Charge Exchange X-ray Emission Detected in Multiple Shells of Supernova Remnant G296.1-0.5

TL;DR

This study provides evidence of charge exchange X-ray emission in multiple shells of supernova remnant G296.1-0.5, supported by spectral analysis and radio observations indicating molecular cloud interactions.

Contribution

First detection of charge exchange X-ray emission in multiple shells of a supernova remnant, combining high-resolution spectroscopy and radio data.

Findings

High forbidden-to-resonance ratio in O VII lines suggests charge exchange presence.

Charge exchange occurs in a thin layer at the SNR shell, consistent with theoretical models.

Molecular clouds are associated with the shells where charge exchange is detected.

Abstract

Recent high-resolution X-ray spectroscopy revealed possible presence of charge exchange (CX) X-ray emission in supernova remnants (SNRs). Although CX is expected to take place at outermost edges of SNR shells, no significant measurement has been reported so far due to the lack of nearby SNR samples. Here we present an X-ray study of SNR G296.1$-$0.5, which has a complicated multiple-shell structure, with the Reflection Grating Spectrometer (RGS) onboard XMM-Newton. We select two shells in different regions and find that in both regions O VII line shows a high forbidden-to-resonance ($f/r$) ratio that cannot be reproduced by a simple thermal model. Our spectral analysis suggests a presence of CX and the result is also supported by our new radio observation, where we discover evidence of molecular clouds associated with these shells. Assuming G296.1$-$0.5 has a spherical shock, we estimate that CX is dominant in a thin layer with a thickness of 0.2--0.3\% of the shock radius. The result is consistent with a previous theoretical expectation and we therefore conclude that CX occurs in G296.1$-$0.5.