Cosmic gamma ray bursts -- recent developments

Abstract

The Gamma Ray Bursts (GRB) have been observed for the last 20 years by a large number of satellites. However, till recently, comprehensive analysis was difficult in view of varying techniques used by different satellites. The launch of the Gamma Ray Observatory (GRO), has produced a large data base of more than 250 GRB that is now available for detailed analysis. The GRO/Burst and Transient Source Experiment (BATSE) observations have cataloged GRBs fainter by three orders of magnitude compared to the previous observations. However, in spite of this large database our understanding of the GRBs remains as poor as ever. This is primarily because (1) no other specific class of objects can be seen in GRB error boxes and in some very well localized GRBs, very deep searches have shown no object; (2) the Log (Number) to Log (Power) distribution indicates that the number of objects increases more slowly with depth than would be expected by geometric considerations; (3) the source distribution remains isotropic even for very faint GRBs and (4) the bursts themselves have a very involved time structure which varies dramatically from burst to burst