The Role of Diffusive Shock Acceleration on Nonequilibrium Ionization in Supernova Remnant Shocks II: Emitted Spectra

TL;DR

This paper models the X-ray spectra of supernova remnants considering efficient diffusive shock acceleration, highlighting how ionization and emission diagnostics vary with acceleration efficiency and emphasizing the importance of self-consistent hydrodynamic and ionization calculations.

Contribution

It introduces a self-consistent grid of nonequilibrium ionization models that incorporate both thermal and nonthermal emissions in supernova remnant shocks with efficient cosmic-ray acceleration.

Findings

Plasma diagnostics like G'-ratio vary with acceleration efficiency.

Thermal X-ray emission differs when ionization is not coupled with hydrodynamics.

Moderate acceleration (~35%) models show distinct X-ray signatures.

Abstract

We present a grid of nonequilibrium ionization models for the X-ray spectra from supernova remnants undergoing efficient diffusive shock acceleration. The calculation follows the hydrodynamics of the blast wave as well as the time-dependent ionization of the plasma behind the shock. The ionization state is passed to a plasma emissivity code to compute the thermal X-ray emission, which is combined with the emission from nonthermal synchrotron emission to produce a self-consistent model for the thermal and nonthermal emission from cosmic-ray dominated shocks. We show how plasma diagnostics such as the G'-ratio of He-like ions, defined as the ratio of the sum of the intercombination, forbidden, and satellite lines to the resonance line, can vary with acceleration efficiency, and discuss how the thermal X-ray emission, when the time-dependent ionization is not calculated self-consistently with the hydrodynamics, can differ from the thermal X-ray emission from models which do account for the hydrodynamics. Finally we compare the thermal X-ray emission from models which show moderate acceleration (~ 35%) to the thermal X-ray emission from test-particle models.