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

TL;DR

This study analyzes the large-scale angular distribution of short Gamma-ray bursts from BATSE, finding they are intrinsically isotropic despite some correlations caused by non-uniform sky exposure.

Contribution

It introduces a new coordinate-free method to analyze angular distributions, accounting for sky exposure and measurement uncertainties, and assesses isotropy of SGRBs.

Findings

SGRBs are consistent with intrinsic isotropy.

Large-angle correlations are influenced by sky exposure effects.

No correlation found with the supergalactic plane.

Abstract

We investigate the large-scale angular distribution of the short-Gamma ray bursts (SGRBs) from BATSE experiment, using a new coordinates-free method. The analyses performed take into account the angular correlations induced by the non-uniform sky exposure during the experiment, and the uncertainty in the measured angular coordinates. Comparising the large-scale angular correlations from the data with those expected from simulations using the exposure function we find similar features. Additionally, 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 36o - 45o, which are likely to be due to the non-uniform 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.