Spectral Characteristics of X-ray Flashes compared to Gamma-Ray Bursts
  X-ray flashes (XRFs) are a new type of fast transient source observed with the BeppoSAX Wide Field Cameras (WFC) at a rate of about four per year. Apart from their large fraction of 2-26 keV X-rays, the bulk properties of these events are similar to those of classical gamma-ray bursts (GRBs). By investigating the wide-band spectra of ten events detected in common with WFC and BATSE, we explore the possibility that XRFs are a low-energy branch of the GRB population. We find that XRF spectra are similar to those of GRBs, and that their low peak energies could be an extension of known GRB properties. 
R. M. Kippen (1 and 2), P. M. Woods (3 and 2), J. Heise (4), J. J. M.   in 't Zand (5 and 4), M. S. Briggs (1 and 2), R. D. ...