An Analytical Density Profile of Dense Circumstellar Medium in Type II Supernovae

Abstract

Observations of Type II supernovae imply that a large fraction of its progenitors experience enhanced mass loss years to decades before core collapse, creating a dense circumstellar medium (CSM). Assuming that the CSM is produced by a single mass eruption event, we analytically model the density profile of the resulting CSM. We find that a double power-law profile gives a good fit to the CSM profile obtained using radiation hydrodynamical simulations. With our profile the CSM is well described by just two parameters, the transition radius r * and density at r = r * (alternatively r * and the total CSM mass). We encourage future studies to include this profile, if possible, when modelling emission from interaction-powered transients.