Gamma-Ray Burst Groups Observed by Different Satellites
  Two classes of gamma-ray bursts have been identified in the BATSE catalogs
characterized by durations shorter and longer than about 2 seconds. There are,
however, some indications for the existence of a third one. Swift satellite
detectors have different spectral sensitivity than pre-Swift ones for gamma-ray
bursts. Therefore it is worth to reanalyze the durations and their distribution
and also the classification of GRBs. In this paper we are going to analyze the
bursts' duration distribution and also the duration-hardness bivariate
distribution, published in The First BAT Catalog, whether it contains two,
three or maybe more groups. Similarly to the BATSE data, to explain the BAT
GRBs duration distribution three components are needed. Although, the relative
frequencies of the groups are different than they were in the BATSE GRB sample,
the difference in the instrument spectral sensitivities can explain this bias
in a natural way. This means theoretical models may have to explain three
different type of gamma-ray bursts.
