Rotational mixing in tidally locked massive main-sequence binaries

TL;DR

This paper investigates how tidal synchronization in massive binary stars influences internal rotational mixing, affecting surface chemical abundances, and proposes eclipsing binaries as a test for mixing efficiency.

Contribution

It introduces detailed models of massive binaries with tidal effects, highlighting their potential to constrain internal mixing processes.

Findings

Surface nitrogen can be enhanced by up to 0.6 dex due to tidal mixing.

Eclipsing binaries offer a promising observational test for internal mixing efficiency.

Models are based on the composition of the Small Magellanic Cloud.

Abstract

One of the main uncertainties in evolutionary calculations of massive stars is the efficiency of internal mixing. It changes the chemical profile inside the star and can therefore affect the structure and further evolution. We demonstrate that eclipsing binaries, in which the tides synchronize the rotation period of the stars and the orbital period, constitute a potentially strong test for the efficiency of rotational mixing. We present detailed stellar evolutionary models of massive binaries assuming the composition of the Small Magellanic Cloud. In these models we find enhancements in the surface nitrogen abundance of up to 0.6 dex.