22nd Texas Symposium on Relativistic Astrophysics at Stanford University
We present an update of our systematic analyses 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 UBV RI 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  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.
Please use publisher's recommended citation.