Stochastic Electron Acceleration in the TeV Supernova Remnant RX J1713.7-3946: The High-Energy Cut-off

TL;DR

This paper investigates how fast-mode waves can accelerate electrons in supernova remnants, explaining observed gamma-ray spectra and high-energy cutoffs, even with weak magnetic fields, through turbulence modeling and shock physics.

Contribution

It demonstrates that fast-mode waves can efficiently accelerate electrons in supernova remnants, providing a viable explanation for observed high-energy emissions in the leptonic scenario.

Findings

Kraichnan turbulence models produce shallower high-energy cutoffs.

The models fit Fermi gamma-ray observations of supernova remnants.

Lower downstream densities are required in Kraichnan models to match spectra.

Abstract

In the leptonic scenario for TeV emission from a few well-observed shell-type TeV supernova remnants (STTSNRs), very weak magnetic fields are inferred. If fast-mode waves are produced efficiently in the shock downstream, we show that they are viable agents for acceleration of relativistic electrons inferred from the observed spectra even in the subsonic phase, in spite that these waves are subject to strong damping by thermal background ions at small dissipation scales. Strong collisionless non-relativistic astrophysical shocks are studied with the assumption of a constant Aflven speed in the downstream. The turbulence evolution is modeled with both the Kolmogorov and Kraichnan phenomenology. Processes determining the high-energy cutoff of nonthermal electron distributions are examined. The Kraichnan models lead to a shallower high-energy cutoff of the electron distribution and require a lower downstream density than the Kolmogorov models to fit a given emission spectrum. With reasonable parameters, the model explains observations of STTSNRs, including recent data obtained with the Fermi gamma-ray telescope. More detailed studies of the turbulence generation and dissipation processes, supernova explosions and progenitors are warranted for better understanding the nature of supernova shocks.