X‐Ray Afterglows

We summarise the X‐ray temporal and spectral variability properties of GRBs as observed using the Swift satellite. Despite much individual complexity, the flux and spectral variability can be reasonably well described by a combination of two components—which we denote as the prompt and the afterglow. The first, prompt component consists of the burst and its initial decay while the second, afterglow component fits the X‐ray plateau phase and subsequent decline observed in the majority of GRBs. When strong spectral variability occurs it is associated with the prompt component while the X‐ray plateau and later emission shows little if any spectral variability. We briefly compare the observations with some of the proposed models. Any model for the early or late emission must explain the differences in both temporal and spectral behaviour.