Population III Wolf-Rayet Stars in the CAK Regime

TL;DR

This paper estimates the mass-loss rate of Population III Wolf-Rayet stars using a modified CAK model, finding very low but non-zero mass-loss rates driven by core burn products, even at zero initial metallicity.

Contribution

It introduces a modified CAK approach to calculate mass-loss rates for Population III WR stars, highlighting the lower limit set by core composition.

Findings

Mass-loss rate between 2x10^{-9} and 3x10^{-8} solar masses per year.

Mass-loss driven by core burn products persists at zero initial metallicity.

Optimal parameters include electron density ≥ 10^{13} cm^{-3} and Gamma between 0.5 and 0.7.

Abstract

Wolf-Rayet (WR) stars near solar metallicity are believed to be driven by radiation pressure on the UV spectral lines of metal ions. As the metallicity decreases so does the line opacity, therefore the mass-loss rate. However, since the composition of a WR atmosphere is determined by the burn products of the core, there is a lower limit on the line opacity -- and therefore the mass-loss rate -- of a WR star, even in a star with zero initial metallicity. This presentation is the result of attempt to calculate the mass-loss rate of a Population III-type WO star using a modified version of the CAK approximation. I find that n_e greater than or equal to 10^{13} cm^{-3} and Gamma between 0.5 and 0.7 give the most plausible results, with the resulting mass-loss rate between 2x10^{-9} M_sun yr^{-1} and 3x10^{-8} M_sun yr^{-1}.