High Energy Gamma Rays from Protons Hitting Compact Objects

Understand

In a previous paper the spectrum of positrons produced by matter initially at rest falling onto a massive compact object was calculated.

• In this paper this calculation is generalized to obtain both the spectrum of in-flight positron annihilation and pi0 decay gamma rays produced when protons with a cosmic ray-like spectrum hit the surface.
• The resulting pi0 decay gamma ray spectrum reflects the high energy proton energy spectrum, and is largely independent of the mass of the compact object.
• One notable prediction for all compact objects is a dip in the spectrum below 70 MeV.