Radial White Dwarf Accretion

Abstract

We discuss radial accretion flow onto white dwarfs for which cyclotron emission is insignificant. We show that a stationary bombardment solution exists for not too large accretion rates in which the accretion energy is transferred to the target atmosphere within one collisional mean free path and then radiated at much lower temperatures than in the shock model. Further, we propose a non-stationary model in which the inhomogeneity of the accretion flow ensures no stand off shock and that the accretion energy is liberated deep in the stellar atmosphere and radiated away predominantly at XUV wavelengths.