Evidence that gamma-ray burst sources repeat

Abstract

We investigate clustering in the angular distribution of the 260gamma-ray bursts in the publicly available BATSE catalog, using anearest neighbor analysis and the measures of burst brightness B andshort-time-scale variability V that we introduced earlier. We find that,while all 260 bursts are only modestly clustered (Q-value = 1.8 x 10 exp-2), the 202 bursts in this sample for which the statistical error inlocation is less than 9 deg are significantly clustered on an angularscale of about 5 deg (Q-value = 2.5 x 10 exp -4, taking into accounthaving chosen the cut-off in the statistical error). We also find asignificant correlation between bright type I bursts and faint type Iand II bursts on an angular scale of about 5 deg (Q-value = 4.0 x 10 exp-3). This angular scale is smaller than the typical (statistical plussystematic) error in burst location of 6.8, suggesting multiplerecurrences from individual sources. We conclude that 'classical'gamma-ray burst sources repeat on a time-scale of months, and that manyfaint type I and II bursts come from the sources of bright type Ibursts.