On Suggestive Correlations between Gamma‐Ray Bursts and Clusters of Galaxies

Recent claims of angular correlations between gamma-ray bursts (GRBs) andclusters of galaxies are evaluated in light of existing but previouslyuncorrelated GRB positional data. Additional GRB data sets we use includesub-samples of soft BATSE 3B bursts, bursts located by the InterplanetaryNetwork (IPN), and GRBs localized by COMPTEL. We confirm a previously reportedexcess by Rood and Struble (1996) of the 185 rich, nearby clusters of galaxies(Abell, Corwin, and Olowin 1989, ACO) in the 1-$\sigma$ error circles of 74BATSE 3B positions, but find a typical correlation strength of only$~$2.5-$\sigma$ for typical sub-samples. However, none of the 185 ACO clustersoccur in the 1-$\sigma$ error boxes of 40 IPN GRBs or 18 COMPTEL GRBs. When allACO clusters are correlated with BATSE 3B GRBs however, we find an increasinglystrong correlation for GRBs with decreasingly small error boxes, reaching abovethe 3.5-$\sigma$ level. We also find a slight excess of {\it soft} BATSE GRBsnear the positions of 185 rich, nearby ACO clusters, but the significance ofthe correlation averages only $~$2.5-$\sigma$ for sub-samples delineated bysoftness. We caution that the statistical significance of all thesecorrelations is marginal, and so conclude that the excess is at best onlysuggestive of a physical association. Statistical fluke is still a strongpossibility. BATSE could confirm or refute such correlations in a 10-yearlifetime.Comment: 17 pages in LateX including 2 postcript figures. To be published in ApJ. One affiliation has been change