Energy Spectrum of Ultra High Energy -Rays from Supernova

Abstract

If a newly born neutron star in SN1987A is a powerful injector of ultra high energy (UHE) protons, UHE γ-rays will be emitted by bombardment of supernova ejecta with these UHE particles. We compute energy spectrum of the UHE γ-rays generated by monoenergetic protons using Monte-Carlo simulations at the period of high flux when the column density is 30 ∼ 100 g/cm². If the column density of the ejecta is less than ∼ 100 g/cm², low energy γ-rays do not increase as E^-2, like the case for Cyg X-3, but they have much harder spectrum close to E^-1. The expected numbers of PeV and TeV region γ-rays per hour are at least 0.16 counts (L_p/10⁴¹ ergs)(S/(50 m)²)(d/56 kpc)^-2 and 132 counts (L_p/10⁴¹ ergs)(S/30000 m²)(d/56 kpc)^-2 where L_p, S and d are the proton luminosity, the area of detectors, and the distance to LMC, respectively.