Close binary evolution based on Gaia DR2: the origin of late WC-type Wolf-Rayet stars with low luminosity

TL;DR

This paper investigates how binary star evolution, particularly mass transfer in close binaries, can explain the origin of low-luminosity late WC Wolf-Rayet stars, which single-star models fail to reproduce.

Contribution

It demonstrates that binary evolution models, including Roche lobe overflow, can account for the formation of low-luminosity WC stars, providing a new perspective on their origins.

Findings

Binary evolution explains low-luminosity WC stars.

Mass transfer alters stellar structure and surface composition.

Single-star models are insufficient for these stars.

Abstract

The observed late-type WC Wolf-Rayet stars (WC7-9) with low luminosity below $\rm \log L/L_{\odot} < 5.4$ in the HR diagram cannot be reproduced satisfactorily by the evolutionary track of single stars. The mass transfer due to Roche lobe overflow drastically modifies the internal structure and surface compositions of two components. Therefore, binaries provide a very promising evolutionary channel to produce these WC stars.