Steady state models of white dwarfs accreting helium or carbon/oxygen-rich matter

Abstract

The authors have calculated steady state models of white dwarfs which accrete helium or carbon/oxygen (C+O)-rich matter. The helium accreting model consists of a highly degenerate C+O core and a helium burning shell, overlaid by a helium envelope. The C+O accreting model consists of a highly degenerate O+Ne+Mg core, a carbon burning shell, and a C+O envelope. For the C+O accreting white dwarfs, there exist minimum accretion rates below which no steady state solution exists. For accretion rates above the minimum value, there exist two branches of solutions: compact and normal branches. All the models in the compact branch are thermally unstable.