Two Classes of Gamma-Ray Bursts

Data from the 3B Catalogue suggest that short and long GRB are the results of different classes of events, rather than different parameter values within a single class: Short bursts have harder spectra in the BATSE bands, but chiefly long bursts are detected at photon energies over 1 MeV, implying that their hard photons are radiated by a process not found in short bursts. The values of \langle V/V_{max} \rangle for short and long bursts differ by 4.3 \sigma, implying different spatial distributions. Only the soft gamma-ray radiation mechanisms are the same in both classes.