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Discovery of superstrong, fading, iron line emission and double-peaked Balmer lines of the galaxy SDSS J095209.56+214313.3: the light echo of a huge flare

Komossa, S. and Zhou, H. and Wang, T. and Ajello, M. and Ge, J. and Greiner, J. and Lu, H. and Salvato, M. and Saxton, R. and Shan, H. and Xu, D. and Yuan, W. (2008) Discovery of superstrong, fading, iron line emission and double-peaked Balmer lines of the galaxy SDSS J095209.56+214313.3: the light echo of a huge flare. Astrophysical Journal Letters, 678 (1). L13-L16. ISSN 2041-8205. https://resolver.caltech.edu/CaltechAUTHORS:20090501-132703065

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Abstract

We report the discovery of superstrong, fading, high-ionization iron line emission in the galaxy SDSS J095209.56+214313.3 (SDSS J0952+2143 hereafter), which must have been caused by an X-ray outburst of large amplitude. SDSS J0952+2143 is unique in its strong multiwavelength variability; such a broadband emission-line and continuum response has not been observed before. The strong iron line emission is accompanied by unusual Balmer line emission with a broad base, narrow core, and double-peaked narrow horns, and strong He II emission. These lines, while strong in the SDSS spectrum taken in 2005, have faded away significantly in new spectra taken in 2007 December. Comparison of SDSS, 2MASS, GALEX, and follow-up GROND photometry reveals variability in the NUV, optical, and NIR band. Taken together, these unusual observations can be explained by a giant outburst in the EUV-X-ray band, detected even in the optical and NIR. The intense and variable iron, helium, and Balmer lines represent the "light echo" of the flare, as it traveled through circumnuclear material. The outburst may have been caused by the tidal disruption of a star by a supermassive black hole. Spectroscopic surveys such as SDSS are well suited to detect emission-line light echoes of such rare flare events. Reverberation-mapping of these light echoes can then be used as a new and efficient probe of the physical conditions in the circumnuclear material in nonactive or active galaxies.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1086/588281DOIUNSPECIFIED
http://www.iop.org/EJ/abstract/1538-4357/678/1/L13PublisherUNSPECIFIED
ORCID:
AuthorORCID
Ajello, M.0000-0002-6584-1703
Salvato, M.0000-0001-7116-9303
Additional Information:© 2008 The American Astronomical Society. Received 2008 February 12; accepted 2008 March 17; published 2008 March 27.
Subject Keywords:galaxies: active; galaxies: evolution; galaxies: individual (SDSS J095209.56+214313.3); quasars: emission lines
Issue or Number:1
Record Number:CaltechAUTHORS:20090501-132703065
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20090501-132703065
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14133
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:14 Aug 2009 15:09
Last Modified:09 Mar 2020 13:18

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