Cosmological Signatures in Temporal and Spectral Characteristics of Gamma-Ray Bursts

Abstract

There have been several suggestions of the existence of cosmological redshift signatures in the temporal and spectral characteristics of gamma-ray bursts. However, recent discoveries of afterglows and redshift measurements indicate the presence of broad ``luminosity functions'' which may overwhelm such weaker cosmological signatures. The primary goal of this paper is to determine if the intrinsic and cosmological dispersions can be separated. We have expanded the search for cosmological signatures to several other temporal and spectral features, have determined correlations which could arise from the cosmological redshift of the sources and have carried out tests to determine if the observed correlations can be due to cosmology. We find that the intrinsic dispersions are the dominant factors and that detection of cosmological signatures must await accumulation of a much larger number of identification with galaxies and measurements of redshifts.