X–Ray Observations of γ–Ray Burst Afterglows

The discovery by the BeppoSAX satellite of X-ray afterglow emission from the γ-ray burst which occurred on 28 February 1997 produced a revolution in our knowledge of the γ-ray burst phenomenon. Along with the discovery of X-ray afterglows, the optical afterglows of γ-ray bursts were discovered and the distance issue was settled, at least for long γ-ray bursts. The 30 year mystery of the γ-ray burst phenomenon is now on the way to solution. Here I rewiew the observational status of the X-ray afterglow emission, its mean properties (detection rate, continuum spectra, line features, and light curves), and the X-ray constraints on theoretical models of γ-ray bursters and their progenitors. I also discuss the early onset afterglow emission, the remaining questions, and the role of future Xray afterglow observations.