Abstract/Summary

Few GRBs clearly present distinct High-Energy (HE) component that evolve independent of the usual Band function that describes the prompt keV-emission. This component can be long or short lasting compared to the burst duration. However, most of models only explain the long duration HE component. We have developed a leptonic model on the external shock framework to describe the HE components. We propose that the short HE component that falls in the MeV regime in coincidence with the prompt phase and, the second long lasting GeV-emission could be understood as synchrotron self-Compton (SSC) emission from the reverse and forward shock respectively. This model requires a magnetized jet and a reverse shock in the thick shell case. This model already has been proven in GRB 980923 and GRB 090926A, the former with a short duration MeV-component and the latter with both long GeV- and short MeV- HE components. All fluxes, energies and durations are consistent with the observed values. Here, we apply this model to GRB 940217 that presented similarities with GRB 090926A and GRB 980923.