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 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090501-132703065
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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.
|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|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||14 Aug 2009 15:09|
|Last Modified:||26 Dec 2012 10:59|
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