Evidence for Supernova light in all GRB afterglows

We present an update of our systematic reanalysis of all Gamma-Ray Burst (GRB) afterglow data published through the end of 2003, in an attempt to detect the predicted supernova light component in the optical bands. The total sample of afterglows with established redshifts contains 28 bursts (GRB 970228 to GRB 031203). For 12 of them a weak supernova excess was found (including GRB 030329). Among them are all bursts with redshift less than ∼ 0.7. These results support our earlier finding (ApJ, 609 (2004) 952) that all afterglows of long-duration GRBs contain light from an associated supernova