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Optical Discovery of Probable Stellar Tidal Disruption Flares

van Velzen, Sjoert and Farrar, Glennys R. and Gezari, Suvi and Morrell, Nidia and Zaritsky, Dennis and Östman, Linda and Smith, Mathew and Gelfand, Joseph and Drake, Andrew J. (2011) Optical Discovery of Probable Stellar Tidal Disruption Flares. Astrophysical Journal, 741 (2). Art. No. 73. ISSN 0004-637X.

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Using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82), we have searched for the tidal disruption of stars by supermassive black holes in non-active galaxies. Two candidate tidal disruption events (TDEs) are identified. The TDE flares have optical blackbody temperatures of 2 × 10^4 K and observed peak luminosities of M_g = –18.3 and –20.4 (νL_ν = 5 × 10^(42), 4 × 10^(43) erg s^(–1), in the rest frame); their cooling rates are very low, qualitatively consistent with expectations for tidal disruption flares. The properties of the TDE candidates are examined using (1) SDSS imaging to compare them to other flares observed in the search, (2) UV emission measured by GALEX, and (3) spectra of the hosts and of one of the flares. Our pipeline excludes optically identifiable AGN hosts, and our variability monitoring over nine years provides strong evidence that these are not flares in hidden AGNs. The spectra and color evolution of the flares are unlike any SN observed to date, their strong late-time UV emission is particularly distinctive, and they are nuclear at high resolution arguing against these being first cases of a previously unobserved class of SNe or more extreme examples of known SN types. Taken together, the observed properties are difficult to reconcile with an SN or an AGN-flare explanation, although an entirely new process specific to the inner few hundred parsecs of non-active galaxies cannot be excluded. Based on our observed rate, we infer that hundreds or thousands of TDEs will be present in current and next-generation optical synoptic surveys. Using the approach outlined here, a TDE candidate sample with O(1) purity can be selected using geometric resolution and host and flare color alone, demonstrating that a campaign to create a large sample of TDEs, with immediate and detailed multi-wavelength follow-up, is feasible. A by-product of this work is quantification of the power spectrum of extreme flares in AGNs.

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Zaritsky, Dennis0000-0002-5177-727X
Additional Information:© 2011 The American Astronomical Society. Received 2010 September 8; accepted 2011 August 25; published 2011 October 18. G.R.F. and S.v.V. acknowledge valuable conversations with M. Blanton, A. Filippenko, J. Frieman, J. Greene, A. Gruzinov, D. Hogg, S. Komossa, M. Modjaz, J. Moustakas, N. Smith, L. Strubbe, N. Zakamska, and G. Zhu; in addition we thank P. Massey for assistance with obtaining the TDE1 spectrum, A. Goobar and R. Nichol for cooperation in use of the TDE2 spectrum, A. Gal-Yam and O. Yaron for cooperation in use of CCCP data, P. Groot and K. Verbeek for help with the WHT spectrum, and G. Djorgovski and E. Beshore for cooperation in use of CRTS and CSS data. We are grateful to the anonymous referee for the comments that improved the manuscript and made the presentation more balanced. The research of S.v.V. was supported in part by the Huygens Scholarship Programme. The research of G.R.F. was supported in part by NSF-PHY-0701451. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web site is The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, with the ESO New Technology Telescope at the La Silla observatory, and with the William Herschel Telescope, operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instítuto de Astrofísica de Canarias. The CSS survey is funded by the National Aeronautics and Space Administration under grant no. NNG05GF22G issued through the Science Mission Directorate Near-Earth Objects Observations Program. J.L.P. is supported by NSF grant AST-0707982. The CRTS survey is supported by the U.S. National Science Foundation under grant AST-0909182. We acknowledge NASA’s support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
Funding AgencyGrant Number
Huygens Scholarship ProgrammeUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Japanese MonbukagakushoUNSPECIFIED
Max Planck SocietyUNSPECIFIED
Higher Education Funding Council for EnglandUNSPECIFIED
American Museum of Natural HistoryUNSPECIFIED
Astrophysical Institute PotsdamUNSPECIFIED
University of Basel UNSPECIFIED
University of CambridgeUNSPECIFIED
Case Western Reserve UniversityUNSPECIFIED
University of ChicagoUNSPECIFIED
Drexel University UNSPECIFIED
Institute for Advanced StudyUNSPECIFIED
Japan Participation GroupUNSPECIFIED
Johns Hopkins UniversityUNSPECIFIED
Joint Institute for Nuclear AstrophysicsUNSPECIFIED
Kavli Institute for Particle Astrophysics and CosmologyUNSPECIFIED
Korean Scientist GroupUNSPECIFIED
Chinese Academy of Sciences (LAMOST)UNSPECIFIED
Los Alamos National LaboratoryUNSPECIFIED
Max Planck Institute for Astronomy (MPIA)UNSPECIFIED
Max Planck Institute for Astrophysics (MPA)UNSPECIFIED
New Mexico State UniversityUNSPECIFIED
Ohio State UniversityUNSPECIFIED
University of PittsburghUNSPECIFIED
University of PortsmouthUNSPECIFIED
Princeton UniversityUNSPECIFIED
United States Naval ObservatoryUNSPECIFIED
University of WashingtonUNSPECIFIED
Subject Keywords: black hole physics; galaxies: nuclei
Issue or Number:2
Record Number:CaltechAUTHORS:20120125-085212536
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Official Citation:Optical Discovery of Probable Stellar Tidal Disruption Flares Sjoert van Velzen et al. 2011 ApJ 741 73
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28954
Deposited By: Ruth Sustaita
Deposited On:25 Jan 2012 17:37
Last Modified:03 Oct 2019 03:37

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