a href="https://arxiv.org/format/2301.12283">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> </div> <p class="title is-5 mathjax"> J2102+6015: a potential distant multimessenger? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Krezinger%2C+M">M谩t茅 Krezinger</a>, <a href="/search/astro-ph?searchtype=author&query=Titov%2C+O">Oleg Titov</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">Tao An</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Yingkang Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Polnarev%2C+A+G">Alexander G. Polnarev</a>, <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">Krisztina 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">Krisztina Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Melnikov%2C+A">Alexey Melnikov</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.12283v3-abstract-short" style="display: inline;"> We present and briefly discuss results of several studies of the source J2102+6015 with tentatively defined redshift z=4:575 which demonstrates unusual properties in imaging and astrometric VLBI observations. Its properties might be considered as indications on the supermassive black hole binary which can be considered as a so far rare example of a high-redshift source of known electromagnetic and… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.12283v3-abstract-full').style.display = 'inline'; document.getElementById('2301.12283v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.12283v3-abstract-full" style="display: none;"> We present and briefly discuss results of several studies of the source J2102+6015 with tentatively defined redshift z=4:575 which demonstrates unusual properties in imaging and astrometric VLBI observations. Its properties might be considered as indications on the supermassive black hole binary which can be considered as a so far rare example of a high-redshift source of known electromagnetic and, possibly, predictable gravitational wave emissions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.12283v3-abstract-full').style.display = 'none'; document.getElementById('2301.12283v3-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 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">To be published in the Proceedings of the IAU Symp. No. 375 "The multimessenger chakra of blazar jets", Kathmandu, Nepal, December 2022</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.09947">arXiv:2301.09947</a> <span> [<a href="https://arxiv.org/pdf/2301.09947">pdf</a>, <a href="https://arxiv.org/ps/2301.09947">ps</a>, <a href="https://arxiv.org/format/2301.09947">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.22323/1.428.0024">10.22323/1.428.0024 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> High-resolution Imaging of Two Radio Quasars at the End of the Reionization Epoch </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">Krisztina Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Yingkang Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">Tao An</a>, <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">Krisztina 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Hwang%2C+C">Chorng-Yuan Hwang</a>, <a href="/search/astro-ph?searchtype=author&query=Koptelova%2C+E">Ekaterina Koptelova</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+A">Ailing Wang</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.09947v2-abstract-short" style="display: inline;"> There are approximately 250 quasars discovered at redshift $z\geq6$, of which only a handful were detected in radio bands, and even fewer were imaged with the highest resolution very long baseline interferometry (VLBI) technique. Here we report the results of our dual-frequency observations with the Very Long Baseline Array (VLBA) of two such recently discovered quasars, VIKING J231818.35$-$311346… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.09947v2-abstract-full').style.display = 'inline'; document.getElementById('2301.09947v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.09947v2-abstract-full" style="display: none;"> There are approximately 250 quasars discovered at redshift $z\geq6$, of which only a handful were detected in radio bands, and even fewer were imaged with the highest resolution very long baseline interferometry (VLBI) technique. Here we report the results of our dual-frequency observations with the Very Long Baseline Array (VLBA) of two such recently discovered quasars, VIKING J231818.35$-$311346.3 at $z=6.44$ and FIRST J233153.20$+$112952.11 at $z=6.57$. Both extremely distant sources were imaged with VLBI for the first time. The radio properties of the former are consistent with those of quasars with young radio jets. The latter has an UV/optical spectrum characteristic of BL Lac objects, of which no others have been found beyond redshift 4 so far. Our VLBA observations revealed a flat-spectrum compact radio source. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.09947v2-abstract-full').style.display = 'none'; document.getElementById('2301.09947v2-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 March, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 2 figures; to appear in the proceedings of the 15th European VLBI Network Symposium and Users' Meeting (EVN2022), 11-15 July 2022, University College Cork, Ireland</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Proceedings of Science, Vol. 428, id. PoS(EVN2022)024 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.07355">arXiv:2301.07355</a> <span> [<a href="https://arxiv.org/pdf/2301.07355">pdf</a>, <a href="https://arxiv.org/format/2301.07355">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.22323/1.428.0022">10.22323/1.428.0022 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> J2102+6015: an Intriguing Radio-loud Active Galactic Nucleus in the Early Universe </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S. Frey</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">T. An</a>, <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K">K. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L">L. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Krezinger%2C+M">M. Krezinger</a>, <a href="/search/astro-ph?searchtype=author&query=Melnikov%2C+A">A. Melnikov</a>, <a href="/search/astro-ph?searchtype=author&query=Mohan%2C+P">P. Mohan</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Z. Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">K. Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Shu%2C+F">F. Shu</a>, <a href="/search/astro-ph?searchtype=author&query=Titov%2C+O">O. Titov</a>, <a href="/search/astro-ph?searchtype=author&query=de+Vicente%2C+P">P. de Vicente</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Y. Zhang</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.07355v1-abstract-short" style="display: inline;"> The powerful high-redshift quasar J2102+6015 (at z=4.575) may provide useful information for studying supermassive black hole growth, galaxy evolution and feedback in the early Universe. The source has so far been imaged with very long baseline interferometry (VLBI) at 2/8 GHz (S/X) bands only, showing complex compact structure. Its total radio spectrum peaks at ~6 GHz in the rest frame. There is… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.07355v1-abstract-full').style.display = 'inline'; document.getElementById('2301.07355v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.07355v1-abstract-full" style="display: none;"> The powerful high-redshift quasar J2102+6015 (at z=4.575) may provide useful information for studying supermassive black hole growth, galaxy evolution and feedback in the early Universe. The source has so far been imaged with very long baseline interferometry (VLBI) at 2/8 GHz (S/X) bands only, showing complex compact structure. Its total radio spectrum peaks at ~6 GHz in the rest frame. There is no sign of Doppler-boosted jet emission, and the separation of the two major features in its east-west oriented structure spanning ~10 milliarcsec does not change significantly on a timescale longer than a decade. However, VLBI astrometric monitoring observations suggest quasi-periodic (~3 yr) variation in its absolute position. J2102+6015 is presumably a young radio source with jets misaligned with respect to the line of sight. Here we briefly report on our new high-resolution imaging observations made with the European VLBI Network (EVN) at 5 and 22 GHz frequencies in 2021 June, and give an overview of what is currently known about this peculiar distant jetted active galactic nucleus. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.07355v1-abstract-full').style.display = 'none'; document.getElementById('2301.07355v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, 2 figures; submitted to the proceedings of the 15th European VLBI Network Symposium and Users' Meeting (EVN2022), 11-15 July 2022, University College Cork, Ireland</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Proceedings of Science, Vol. 428, id. PoS(EVN2022)022 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.04533">arXiv:2301.04533</a> <span> [<a href="https://arxiv.org/pdf/2301.04533">pdf</a>, <a href="https://arxiv.org/format/2301.04533">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/pasa.2023.2">10.1017/pasa.2023.2 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Very long baseline interferometry observations of the high-redshift blazar candidate J0141-5427 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">K. 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Belladitta%2C+S">S. Belladitta</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S. Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Orosz%2C+G">G. Orosz</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Rozgonyi%2C+K">K. Rozgonyi</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">T. An</a>, <a href="/search/astro-ph?searchtype=author&query=Cao%2C+H">H. Cao</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Z. Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">K. Perger</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.04533v1-abstract-short" style="display: inline;"> Active galactic nuclei (AGN) have been observed as far as redshift z~7. They are crucial in investigating the early Universe as well as the growth of supermassive black holes at their centres. Radio-loud AGN with their jets seen at a small viewing angle are called blazars and show relativistic boosting of their emission. Thus, their apparently brighter jets are easier to detect in the high-redshif… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.04533v1-abstract-full').style.display = 'inline'; document.getElementById('2301.04533v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.04533v1-abstract-full" style="display: none;"> Active galactic nuclei (AGN) have been observed as far as redshift z~7. They are crucial in investigating the early Universe as well as the growth of supermassive black holes at their centres. Radio-loud AGN with their jets seen at a small viewing angle are called blazars and show relativistic boosting of their emission. Thus, their apparently brighter jets are easier to detect in the high-redshift Universe. DES J014132.4-542749.9 is a radio-luminous but X-ray weak blazar candidate at z = 5. We conducted high-resolution radio interferometric observations of this source with the Australian Long Baseline Array at 1.7 and 8.5 GHz. A single, compact radio emitting feature was detected at both frequencies with a flat radio spectrum. We derived the milliarcsecond-level accurate position of the object. The frequency dependence of its brightness temperature is similar to that of blazar sources observed at lower redshifts. Based on our observations, we can confirm its blazar nature. We compared its radio properties with those of two other similarly X-ray-weak and radio-bright AGN, and found that they show very different relativistic boosting characteristics. