Luminosity distributions of cosmological gamma-ray bursts

The intrinsic luminosities of gamma-ray bursts are found to be constrained by the BATSE/PVO combined intensity distribution, assuming that (1) bursts originate in Lambda = 0, Omega = 1 Friedmann cosmology with a nonevolving density distribution, (2) the nonevolving intrinsic luminosity function can be modeled as a truncated power law, and (3) burst spectra are modeled as power laws with identical spectral indices. These simplifying assumptions allow constraints to be placed on luminosity functions in cosmological gamma-ray burst scenarios and indicate that standard-candle sources are not favored. In general, either the minimum burst luminosity L(min) or the maximum burst luminosity L(max) are known, with the opposite end of the luminosity function unconstrained. Both L(max) and L(min) must be specified for luminosity power-law indices near 2. When these results are combined with other studies measuring other cosmological burst signatures, it is possible that the intrinsic luminosity function contains more low-luminosity bursts than high-luminosity ones.