Possibility of direct observations of supernovae reverse-shock accelerated ions via broad gamma lines
Phys. Rev. D 114, 043037 – Published 17 August, 2026
DOI: https://doi.org/10.1103/xm75-49mc
Abstract
We are investigating the possibilities to directly detect the presence of heavy ions accelerated by supernova remnants (SNRs) reverse shocks. For this purpose we model the spectrum of 0.1–10 MeV gamma-ray emission produced by accelerated ejecta ions interacting with ambient protons. The resulting spectral lines are broad and have complex shapes due to the Doppler-broadening of anisotropic nuclear emission. We focus on young, historical Galactic SNRs; SN 1006, Tycho, Kepler, and Cassiopeia A. For each remnant, we compute total line fluxes and compare them with the projected sensitivities of future gamma-ray missions (e-ASTROGAM, COSI, and AMEGO). Our findings indicate that Cassiopeia A is the most promising candidate, for which we predict a peak intensity of for the 6.13 MeV oxygen line. However, under realistic parameters, the flux maximum only marginally exceeds the e-ASTROGAM sensitivity threshold (), while lines from other species fall below detectability. Thus, only under favorable conditions—such as enhanced acceleration efficiency or a concave particle spectrum—could the oxygen line be detectable, making Cas A a key target for future MeV missions.
