Energy spectrum of ultra high energy γ-rays from supernova

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 (Lp/1041 ergs)(S/(50 m)2)(d/56 kpc)-2 and 132 counts (Lp/1041 ergs)(S/30000 m2)(d/56 kpc)-2 where Lp, S and d are the proton luminosity, the area of detectors, and the distance to LMC, respectively. (author)