The transition between the main event and the afterglow: BeppoSAX

Abstract

One of the two Wide Field Cameras (WFCs) on board BeppoSAX was pointed towards the burst position for few orbits after the detection of the X-ray counterpart of the Gamma Ray Burst (GRB) till the repointing of Narrow Field Instruments (NFI). Therefore the WFC can provide a piece of knowledge on the different types of the transition between the main event and the afterglow. Results on a sub-samples of bursts show that the transition between the main event and the afterglow can be either smooth or can present gaps. In other cases the WFC data strongly suggest that a break should occur in the back extrapolation of the afterglow lightcurve detected by the NFI, nevertheless they do not rule-out a possible late appearing of the afterglow.