X-ray afterglows and spectroscopy of Gamma-Ray Bursts

Abstract

I will review the constraints set by X-ray measurements of afterglows on several issues of GRB, with particular regard to the fireball model, the environment, the progenitor and dark GRB.

Invited talk at the 4th workshop on Gamma-Ray Bursts in the Afterglow Era, ASP Vol.312, in press