The Progenitors of Gamma-Ray Bursts
This chapter discusses the object or objects responsible for gramma-ray bursts (GRBs). Until now, there are few absolute certainties with regard to the progenitors of GRBs. One clear standout is the progenitors of soft gamma-ray repeaters (SGRs) which are very obviously neutron stars. There are a number of corroborating lines of evidence for this progenitor association: (1) some well-localized SGRs are associated with supernova remnants, suggesting they are byproducts of recent supernovae; (2) there is quiescent X-ray emission from the sites of SGRs, similar to a class of neutron stars called “anomalous X-ray pulsars”; (3) Galactic SGRs tend to be found in the Galactic plane, where most young neutron stars reside; and (4) the ringdown emission after SGR pulses is periodic, with periods comparable to that of slowly rotating neutron stars (few seconds).