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.04533v1-abstract-full').style.display = 'none'; document.getElementById('2301.04533v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 11 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">8 pages, 4 figures, accepted for publication in PASA</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Publications of the Astronomical Society of Australia, Vol. 40, id. E004 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2212.09590">arXiv:2212.09590</a> <span> [<a href="https://arxiv.org/pdf/2212.09590">pdf</a>, <a href="https://arxiv.org/format/2212.09590">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="Earth and Planetary Astrophysics">astro-ph.EP</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s10686-022-09887-0">10.1007/s10686-022-09887-0 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ultra-Low-Frequency Radio Astronomy Observations from a Selenocentric Orbit: first results of the Longjiang-2 experiment </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Yan%2C+J">Jingye Yan</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+J">Ji Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+L">Lin Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Deng%2C+L">Li Deng</a>, <a href="/search/astro-ph?searchtype=author&query=Zhao%2C+F">Fei Zhao</a>, <a href="/search/astro-ph?searchtype=author&query=Zhou%2C+L">Li Zhou</a>, <a href="/search/astro-ph?searchtype=author&query=Lan%2C+A">Ailan Lan</a>, <a href="/search/astro-ph?searchtype=author&query=Fan%2C+W">Wenjie Fan</a>, <a href="/search/astro-ph?searchtype=author&query=Yi%2C+M">Min Yi</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+Y">Yang Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+Z">Zhen Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Wei%2C+M">Mingchuan Wei</a>, <a href="/search/astro-ph?searchtype=author&query=Guo%2C+J">Jinsheng Guo</a>, <a href="/search/astro-ph?searchtype=author&query=Qiu%2C+S">Shi Qiu</a>, <a href="/search/astro-ph?searchtype=author&query=Wu%2C+F">Fan Wu</a>, <a href="/search/astro-ph?searchtype=author&query=Hu%2C+C">Chaoran Hu</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+X">Xuelei Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Rothkaehl%2C+H">Hanna Rothkaehl</a>, <a href="/search/astro-ph?searchtype=author&query=Morawski%2C+M">Marek Morawski</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="2212.09590v1-abstract-short" style="display: inline;"> This paper introduces the first results of observations with the Ultra-Long-Wavelength (ULW) -- Low Frequency Interferometer and Spectrometer (LFIS) on board the selenocentric satellite Longjiang-2. We present a brief description of the satellite and focus on the LFIS payload. The in-orbit commissioning confirmed a reliable operational status of the instrumentation. We also present results of a tr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2212.09590v1-abstract-full').style.display = 'inline'; document.getElementById('2212.09590v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2212.09590v1-abstract-full" style="display: none;"> This paper introduces the first results of observations with the Ultra-Long-Wavelength (ULW) -- Low Frequency Interferometer and Spectrometer (LFIS) on board the selenocentric satellite Longjiang-2. We present a brief description of the satellite and focus on the LFIS payload. The in-orbit commissioning confirmed a reliable operational status of the instrumentation. We also present results of a transition observation, which offers unique measurements on several novel aspects. We estimate the RFI suppression required for such a radio astronomy instrumentation at the Moon distances from Earth to be of the order of 80 dB. We analyse a method of separating Earth- and satellite-originated radio frequency interference (RFI). It is found that the RFI level at frequencies lower than a few MHz is smaller than the receiver noise floor. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2212.09590v1-abstract-full').style.display = 'none'; document.getElementById('2212.09590v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 December, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 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 Experimental Astronomy; 22 pages, 11 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2206.10964">arXiv:2206.10964</a> <span> [<a href="https://arxiv.org/pdf/2206.10964">pdf</a>, <a href="https://arxiv.org/format/2206.10964">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stac1753">10.1093/mnras/stac1753 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Is there a sub-parsec-scale jet base in the nearby dwarf galaxy NGC 4395? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Yang%2C+J">Jun Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+X">Xiaolong Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Wrobel%2C+J+M">Joan M. Wrobel</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Ho%2C+L+C">Luis C. Ho</a>, <a href="/search/astro-ph?searchtype=author&query=Nyland%2C+K">Kristina Nyland</a>, <a href="/search/astro-ph?searchtype=author&query=Fan%2C+L">Lulu Fan</a>, <a href="/search/astro-ph?searchtype=author&query=Tafoya%2C+D">Daniel Tafoya</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2206.10964v1-abstract-short" style="display: inline;"> NGC 4395 is a dwarf galaxy at a distance of about 4.3 Mpc (scale: ~0.021 pc mas$^{-1}$). It hosts an intermediate-mass black hole (IMBH) with a mass between ~10$^4$ and ~10$^5$ solar masses. The early radio observations of NGC 4395 with the very long baseline interferometry (VLBI) network, High Sensitivity Array (HSA), at 1.4 GHz in 2005 showed that its nucleus has a sub-mJy outflow-like feature (… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.10964v1-abstract-full').style.display = 'inline'; document.getElementById('2206.10964v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2206.10964v1-abstract-full" style="display: none;"> NGC 4395 is a dwarf galaxy at a distance of about 4.3 Mpc (scale: ~0.021 pc mas$^{-1}$). It hosts an intermediate-mass black hole (IMBH) with a mass between ~10$^4$ and ~10$^5$ solar masses. The early radio observations of NGC 4395 with the very long baseline interferometry (VLBI) network, High Sensitivity Array (HSA), at 1.4 GHz in 2005 showed that its nucleus has a sub-mJy outflow-like feature (E) extending over 15 mas. To probe the possibility of the feature E as a continuous jet with a base physically coupled with the accretion disc, we performed deep VLBI observations with the European VLBI Network (EVN) at 5 GHz, and analysed the archival data obtained with the HSA at 1.4 GHz in 2008, NSF's Karl G. Jansky Very Large Array (VLA) at 12-18 GHz and the Atacama Large Millimetre/submillimetre Array (ALMA) at 237 GHz. The feature E displays more diffuse structure in the HSA image of 2008 and has no compact substructure detected in the EVN image. Together with the optically thin steep spectrum and the extremely large angular offset (about 220 mas) from the accurate optical Gaia position, we explain the feature E as nuclear shocks likely formed by the IMBH's episodic ejection or wide-angle outflow. The VLA and ALMA observations find a sub-mJy pc-scale diffuse feature, possibly tracing a thermal free-free emission region near the IMBH. There is no detection of a jet base at the IMBH position in the VLBI maps. The non-detections give an extremely low luminosity of <=4.7 x 10$^{33}$ erg s$^{-1}$ at 5 GHz and indicate no evidence of a disc-jet coupling on sub-pc scales. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.10964v1-abstract-full').style.display = 'none'; document.getElementById('2206.10964v1-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 June, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 4 figures, accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.05859">arXiv:2205.05859</a> <span> [<a href="https://arxiv.org/pdf/2205.05859">pdf</a>, <a href="https://arxiv.org/format/2205.05859">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Experiment">hep-ex</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Physics - Phenomenology">hep-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/10.1051/0004-6361/202243785">10.1051/0004-6361/202243785 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> VLBI observations of VIK J2318-3113, a quasar at z = 6.44 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Y. Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">T. An</a>, <a href="/search/astro-ph?searchtype=author&query=Wang%2C+A">A. Wang</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S. Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Gabanyi%2C+K+E">K. E. Gabanyi</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">K. Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Z. Paragi</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.05859v2-abstract-short" style="display: inline;"> The nature of jets in active galactic nuclei (AGN) in the early Universe and their feedback to the host galaxy remain a highly topical question. Observations of the radio structure of high-redshift AGNs enabled by very long baseline interferometry (VLBI) provide indispensable input into studies of their properties and role in the galaxies' evolution. Up to now, only five AGNs at redshift $z > 6$ h… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.05859v2-abstract-full').style.display = 'inline'; document.getElementById('2205.05859v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.05859v2-abstract-full" style="display: none;"> The nature of jets in active galactic nuclei (AGN) in the early Universe and their feedback to the host galaxy remain a highly topical question. Observations of the radio structure of high-redshift AGNs enabled by very long baseline interferometry (VLBI) provide indispensable input into studies of their properties and role in the galaxies' evolution. Up to now, only five AGNs at redshift $z > 6$ have been studied with the VLBI technique. VIKJ2318-3113 is a recently discovered quasar at z = 6.44 that has not been imaged with VLBI before the current work. Here we present the first VLBI imaging results of this high-redshift quasar, with the aim of corroborating its high-resolution appearance with the physical model of the object. We carried out VLBI phase-referencing observations of VIKJ2318-3113 using the Very Long Baseline Array at two frequencies, 1.6 and 4.7 GHz, and obtained the first view at the radio structure on the milliarcsecond scale. The source was clearly detected at 1.6 GHz. We found that almost all of its radio emission comes from the pc-scale core region. Our dual-frequency observations constrain the spectral index and brightness temperature of the radio core. Its properties are similar to those of other known high-redshift radio-loud AGNs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.05859v2-abstract-full').style.display = 'none'; document.getElementById('2205.05859v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 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">6 pages, 2 figures, accepted by A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 662, L2 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2204.09144">arXiv:2204.09144</a> <span> [<a href="https://arxiv.org/pdf/2204.09144">pdf</a>, <a href="https://arxiv.org/format/2204.09144">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="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/10.1016/j.actaastro.2022.04.020">10.1016/j.actaastro.2022.04.020 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The science case and challenges of space-borne sub-millimeter interferometry </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Amils%2C+R+I">Ricardo I. Amils</a>, <a href="/search/astro-ph?searchtype=author&query=van+Bemmel%2C+I">Ilse van Bemmel</a>, <a href="/search/astro-ph?searchtype=author&query=Boven%2C+P">Paul Boven</a>, <a href="/search/astro-ph?searchtype=author&query=Casasola%2C+V">Viviana Casasola</a>, <a href="/search/astro-ph?searchtype=author&query=Conway%2C+J">John Conway</a>, <a href="/search/astro-ph?searchtype=author&query=Davelaar%2C+J">Jordy Davelaar</a>, <a href="/search/astro-ph?searchtype=author&query=D%C3%ADez-Gonz%C3%A1lez%2C+M+C">M. Carmen D铆ez-Gonz谩lez</a>, <a href="/search/astro-ph?searchtype=author&query=Falcke%2C+H">Heino Falcke</a>, <a href="/search/astro-ph?searchtype=author&query=Fender%2C+R">Rob Fender</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Fromm%2C+C+M">Christian M. Fromm</a>, <a href="/search/astro-ph?searchtype=author&query=Gallego-Puyol%2C+J+D">Juan D. Gallego-Puyol</a>, <a href="/search/astro-ph?searchtype=author&query=Garc%C3%ADa-Mir%C3%B3%2C+C">Cristina Garc铆a-Mir贸</a>, <a href="/search/astro-ph?searchtype=author&query=Garrett%2C+M+A">Michael A. Garrett</a>, <a href="/search/astro-ph?searchtype=author&query=Giroletti%2C+M">Marcello Giroletti</a>, <a href="/search/astro-ph?searchtype=author&query=Goddi%2C+C">Ciriaco Goddi</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez%2C+J+L">Jos茅 L. G贸mez</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Gucht%2C+J">Jeffrey van der Gucht</a>, <a href="/search/astro-ph?searchtype=author&query=Guirado%2C+J+C">Jos茅 Carlos Guirado</a>, <a href="/search/astro-ph?searchtype=author&query=Haiman%2C+Z">Zolt谩n Haiman</a>, <a href="/search/astro-ph?searchtype=author&query=Helmich%2C+F">Frank Helmich</a>, <a href="/search/astro-ph?searchtype=author&query=Hudson%2C+B">Ben Hudson</a>, <a href="/search/astro-ph?searchtype=author&query=Humphreys%2C+E">Elizabeth Humphreys</a> , et al. (29 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="2204.09144v2-abstract-short" style="display: inline;"> Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular reso… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2204.09144v2-abstract-full').style.display = 'inline'; document.getElementById('2204.09144v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2204.09144v2-abstract-full" style="display: none;"> Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10-20 microrcseconds. Further developments toward at least an order of magnitude "sharper" values are dictated by the needs of astrophysical studies and can only be achieved by placing millimeter and submillimeter wavelength interferometric systems in space. A concept of such the system, called Terahertz Exploration and Zooming-in for Astrophysics (THEZA), has been proposed in the framework of the ESA Call for White Papers for the Voayage 2050 long term plan in 2019. In the current paper we discuss several approaches for addressing technological challenges of the THEZA concept. In particular, we consider a novel configuration of a space-borne millimeter/sub-millimeter antenna which might resolve several bottlenecks in creating large precise mechanical structures. The paper also presents an overview of prospective space-qualified technologies of low-noise analogue front-end instrumentation for millimeter/sub-millimeter telescopes, data handling and processing. The paper briefly discusses approaches to the interferometric baseline state vector determination and synchronisation and heterodyning system. In combination with the original ESA Voyage 2050 White Paper, the current work sharpens the case for the next generation microarcsceond-level imaging instruments and provides starting points for further in-depth technology trade-off studies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2204.09144v2-abstract-full').style.display = 'none'; document.getElementById('2204.09144v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">The paper on 29 pages contains 12 figures, accepted for publication in Acta Astronautica, based on the presentation at the 72nd IAC, Dubai, UAE, October 2021</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Acta Astronautica 196 (2022) 314 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2204.02114">arXiv:2204.02114</a> <span> [<a href="https://arxiv.org/pdf/2204.02114">pdf</a>, <a href="https://arxiv.org/format/2204.02114">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4365/ac63b8">10.3847/1538-4365/ac63b8 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Radio-loud Quasars above Redshift 4: VLBI Imaging of an Extended Sample </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Krezinger%2C+M">M. Krezinger</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">K. Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">K. 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S. Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zs. Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">T. An</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Y. Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Cao%2C+H">H. Cao</a>, <a href="/search/astro-ph?searchtype=author&query=Sbarrato%2C+T">T. Sbarrato</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="2204.02114v1-abstract-short" style="display: inline;"> High-redshift radio sources provide plentiful opportunities for studying the formation and evolution of early galaxies and supermassive black holes. However, the number of known radio-loud active galactic nuclei (AGN) above redshift 4 is rather limited. At high redshifts, it appears that blazars, with relativistically beamed jets pointing towards the observer, are in majority compared to radio-lou… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2204.02114v1-abstract-full').style.display = 'inline'; document.getElementById('2204.02114v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2204.02114v1-abstract-full" style="display: none;"> High-redshift radio sources provide plentiful opportunities for studying the formation and evolution of early galaxies and supermassive black holes. However, the number of known radio-loud active galactic nuclei (AGN) above redshift 4 is rather limited. At high redshifts, it appears that blazars, with relativistically beamed jets pointing towards the observer, are in majority compared to radio-loud sources with jets misaligned with respect to the line of sight. To find more of these misaligned AGN, milliarcsec-scale imaging studies carried out with very long baseline interferometry (VLBI) are needed, as they allow us to distinguish between compact core--jet radio sources and those with more extended emission. Previous high-resolution VLBI studies revealed that some of the radio sources among blazar candidates in fact show unbeamed radio emission on milliarcsecond scales. The most accurate optical coordinates determined with the Gaia astrometric space mission are also useful in the classification process. Here, we report on dual-frequency imaging observations of 13 high-redshift (4 < z < 4.5) quasars at 1.7 and 5 GHz with the European VLBI Network. This sample increases the number of z>4 radio sources for which VLBI observations are available by about a quarter. Using structural and physical properties, such as radio morphology, spectral index, variability, brightness temperature, as well as optical coordinates, we identified six blazars and six misaligned radio AGNs, with the remaining one tentatively identified as blazar. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2204.02114v1-abstract-full').style.display = 'none'; document.getElementById('2204.02114v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2112.12526">arXiv:2112.12526</a> <span> [<a href="https://arxiv.org/pdf/2112.12526">pdf</a>, <a href="https://arxiv.org/format/2112.12526">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnras/stab3804">10.1093/mnras/stab3804 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Structural and spectral properties of Galactic plane variable radio sources </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Yang%2C+J">Jun Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Chen%2C+Y">Yongjun Chen</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+A">Aiyuan Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+X">Xiaolong Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Shen%2C+Z">Zhiqiang Shen</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="2112.12526v1-abstract-short" style="display: inline;"> In the time domain, the radio sky in particular along the Galactic plane direction may vary significantly because of various energetic activities associated with stars, stellar and supermassive black holes. Using multi-epoch Very Large Array surveys of the Galactic plane at 5.0 GHz, Becker et al. (2010) presented a catalogue of 39 variable radio sources in the flux density range 1-70 mJy. To probe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.12526v1-abstract-full').style.display = 'inline'; document.getElementById('2112.12526v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2112.12526v1-abstract-full" style="display: none;"> In the time domain, the radio sky in particular along the Galactic plane direction may vary significantly because of various energetic activities associated with stars, stellar and supermassive black holes. Using multi-epoch Very Large Array surveys of the Galactic plane at 5.0 GHz, Becker et al. (2010) presented a catalogue of 39 variable radio sources in the flux density range 1-70 mJy. To probe their radio structures and spectra, we observed 17 sources with the very-long-baseline interferometric (VLBI) imaging technique and collected additional multi-frequency data from the literature. We detected all of the sources at 5 GHz with the Westerbork Synthesis Radio Telescope, but only G23.6644-0.0372 with the European VLBI Network (EVN). Together with its decadal variability and multi-frequency radio spectrum, we interpret it as an extragalactic peaked-spectrum source with a size of <~10 pc. The remaining sources were resolved out by the long baselines of the EVN because of either strong scatter broadening at the Galactic latitude <1 deg or intrinsically very extended structures on centi-arcsec scales. According to their spectral and structural properties, we find that the sample has a diverse nature. We notice two young H II regions and spot a radio star and a candidate planetary nebula. The rest of the sources are very likely associated with radio active galactic nuclei (AGN). Two of them also displays arcsec-scale faint jet activity. The sample study indicates that AGN are commonplace even among variable radio sources in the Galactic plane. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2112.12526v1-abstract-full').style.display = 'none'; document.getElementById('2112.12526v1-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, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">15 pages, 18 figures, accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.11200">arXiv:2111.11200</a> <span> [<a href="https://arxiv.org/pdf/2111.11200">pdf</a>, <a href="https://arxiv.org/format/2111.11200">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ac3bcc">10.3847/1538-4357/ac3bcc <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron. V. Space and ground millimeter-VLBI imaging of OJ 287 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez%2C+J+L">Jose L. G贸mez</a>, <a href="/search/astro-ph?searchtype=author&query=Traianou%2C+E">Efthalia Traianou</a>, <a href="/search/astro-ph?searchtype=author&query=Krichbaum%2C+T+P">Thomas P. Krichbaum</a>, <a href="/search/astro-ph?searchtype=author&query=Lobanov%2C+A">Andrei Lobanov</a>, <a href="/search/astro-ph?searchtype=author&query=Fuentes%2C+A">Antonio Fuentes</a>, <a href="/search/astro-ph?searchtype=author&query=Lico%2C+R">Rocco Lico</a>, <a href="/search/astro-ph?searchtype=author&query=Zhao%2C+G">Guang-Yao Zhao</a>, <a href="/search/astro-ph?searchtype=author&query=Bruni%2C+G">Gabriele Bruni</a>, <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+Y">Yuri Y. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=Lahteenmaki%2C+A">Anne Lahteenmaki</a>, <a href="/search/astro-ph?searchtype=author&query=Voitsik%2C+P+A">Petr A. Voitsik</a>, <a href="/search/astro-ph?searchtype=author&query=Lisakov%2C+M+M">Mikhail M. Lisakov</a>, <a href="/search/astro-ph?searchtype=author&query=Angelakis%2C+E">Emmanouil Angelakis</a>, <a href="/search/astro-ph?searchtype=author&query=Bach%2C+U">Uwe Bach</a>, <a href="/search/astro-ph?searchtype=author&query=Casadio%2C+C">Carolina Casadio</a>, <a href="/search/astro-ph?searchtype=author&query=Cho%2C+I">Ilje Cho</a>, <a href="/search/astro-ph?searchtype=author&query=Dey%2C+L">Lankeswar Dey</a>, <a href="/search/astro-ph?searchtype=author&query=Gopakumar%2C+A">Achamveedu Gopakumar</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L">Leonid Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Jorstad%2C+S+G">Svetlana G. Jorstad</a>, <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+A">Yuri A. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=Lister%2C+M+L">Matthew L. Lister</a>, <a href="/search/astro-ph?searchtype=author&query=Marscher%2C+A+P">Alan P. Marscher</a>, <a href="/search/astro-ph?searchtype=author&query=Myserlis%2C+I">Ioannis Myserlis</a>, <a href="/search/astro-ph?searchtype=author&query=Pushkarev%2C+A">Alexander Pushkarev</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="2111.11200v2-abstract-short" style="display: inline;"> We present the first polarimetric space VLBI observations of OJ 287, observed with RadioAstron at 22 GHz during a perigee session on 2014 April 4 and five near-in-time snapshots, together with contemporaneous ground VLBI observations at 15, 43, and 86 GHz. Ground-space fringes were obtained up to a projected baseline of 3.9 Earth diameters during the perigee session, and at a record 15.1 Earth dia… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.11200v2-abstract-full').style.display = 'inline'; document.getElementById('2111.11200v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.11200v2-abstract-full" style="display: none;"> We present the first polarimetric space VLBI observations of OJ 287, observed with RadioAstron at 22 GHz during a perigee session on 2014 April 4 and five near-in-time snapshots, together with contemporaneous ground VLBI observations at 15, 43, and 86 GHz. Ground-space fringes were obtained up to a projected baseline of 3.9 Earth diameters during the perigee session, and at a record 15.1 Earth diameters during the snapshot sessions, allowing us to image the innermost jet at an angular resolution of $\sim50渭$as, the highest ever achieved at 22 GHz for OJ 287. Comparison with ground-based VLBI observations reveals a progressive jet bending with increasing angular resolution that agrees with predictions from a supermassive binary black hole model, although other models cannot be ruled out. Spectral analyses suggest that the VLBI core is dominated by the internal energy of the emitting particles during the onset of a multi-wavelength flare, while the parsec-scale jet is consistent with being in equipartition between the particles and magnetic field. Estimated minimum brightness temperatures from the visibility amplitudes show a continued rising trend with projected baseline length up to $10^{13}$ K, reconciled with the inverse Compton limit through Doppler boosting for a jet closely oriented to the line of sight. The observed electric vector position angle suggests that the innermost jet has a predominantly toroidal magnetic field, which together with marginal evidence of a gradient in rotation measure across the jet width indicate that the VLBI core is threaded by a helical magnetic field, in agreement with jet formation models. