Swift 1644+57: The Longest Gamma-ray Burst?

Understand

Swift recently discovered an unusual gamma-ray and x-ray transient (Sw 1644+57) that was initially identified as a long-duration gamma-ray burst (GRB).

• However, the ~ 10 keV x-ray emission has persisted for over a month with a luminosity comparable to its peak value.
• The astrometric coincidence of the source with the center of its host galaxy, together with other considerations, motivated the interpretation that Sw 1644+57 was produced by an outburst from a 10^{6-7} M_sun black hole at the center of the galaxy.
• Here we consider the alternate possibility that Sw 1644+57 is indeed a long-duration GRB, albeit a particularly long one.