A wide ranging search for correlations among burst properties

Abstract

One primary reason that Gamma Ray Bursts (GRBs) have remained such a mystery is that there are virtually no known significant, non-definitional correlations or bimodalities among the burst properties. The best we have at the present time is a weak hardness/duration correlation, a disputed duration/intensity correlation, a problem plagued hardness/intensity correlation, and a duration bimodality. But these have not provided the sort of break-through similar to those provided by the H-R diagram or the PopI/PopII results in stellar astronomy. The physical processes which relate burst properties to one another are masked by the lack of correlations and bimodalities. In the past, searches for correlations and bimodalities in the data have been made for a relatively small set of properties, usually with no regard for the light curve shape. We present our results of a systematic search for statistically significant correlations and bimodalities from a set of 49 burst properties, with particular emphasis on the inclusion of light curve characteristics. We have used the data base of the 260 bursts in the BATSE 1B catalog. We keep an accurate account of the number of trials for which we test the data, and then fold this into our detection threshold. Our method recovered the known correlation between the log of the duration and the spectral hardness, with a significance of 9.3×10−5 after correcting for trials. We also recovered the expected risetime/decay time correlation and the bimodality of the logarithm of duration. We found no original, significant, non-definitional correlations or bimodalities.