High-energy gamma-ray emission from gamma-ray bursts

GRBs an nowadays a rather well understood phenomenon in the soft (KeV-MeV) gamma-ray energy band, while only a few GRBs have been observed at high pho ton energies (E gamma greater than or similar to 1 GeV). It is also widely recognized that GRBs accelerate protons to relativistic energies and that d ense media are often present nearby the sources. Within this framework and by further adopting Totani's suggestion that GRB events release an amount o f energy similar to 10(54) Delta Omega erg, we compute in detail the high-e nergy gamma-ray flux from the decay of neutral pious produced through the i nteraction of accelerate protons with nucleons in the surrounding medium. W e also take into account the local and intergalactic gamma-ray absorption. The presence of magnetic fields around the GRB sources causes the deflectio n of the accelerated protons and so a temporal spread of the produced high- energy gamma-rays with respect to the signal in the soft gamma-ray band. Mo reover, we analyze the possibility to detect the gamma-ray signal in the Ge V-TeV energy range by the ARGO detector under construction in Tibet.