TeV photons from gamma-ray bursts

Abstract

We show that the massive production of ultra-energetic photons is unavoidable in cosmological Gamma-Ray Bursts (GRBs) as far as the synchrotron-self-Compton emission mechanism is assumed to be the main one. Using the primary result of our analisys — that the observed emission is of synchrotron origin — we derive information on the physical parameters of GRB emitting regions. The parameters found imply that at least few per cent of the energy initially deposited in sub-MeV domain is converted into ultra-energetic photons due to the inverse Compton scattering off electrons accelerated in relativistic shocks. Hence, GRBs should be the brightest sources in the corresponding spectral range, several orders of magnitude more luminous than active galactic nuclei. Taking into account angular resolution of Cherenkov telescopes, we expect that TeV gamma-ray flux from a typical GRB is comparable to the background. The energies of ultra-hard photons from GRBs typically exceed 1 TeV, in some cases approaching 100 TeV. Together with high luminosity and the possibility to carry out simultaneous observations at other wavelengths, this makes GRBs an ideal probes for the two-photon absorption by the infrared background radiation at high redshifts. The presented theory of ultra-hard GRB emission is necessary for the interpretation of new observations started at MILAGRO and planned by other groups.