AT 2019avd: A novel addition to the diverse population of nuclear transients

A. Malyali*, A. Rau, A. Merloni, K. Nandra, J. Buchner, Z. Liu, S. Gezari, J. Sollerman, B. Shappee, B. Trakhtenbrot, I. Arcavi, C. Ricci, S. Van Velzen, A. Goobar, S. Frederick, A. Kawka, L. Tartaglia, J. Burke, D. Hiramatsu, M. SchrammD. Van Der Boom, G. Anderson, J. C.A. Miller-Jones, E. Bellm, A. Drake, D. Duev, C. Fremling, M. Graham, F. Masci, B. Rusholme, M. Soumagnac, R. Walters

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

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 85 eV) that was a 90 times brighter in the 0.2-2 keV band than a previous 3σ upper flux detection limit (with no archival X-ray detection at this position). The ZTF optical light curve in the 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 ([Fea» X] 6375 Å, [Fea» XIV] 5303 Å), along with persistent broad Balmer emission lines (FWHM 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.

Original languageEnglish
Article numberA9
JournalAstronomy and Astrophysics
Volume647
DOIs
StatePublished - 1 Mar 2021

Funding

FundersFunder number
Deutsches Elektronen-Synchrotron and Humboldt University
IPAC
Israeli Council for Higher Education Alon Fellowship
Max Planck Institute for Extraterrestrial Physics
National Central University of Taiwan
Weizmann Institute for Science
National Science Foundation1440341, 0908816, AST-1515927, AST-123877, 852097, 1106171, AST-0908816, AST-1907570, 1515927, AST-1440341, AST-1908570, 1238877
National Aeronautics and Space Administration80NSSC19K1717, AST-1911074, AST-1920392
Gordon and Betty Moore FoundationGBMF5490
United States - Israel Binational Science Foundation
Lawrence Berkeley National Laboratory
University of Wisconsin-Milwaukee
Ohio State University
California Institute of Technology
University of Washington
Johns Hopkins University
Villum Fonden
University of Maryland
University of Hawai'i
Los Alamos National Laboratory
Smithsonian Astrophysical Observatory
Horizon 2020 Framework Programme2752/19, 2108/18
Space Telescope Science InstituteNNX08AR22G
Mt. Cuba Astronomical Foundation
Australian GovernmentDP200102471
Chinese Academy of Sciences South America Center for Astronomy
International Max Planck Research School for Environmental, Cellular and Molecular Microbiology
European Research Council
University of Edinburgh
Queen's University Belfast
Australian Research CouncilDE180100346
Durham University
United States-Israel Binational Science Foundation
Ministero dell’Istruzione, dell’Università e della Ricerca20179ZF5KS
Israel Science Foundation1849/19
Max-Planck-Gesellschaft
Ludwig-Maximilians-Universität München
Eötvös Loránd Tudományegyetem
Max-Planck-Institut für Astronomie

    Keywords

    • Accretion, accretion disks
    • Galaxies: nuclei
    • X-rays: galaxies

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