Swift J2058.4+0516: Discovery of a Possible Second Relativistic Tidal Disruption Flare?
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 × 1047 erg s-1) and radio (νL ν, iso ≈ 1042 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).
- Publication:
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The Astrophysical Journal
- Pub Date:
- July 2012
- DOI:
- 10.1088/0004-637X/753/1/77
- arXiv:
- arXiv:1107.5307
- Bibcode:
- 2012ApJ...753...77C
- Keywords:
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- accretion;
- accretion disks;
- black hole physics;
- galaxies: nuclei;
- X-rays: bursts;
- X-rays: individual: Sw J1644+57;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Minor typos corrected