Frequency of fast, narrow gamma-ray bursts

A duration histogram for 24 gamma-ray burst events detected by an ISEE-3 experiment is presented which suggests the existence of two gamma-ray burst populations. A distribution is also shown of 123 Venera 13 and 14 events which suggests two such populations in each experimental sample, the domains separated with a minimum near 1 or 2 sec. It is pointed out that the results of the Goddard ISEE-3 gamma-ray burst spectrometer actually enhance the appearance of two burst populations suggested in the Venera data.