On the large-scale angular distribution of short gamma-ray bursts

We investigate the large-scale angular distribution of the short gamma-ray bursts (SGRBs) from BATSE experiment, using a new coordinate-free method. The analyses performed take into account the angular correlations induced by the nonuniform sky exposure during the experiment, and the uncertainty in the measured angular coordinates. Comparing the large-scale angular correlations from the data with those expected from simulations using the exposure function, we find similar features. In addition, confronting the large-angle correlations computed from the data with those obtained from simulated maps produced under the assumption of statistical isotropy, we found that they are incompatible at 95% confidence level. However, such differences are restricted to the angular scales 36 degrees-45 degrees, which are likely to be due to the nonuniform sky exposure. This result strongly suggests that the set of SGRBs from BATSE are intrinsically isotropic. Moreover, we also investigated a possible large-angle correlation of these data with the supergalactic plane. No evidence for such large-scale anisotropy was found.