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.11200v2-abstract-full').style.display = 'none'; document.getElementById('2111.11200v2-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 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ApJ 924 (2022) 122 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2111.05622">arXiv:2111.05622</a> <span> [<a href="https://arxiv.org/pdf/2111.05622">pdf</a>, <a href="https://arxiv.org/format/2111.05622">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="Space Physics">physics.space-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/pasa.2021.56">10.1017/pasa.2021.56 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> High spectral resolution multi-tone Spacecraft Doppler tracking software: Algorithms and implementations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Calv%C3%A9s%2C+G+M">Guifr茅 Molera Calv茅s</a>, <a href="/search/astro-ph?searchtype=author&query=Pogrebenko%2C+S+V">Sergei V. Pogrebenko</a>, <a href="/search/astro-ph?searchtype=author&query=Wagner%2C+J+F">Jan F. Wagner</a>, <a href="/search/astro-ph?searchtype=author&query=Cim%C3%B2%2C+G">Giuseppe Cim貌</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Bocanegra-Baham%C3%B3n%2C+T+M">Tatiana M. Bocanegra-Baham贸n</a>, <a href="/search/astro-ph?searchtype=author&query=Duev%2C+D+A">Dmitry A. Duev</a>, <a href="/search/astro-ph?searchtype=author&query=Nunes%2C+N+V">Nelson V. Nunes</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="2111.05622v1-abstract-short" style="display: inline;"> We present a software package for single-dish data processing of spacecraft signals observed with VLBI-equipped radio telescopes. The Spacecraft Doppler tracking (SDtracker) software allows one to obtain topocentric frequency detections with a sub-Hz precision, and reconstructed and residual phases of the carrier signal of any spacecraft or landing vehicle at any location in the Solar System. Thes… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.05622v1-abstract-full').style.display = 'inline'; document.getElementById('2111.05622v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2111.05622v1-abstract-full" style="display: none;"> We present a software package for single-dish data processing of spacecraft signals observed with VLBI-equipped radio telescopes. The Spacecraft Doppler tracking (SDtracker) software allows one to obtain topocentric frequency detections with a sub-Hz precision, and reconstructed and residual phases of the carrier signal of any spacecraft or landing vehicle at any location in the Solar System. These data products are estimated using the ground-based telescope's highly stable oscillator as a reference, without requiring an a priori model of the spacecraft dynamics nor the downlink transmission carrier frequency. The software has been extensively validated in multiple observing campaigns of various deep space missions and is compatible with the raw sample data acquired by any standard VLBI radio telescope worldwide. In this paper, we report the numerical methodology of SDtracker, the technical operations for deployment and usage, and a summary of use cases and scientific results produced since its initial release. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2111.05622v1-abstract-full').style.display = 'none'; document.getElementById('2111.05622v1-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 November, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">The paper has been accepted for publication in PASA</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> ID PAS-21068.R1 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.10964">arXiv:2110.10964</a> <span> [<a href="https://arxiv.org/pdf/2110.10964">pdf</a>, <a href="https://arxiv.org/format/2110.10964">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1002/asna.20210057">10.1002/asna.20210057 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A small radio galaxy at z=4.026 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">Krisztina 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">Tao An</a>, <a href="/search/astro-ph?searchtype=author&query=Cao%2C+H">Hongmin Cao</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Yingkang Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Sbarrato%2C+T">Tullia Sbarrato</a>, <a href="/search/astro-ph?searchtype=author&query=Krezinger%2C+M">M谩t茅 Krezinger</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">Krisztina Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Mez%C5%91%2C+G">Gy枚rgy Mez艖</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="2110.10964v1-abstract-short" style="display: inline;"> Less than $200$ radio-loud active galactic nuclei (AGN) are known above redshift $4$. Around $40$ of them have been observed at milliarcsecond (mas) scale resolution with very long baseline interferometry (VLBI) technique. Some of them are unresolved, compact, relativistically beamed objects, blazars with jets pointing at small angles to the observer's line of sight. But there are also objects wit… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.10964v1-abstract-full').style.display = 'inline'; document.getElementById('2110.10964v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.10964v1-abstract-full" style="display: none;"> Less than $200$ radio-loud active galactic nuclei (AGN) are known above redshift $4$. Around $40$ of them have been observed at milliarcsecond (mas) scale resolution with very long baseline interferometry (VLBI) technique. Some of them are unresolved, compact, relativistically beamed objects, blazars with jets pointing at small angles to the observer's line of sight. But there are also objects with no sign of relativistic beaming possibly having larger jet inclination angles. In a couple of cases, X-ray observations indicate the presence of relativistic beaming in contrary to the VLBI measurements made with the European VLBI Network (EVN). J1420$+$1205 is a prominent example, where our $30-100$ mas-scale enhanced Multi Element Remotely Linked Interferometer Network (e-MERLIN) radio observations revealed a rich structure reminiscent of a small radio galaxy. It shows a bright hotspot which might be related to the denser interstellar medium around a young galaxy at an early cosmological epoch. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.10964v1-abstract-full').style.display = 'none'; document.getElementById('2110.10964v1-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, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Astronomische Nachrichten, proceeding for the 6th Workshop on CSS and GPS Sources, 4 pages, 2 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2110.02437">arXiv:2110.02437</a> <span> [<a href="https://arxiv.org/pdf/2110.02437">pdf</a>, <a href="https://arxiv.org/format/2110.02437">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Space Physics">physics.space-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="General Relativity and Quantum Cosmology">gr-qc</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.asr.2021.07.036">10.1016/j.asr.2021.07.036 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The antenna phase center motion effect in high-accuracy spacecraft tracking experiments </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Litvinov%2C+D+A">D. A. Litvinov</a>, <a href="/search/astro-ph?searchtype=author&query=Nunes%2C+N+V">N. V. Nunes</a>, <a href="/search/astro-ph?searchtype=author&query=Filetkin%2C+A+I">A. I. Filetkin</a>, <a href="/search/astro-ph?searchtype=author&query=Bartel%2C+N">N. Bartel</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Calves%2C+G+M">G. Molera Calves</a>, <a href="/search/astro-ph?searchtype=author&query=Rudenko%2C+V+N">V. N. Rudenko</a>, <a href="/search/astro-ph?searchtype=author&query=Zakhvatkin%2C+M+V">M. V. Zakhvatkin</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="2110.02437v1-abstract-short" style="display: inline;"> We present an improved model for the antenna phase center motion effect for high-gain mechanically steerable ground-based and spacecraft-mounted antennas that takes into account non-perfect antenna pointing. Using tracking data of the RadioAstron spacecraft we show that our model can result in a correction of the computed value of the effect of up to $2\times10^{-14}$ in terms of the fractional fr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.02437v1-abstract-full').style.display = 'inline'; document.getElementById('2110.02437v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2110.02437v1-abstract-full" style="display: none;"> We present an improved model for the antenna phase center motion effect for high-gain mechanically steerable ground-based and spacecraft-mounted antennas that takes into account non-perfect antenna pointing. Using tracking data of the RadioAstron spacecraft we show that our model can result in a correction of the computed value of the effect of up to $2\times10^{-14}$ in terms of the fractional frequency shift, which is significant for high-accuracy spacecraft tracking experiments. The total fractional frequency shift due to the phase center motion effect can exceed $1\times10^{-11}$ both for the ground and space antennas depending on the spacecraft orbit and antenna parameters. We also analyze the error in the computed value of the effect and find that it can be as large as $4\times10^{-14}$ due to uncertainties in the spacecraft antenna axis position, ground antenna axis offset and misalignment, and others. Finally, we present a way to reduce both the ground and space antenna phase center motion effects by several orders of magnitude, e.g. for RadioAstron to below $1\times10^{-16}$, by tracking the spacecraft simultaneously in the one-way downlink and two-way phase-locked loop modes, i.e. using the Gravity Probe A configuration of the communications links. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2110.02437v1-abstract-full').style.display = 'none'; document.getElementById('2110.02437v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 October, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 15 figures, to appear in Advances in Space Research</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2105.06307">arXiv:2105.06307</a> <span> [<a href="https://arxiv.org/pdf/2105.06307">pdf</a>, <a href="https://arxiv.org/ps/2105.06307">ps</a>, <a href="https://arxiv.org/format/2105.06307">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.3847/1538-4357/ac0144">10.3847/1538-4357/ac0144 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multi-scale Radio and X-ray Structure of the High-redshift Quasar PMN J0909+0354 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">Krisztina Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Schwartz%2C+D+A">Daniel A. Schwartz</a>, <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">Krisztina 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</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="2105.06307v1-abstract-short" style="display: inline;"> The high-redshift quasar PMN J0909+0354 ($z=3.288$) is known to have a pc-scale compact jet structure, based on global 5-GHz very long baseline interferometry (VLBI) observations performed in 1992. Its kpc-scale structure was studied with the Karl G. Jansky Very Large Array (VLA) in the radio and the Chandra space telescope in X-rays. Apart from the north-northwestern jet component seen in both th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.06307v1-abstract-full').style.display = 'inline'; document.getElementById('2105.06307v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2105.06307v1-abstract-full" style="display: none;"> The high-redshift quasar PMN J0909+0354 ($z=3.288$) is known to have a pc-scale compact jet structure, based on global 5-GHz very long baseline interferometry (VLBI) observations performed in 1992. Its kpc-scale structure was studied with the Karl G. Jansky Very Large Array (VLA) in the radio and the Chandra space telescope in X-rays. Apart from the north-northwestern jet component seen in both the VLA and Chandra images at $2.3''$ separation from the core, there is another X-ray feature at $6.48''$ in the northeastern (NE) direction. To uncover more details and possibly structural changes in the inner jet, we conducted new observations at 5 GHz using the European VLBI Network (EVN) in 2019. These data confirm the northward direction of the one-sided inner jet already suspected from the 1992 observations. A compact core and multiple jet components were identified that can be traced up to $\sim0.25$ kpc projected distance towards the north, while the structure becomes more and more diffuse. A comparison with arcsec-resolution imaging with the VLA shows that the radio jet bends by $\sim30^\circ$ between the two scales. The direction of the pc-scale jet as well as the faint optical counterpart found for the newly-detected X-ray point source (NE) favors the nature of the latter as a background or foreground object in the field of view. However, the extended ($\sim160$ kpc) emission around the positions of the quasar core and NE detected by the Wide-field Infrared Survey Explorer (WISE) in the mid-infrared might suggest physical interaction of the two objects. