Evidence for Supernova light in all Gamma-Ray Burst afterglows

TL;DR

This study systematically analyzes GRB afterglow data up to 2004, finding evidence of supernova light in all long-duration GRBs with redshift below 0.7, supporting the connection between GRBs and supernovae.

Contribution

It provides updated evidence that all long-duration GRBs with redshift < 0.7 have associated supernova light, using a larger sample and refined analysis.

Findings

13 out of 29 GRBs show supernova excess

Supernova light is detected in all GRBs with z<0.7

Detection at higher redshifts is limited by selection effects

Abstract

We present an update of our systematic analysis of all Gamma-Ray Burst (GRB) afterglow data, now published through the end of 2004, in an attempt to detect the predicted supernova light component. We fit the observed photometric light curves as the sum of an afterglow, an underlying host galaxy, and a supernova component. The latter is modeled using published UBVRI light curves of SN 1998bw as a template. The total sample of afterglows with established redshifts contains now 29 bursts (GRB 970228 - GRB 041006). For 13 of them a weak supernova excess (scaled to SN 1998bw) was found. In agreement with our earlier result (Zeh et al. 2004) we find that also in the updated sample all bursts with redshift < 0.7 show a supernova excess in their afterglow light curves. The general lack of a detection of a supernova component at larger redshifts can be explained with selection effects. These results strongly support our previous conclusion based on all afterglow data of the years 1997 to 2002 that in fact all afterglows of long-duration GRBs contain light from an associated supernova.