New estimation of the nuclear de-excitation line emission from the supernova remnant Cassiopeia A

TL;DR

This paper estimates nuclear de-excitation line emissions from supernova remnant Cassiopeia A to aid in understanding low-energy cosmic rays, highlighting the model dependence of predicted fluxes and detection prospects.

Contribution

It provides the first detailed flux predictions for nuclear de-excitation lines from Cassiopeia A considering various cosmic ray spectra and interaction models.

Findings

Predicted fluxes vary significantly with model assumptions.

Strong narrow line emissions are detectable within certain flux ranges.

Detection probability depends on instrument response and background conditions.

Abstract

MeV nuclear de-excitation lines serve as a unique tool to study low-energy cosmic rays (CRs), containing both spectral and elemental information of the interacting material. In this paper, we estimated the possible nuclear de-excitation lines from the young supernova remnant Cassiopeia A. Given different CR spectral shapes and interacting materials, we found the predicted fluxes of strong narrow line emissions from the remnant are highly model-dependent, ranging from about $1\times10^{-10}\,{\rm \,cm^{-2}\,s^{-1}}$ to $1\times10^{-6}\, {\rm \,cm^{-2}\,s^{-1}}$ for the 4.44 MeV narrow line and from about $4\times10^{-11}\,{\rm \,cm^{-2}\,s^{-1}}$ to $2\times10^{-7}{\rm \,cm^{-2}\,s^{-1}}$ for the 6.13 MeV narrow line, respectively. Based on the new estimation, we also discussed the detection probability of these line emissions against the MeV diffuse Galactic background under different assumptions of instrument response functions.