Gamma rays from reaccelerated particles at supernova remnant shocks

Abstract

Diffusive shock acceleration is considered as the main mechanism for particle energization in supernova remnants, as well as in other classes of sources. The existence of some remnants that show a bilateral morphology in the X-rays and gamma rays suggests that this process occurs with an efficiency that depends upon the inclination angle between the shock normal and the large scale magnetic field in which the shock propagates. This interpretation is additionally supported by recent particle-in-cell simulations that show how ions are not injected if the shock is more oblique than $\sim 45^o$. These shocks provide an excellent test bench for the process of reacceleration at the same shock: non-thermal seed particles that are reached by the shock front are automatically injected and accelerated. This process was recently discussed as a possible reason for some anomalous behaviour of the spectra of secondary cosmic ray nuclei. Here we discuss how gamma--ray observations of selected supernova remnants can provide us with precious information about this process and lead us to a better assessment of particle diffusive shock reacceleration for other observables in cosmic ray physics.

9 pages, 6 figures, Accepted for publication in MNRAS

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• Cosmic-ray acceleration and escape from post-adiabatic Supernova remnants
• Particle acceleration at colliding shock waves
• Gamma rays and neutrinos from RX J1713.7-3946 in a lepto-hadronic scenario
• The population of Galactic supernova remnants in the TeV range
• Hadronic particle acceleration in the supernova remnant SN 1006 as traced by Fermi-LAT observations
• Fermi-LAT detection of GeV $\gamma$-ray emission from Type Ia supernova remnant G272.2-3.2
• On the stochastic nature of Galactic cosmic-ray sources
• Runaway stars and the Galactic supernova remnant landscape: non-thermal emission and observational evidence