Luminosities and Space Densities of Gamma-Ray Bursts

We use a homogeneous sample of gamma-ray bursts (GRB) extracted from 5.9years of BATSE DISCLA data (astro-ph/9908190) and a variety of broken power-lawluminosity functions to derive GRB luminosities and space densities. Luminosityfunctions that are narrow or exhibit no density evolution produce expectedredshift distributions that are incompatible with the observation of a GRBredshift of 3.4. For q_o=0.1 and density evolution rising to 10 at z=1, we findfor a variety of slopes of the luminosity function values of the local spacedensity around 0.18 Gpc^{-3} y^{-1} with a range of only 40%. Characteristic50--300 keV peak luminosities exhibit a range of a factor of 6 around 6e51erg/s corresponding to a characteristic total luminosity of 1.2e53 erg in the10--1000 keV band. For q_o=0.5, densities are higher and luminosities lower,both by a factor of 2.5. The local emissivity of GRBs is 1.0e52 erg Gpc^{-3}y^{-1} in the 10--1000 keV band.Comment: 9 pages, 3 figures, accepted for publication in Astrophysical Journal Letter