γ-rays from discrete radio sources

Abstract

The fluxes of low energy (∼100 MeV) and high energy (∼5×1012 eV)γ-rays from intense radio sources have been calculated under the hypothesis that radio electrons are continuously produced through nuclear collisions. The effect of expansion of the source which gives rise to a decrease in production rate with time has been taken into account in these calculations. It is found that the fluxes expected from nuclear collision process are generally higher than the fluxes from other processes like bremstrahlung and inverse compton scattering by factors of 10 or more. While the calculated fluxes ofγ-rays of energy >100 MeV are less than the observed upper limits for all the processes, the fluxes calculated for nuclear collision process for E>5×1012 eV, exceed the experimental upper limits for Crab, Cas A and the jet in Virgo A. More sensitive experiments should be able to decide whether the nuclear collision process is ruled out for low energies as well: in this respect Cas A seems to be the most promising source.