Gamma Ray Bursts and their afterglow properties

Abstract

In this paper, we review the afterglow properties of 304 Gamma Ray Bursts observed with various radio telescopes between the year 1997 to January 2011. Most of the observations in the sample presented here were performed in the 8.5 GHz band with the Very Large Array. Our sample shows that the detection rate for the radio afterglows has stayed at about 31% for the pre-Swift as well as the post-Swift bursts, in contrast to large increases in the optical and X-ray afterglow detection rates. Our detailed analysis of the detected versus the non-detected radio afterglows shows that these are severely limited by the instrument sensitivity. We also find that there is no obvious correlation between the radio luminosity with the isotropic γ-ray energy release, the γ-ray fluence, or with the X-ray flux; however, the optical afterglows fluxes show a weak correlation with the radio flux density. Radio afterglow detection is dependent upon a relatively narrow range of circumburst densities (1-10 cm^{-3}) and microscopic shock parameters, especially the magnetic energy density. Finally we discuss the most interesting bursts and some of the interesting current topics in the GRB field.