EVIDENCE FOR THE GALACTIC ORIGIN OF GAMMA-RAY BURSTS

We investigate the angular distribution of the gamma-ray bursts in the publicly available BATSE catalogue, using the measures of burst brightness B and short-time-scale (less than or similar to 0.3 s) variability V which we introduced earlier. We show that the 54 type I (log V less than or equal to-0.8) bursts lying in the middle brightness range of 490 less than or equal to B less than or equal to 1250 count (corresponding to one-third of all type I bursts) exhibit a Galactic dipole moment of (cos theta)=0.204 +/- 0.079 and a deviation of the Galactic quadrupole moment from 1/3 of (sin(2) b)- 1/3 = - 0.104 +/- 0.041. Using Monte Carlo simulations that include the BATSE sky exposure map, and taking into account division of the type I bursts into three equal samples, we find that the probability by chance of an isotropic distribution of 54 bursts exhibiting values of(cos theta) and the negative of(sin(2) b)- 1/3 that equal or exceed the observed values is 6.6 x 10(-5). We conclude that gamma-ray bursts are Galactic in origin.