STATISTICAL EVIDENCE FOR A GALACTIC ORIGIN OF GAMMA-RAY BURSTS

ASTRONOMICAL bursts of gamma-rays (GRBs) were first discovered 20 years ago, and approximately 100 are recorded every year by satellite-borne instruments. Bursts last for at most a few seconds, recur only on a timescale of years, if at all, and come from objects which have remained undetected at all other wavelengths. It has been impossible to establish a distance scale for GRBs, and no association with known astronomical objects has been demonstrated. Here we analyse the spatial distribution of GRBs 1,2 with a view to understanding their true radial distribution. Our data consist of three samples, totalling 244 GRBs, obtained by three French-Soviet experiments flown on the Venera 13 and 14 and the Phobos missions. We conclude that the underlying GRB distribution is not uniformly distributed in space, but falls off with distance. Our analysis of the weak sources in particular suggests that GRBs are associated with the galactic plane.