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UV/optical detections of candidate tidal disruption events by GALEX and CFHTLS

Gezari, S. and Basa, S. and Martin, D. C. and Bazin, G. and Forster, K. and Milliard, B. and Halpern, J. P. and Friedman, P. G. and Morrissey, P. and Neff, S. G. and Schiminovich, D. and Seibert, M. and Small, T. and Wyder, T. K. (2008) UV/optical detections of candidate tidal disruption events by GALEX and CFHTLS. Astrophysical Journal, 676 (2). pp. 944-969. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20090507-125659445

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Abstract

We present two luminous UV/optical flares from the nuclei of apparently inactive early-type galaxies at z = 0.37 and 0.33 that have the radiative properties of a flare from the tidal disruption of a star. In this paper we report the second candidate tidal disruption event discovery in the UV by the GALEX Deep Imaging Survey and present simultaneous optical light curves from the CFHTLS Deep Imaging Survey for both UV flares. The first few months of the UV/optical light curves are well fitted with the canonical t^(−5/3) power-law decay predicted for emission from the fallback of debris from a tidally disrupted star. Chandra ACIS X-ray observations during the flares detect soft X-ray sources with T_(bb) = (2–5) × 10^5 K or Γ > 3 and place limits on hard X-ray emission from an underlying AGN down to L_X(2–10 keV) ≾ 10^41 ergs s^−1. Blackbody fits to the UV/optical spectral energy distributions of the flares indicate peak flare luminosities of ≳ 10^44-10^45 ergs s^−1. The temperature, luminosity, and light curves of both flares are in excellent agreement with emission from a tidally disrupted main-sequence star onto a central black hole of several times 10^7 M⊙. The observed detection rate of our search over ~2.9 deg^2 of GALEX Deep Imaging Survey data spanning from 2003 to 2007 is consistent with tidal disruption rates calculated from dynamical models, and we use these models to make predictions for the detection rates of the next generation of optical synoptic surveys.


Item Type:Article
Related URLs:
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http://dx.doi.org/10.1086/529008DOIUNSPECIFIED
http://www.iop.org/EJ/abstract/0004-637X/676/2/944/PublisherUNSPECIFIED
Additional Information:© 2008 The American Astronomical Society. Received 2007 August 14; accepted 2007 December 25. We thank our anonymous referee for their insightful comments that helped us improve our paper. We are grateful for the public database of SN candidates produced by the Supernova Legacy Survey, which has been very useful for this study. S. G. was supported in part by the Volontariat International-CNES of France and through Chandra grant G06-7099X issued by the Chandra X-Ray Observatory, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA. We gratefully 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. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada- France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National de Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the CFHT Legacy Survey, a collaborative project of NRC and CNRS. This paper makes use of photometric redshifts produced jointly by Terapix and the VVDS teams, and the CENCOS interface (http://cencosw.oamp.fr) was used for data retrieval and analyses.
Group:Space Radiation Laboratory, Space Astrophysics Laboratory
Funders:
Funding AgencyGrant Number
Chandra X-Ray ObservatoryG06-7099X
Subject Keywords:galaxies: g nuclei; ultraviolet: galaxies; X-rays: galaxies
Record Number:CaltechAUTHORS:20090507-125659445
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20090507-125659445
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14180
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:11 May 2009 20:54
Last Modified:28 Aug 2016 20:57

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