Swift J2058.4+0516: Discovery of a possible second relativistic tidal disruption flare?

S. Bradley Cenko, Hans A. Krimm, Assaf Horesh, Arne Rau, Dale A. Frail, Jamie A. Kennea, Andrew J. Levan, Stephen T. Holland, Nathaniel R. Butler, Robert M. Quimby, Joshua S. Bloom, Alexei V. Filippenko, Avishay Gal-Yam, Jochen Greiner, S. R. Kulkarni, Eran O. Ofek, Felipe Olivares E., Patricia Schady, Jeffrey M. Silverman, Nial R. TanvirDong Xu

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Abstract

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 × 1047ergs-1) and radio (νL ν, iso 1042ergs-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 GRB110328A/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).

Original languageEnglish (US)
Article number77
JournalAstrophysical Journal
Volume753
Issue number1
DOIs
StatePublished - Jul 1 2012

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Bradley Cenko, S., Krimm, H. A., Horesh, A., Rau, A., Frail, D. A., Kennea, J. A., Levan, A. J., Holland, S. T., Butler, N. R., Quimby, R. M., Bloom, J. S., Filippenko, A. V., Gal-Yam, A., Greiner, J., Kulkarni, S. R., Ofek, E. O., Olivares E., F., Schady, P., Silverman, J. M., ... Xu, D. (2012). Swift J2058.4+0516: Discovery of a possible second relativistic tidal disruption flare? Astrophysical Journal, 753(1), [77]. https://doi.org/10.1088/0004-637X/753/1/77