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.06307v1-abstract-full').style.display = 'none'; document.getElementById('2105.06307v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">20 pages, 10 figures, 4 tables, accepted for publication in ApJ</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> The Astrophysical Journal, Volume 915, Issue 2, id. 98 (July 2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.01367">arXiv:2103.01367</a> <span> [<a href="https://arxiv.org/pdf/2103.01367">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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Atmospheric and Oceanic Physics">physics.ao-ph</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Detectors">physics.ins-det</span> </div> </div> <p class="title is-5 mathjax"> The Future Of The Arecibo Observatory: The Next Generation Arecibo Telescope </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Roshi%2C+D+A">D. Anish Roshi</a>, <a href="/search/astro-ph?searchtype=author&query=Aponte%2C+N">N. Aponte</a>, <a href="/search/astro-ph?searchtype=author&query=Araya%2C+E">E. Araya</a>, <a href="/search/astro-ph?searchtype=author&query=Arce%2C+H">H. Arce</a>, <a href="/search/astro-ph?searchtype=author&query=Baker%2C+L+A">L. A. Baker</a>, <a href="/search/astro-ph?searchtype=author&query=Baan%2C+W">W. Baan</a>, <a href="/search/astro-ph?searchtype=author&query=Becker%2C+T+M">T. M. Becker</a>, <a href="/search/astro-ph?searchtype=author&query=Breakall%2C+J+K">J. K. Breakall</a>, <a href="/search/astro-ph?searchtype=author&query=Brown%2C+R+G">R. G. Brown</a>, <a href="/search/astro-ph?searchtype=author&query=Brum%2C+C+G+M">C. G. M. Brum</a>, <a href="/search/astro-ph?searchtype=author&query=Busch%2C+M">M. Busch</a>, <a href="/search/astro-ph?searchtype=author&query=Campbell%2C+D+B">D. B. Campbell</a>, <a href="/search/astro-ph?searchtype=author&query=Cohen%2C+T">T. Cohen</a>, <a href="/search/astro-ph?searchtype=author&query=Cordova%2C+F">F. Cordova</a>, <a href="/search/astro-ph?searchtype=author&query=Deneva%2C+J+S">J. S. Deneva</a>, <a href="/search/astro-ph?searchtype=author&query=Devogele%2C+M">M. Devogele</a>, <a href="/search/astro-ph?searchtype=author&query=Dolch%2C+T">T. Dolch</a>, <a href="/search/astro-ph?searchtype=author&query=Fernandez-Rodriguez%2C+F+O">F. O. Fernandez-Rodriguez</a>, <a href="/search/astro-ph?searchtype=author&query=Ghosh%2C+T">T. Ghosh</a>, <a href="/search/astro-ph?searchtype=author&query=Goldsmith%2C+P+F">P. F. Goldsmith</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Haynes%2C+M">M. Haynes</a>, <a href="/search/astro-ph?searchtype=author&query=Heiles%2C+C">C. Heiles</a>, <a href="/search/astro-ph?searchtype=author&query=Hessel%2C+J+W+T">J. W. T. Hessel</a>, <a href="/search/astro-ph?searchtype=author&query=Hickson%2C+D">D. Hickson</a> , et al. (49 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2103.01367v2-abstract-short" style="display: inline;"> The Arecibo Observatory (AO) is a multidisciplinary research and education facility that is recognized worldwide as a leading facility in astronomy, planetary, and atmospheric and space sciences. AO's cornerstone research instrument was the 305-m William E. Gordon telescope. On December 1, 2020, the 305-m telescope collapsed and was irreparably damaged. In the three weeks following the collapse, A… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.01367v2-abstract-full').style.display = 'inline'; document.getElementById('2103.01367v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.01367v2-abstract-full" style="display: none;"> The Arecibo Observatory (AO) is a multidisciplinary research and education facility that is recognized worldwide as a leading facility in astronomy, planetary, and atmospheric and space sciences. AO's cornerstone research instrument was the 305-m William E. Gordon telescope. On December 1, 2020, the 305-m telescope collapsed and was irreparably damaged. In the three weeks following the collapse, AO's scientific and engineering staff and the AO users community initiated extensive discussions on the future of the observatory. The community is in overwhelming agreement that there is a need to build an enhanced, next-generation radar-radio telescope at the AO site. From these discussions, we established the set of science requirements the new facility should enable. These requirements can be summarized briefly as: 5 MW of continuous wave transmitter power at 2 - 6 GHz, 10 MW of peak transmitter power at 430 MHz (also at 220MHz under consideration), zenith angle coverage 0 to 48 deg, frequency coverage 0.2 to 30 GHz and increased Field-of-View. These requirements determine the unique specifications of the proposed new instrument. The telescope design concept we suggest consists of a compact array of fixed dishes on a tiltable, plate-like structure with a collecting area equivalent to a 300m dish. This concept, referred to as the Next Generation Arecibo Telescope (NGAT), meets all of the desired specifications and provides significant new science capabilities to all three research groups at AO. This whitepaper presents a sample of the wide variety of the science that can be achieved with the NGAT, the details of the telescope design concept and the need for the new telescope to be located at the AO site. We also discuss other AO science activities that interlock with the NGAT in the white paper. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.01367v2-abstract-full').style.display = 'none'; document.getElementById('2103.01367v2-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 April, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 1 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 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">82 pages (executive summary 10 pages), 21 figures, Arecibo observatory white paper (Updated with the complete author list and minor edits)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2102.04441">arXiv:2102.04441</a> <span> [<a href="https://arxiv.org/pdf/2102.04441">pdf</a>, <a href="https://arxiv.org/format/2102.04441">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/10.1051/0004-6361/202039493">10.1051/0004-6361/202039493 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron IV. The quasar 3C 345 at 18 cm: Magnetic field structure and brightness temperature </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=P%C3%B6tzl%2C+F+M">F. M. P枚tzl</a>, <a href="/search/astro-ph?searchtype=author&query=Lobanov%2C+A+P">A. P. Lobanov</a>, <a href="/search/astro-ph?searchtype=author&query=Ros%2C+E">E. Ros</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez%2C+J+L">J. L. G贸mez</a>, <a href="/search/astro-ph?searchtype=author&query=Bruni%2C+G">G. Bruni</a>, <a href="/search/astro-ph?searchtype=author&query=Bach%2C+U">U. Bach</a>, <a href="/search/astro-ph?searchtype=author&query=Fuentes%2C+A">A. Fuentes</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Jauncey%2C+D+L">D. L. Jauncey</a>, <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+Y">Y. Y. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=Kravchenko%2C+E+V">E. V. Kravchenko</a>, <a href="/search/astro-ph?searchtype=author&query=Lisakov%2C+M+M">M. M. Lisakov</a>, <a href="/search/astro-ph?searchtype=author&query=Savolainen%2C+T">T. Savolainen</a>, <a href="/search/astro-ph?searchtype=author&query=Sokolovsky%2C+K+V">K. V. Sokolovsky</a>, <a href="/search/astro-ph?searchtype=author&query=Zensus%2C+J+A">J. A. Zensus</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2102.04441v1-abstract-short" style="display: inline;"> Context. Supermassive black holes in the centres of radio-loud active galactic nuclei (AGN) can produce collimated relativistic outflows (jets). Magnetic fields are thought to play a key role in the formation and collimation of these jets, but the details are much debated. Aims. We study the innermost jet morphology and magnetic field strength in the AGN 3C 345 with an unprecedented resolution usi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.04441v1-abstract-full').style.display = 'inline'; document.getElementById('2102.04441v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2102.04441v1-abstract-full" style="display: none;"> Context. Supermassive black holes in the centres of radio-loud active galactic nuclei (AGN) can produce collimated relativistic outflows (jets). Magnetic fields are thought to play a key role in the formation and collimation of these jets, but the details are much debated. Aims. We study the innermost jet morphology and magnetic field strength in the AGN 3C 345 with an unprecedented resolution using images obtained within the framework of the key science programme on AGN polarisation of the Space VLBI mission RadioAstron. Methods. We observed the flat spectrum radio quasar 3C 345 at 1.6 GHz on 2016 March 30 with RadioAstron and 18 ground-based radio telescopes in full polarisation mode. Results. Our images, in both total intensity and linear polarisation, reveal a complex jet structure at 300 $渭$as angular resolution, corresponding to a projected linear scale of about 2 pc or a few thousand gravitational radii. We identify the synchrotron self-absorbed core at the jet base and find the brightest feature in the jet 1.5 mas downstream of the core. Several polarised components appear in the Space VLBI images that cannot be seen from ground array-only images. Except for the core, the electric vector position angles follow the local jet direction, suggesting a magnetic field perpendicular to the jet. This indicates the presence of plane perpendicular shocks in these regions. Additionally, we infer a minimum brightness temperature at the largest $(u,v)$-distances of $1.1\times 10^{12}$ K in the source frame, which is above the inverse Compton limit and an order of magnitude larger than the equipartition value. This indicates locally efficient injection or re-acceleration of particles in the jet to counter the inverse Compton cooling or the geometry of the jet creates significant changes in the Doppler factor, which has to be $>11$ to explain the high brightness temperatures. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2102.04441v1-abstract-full').style.display = 'none'; document.getElementById('2102.04441v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 February, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 9 figures. Accepted for publication in Astronomy & Astrophysics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 648, A82 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.07324">arXiv:2101.07324</a> <span> [<a href="https://arxiv.org/pdf/2101.07324">pdf</a>, <a href="https://arxiv.org/format/2101.07324">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/202039423">10.1051/0004-6361/202039423 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> RadioAstron reveals a spine-sheath jet structure in 3C 273 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bruni%2C+G">G. Bruni</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez%2C+J+L">J. L. G贸mez</a>, <a href="/search/astro-ph?searchtype=author&query=Vega-Garc%C3%ADa%2C+L">L. Vega-Garc铆a</a>, <a href="/search/astro-ph?searchtype=author&query=Lobanov%2C+A+P">A. P. Lobanov</a>, <a href="/search/astro-ph?searchtype=author&query=Fuentes%2C+A">A. Fuentes</a>, <a href="/search/astro-ph?searchtype=author&query=Savolainen%2C+T">T. Savolainen</a>, <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+Y">Y. Y. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=Perucho%2C+M">M. Perucho</a>, <a href="/search/astro-ph?searchtype=author&query=Mart%C3%AD%2C+J+-">J. -M. Mart铆</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J+M">J. M. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Edwards%2C+P+G">P. G. Edwards</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Lisakov%2C+M+M">M. M. Lisakov</a>, <a href="/search/astro-ph?searchtype=author&query=Pushkarev%2C+A+B">A. B. Pushkarev</a>, <a href="/search/astro-ph?searchtype=author&query=Sokolovsky%2C+K+V">K. V. Sokolovsky</a>, <a href="/search/astro-ph?searchtype=author&query=Zensus%2C+J+A">J. A. Zensus</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2101.07324v2-abstract-short" style="display: inline;"> We present Space-VLBI RadioAstron observations at 1.6 GHz and 4.8 GHz of the flat spectrum radio quasar 3C 273, with detections on baselines up to 4.5 and 3.3 Earth Diameters, respectively. Achieving the best angular resolution at 1.6 GHz to date, we have imaged limb-brightening in the jet, not previously detected in this source. In contrast, at 4.8 GHz, we detected emission from a central stream… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.07324v2-abstract-full').style.display = 'inline'; document.getElementById('2101.07324v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.07324v2-abstract-full" style="display: none;"> We present Space-VLBI RadioAstron observations at 1.6 GHz and 4.8 GHz of the flat spectrum radio quasar 3C 273, with detections on baselines up to 4.5 and 3.3 Earth Diameters, respectively. Achieving the best angular resolution at 1.6 GHz to date, we have imaged limb-brightening in the jet, not previously detected in this source. In contrast, at 4.8 GHz, we detected emission from a central stream of plasma, with a spatial distribution complementary to the limb-brightened emission, indicating an origin in the spine of the jet. While a stratification across the jet width in the flow density, internal energy, magnetic field, or bulk flow velocity are usually invoked to explain the limb-brightening, the different jet structure detected at the two frequencies probably requires a stratification in the emitting electron energy distribution. Future dedicated numerical simulations will allow the determination of which combination of physical parameters are needed to reproduce the spine/sheath structure observed by Space-VLBI with RadioAstron in 3C 273 <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.07324v2-abstract-full').style.display = 'none'; document.getElementById('2101.07324v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 18 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted by A&A</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 654, A27 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2007.02347">arXiv:2007.02347</a> <span> [<a href="https://arxiv.org/pdf/2007.02347">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> <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="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> </div> <p class="title is-5 mathjax"> VLBI20-30: a scientific roadmap for the next decade -- The future of the European VLBI Network </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Venturi%2C+T">Tiziana Venturi</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Lindqvist%2C+M">Michael Lindqvist</a>, <a href="/search/astro-ph?searchtype=author&query=Bartkiewicz%2C+A">Anna Bartkiewicz</a>, <a href="/search/astro-ph?searchtype=author&query=Beswick%2C+R">Rob Beswick</a>, <a href="/search/astro-ph?searchtype=author&query=Bogdanovi%C4%87%2C+T">Tamara Bogdanovi膰</a>, <a href="/search/astro-ph?searchtype=author&query=Brisken%2C+W">Walter