Cross-ionisation effects in reverse-shocked iron ejecta

Determine the cross-ionisation effects between different ionised species in non-equilibrium ionisation models of the reverse-shocked iron ejecta of SNR 0509-67.5, in order to assess their impact on predicted coronal-line surface brightnesses.

Background

The paper compares observed Fe coronal-line surface brightnesses in SNR 0509-67.5 with two one-dimensional analytical models. The model with enhanced Fe abundance and density reproduces several observed lines, particularly [Fe XIV] and [Fe IX], but does not provide a fully satisfactory explanation for all of the observations.

The authors explicitly identify cross-ionisation effects between different ionised species as unknown. Such effects could alter the calculated ion populations and line emissivities, and therefore represent an unresolved modeling issue for accurately interpreting the ionisation structure and emission strengths of reverse-shocked ejecta. They also note that the ejecta may not be uniformly denser by a factor of two, but the explicitly identified unknown in the quoted sentence is the cross-ionisation physics.