Photon–photon pair production and the opacity of SN1987A to TeV and PeV γ-rays

Abstract

Supernovae have long been considered as likely sites of cosmic-ray acceleration. Interaction of newly accelerated cosmic-ray nuclei with target material within the expanding supernova is expected to produce an observable flux from SN1987A of very high-energy and possibly ultra high-energy γ-rays in the TeV and PeV (1015 eV) ranges, and several experiments are being constructed to detect this radiation. The presence of intense infrared emission from the supernova itself will, however, make some regions of SN1987A opaque to TeV and PeV γ-rays due to pair-production interactions. Observations at these energies, combined with a knowledge of which regions of SN1987A could be contributing γ-rays may thus give information about the nature and location of particle accelerators in supernovae. Here I discuss the important question of photon–photon pair-production interactions and calculate from which regions of SN1987A may be observed TeV and PeV γ-rays.