Gamma-rays produced in cosmic-ray interactions and the TeV-band spectrum of RX J1713.7-3946

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 shock-accelerated hadronic cosmic rays. This scenario implies a very high efficacy of particle acceleration, so the particle spectrum is expected to continuously harden toward high energies on account of cosmic-ray modification of the shock. Using the χ2 statistics we find that a continuously softening spectrum is strongly preferred, in contrast to expectations. A hardening spectrum has about 1% probability to explain the HESS data, but then only if a hard cut-off at 50-100 TeV is imposed on the particle spectrum.