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Register a new userA Comparison of Gamma-ray Burst Subgroups Measured by RHESSI and BATSE
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A sample of almost 400 Gamma-ray bursts (GRBs) detected by the RHESSI satellite is studied statistically. We focus on GRB duration and hardness ratio and use the statistical chi^2 test and the F-test to compare the number of GRB subgroups in the RHESSI database with that of the BATSE database. Although some previous articles based on the BATSE catalog claim the existence of an intermediate GRB subgroup, besides long and short, we have not found a statistically significant intermediate subgroup in the RHESSI data.
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A sample of 286 gamma-ray bursts (GRBs) detected by the Swift satellite and 358 GRBs detected by the RHESSI satellite are studied statistically. Previously published articles, based on the BATSE GRB Catalog, claimed the existence of an intermediate subgroup of GRBs with respect to duration. We use the statistical chi^2 test and the F-test to compare the number of GRB subgroups in our databases with the earlier BATSE results. Similarly to the BATSE database, the short and long subgroups are well detected in the Swift and RHESSI data. However, contrary to the BATSE data, we have not found a statistically significant intermediate subgroup in either Swift or RHESSI data.
Short and long bursts were identified by the BATSE team in the early 90s. A decade ago there were some suggestions about the intermediate duration type of bursts. We are going to summarize recent analyses of the duration distributions of the Beppo-Sax and Swift data. Our conclusion is all the three satellites (CGRO, Swift, Beppo-Sax) can see the third type of the GRBs. The properties of the group members are very similar in the different data sets.
We present systematic spectral analyses of GRBs detected with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory (CGRO) during its entire nine years of operation. This catalog contains two types of spectra extracted from 2145 GRBs and fitted with five different spectral models resulting in a compendium of over 19000 spectra. The models were selected based on their empirical importance to the spectral shape of many GRBs, and the analysis performed was devised to be as thorough and objective as possible. We describe in detail our procedures and criteria for the analyses, and present the bulk results in the form of parameter distributions. This catalog should be considered an official product from the BATSE Science Team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center (HEASARC).
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.
The performance of the nine RHESSI germanium detectors has been gradually deteriorating since its launch in 2002 because of radiation damage. To restore its former sensitivity, the spectrometer underwent an annealing procedure in November 2007. However, it changed the RHESSI response and affected gamma-ray burst measurements, e.g., the hardness ratios and the spectral capabilities below ~100keV.
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