Integrated criteria of gamma-ray bursts spectral hardness

Abstract

Most part of gamma-ray bursts (GRBs) spectra are well described by Band model with following parameters: α, β (spectral indices in low and high energy bands) and Epeak (energy of spectral peak). For several GRB parameter β characterizing the spectral shape in the region up to some hundred MeV (for example, GRB100724B). Moreover, Band spectrum of GRB080916C covering 6 orders of magnitude. Until recently spectral hardness parameter H32 (the ratio of total counts in the 100 − 300 keV and 50 − 100 keV energy range) was used for additional classification events on hard and soft, for GRBs groups selection on hardness and duration distributions (subgroup of intermediate bursts) and so on. However, H32 is defined in energy intervals 50−100 keV and 100−300 keV, but for some GRB Epeak> 300 keV and this value is outside regions of H32 definition. Thus, parameter H32 is incompletely represents spectral properties of such events. Basing on Band model we introduce new integral criteria could be used in the wide energy band for data analysis in past experiments such as BATSE (0.02 − 2 MeV), COMPTEL (0.8 − 30 MeV); EGRET (20 MeV − 30 GeV); in now operated experiments Fermi (8 keV − 1MeV, 200 keV − 40 MeV and 300 MeV − 300 GeV), AGILE (18 − 60 keV and 30 MeV − 50 GeV) and in future experiments: GAMMA−400 (0.1 − 3000 GeV) and so on. In the present work spectral parameters taken from BATSE and from Fermi catalogues were analyzed and the new integral criteria were investigated. Results of data studying have shown that new criteria allow making GRB classification including intermediate bursts subgroup separation.