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

Measurements of the two-point angular correlation function w (theta) for 407 short gamma-ray bursts collected in the Current BATSE Catalogue reveal a similar to2sigma deviation from isotropy on angular scales thetasimilar to2degrees-4degrees. 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 similar to13 per cent 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 (theta) is compatible with those derived for different populations of galaxies up to redshifts similar or equal to0.5, a result that suggests short gamma-ray bursts to be relatively local sources.