Evidence that gamma-ray burst sources repeat

We investigate the angular distribution of the $\gamma$-ray bursts in thepublicly available BATSE catalogue, using the measures of burst brightness $B$and short time scale ($\simless$ 0.3 s) variability $V$ which we introducedearlier. We show that the 54 type I ($\log V \le -0.8$) bursts lying in themiddle brightness range 490 counts $\le B \le$ 1250 counts (corresponding to1/3 of all type I bursts) exhibit a Galactic dipole moment of $\langle \cos\theta \rangle = 0.204 \pm 0.079$ {\it and} a deviation of the Galacticquadrupole moment from 1/3 of $\langle \sin^2 b \rangle - 1/3 = -0.104 \pm0.041$. Using Monte Carlo simulations which include the BATSE sky exposure mapand 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 54bursts exhibiting values of $\langle \cos \theta \rangle$ {\it and} thenegative of $\langle \sin^2 b \rangle - 1/3$ which equal or exceed the observedvalues is $6.6 \times 10^{-5}$. We conclude that $\gamma$-ray bursts areGalactic in origin.Comment: 6 pages, 3 figures available upon request, LATEX v. 2.09, MNRAS document style mn.sty included,