Line Driven Instabilities due to Continuum Radiation Transport in Stellar Winds

Abstract: We study line driven stellar winds using time-dependent radiation hydrodynamics where the continuum radiation couples to the gas via either a scattering or absorption opacity and there is an additional radiation force due to spectral lines that we model in the Sobolev approximation. We find that in winds with scattering opacities, instabilties tend to be suppressed and the wind reaches a steady state. Winds with absorption opacities are unstable and remain clumpy at late times. Clumps persist because they are continually regenerated in the subcritical part of the flow. Azimuthal gradients in the radial velocity distribution cause a drop in the radial radiation force and provide a mechanism for generating clumps. These clumps form on super-Sobolev scales, but at late times become Sobolev-length sized indicating that our radiation transfer model is breaking down. Inferring the clump distribution at late times therefore requires radiation-hydrodynamic modeling below the Sobolev scale.