THE CONSISTENCY OF STANDARD COSMOLOGY AND THE BATSE NUMBER VERSUS BRIGHTNESS RELATION

The integrated number peak-flux relation measured by the Burst and Tra nsient Source Experiment (BATSE) on board the Compton Gamma Ray Observ atory is compared with several standard cosmological distributions for gamma-ray bursts (GRBs). Friedmann-Robertson-Walker models were used along with the assumption that the bursts are standard candles and hav e no number or luminosity evolution. For a given OMEGA and spectral sh ape, we used a free parameter, essentially the comoving number density of bursts, to generate a best fit between the cosmology and the measu red relation. Our results are shown for a subsample of the first 260 G RBs recorded by BATSE. We find acceptable fits between simple cosmolog ical models and the brightness distribution data, as determined by the Kolmogorov-Smirnov one-distribution statistical test. One cannot dist inguish a single best cosmological model from the goodness of the fits . The best fit implies that BATSE GRBs arc complete out to a redshift of about unity. However, significantly higher and lower redshifts, by as much as a factor of 2, are possible for other marginally acceptable fits.