Smoking Gun Evidence: Analogs of Supernovae in Long-Duration GRBs?
Both the afterglows and host galaxies of long-duration GRBs provided powerful circumstantial evidence for a massive star progenitor. However, direct confirmation of this association required a smoking gun signature, in this case the appearance of a (relatively rare) type of core-collapse supernovae in the late-time light curve of nearby long-duration GRBs (Figure 22). The discovery of a so-called broad-lined type Ic supernova in the days and weeks following nearby long-duration GRBs put to rest any doubt as to the origin of these events \cite{Hjorth}.