The Peak Energy Distribution of the νF_ν Spectra Obtained by Different Satellites

Gamma-ray bursts (GRBs) is one of the most violent events in the universe. The gamma-ray telescope CGRO/BATSE (Compton Gamma-Ray Observatory/Bursts and Transient Source Experiment) consists of 8 Large NaI Area Detectors (LADs) and it can detect more than 2700 GRBs due to its wide energy coverage (-25keV to -1MeV) and large field of view. Fermi (Fermi Gamma-Ray Space Telescope) can measure the spectra in a very wide energy band (from 8keV to more than 300GeV). It opens a new era of observational astronomy in the energetic gamma-ray band. Another mission HETE-2, as the first satellite entirely dedicated to the detection and study of GRBs, the FREGATE (French Gamma Telescope) gamma ray detector on board of HETE-2 is sensitive to photons in the energy band of ~10 to ~400keV. This sensitivity range, extended towards low energies, allows us to explore the emission of GRBs in hard X-rays and X-ray flashes (XRFs), which extend the E_p distribution to a few keV. These three satellites together provide us plenty of GRB samples. It is necessary to perform a detailed analysis of these data, and to find the contained GRB radiation physics information using statistical methods. The peak energy of the νF_ν spectra E_p is an important quantity of the GRBs and it is dramatically different from burst to burst. We study the peak energy E_p distribution of the νF_ν spectra of GRBs with samples of 57 bursts observed by HETE-2, 156 bright bursts observed by BATSE and 1407 bursts observed by Fermi. Our results show that the distribution of E_p is wide, and the distribution profile of the observed E_p from BATSE, HETE-2 and Fermi/GBM GRBs is consistent. The peak energy of the BATSE sample is statistically higher than that of HETE-2 and Fermi samples, but maybe this is because the selection of the BATSE samples are bright bursts. And the distributions of LogN-LogE_p observed by these three satellites are also consistent with each other. These results indicate that the E_p distributions of GRBs observed by different satellites are similar, and the radiation physics of of these GRBs may be similar.