Extragalactic scenarios for gamma-ray bursts

Abstract

The cosmological distance scale to gamma‐ray bursts is indicated by the observed distribution of the bursts in angle and intensity. The redshifts of the weakest and the strongest bursts detected by the BATSE experiment are estimated to be z≊1.5 and z≊0.2, respectively, while the strongest bursts detect by the PVO in its 11 years of operation were at z≊0.05. The bursts’ rate is ∼10−6 per year in a galaxy like ours, and a typical energy release if ∼1051 ergs, assuming isotropic emission. The rate of the neutron star and black hole collisions in close binaries is somewhat higher, and those collision release 1053–1054 ergs in a burst like form, making them the primary candidates for the observed gamma‐ray events. Contrary to the common belief no observations available to date are in conflict with the cosmological distance to the bursters. A detection of gravitational lensing of some bursts, the redshift of the weakest events, and the absorption of soft x‐rays by the interstellar matter in the plane of our galaxy, are the specific predictions of the cosmological scenario.