A hydrodynamic scheme for two-component winds from hot stars

TL;DR

This paper presents a new time-dependent two-component hydrodynamics code for simulating radiatively-driven stellar winds from hot stars, capable of modeling both well-coupled and poorly coupled wind scenarios.

Contribution

The authors developed a novel explicit-implicit hydrodynamics scheme to accurately simulate two-component stellar winds, including Coulomb collision effects and wind decoupling phenomena.

Findings

Reproduces mCAK solution for poorly coupled winds

Demonstrates wind decoupling in well-coupled wind models

Provides stable numerical results despite problem stiffness

Abstract

We have developed a time-dependent two-component hydrodynamics code to simulate radiatively-driven stellar winds from hot stars. We use a time-explicit van Leer scheme to solve the hydrodynamic equations of a two-component stellar wind. Dynamical friction due to Coulomb collisions between the passive bulk plasma and the line-scattering ions is treated by a time-implicit, semi-analytic method using a polynomial fit to the Chandrasekhar function. This gives stable results despite the stiffness of the problem. This method was applied to model stars with winds that are both poorly and well-coupled. While for the former case we reproduce the mCAK solution, for the latter case our solution leads to wind decoupling.