Gamma-Rays Produced in Cosmic-Ray Interactions and the TeV-band Spectrum of RX J1713.7-3946

Abstract

We employ the Monte Carlo particle collision code DPMJET3.04 to determine the multiplicity spectra of various secondary particles (in addition to π0’s) with γ’s as the final decay state, that are produced in cosmic‐ray (p’s and α’s) interactions with the interstellar medium. We derive an easy‐to‐use γ‐ray production matrix for cosmic rays with energies up to about 10 PeV, This γ‐ray production matrix is applied to the GeV excess in diffuse Galactic γ‐rays observed by EGRET, and we conclude the non‐π0 decay components are insufficient to explain the GeV excess, although they have contributed a different spectrum from the π0‐decay component. We also test the hypothesis that the TeV‐band γ‐ray emission of the shell‐type SNR RX J1713.7‐3946 observed with HESS is caused by hadronic cosmic rays which are accelerated by a cosmic‐ray modified shock. By the χ2 statistics, we find a continuously softening spectrum is strongly preferred, in contrast to expectations. A hardening spectrum has about 1% probability to e...