Can relativistic beaming of gamma-ray bursts mimic cosmological time dilation?

Abstract

If gamma-ray bursts are at cosmological distances, durations and variability time scales of faint bursts are expected to be systematically longer than those of bright bursts due to cosmological time dilation. A recent analysis of data from the Burst and Transient Source Experiment (BATSE) reported detection of such a signal. We show that relativistic beaming can produce similar flux-duration relations both in the Galactic halo model and in the cosmological model with duration ranges comparable to the reported one.