Gamma-ray spectrum of RX J1713.7-3946 in the Fermi era and future detection of neutrinos

¹ Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan e-mail: ryo@theo.phys.sci.hiroshima-u.ac.jp; katagiri@hep01.hepl.hiroshima-u.ac.jp
² Physics Department, Lancaster University, LA1 4YB, UK e-mail: k.kohri@lancaster.ac.uk

Received: 22 August 2008
Accepted: 5 December 2008

Abstract

The recently launched satellite, Fermi Gamma-ray Space Telescope , is expected to find out if cosmic-ray (CR) protons are generated from supernova remnants (SNRs), especially RX J1713.7-3946, by observing the GeV-to-TeV γ-rays. The GeV emission is thought to be bright if the TeV emission is hadronic, i.e., of proton origin, while dim if leptonic.
We reexamine the above view using a simple theoretical model of nonlinear acceleration of particles to calculate the gamma-ray spectrum of Galactic young SNRs.
 If the nonlinear effects of CR acceleration are considered, it may be impossible to distinguish the evidence of proton acceleration from leptonic in the γ-ray spectrum of Galactic young SNRs like RX J1713.7-3946. On the other hand, future km³-class neutrino observations will likely find a clear evidence of the proton acceleration there.