On the radio spectra of supernova remnants

TL;DR

This review explains the theoretical foundations of supernova remnant radio spectra, predicting their shapes based on shock acceleration mechanisms and comparing them with observations to aid astronomers.

Contribution

It provides a comprehensive theoretical framework for understanding SNR radio spectra, including new predictions for various spectral shapes and an observational comparison.

Findings

Different spectral shapes predicted for young and evolved SNRs

Inclusion of Fermi 2 and thermal bremsstrahlung processes explains older SNR spectra

Comparison with observed spectra validates theoretical models

Abstract

The theoretical fundamentals of formation of the supernova remnant (SNR) continuum radio spectra are presented in this review. Mainly based on the Fermi 1 theory - also known as diffuse shock acceleration (DSA) - the different shapes (linear or curved in log-log scale) of SNR radio spectra are predicted for both young and evolved SNRs. On the other hand, some particular forms of spectra of older SNRs can be predicted by including the additional processes such as Fermi 2 acceleration mechanism or thermal bremsstrahlung radiation. Also, all of these theoretically predicted forms of radio spectra are compared with real spectra obtained from observations. Finally this review can represent some kind of "atlas" with initial patterns for the different kinds of SNR radio spectra - it should be helpful for radio astronomers in their interpretation of the observed radio spectra.