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 brigh tness B and short-time-scale (less than or similar to 0.3 s) variabili ty V which we introduced earlier. We show that the 54 type I (log V le ss than or equal to-0.8) bursts lying in the middle brightness range o f 490 less than or equal to B less than or equal to 1250 count (corres ponding to one-third of all type I bursts) exhibit a Galactic dipole m oment of (cos theta)=0.204 +/- 0.079 and a deviation of the Galactic q uadrupole moment from 1/3 of (sin(2) b)- 1/3 = - 0.104 +/- 0.041. Usin g Monte Carlo simulations that include the BATSE sky exposure map, and taking into account division of the type I bursts into three equal sa mples, we find that the probability by chance of an isotropic distribu tion 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.