Gamma-Ray Burst Classes Found in the RHESSI Data Sample

TL;DR

This study analyzes RHESSI satellite data of 427 gamma-ray bursts to investigate the existence of distinct GRB groups, confirming the intermediate class through statistical tests, consistent with previous BATSE and Swift findings.

Contribution

It demonstrates the presence of an intermediate gamma-ray burst group in RHESSI data using advanced statistical methods, supporting prior evidence from other datasets.

Findings

Maximum likelihood ratio test confirms intermediate group

No significant intermediate group with simple T90 and chi^2 or F-test

Results align with BATSE and Swift data

Abstract

A sample of 427 gamma-ray bursts (GRBs), measured by the RHESSI satellite, is studied statistically to determine the number of GRB groups. Previous studies based on the BATSE Catalog and recently on the Swift data claim the existence of an intermediate GRB group, besides the long and short groups. Using only the GRB durations T90 and chi^2 or F-test, we have not found any statistically significant intermediate group. However, the maximum likelihood ratio test, one-dimensional as well as two-dimensional hardness vs. T90 plane, reveal the reality of an intermediate group. Hence, the existence of this group follows not only from the BATSE and Swift datasets, but also from the RHESSI results.