CAN RELATIVISTIC BEAMING OF GAMMA-RAY BURSTS MIMIC COSMOLOGICAL TIME DILATION

If gamma-ray bursts are at cosmological distances, durations and varia bility time scales of faint bursts are expected to be systematically l onger than those of bright bursts due to cosmological time dilation. A recent analysis of data from the Burst and Transient Source Experimen t (BATSE) reported detection of such a signal. We show that relativist ic beaming can produce similar flux-duration relations both in the Gal actic halo model and in the cosmological model with duration ranges co mparable to the reported one.