Nonlinear shock acceleration and gamma-ray emission from Tycho and Kepler

TL;DR

This paper models the shock acceleration processes in Tycho and Kepler supernova remnants, revealing efficient cosmic ray acceleration up to hundreds of TeV and magnetic field amplification, with implications for gamma-ray emission detection.

Contribution

It applies non-linear diffusive shock acceleration theory to two supernova remnants, providing detailed predictions of cosmic ray acceleration and gamma-ray emission.

Findings

Protons are accelerated up to ~500 TeV in both remnants.

Magnetic fields are amplified up to ~300 microG.

Tycho's gamma-ray spectrum is explained by pion decay.

Abstract

We apply the non-linear diffusive shock acceleration theory in order to describe the properties of two supernova remnants, SN 1572 (Tycho) and SN 1604 (Kepler). By analyzing the multi-wavelength spectra, we infer that both Tycho's and Kepler's forward shocks are accelerating protons up to ~500 TeV, channeling into cosmic rays more than 10 per cent of their kinetic energy. We find that the streaming instability induced by cosmic rays is consistent with the X-ray morphology of the remnants, indicating a very efficient magnetic field amplification (up to ~300 microG). In the case of Tycho we explain the gamma-ray spectrum from the GeV up to the TeV band as due to pion decay produced in nuclear collisions by accelerated nuclei scattering against the background gas. On the other hand, due to the larger distance, the gamma-ray emission from Kepler is not detected, being below the sensitivity of the present detectors, but it should be detectable by the Cerenkov Telescope Array.