Brisken</a>, <a href="/search/astro-ph?searchtype=author&query=Charlot%2C+P">Patrick Charlot</a>, <a href="/search/astro-ph?searchtype=author&query=Colomer%2C+F">Francisco Colomer</a>, <a href="/search/astro-ph?searchtype=author&query=Conway%2C+J">John Conway</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Guirado%2C+J+C">Jos茅 Carlos Guirado</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L">Leonid Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=van+Langevelde%2C+H">Huib van Langevelde</a>, <a href="/search/astro-ph?searchtype=author&query=Lobanov%2C+A">Andrei Lobanov</a>, <a href="/search/astro-ph?searchtype=author&query=McKean%2C+J">John McKean</a>, <a href="/search/astro-ph?searchtype=author&query=Morganti%2C+R">Raffaella Morganti</a>, <a href="/search/astro-ph?searchtype=author&query=Muxlow%2C+T">Tom Muxlow</a>, <a href="/search/astro-ph?searchtype=author&query=P%C3%A9rez-Torres%2C+M">Miguel P茅rez-Torres</a>, <a href="/search/astro-ph?searchtype=author&query=Rygl%2C+K">Kazi Rygl</a>, <a href="/search/astro-ph?searchtype=author&query=Schulz%2C+R">Robert Schulz</a>, <a href="/search/astro-ph?searchtype=author&query=Szomoru%2C+A">Arpad Szomoru</a>, <a href="/search/astro-ph?searchtype=author&query=de+Vicente%2C+P">Pablo de Vicente</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">Tao An</a>, <a href="/search/astro-ph?searchtype=author&query=Anglada%2C+G">Guillem Anglada</a> , et al. (55 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="2007.02347v1-abstract-short" style="display: inline;"> This white paper describes the science case for Very Long Baseline Interferometry (VLBI) and provides suggestions towards upgrade paths for the European VLBI Network (EVN). The EVN is a distributed long-baseline radio interferometric array, that operates at the very forefront of astronomical research. Recent results, together with the new science possibilities outlined in this vision document, dem… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.02347v1-abstract-full').style.display = 'inline'; document.getElementById('2007.02347v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2007.02347v1-abstract-full" style="display: none;"> This white paper describes the science case for Very Long Baseline Interferometry (VLBI) and provides suggestions towards upgrade paths for the European VLBI Network (EVN). The EVN is a distributed long-baseline radio interferometric array, that operates at the very forefront of astronomical research. Recent results, together with the new science possibilities outlined in this vision document, demonstrate the EVN's potential to generate new and exciting results that will transform our view of the cosmos. Together with e-MERLIN, the EVN provides a range of baseline lengths that permit unique studies of faint radio sources to be made over a wide range of spatial scales. The science cases are reviewed in six chapters that cover the following broad areas: cosmology, galaxy formation and evolution, innermost regions of active galactic nuclei, explosive phenomena and transients, stars and stellar masers in the Milky Way, celestial reference frames and space applications. The document concludes with identifying the synergies with other radio, as well as multi-band/multi-messenger instruments, and provide the recommendations for future improvements. The appendices briefly describe other radio VLBI arrays, the technological framework for EVN developments, and a selection of spectral lines of astrophysical interest below 100 GHz. The document includes a glossary for non-specialists, and a list of acronyms at the end. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2007.02347v1-abstract-full').style.display = 'none'; document.getElementById('2007.02347v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 July, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Editors: Tiziana Venturi, Zsolt Paragi, Michael Lindqvist. "EVN Vision Document (2020)", 7 chapters, 3 appendices, 191 pages, 64 figures. Chapter coordinators and all the contributors are listed in the document</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2005.01339">arXiv:2005.01339</a> <span> [<a href="https://arxiv.org/pdf/2005.01339">pdf</a>, <a href="https://arxiv.org/format/2005.01339">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921318007676">10.1017/S1743921318007676 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> On the prospects of imaging Sagittarius A* from space </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Roelofs%2C+F">Freek Roelofs</a>, <a href="/search/astro-ph?searchtype=author&query=Falcke%2C+H">Heino Falcke</a>, <a href="/search/astro-ph?searchtype=author&query=Brinkerink%2C+C">Christiaan Brinkerink</a>, <a href="/search/astro-ph?searchtype=author&query=Moscibrodzka%2C+M">Monika Moscibrodzka</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Martin-Neira%2C+M">Manuel Martin-Neira</a>, <a href="/search/astro-ph?searchtype=author&query=Kudriashov%2C+V">Volodymyr Kudriashov</a>, <a href="/search/astro-ph?searchtype=author&query=Klein-Wolt%2C+M">Marc Klein-Wolt</a>, <a href="/search/astro-ph?searchtype=author&query=Tilanus%2C+R">Remo Tilanus</a>, <a href="/search/astro-ph?searchtype=author&query=Kramer%2C+M">Michael Kramer</a>, <a href="/search/astro-ph?searchtype=author&query=Rezzolla%2C+L">Luciano Rezzolla</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2005.01339v1-abstract-short" style="display: inline;"> Very Long Baseline Interferometry (VLBI) at sub-millimeter waves has the potential to image the shadow of the black hole in the Galactic Center, Sagittarius A* (Sgr A*), and thereby test basic predictions of the theory of general relativity. We investigate the imaging prospects of a new Space VLBI mission concept. The setup consists of two satellites in polar or equatorial circular Medium-Earth Or… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.01339v1-abstract-full').style.display = 'inline'; document.getElementById('2005.01339v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2005.01339v1-abstract-full" style="display: none;"> Very Long Baseline Interferometry (VLBI) at sub-millimeter waves has the potential to image the shadow of the black hole in the Galactic Center, Sagittarius A* (Sgr A*), and thereby test basic predictions of the theory of general relativity. We investigate the imaging prospects of a new Space VLBI mission concept. The setup consists of two satellites in polar or equatorial circular Medium-Earth Orbits with slightly different radii, resulting in a dense spiral-shaped uv-coverage with long baselines, allowing for extremely high-resolution and high-fidelity imaging of radio sources. We simulate observations of a general relativistic magnetohydrodynamics model of Sgr A* for this configuration with noise calculated from model system parameters. After gridding the $uv$-plane and averaging visibilities accumulated over multiple months of integration, images of Sgr A* with a resolution of up to 4 $渭$as could be reconstructed, allowing for stronger tests of general relativity and accretion models than with ground-based VLBI. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2005.01339v1-abstract-full').style.display = 'none'; document.getElementById('2005.01339v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 May, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages, 4 figures, published in Proceedings IAU Symposium No. 342, 2018</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Perseus in Sicily: From Black Hole to Cluster Outskirts. Proceedings of the International Astronomical Union, Volume 342, pp. 24-28, 2020 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2003.11412">arXiv:2003.11412</a> <span> [<a href="https://arxiv.org/pdf/2003.11412">pdf</a>, <a href="https://arxiv.org/ps/2003.11412">ps</a>, <a href="https://arxiv.org/format/2003.11412">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1093/mnrasl/slaa052">10.1093/mnrasl/slaa052 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A parsec-scale radio jet launched by the central intermediate-mass black hole in the dwarf galaxy SDSS J090613.77+561015.2? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Yang%2C+J">Jun Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">Sandor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Conway%2C+J+E">John E. Conway</a>, <a href="/search/astro-ph?searchtype=author&query=Liu%2C+X">Xiang Liu</a>, <a href="/search/astro-ph?searchtype=author&query=Cui%2C+L">Lang Cui</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="2003.11412v1-abstract-short" style="display: inline;"> The population of intermediate-mass black holes (IMBHs) in nearby dwarf galaxies plays an important "ground truth" role in exploring black hole formation and growth in the early Universe. In the dwarf elliptical galaxy SDSS J090613.77+561015.2 (z=0.0465), an accreting IMBH has been revealed by optical and X-ray observations. Aiming to search for possible radio core and jet associated with the IMBH… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2003.11412v1-abstract-full').style.display = 'inline'; document.getElementById('2003.11412v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2003.11412v1-abstract-full" style="display: none;"> The population of intermediate-mass black holes (IMBHs) in nearby dwarf galaxies plays an important "ground truth" role in exploring black hole formation and growth in the early Universe. In the dwarf elliptical galaxy SDSS J090613.77+561015.2 (z=0.0465), an accreting IMBH has been revealed by optical and X-ray observations. Aiming to search for possible radio core and jet associated with the IMBH, we carried out very long baseline interferometry (VLBI) observations with the European VLBI Network (EVN) at 1.66 GHz. Our imaging results show that there are two 1-mJy components with a separation of about 52 mas (projected distance 47 pc) and the more compact component is located within the 1-sigma error circle of the optical centroid from available Gaia astrometry. Based on their positions, elongated structures and relatively high brightness temperatures, as well as the absence of star-forming activity in the host galaxy, we argue that the radio morphology originates from the jet activity powered by the central IMBH. The existence of the large-scale jet implies that violent jet activity might occur in the early epochs of black hole growth and thus help to regulate the co-evolution of black holes and galaxies. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2003.11412v1-abstract-full').style.display = 'none'; document.getElementById('2003.11412v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 March, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication as a Letter in MNRAS</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Monthly Notices of the Royal Astronomical Society Letters, Vol. 495, pp. L71-L75 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2002.10024">arXiv:2002.10024</a> <span> [<a href="https://arxiv.org/pdf/2002.10024">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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Instrumentation and Detectors">physics.ins-det</span> </div> </div> <p class="title is-5 mathjax"> Spacecraft Tracking Applications of the Square Kilometre Array </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=de+Vaate%2C+J+G+B">J. G. Bij de Vaate</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Pogrebenko%2C+S+V">S. V. Pogrebenko</a>, <a href="/search/astro-ph?searchtype=author&query=Klooster%2C+C+G+M+v+t">C. G. M. van t Klooster</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="2002.10024v1-abstract-short" style="display: inline;"> The Square Kilometre Array (SKA) is the next generation radio telescope distinguished by a superb sensitivity due to its large aperture (about one square kilometre) and advanced instrumentation. It will cover a broad range of observing bands including those used for tracking of and communications to deep space missions. While spacecraft tracking is not a main application defining the technical spe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.10024v1-abstract-full').style.display = 'inline'; document.getElementById('2002.10024v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2002.10024v1-abstract-full" style="display: none;"> The Square Kilometre Array (SKA) is the next generation radio telescope distinguished by a superb sensitivity due to its large aperture (about one square kilometre) and advanced instrumentation. It will cover a broad range of observing bands including those used for tracking of and communications to deep space missions. While spacecraft tracking is not a main application defining the technical specifications of the SKA, this facility might play a role in tracking deep space probes as a backup to the ``dedicated'' deep space tracking networks. This paper presents possible applications of the SKA as a deep space tracking facility and major related technical specifications of various concepts of the SKA. It was presented at the 3rd International Workshop on Tracking, Telemetry and Command Systems for Space Applications, ESA-ESOC, Darmstadt, Germany, 7-9 September 2004. Over the past years, the SKA concept has developed to a much higher level of detalisation and is currently at the implementation phase. A number of specific considerations in this presentation no longer correspond to the actual status of the SKA project. However, the overall concept of the SKA applications for communication and tracking of