X-ray Afterglows

The X-ray afterglow is detected in almost all cases (one of the notable exceptions is represented by the bright GRB970111, albeit the 17 hours delay taken to start observing). The observed afterglows are usually characterized by a power law decaying flux $F \propto t^{-\alpha}$ in optical and X-ray bands, where typical values for $\alpha$ are in the range $1.0-1.5$, although some afterglows show a steeper decline with $\alpha \sim 2$.