Evidence for anisotropy in the distribution of short-lived gamma-ray bursts

Abstract

Measurements of the two-point angular correlation function w(θ) for 407 short gamma-ray bursts collected in the Current BATSE Catalogue reveal a ~2 σdeviation from isotropy on angular scales θ~ 2-4 degrees. Such an anisotropy is not observed in the distribution of long gamma-ray bursts and hints to the presence of repeated bursts for up to ~13% of the sources under exam. However, the available data cannot exclude the signal as due to the presence of large-scale structure. Under this assumption, the amplitude of the observed w(θ) is compatible with those derived for different populations of galaxies up to redshifts ~0.5, result that suggests short gamma-ray bursts to be relatively local sources.

5 pages, 4 figures, submitted to MNRAS