Constraints on rotational mixing from surface evolution of light elements in massive stars

TL;DR

This study tests rotational mixing models in massive stars by tracking surface light element abundances, finding that current prescriptions can explain most observations but uncertainties remain significant.

Contribution

Extended the Geneva stellar evolution code with light element reactions to evaluate rotational mixing effects in massive stars.

Findings

Faster rotation leads to quicker depletion of light isotopes.

More massive stars show more significant light element depletion.

Current mixing models align with most observed surface abundance patterns.

Abstract

Context. Light elements and nitrogen surface abundances together can constrain the mixing efficiencies in massive stars on the main sequence, because moderate mixing at the surface leads to a depletion of light elements but only later to an enrichment in nitrogen. Aims. We want to test the rotational mixing prescriptions included in the Geneva stellar evolution code (GENEC) by following the evolution of surface abundances of light isotopes in massive stars. Methods. The GENEC is a 1D code containing sophisticated prescriptions for rotational mixing. We implemented an extended reaction network into this code including the light elements Li, Be and B, which allowed us to perform calculations testing the rotation induced mixing. Results. We followed 9, 12 and 15 solar mass models with rotation from the zero age main sequence up to the end of He burning. The calculations show the expected behaviour with faster depletion of light isotopes for faster rotating stars and more massive stars. Conclusions. We find that the mixing prescriptions used in the present rotating models for massive single stars can account for most of the observations. However the uncertainties are quite large making it hard to draw a firm conclusion on the mixing scenario.