TeV emission of Gamma-Ray Bursts as an instrument to test the universe at high redshifts Original Research Article

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. 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 cosmic ray flux from a typical GRB is comparable to the background. The energies of VHE 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. Observations of sub-TeV cosmic rays from GRBs even with moderate spectral resolution should provide important information about the evironment of GRB progenitors, the star formation history and large-scale inhomogeneity of the Universe.