interplanetary spacecraft remain topical, and some approaches presented here remain of interest for prospective deep space missions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.10024v1-abstract-full').style.display = 'none'; document.getElementById('2002.10024v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 5 tables, 2 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Proceedings of the 3rd International Workshop on Tracking, Telemetry and Command Systems for Space Applications, ESA-ESOC, Darmstadt, Germany, 2004 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2001.04576">arXiv:2001.04576</a> <span> [<a href="https://arxiv.org/pdf/2001.04576">pdf</a>, <a href="https://arxiv.org/format/2001.04576">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Instrumentation and Methods for Astrophysics">astro-ph.IM</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921320002744">10.1017/S1743921320002744 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> High-resolution radio astronomy: an outlook for Africa </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Beswick%2C+R">Robert Beswick</a>, <a href="/search/astro-ph?searchtype=author&query=Hoare%2C+M">Melvin Hoare</a>, <a href="/search/astro-ph?searchtype=author&query=Njeri%2C+A">Ann Njeri</a>, <a href="/search/astro-ph?searchtype=author&query=Blanchard%2C+J">Jay Blanchard</a>, <a href="/search/astro-ph?searchtype=author&query=Sharpe%2C+C">Carla Sharpe</a>, <a href="/search/astro-ph?searchtype=author&query=Tiplady%2C+A">Adrian Tiplady</a>, <a href="/search/astro-ph?searchtype=author&query=de+Witt%2C+A">Aletha de Witt</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="2001.04576v1-abstract-short" style="display: inline;"> Very Long Baseline Interferometry (VLBI) offers unrivalled resolution in studies of celestial radio sources. The subjects of interest of the IAU Symposium No. 356, the Active Galactic Nuclei (AGN) of all types, constitute the major observing sample of modern VLBI networks. At present, the largest in the world in terms of the number of telescopes and geographical coverage is the European VLBI Netwo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.04576v1-abstract-full').style.display = 'inline'; document.getElementById('2001.04576v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2001.04576v1-abstract-full" style="display: none;"> Very Long Baseline Interferometry (VLBI) offers unrivalled resolution in studies of celestial radio sources. The subjects of interest of the IAU Symposium No. 356, the Active Galactic Nuclei (AGN) of all types, constitute the major observing sample of modern VLBI networks. At present, the largest in the world in terms of the number of telescopes and geographical coverage is the European VLBI Network (EVN), which operates under the open sky policy via peer-reviewed observing proposals. Recent EVN observations cover a broad range of science themes from high-sensitivity monitoring of structural changes in inner AGN areas to observations of tidal eruptions in AGN cores and investigation of redshift-dependent properties of parsec-scale radio structures of AGN. All the topics above should be considered as potentially rewarding scientific activities of the prospective African VLBI Network (AVN), a natural scientific ally of EVN. This contribution briefly describes the status and near-term strategy for the AVN development as a southern extension of the EVN-AVN alliance and as an eventual bridge to the Square Kilometre Array (SKA) with its mid-frequency core in South Africa. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.04576v1-abstract-full').style.display = 'none'; document.getElementById('2001.04576v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 January, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Presentation at the IAU Symposium. No. 356, Addis Ababa, Ethiopia, Oct 2020; 5 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Proc. IAU 15 (2019) 137-142 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2001.02809">arXiv:2001.02809</a> <span> [<a href="https://arxiv.org/pdf/2001.02809">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41467-019-14093-2">10.1038/s41467-019-14093-2 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Evolving parsec-scale radio structure in the most distant blazar known </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=An%2C+T">Tao An</a>, <a href="/search/astro-ph?searchtype=author&query=Mohan%2C+P">Prashanth Mohan</a>, <a href="/search/astro-ph?searchtype=author&query=Zhang%2C+Y">Yingkang Zhang</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Yang%2C+J">Jun Yang</a>, <a href="/search/astro-ph?searchtype=author&query=Gab%C3%A1nyi%2C+K+%C3%89">Krisztina 脡. Gab谩nyi</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Perger%2C+K">Krisztina Perger</a>, <a href="/search/astro-ph?searchtype=author&query=Zheng%2C+Z">Zhenya Zheng</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="2001.02809v1-abstract-short" style="display: inline;"> Blazars are a sub-class of quasars with Doppler boosted jets oriented close to the line of sight, and thus efficient probes of supermassive black hole growth and their environment, especially at high redshifts. Here we report on Very Long Baseline Interferometry observations of a blazar J0906+6930 at z = 5.47, which enabled the detection of polarised emission and measurement of jet proper motion a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.02809v1-abstract-full').style.display = 'inline'; document.getElementById('2001.02809v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2001.02809v1-abstract-full" style="display: none;"> Blazars are a sub-class of quasars with Doppler boosted jets oriented close to the line of sight, and thus efficient probes of supermassive black hole growth and their environment, especially at high redshifts. Here we report on Very Long Baseline Interferometry observations of a blazar J0906+6930 at z = 5.47, which enabled the detection of polarised emission and measurement of jet proper motion at parsec scales. The observations suggest a less powerful jet compared with the general blazar population, including lower proper motion and bulk Lorentz factor. This coupled with a previously inferred high accretion rate indicate a transition from an accretion radiative power to a jet mechanical power based transfer of energy and momentum to the surrounding gas.While alternative scenarios could not be fully ruled out, our results indicate a possibly nascent jet embedded in and interacting with a dense medium resulting in a jet bending. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.02809v1-abstract-full').style.display = 'none'; document.getElementById('2001.02809v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 January, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">3 figures, 2 supplementary figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nat Commun 11, 143 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1910.03899">arXiv:1910.03899</a> <span> [<a href="https://arxiv.org/pdf/1910.03899">pdf</a>, <a href="https://arxiv.org/format/1910.03899">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Earth and Planetary Astrophysics">astro-ph.EP</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/10.1016/j.pss.2019.104776">10.1016/j.pss.2019.104776 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The radioscience LaRa instrument onboard ExoMars 2020 to investigate the rotation and interior of Mars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Dehant%2C+V">Veronique Dehant</a>, <a href="/search/astro-ph?searchtype=author&query=Maistre%2C+S+L">Sebastien Le Maistre</a>, <a href="/search/astro-ph?searchtype=author&query=Baland%2C+R">Rose-Marie Baland</a>, <a href="/search/astro-ph?searchtype=author&query=Bergeot%2C+N">Nicolas Bergeot</a>, <a href="/search/astro-ph?searchtype=author&query=Karatekin%2C+O">Ozgur Karatekin</a>, <a href="/search/astro-ph?searchtype=author&query=Peters%2C+M">Marie-Julie Peters</a>, <a href="/search/astro-ph?searchtype=author&query=Rivoldini%2C+A">Attilio Rivoldini</a>, <a href="/search/astro-ph?searchtype=author&query=Lozano%2C+L+R">Luca Ruiz Lozano</a>, <a href="/search/astro-ph?searchtype=author&query=Temel%2C+O">Orkun Temel</a>, <a href="/search/astro-ph?searchtype=author&query=Van+Hoolst%2C+T">Tim Van Hoolst</a>, <a href="/search/astro-ph?searchtype=author&query=Yseboodt%2C+M">Marie Yseboodt</a>, <a href="/search/astro-ph?searchtype=author&query=Mitrovic%2C+M">Michel Mitrovic</a>, <a href="/search/astro-ph?searchtype=author&query=Kosov%2C+A">Alexander Kosov</a>, <a href="/search/astro-ph?searchtype=author&query=Valenta%2C+V">Vaclav Valenta</a>, <a href="/search/astro-ph?searchtype=author&query=Thomassen%2C+L">Lieven Thomassen</a>, <a href="/search/astro-ph?searchtype=author&query=Karki%2C+S">Sumit Karki</a>, <a href="/search/astro-ph?searchtype=author&query=Khalifeh%2C+K+A">Khaldoun Al Khalifeh</a>, <a href="/search/astro-ph?searchtype=author&query=Craeye%2C+C">Christophe Craeye</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L">Leonid Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Marty%2C+J">Jean-Charles Marty</a>, <a href="/search/astro-ph?searchtype=author&query=Asmar%2C+S">Sami Asmar</a>, <a href="/search/astro-ph?searchtype=author&query=Folkner%2C+W">William Folkner</a>, <a href="/search/astro-ph?searchtype=author&query=Team%2C+t+L">the LaRa Team</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1910.03899v2-abstract-short" style="display: inline;"> LaRa (Lander Radioscience) is an experiment on the ExoMars 2020 mission that uses the Doppler shift on the radio link due to the motion of the ExoMars platform tied to the surface of Mars with respect to the Earth ground stations (e.g. the deep space network stations of NASA), in order to precisely measure the relative velocity of the lander on Mars with respect to the Earth. The LaRa measurements… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.03899v2-abstract-full').style.display = 'inline'; document.getElementById('1910.03899v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1910.03899v2-abstract-full" style="display: none;"> LaRa (Lander Radioscience) is an experiment on the ExoMars 2020 mission that uses the Doppler shift on the radio link due to the motion of the ExoMars platform tied to the surface of Mars with respect to the Earth ground stations (e.g. the deep space network stations of NASA), in order to precisely measure the relative velocity of the lander on Mars with respect to the Earth. The LaRa measurements shall improve the understanding of the structure and processes in the deep interior of Mars by obtaining the rotation and orientation of Mars with a better precision compared to the previous missions. In this paper, we provide the analysis done until now for the best realization of these objectives. We explain the geophysical observation that will be reached with LaRa (Length-of-day variations, precession, nutation, and possibly polar motion). We develop the experiment set up, which includes the ground stations on Earth (so-called ground segment). We describe the instrument, i.e. the transponder and its three antennas. We further detail the link budget and the expected noise level that will be reached. Finally, we detail the expected results, which encompasses the explanation of how we shall determine Mars' orientation parameters, and the way we shall deduce Mars' interior structure and Mars' atmosphere from them. Lastly, we explain briefly how we will be able to determine the Surface platform position. