Relationship between oscillatory thermal instability and dynamical thin-shell overstability of radiative shocks

Abstract

We give an analytic treatment of radiative cooling behind radiative shocks following solutions given by Chevalier and Imamura. We demonstrate that within the approximation of a steady state radiative shock, the radiative cooling laws Lambda is proportional to Talpha that give rise to the oscillatory instability modeled by Chevalier and Imamura in gamma=5/3 cooling gas are stable to the dynamical thin-shell overstability in this gas, and vice versa. We also show that the fundamental features of the dynamical overstability observed by Grun et al. can also be understood on these bases.