Author: Tanmoy Laskar
Abstract: Long-duration GRBs at high redshifts trace the first generations of massive stars in the Universe. These events have the potential to shed light on both the redshift evolution of the progenitor population and direct discovery of Population III stars. Multi-wavelength modeling of GRB afterglows is an efficient means to obtain information about the progenitor system and the circumburst environment. In particular, radio observations provide crucial constraints on the energy scale and the density of the circumburst medium. We report on recent results from the last one year of our radio program at the Karl G. Jansky VLA and present the interesting case of GRB 120521 at z∼6, one of the highest redshift GRBs known. Through multi-wavelength modeling from the X-rays to the radio, we constrain properties of the progenitor and compare the results to other high-z GRBs with radio detections.