ANISOTROPY OF THE SKY DISTRIBUTION OF GAMMA-RAY BURSTS

The isotropy of gamma-ray bursts collected in current BATSE catalog is studied. It is shown that the quadrupole term being proportional to N sin 2b sin l is non-zero with a probability of 99.9%. The occurrence of this anisotropy term is then confirmed by the binomial test even wi th the probability of 99.97 %. Hence, the sky distribution of all know n gamma-ray bursts is anisotropic. It is also argued that this anisotr opy cannot be caused exclusively by instrumental effects due to the no nuniform sky exposure of BATSE instrument. Separating the GRBs into sh ort and long subclasses, it is shown that the short ones are distribut ed anisotropically, but the long ones seem to be distributed still iso tropically. The character of anisotropy suggests that the cosmological origin of short GRBs further holds, and there is no evidence for thei r Galactical origin.