SWIFT and BATSE bursts' classification

Two classes of gamma-ray bursts were identified in the BATSE catalogs characterized by their durations. There were also some indications for the existence of a third type of gamma-ray bursts. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for GRBs. Therefore in this paper we analyze the bursts' duration distribution and also the duration-hardness bivariate distribution, published in The First BAT Catalog. 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.