Swift 1644+57: the longest gamma-ray burst?
Abstract
Swift recently discovered an unusual gamma-ray and X-ray transient (Swift 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 approximately a month with a luminosity comparable to its peak value. The astrometric coincidence of the source with the centre of its host galaxy, together with other considerations, motivated the interpretation that Swift 1644+57 was produced by an outburst from a ∼106-107 M⊙ black hole at the centre of the galaxy. Here we consider the alternate possibility that Swift 1644+57 is indeed a long-duration GRB, albeit a particularly long one! We discuss the general properties of very long-duration, low-power GRB-like transients associated with the core-collapse of a massive star. Both neutron star (magnetar) spin-down and black hole accretion can power such events. The requirements for producing low-power, very long duration GRBs by magnetar spin-down are similar to those for powering extremely luminous supernovae by magnetar spin-down, suggesting a possible connection between these two unusual types of transients. Alternatively, Swift 1644+57 could be associated with the faintest core-collapse explosions: the collapse of a rotating red supergiant in a nominally failed supernova can power accretion on to a solar-mass black hole for up to ∼100 d; the jet produced by black hole accretion inevitably unbinds the outer envelope of the progenitor, leading to a weak ∼1049 erg explosion. In both neutron-star and black hole models, a jet can burrow through the host star in a few days, with a kinetic luminosity ∼1045-1046 erg s-1, sufficient to power the observed emission of Swift 1644+57.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2012
- DOI:
- 10.1111/j.1745-3933.2011.01151.x
- arXiv:
- arXiv:1105.3209
- Bibcode:
- 2012MNRAS.419L...1Q
- Keywords:
-
- gamma-ray burst: general;
- stars: neutron;
- supernovae: general;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- submitted to MNRAS Letters