Gamma-Ray Burst high energy emission from Internal Shocks

In this paper we study synchrotron and Self Compton (SSC) emission from internal shocks (IS) during the prompt and X-ray flare phases of Gamma-Ray Bursts (GRBs). The aim is to test the IS model for the flare emission and if GRBs can be GeV sources. We determine the parameters for which the IS model can account for the observed prompt and X-ray flares emission, and study the detectability of the high energy SSC emission by the AGILE and GLAST satellites. We find that the detectability of the SSC emission during the prompt phase of GRBs improves for higher values of the fireball Lorentz factor Γ and of the temporal variability tv. If IS is the mechanism responsible of the flare emission, the flares light curves must present some substructures with temporal variability tv = 10 − 100 ms much smaller than the average duration of flares, and similar to those observed during the prompt phase of GRBs. An investigation on the substructures of the X-ray flares light curves will allow to corroborate the hypothesis that late IS are responsible of the X-ray flares. We find that higher values of Lorentz factor and variability time favor the detection by AGILE and GLAST of the X-ray flare high energy counterpart.