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1910.03899v2-abstract-full').style.display = 'none'; document.getElementById('1910.03899v2-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 October, 2019; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 9 October, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">43 pages, 39 figures, accepted in Planetary and Space Science</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.08951">arXiv:1909.08951</a> <span> [<a href="https://arxiv.org/pdf/1909.08951">pdf</a>, <a href="https://arxiv.org/format/1909.08951">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.asr.2019.09.007">10.1016/j.asr.2019.09.007 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A Roadmap towards a Space-based Radio Telescope for Ultra-Low Frequency Radio Astronomy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Bentum%2C+M+J">M. J. Bentum</a>, <a href="/search/astro-ph?searchtype=author&query=Verma%2C+M+K">M. K. Verma</a>, <a href="/search/astro-ph?searchtype=author&query=Rajan%2C+R+T">R. T. Rajan</a>, <a href="/search/astro-ph?searchtype=author&query=Boonstra%2C+A+-">A. -J. Boonstra</a>, <a href="/search/astro-ph?searchtype=author&query=Verhoeven%2C+C+J+M">C. J. M. Verhoeven</a>, <a href="/search/astro-ph?searchtype=author&query=Gill%2C+E+K+A">E. K. A. Gill</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Veen%2C+A+J">A. J. van der Veen</a>, <a href="/search/astro-ph?searchtype=author&query=Falcke%2C+H">H. Falcke</a>, <a href="/search/astro-ph?searchtype=author&query=Wolt%2C+M+K">M. Klein Wolt</a>, <a href="/search/astro-ph?searchtype=author&query=Monna%2C+B">B. Monna</a>, <a href="/search/astro-ph?searchtype=author&query=Engelen%2C+S">S. Engelen</a>, <a href="/search/astro-ph?searchtype=author&query=Rotteveel%2C+J">J. Rotteveel</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1909.08951v1-abstract-short" style="display: inline;"> The past two decades saw a renewed interest in low frequency radio astronomy, with a particular focus on frequencies above 30 MHz. However, at frequencies below 30 MHz, Earth-based observations are limited due to a combination of severe ionospheric distortions, almost full reflection of radio waves below 10 MHz, solar eruptions and human-made radio frequency interference (RFI). A space or Lunar-ba… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.08951v1-abstract-full').style.display = 'inline'; document.getElementById('1909.08951v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.08951v1-abstract-full" style="display: none;"> The past two decades saw a renewed interest in low frequency radio astronomy, with a particular focus on frequencies above 30 MHz. However, at frequencies below 30 MHz, Earth-based observations are limited due to a combination of severe ionospheric distortions, almost full reflection of radio waves below 10 MHz, solar eruptions and human-made radio frequency interference (RFI). A space or Lunar-based ultra-low-frequency (or ultra-long-wavelength, ULW) array would suffer significantly less from these limitations and hence would open up the last, virtually unexplored frequency domain in the electromagnetic spectrum. A roadmap has been initiated in order to explore the opportunity of building a swarm of satellites to observe at the frequency band below 30 MHz. This roadmap, dubbed Orbiting Low Frequency Antennas for Radio Astronomy (OLFAR), presents a space-based ultra-low frequency radio telescope that will explore the Universe's so-called dark ages, map the interstellar medium, and study planetary and solar bursts in the solar system and search them in other planetary systems. Such a system will comprise of a swarm of hundreds to thousands of satellites, working together as a single aperture synthesis instrument deployed sufficiently far away from Earth to avoid terrestrial RFI. A number of key technologies of OLFAR are still to be developed and proven. The first step in this roadmap is the NCLE (Netherlands China Low Frequency Explorer) experiment launched in May 2018 on the Chinese Chang'e-4 mission. The NCLE payload consists of a three monopole antenna system from which the first data stream is expected in the second half of 2019, which will provide important feedback for future science and technology opportunities. In this paper, the roadmap towards OLFAR, a brief overview of the science opportunities, and the technological and programmatic challenges of the mission are presented. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.08951v1-abstract-full').style.display = 'none'; document.getElementById('1909.08951v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">28 pages, 2 figures, 5 tables; accepted</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Advances in Space Research, 2019 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1909.00785">arXiv:1909.00785</a> <span> [<a href="https://arxiv.org/pdf/1909.00785">pdf</a>, <a href="https://arxiv.org/format/1909.00785">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1016/j.asr.2019.08.035">10.1016/j.asr.2019.08.035 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Detection statistics of the RadioAstron AGN survey </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Kovalev%2C+Y+Y">Y. Y. Kovalev</a>, <a href="/search/astro-ph?searchtype=author&query=Kardashev%2C+N+S">N. S. Kardashev</a>, <a href="/search/astro-ph?searchtype=author&query=Sokolovsky%2C+K+V">K. V. Sokolovsky</a>, <a href="/search/astro-ph?searchtype=author&query=Voitsik%2C+P+A">P. A. Voitsik</a>, <a href="/search/astro-ph?searchtype=author&query=An%2C+T">T. An</a>, <a href="/search/astro-ph?searchtype=author&query=Anderson%2C+J+M">J. M. Anderson</a>, <a href="/search/astro-ph?searchtype=author&query=Andrianov%2C+A+S">A. S. Andrianov</a>, <a href="/search/astro-ph?searchtype=author&query=Avdeev%2C+V+Y">V. Yu. Avdeev</a>, <a href="/search/astro-ph?searchtype=author&query=Bartel%2C+N">N. Bartel</a>, <a href="/search/astro-ph?searchtype=author&query=Bignall%2C+H+E">H. E. Bignall</a>, <a href="/search/astro-ph?searchtype=author&query=Burgin%2C+M+S">M. S. Burgin</a>, <a href="/search/astro-ph?searchtype=author&query=Edwards%2C+P+G">P. G. Edwards</a>, <a href="/search/astro-ph?searchtype=author&query=Ellingsen%2C+S+P">S. P. Ellingsen</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S. Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Garcia-Miro%2C+C">C. Garcia-Miro</a>, <a href="/search/astro-ph?searchtype=author&query=Gawronski%2C+M+P">M. P. Gawronski</a>, <a href="/search/astro-ph?searchtype=author&query=Ghigo%2C+F+D">F. D. Ghigo</a>, <a href="/search/astro-ph?searchtype=author&query=Ghosh%2C+T">T. Ghosh</a>, <a href="/search/astro-ph?searchtype=author&query=Giovannini%2C+G">G. Giovannini</a>, <a href="/search/astro-ph?searchtype=author&query=Girin%2C+I+A">I. A. Girin</a>, <a href="/search/astro-ph?searchtype=author&query=Giroletti%2C+M">M. Giroletti</a>, <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">L. I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Jauncey%2C+D+L">D. L. Jauncey</a>, <a href="/search/astro-ph?searchtype=author&query=Horiuchi%2C+S">S. Horiuchi</a>, <a href="/search/astro-ph?searchtype=author&query=Ivanov%2C+D+V">D. V. Ivanov</a> , et al. (35 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1909.00785v1-abstract-short" style="display: inline;"> The largest Key Science Program of the RadioAstron space VLBI mission is a survey of active galactic nuclei (AGN). The main goal of the survey is to measure and study the brightness of AGN cores in order to better understand the physics of their emission while taking interstellar scattering into consideration. In this paper we present detection statistics for observations on ground-space baselines… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.00785v1-abstract-full').style.display = 'inline'; document.getElementById('1909.00785v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1909.00785v1-abstract-full" style="display: none;"> The largest Key Science Program of the RadioAstron space VLBI mission is a survey of active galactic nuclei (AGN). The main goal of the survey is to measure and study the brightness of AGN cores in order to better understand the physics of their emission while taking interstellar scattering into consideration. In this paper we present detection statistics for observations on ground-space baselines of a complete sample of radio-strong AGN at the wavelengths of 18, 6, and 1.3 cm. Two-thirds of them are indeed detected by RadioAstron and are found to contain extremely compact, tens to hundreds of $渭$as structures within their cores. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1909.00785v1-abstract-full').style.display = 'none'; document.getElementById('1909.00785v1-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 September, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted to the Advances in Space Research special issue "High-resolution Space-Borne Radio Astronomy"</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Advances in Space Research 65 (2020) 705-711 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1908.10767">arXiv:1908.10767</a> <span> [<a href="https://arxiv.org/pdf/1908.10767">pdf</a>, <a href="https://arxiv.org/format/1908.10767">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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="High Energy Astrophysical Phenomena">astro-ph.HE</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1007/s10686-021-09714-y">10.1007/s10686-021-09714-y <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> TeraHertz Exploration and Zooming-in for Astrophysics (THEZA): ESA Voyage 2050 White Paper </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/astro-ph?searchtype=author&query=Gurvits%2C+L+I">Leonid I. Gurvits</a>, <a href="/search/astro-ph?searchtype=author&query=Paragi%2C+Z">Zsolt Paragi</a>, <a href="/search/astro-ph?searchtype=author&query=Casasola%2C+V">Viviana Casasola</a>, <a href="/search/astro-ph?searchtype=author&query=Conway%2C+J">John Conway</a>, <a href="/search/astro-ph?searchtype=author&query=Davelaar%2C+J">Jordy Davelaar</a>, <a href="/search/astro-ph?searchtype=author&query=Falcke%2C+H">Heino Falcke</a>, <a href="/search/astro-ph?searchtype=author&query=Fender%2C+R">Rob Fender</a>, <a href="/search/astro-ph?searchtype=author&query=Frey%2C+S">S谩ndor Frey</a>, <a href="/search/astro-ph?searchtype=author&query=Fromm%2C+C+M">Christian M. Fromm</a>, <a href="/search/astro-ph?searchtype=author&query=Mir%C3%B3%2C+C+G">Cristina Garc铆a Mir贸</a>, <a href="/search/astro-ph?searchtype=author&query=Garrett%2C+M+A">Michael A. Garrett</a>, <a href="/search/astro-ph?searchtype=author&query=Giroletti%2C+M">Marcello Giroletti</a>, <a href="/search/astro-ph?searchtype=author&query=Goddi%2C+C">Ciriaco Goddi</a>, <a href="/search/astro-ph?searchtype=author&query=G%C3%B3mez%2C+J">Jos茅-Luis G贸mez</a>, <a href="/search/astro-ph?searchtype=author&query=van+der+Gucht%2C+J">Jeffrey van der Gucht</a>, <a href="/search/astro-ph?searchtype=author&query=Guirado%2C+J+C">Jos茅 Carlos Guirado</a>, <a href="/search/astro-ph?searchtype=author&query=Haiman%2C+Z">Zolt谩n Haiman</a>, <a href="/search/astro-ph?searchtype=author&query=Helmich%2C+F">Frank Helmich</a>, <a href="/search/astro-ph?searchtype=author&query=Humphreys%2C+E">Elizabeth Humphreys</a>, <a href="/search/astro-ph?searchtype=author&query=Impellizzeri%2C+V">Violette Impellizzeri</a>, <a href="/search/astro-ph?searchtype=author&query=Kramer%2C+M">Michael Kramer</a>, <a href="/search/astro-ph?searchtype=author&query=Lindqvist%2C+M">Michael Lindqvist</a>, <a href="/search/astro-ph?searchtype=author&query=Linz%2C+H">Hendrik Linz</a>, <a href="/search/astro-ph?searchtype=author&query=Liuzzo%2C+E">Elisabetta Liuzzo</a>, <a href="/search/astro-ph?searchtype=author&query=Lobanov%2C+A+P">Andrei P. Lobanov</a> , et al. (10 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="1908.10767v3-abstract-short" style="display: inline;"> This paper presents the ESA Voyage 2050 White Paper for a concept of TeraHertz Exploration and Zooming-in for Astrophysics (THEZA). It addresses the science case and some implementation issues of a space-borne radio interferometric system for ultra-sharp imaging of celestial radio sources at the level of angular resolution down to (sub-) microarcseconds. THEZA focuses at millimetre and sub-millime… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.10767v3-abstract-full').style.display = 'inline'; document.getElementById('1908.10767v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1908.10767v3-abstract-full" style="display: none;"> This paper presents the ESA Voyage 2050 White Paper for a concept of TeraHertz Exploration and Zooming-in for Astrophysics (THEZA). It addresses the science case and some implementation issues of a space-borne radio interferometric system for ultra-sharp imaging of celestial radio sources at the level of angular resolution down to (sub-) microarcseconds. THEZA focuses at millimetre and sub-millimetre wavelengths (frequencies above $\sim$300~GHz), but allows for science operations at longer wavelengths too. The THEZA concept science rationale is focused on the physics of spacetime in the vicinity of supermassive black holes as the leading science driver. The main aim of the concept is to facilitate a major leap by providing researchers with orders of magnitude improvements in the resolution and dynamic range in direct imaging studies of the most exotic objects in the Universe, black holes. The concept will open up a sizeable range of hitherto unreachable parameters of observational astrophysics. It unifies two major lines of development of space-borne radio astronomy of the past decades: Space VLBI (Very Long Baseline Interferometry) and mm- and sub-mm astrophysical studies with "single dish" instruments. It also builds upon the recent success of the Earth-based Event Horizon Telescope (EHT) -- the first-ever direct image of a shadow of the super-massive black hole in the centre of the galaxy M87. As an amalgam of these three major areas of modern observational astrophysics, THEZA aims at facilitating a breakthrough in high-resolution high image quality studies in the millimetre and sub-millimetre domain of the electromagnetic spectrum. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.10767v3-abstract-full').style.display = 'none'; document.getElementById('1908.10767v3-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 28 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">White Paper submitted in response to the ESA Call Voyage 2050</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Experimental Astronomy, 2021 </p> </li> </ol> <nav class="pagination is-small is-centered breathe-horizontal" role="navigation" aria-label="pagination"> <a href="" class="pagination-previous is-invisible">Previous </a> <a href="/search/?searchtype=author&query=Gurvits%2C+L&start=50" class="pagination-next" >Next </a> <ul class="pagination-list"> <li> <a href="/search/?searchtype=author&query=Gurvits%2C+L&start=0" class="pagination-link is-current" aria-label="Goto page 1">1 </a> </li> <li> <a href="/search/?searchtype=author&query=Gurvits%2C+L&start=50" class="pagination-link " aria-label="Page 2" aria-current="page">2 </a> </li> <li> <a href="/search/?searchtype=author&query=Gurvits%2C+L&start=100" class="pagination-link " aria-label="Page 3" aria-current="page">3 </a> </li> </ul> </nav> <div class="is-hidden-tablet">  <span class="help" style="display: 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