Journal
ASTRONOMY & ASTROPHYSICS
Volume 647, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/202039681
Keywords
X-rays: galaxies; accretion; accretion disks; galaxies: nuclei
Categories
Funding
- International Max-Planck Research School (IMPRS) on Astrophysics at the Ludwig-Maximilians University of Munich (LMU)
- NSF [AST-1907570, AST-1920392, AST-1911074]
- NASA [80NSSC19K1717]
- Israel Science Foundation [1849/19, 2108/18, 2752/19]
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program [852097]
- United States - Israel Binational Science Foundation (BSF)
- Israeli Council for Higher Education Alon Fellowship
- MIUR (PRIN 2017 grant) [20179ZF5KS]
- Australian Research Council - Australian Government [DE180100346]
- Australian Government through the Australian Research Council [DP200102471]
- Russian Space Agency (Roskosmos)
- Russian Academy of Sciences
- Max Planck Institute for Extraterrestrial Physics (MPE)
- DLR
- Max Planck Society
- National Science Foundation [AST-1440341, 1106171, AST-1515927, AST-1908570, AST-0908816, AST-123877]
- Caltech
- IPAC
- Weizmann Institute for Science
- Oskar Klein Center at Stockholm University
- University of Maryland
- University of Washington
- Deutsches Elektronen-Synchrotron and Humboldt University
- Los Alamos National Laboratories
- TANGO Consortium of Taiwan
- University of Wisconsin at Milwaukee
- Lawrence Berkeley National Laboratories
- National Aeronautics and Space Administration [NNX08AR22G]
- Gordon and Betty Moore Foundation [GBMF5490]
- Mt. Cuba Astronomical Foundation
- Center for Cosmology and AstroParticle Physics at the Ohio State University
- Chinese Academy of Sciences South America Center for Astronomy (CAS-SACA)
- Villum Foundation
- Australian Research Council [DE180100346, DP200102471] Funding Source: Australian Research Council
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This study reports on multiple astronomical observations of the ongoing AT 2019avd event, located in the nucleus of a previously inactive galaxy, showing potential features of a tidal disruption event (TDE) candidate, while the optical properties are atypical. Additionally, spectroscopic observations reveal the emergence of specific emission line features.
We report on SRG/eROSITA, ZTF, ASAS-SN, Las Cumbres, NEOWISE-R, and Swift XRT/UVOT observations of the unique ongoing event AT 2019avd, located in the nucleus of a previously inactive galaxy at z = 0.029. eROSITA first observed AT 2019avd on 2020-04-28 during its first all sky survey, when it was detected as an ultra-soft X-ray source (kT similar to 85 eV) that was greater than or similar to 90 times brighter in the 0.2-2 keV band than a previous 3 sigma upper flux detection limit (with no archival X-ray detection at this position). The ZTF optical light curve in the similar to 450 days preceding the eROSITA detection is double peaked, and the eROSITA detection coincides with the rise of the second peak. Follow-up optical spectroscopy shows the emergence of a Bowen fluorescence feature and high-ionisation coronal lines ([FeX] 6375 angstrom, [FeXIV] 5303 angstrom), along with persistent broad Balmer emission lines (FWHM similar to 1400 km s(-1)). Whilst the X-ray properties make AT 2019avd a promising tidal disruption event (TDE) candidate, the optical properties are atypical for optically selected TDEs. We discuss potential alternative origins that could explain the observed properties of AT 2019avd, such as a stellar binary TDE candidate, or a TDE involving a super massive black hole binary.
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