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

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 $1\times 10^{-10}\, {\rm \, cm^{-2}\, s^{-1}}$ to $1\times 10^{-6}\, {\rm \, cm^{-2}\, s^{-1}}$ for the 4.44 MeV narrow line and from about $4\times 10^{-11}\, {\rm \, cm^{-2}\, s^{-1}}$ to $2\times 10^{-7}{\rm \, cm^{-2}\, s^{-1}}$ 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.