Particle Acceleration in Tycho's SNR

Supernova remnants (SNRs) have long been considered prime candidates for cosmic‐ray sources in our Galaxy. Observations of SNRs in TeV gamma‐rays can help in solving the problem of the origin of cosmic rays and are key to understanding the mechanism of particle acceleration at a propagating shock wave. Tycho's SNR belongs to a rare subclass of Galactic SNRs' known as historical supernovae; the supernova was observed by Tycho Brahe in 1572. Tycho's SNR has been widely studied across the electromagnetic spectrum. Non‐thermal emission from Tycho's SNR has been detected in radio and X‐rays. These studies show a shell‐like morphology of Tycho's SNR, whose configuration results in the efficient cosmic ray acceleration at the supernova shock. Thus, Tycho's SNR has become a candidate for the investigation of particle acceleration in SNR shocks at high and very high‐energies. At TeV energies, the SHALON telescopes discovered emission with a hard spectrum, extending from 800 GeV up to 80 TeV, correlated with the supernova shells contributing to the very‐high‐energy gamma‐ray flux. A nonlinear kinetic model of cosmic‐ray acceleration in SNRs was applied to Tycho's SNR to compare the observed TeV gamma‐ray emission spectra with the model predictions. The collected experimental data support the theoretical prediction of a hadronic mechanism of generation of very‐high‐energy (800 GeV–100 TeV) gamma‐rays from Tycho's SNR.