THE EDGE OF A GAMMA-RAY BURST AFTERGLOW

We discuss the formation of spectral features in the decelerating ejec ta of gamma-ray bursts, including the possible effect of inhomogeneiti es. These should lead to blueshifted and broadened absorption edges an d resonant features, especially from H and He. An external neutral ISM could produce detectable H and He, as well as Fe X-ray absorption edg es and lines. Hypernova scenarios may be diagnosed by Fe K alpha and H Ly alpha emission lines.