2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/102893Following a brief introduction we show that the observations obtained so far with the Swift satellite begin to shed light over a variety of problems that were left open following the excellent performance and related discoveries of the Italian - Dutch Beppo SAX satellite. The XRT light curves show common characteristics that are reasonably understood within the framework of the fireball model. Unforeseen flares are however detected in a large fraction of the GRB observed and the energy emitted by the brightest ones may be as much as 85% of the total soft X ray emission measured by XRT. These characteristics seems to be common to long and short bursts.6 pages, 9 figures. Proceedings of conference "The X-Ray Universe", San Lorenzo de El Escorial (Madrid, Spain), 26-30 September 2005Astrophysicstext