Spectral analysis of 35 GRBs/XRFs observed with HETE-2/FREGATE
  We present a spectral analysis of 35 GRBs detected with the HETE-2 gamma-ray detectors (the FREGATE instrument) in the energy range 7-400 keV. The GRB sample analyzed is made of GRBs localized with the Wide Field X-ray Monitor onboard HETE-2 or with the GRB Interplanetary Network. We derive the spectral parameters of the time-integrated spectra, and present the distribution of the low-energy photon index, alpha, and of the peak energy, e_peak . We then discuss the existence and nature of the recently discovered X-Ray Flashes and their relationship with classical GRBs. 
C. Barraud, J-F. Olive, J.P. Lestrade, J-L. Atteia, K. Hurley, G.   Ricker, D. Q. Lamb, N. Kawai, M. Boer, J-P. Dezalay, G. ...