Cenko, S. Bradley and Krimm, Hans A. and Horesh, Assaf and Rau, Arne and Frail, Dale A. and Kennea, Jamie A. and Levan, Andrew J. and Holland, Stephen T. and Butler, Nathaniel R. and Quimby, Robert M. and Bloom, Joshua S. and Filippenko, Alexei V. and Gal-Yam, Avishay and Greiner, Jochen and Kulkarni, S. R. and Ofek, Eran O. and Olivares E., Felipe and Schady, Patricia and Silverman, Jeffrey M. and Tanvir, Nial R. and Xu, Dong (2012) Swift J2058.4+0516: Discovery of a Possible Second Relativistic Tidal Disruption Flare? Astrophysical Journal, 753 (1). Art. No. 77. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20120720-094719716
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We report the discovery by the Swift hard X-ray monitor of the transient source Swift J2058.4+0516 (Sw J2058+05). Our multi-wavelength follow-up campaign uncovered a long-lived (duration ≳ months), luminous X-ray (L_(X, iso) ≈ 3 × 10^(47) erg s^(–1)) and radio (νL_(ν, iso) ≈ 10^(42) erg s^(–1)) counterpart. The associated optical emission, however, from which we measure a redshift of 1.1853, is relatively faint, and this is not due to a large amount of dust extinction in the host galaxy. Based on numerous similarities with the recently discovered GRB 110328A/Swift J164449.3+573451 (Sw J1644+57), we suggest that Sw J2058+05 may be the second member of a new class of relativistic outbursts resulting from the tidal disruption of a star by a supermassive black hole. If so, the relative rarity of these sources (compared with the expected rate of tidal disruptions) implies that either these outflows are extremely narrowly collimated (θ < 1°) or only a small fraction of tidal disruptions generate relativistic ejecta. Analogous to the case of long-duration gamma-ray bursts and core-collapse supernovae, we speculate that rapid spin of the black hole may be a necessary condition to generate the relativistic component. Alternatively, if powered by gas accretion (i.e., an active galactic nucleus (AGN)), Sw J2058+05 would seem to represent a new mode of variability in these sources, as the observed properties appear largely inconsistent with known classes of AGNs capable of generating relativistic jets (blazars, narrow-line Seyfert 1 galaxies).
|Additional Information:||© 2012 American Astronomical Society. Received 2011 July 26; accepted 2012 April 23; published 2012 June 15. We thank the Swift PI N. Gehrels and the entire Swift team for their work on the remarkable facilities that enabled the discovery of this event. We thank H. Tananbaum for approving our Chandra ToO request (ObsID 13423), and the entire Chandra staff for the prompt scheduling and execution of these observations. We are grateful to G. Fossati for providing the blazar models in tabular form, D. Poznanski for providing software to calculate the host-galaxy K-corrections, and D. Perley for assistance with the reduction of the Keck/LRIS images. We also acknowledge B. Metzger, D. Giannos, and M. Kasliwal for valuable discussions. Public data from the Swift data archive were used for part of this study. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration; the Observatory was made possible by the generous financial support of the W. M. Keck Foundation. S.B.C. and A.V.F. acknowledge generous financial assistance from Gary & Cynthia Bengier, the Richard & Rhoda Goldman Fund, NASA/Swift grants NNX10AI21G and NNX12AD73G, the TABASGO Foundation, and NSF grant AST-0908886. Facilities: Swift (BAT,XRT,UVOT), UKIRT (WFCAM), Keck:I (LRIS), Keck:II (DEIMOS), Max Planck:2.2m (GROND), ING:Herschel (ACAM).|
|Subject Keywords:||accretion, accretion disks; black hole physics; galaxies: nuclei; X-rays: bursts; X-rays: individual (Sw J1644+57)|
|Official Citation:||Swift J2058.4+0516: Discovery of a Possible Second Relativistic Tidal Disruption Flare? S. Bradley Cenko et al. 2012 ApJ 753 77|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||20 Jul 2012 18:44|
|Last Modified:||26 Dec 2012 15:38|
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