Swift J2058.4+0516: Discovery of a Possible Second Relativistic Tidal Disruption Flare?

Understand

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 x 10^47 erg s^-1) and radio (nu L_nu,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.