Very high energy phenomena in GRBs

Reviews production of very high energy particles and expected radiations from them in the standard relativistic blastwave model of GRBs. Electrons and protons can be accelerated in the internal shock of GRBs up to ~10/sup 14/ and 10/sup 20/ eV, respectively, and GRBs are one of the possible sites of the production of ultra high energy cosmic rays observed on the Earth. Three radiation processes can be considered for very high energy gamma-ray production: inverse- Compton, photo-pion production, and proton synchrotron, all of which could be an efficient energy loss process of GRBs. Photo-pion production is also interesting as the high energy neutrino emission mechanism. Internal absorption of hadron-origin gamma-rays may be crucial for the energetics of GRBs in the soft gamma-ray bands. The evidence of TeV emission from GRB 970417 A can best be interpreted by the synchrotron radiation of 10/sup 20/ eV protons. (20 refs).