On the diversity of mixing and helium core masses of B-type dwarfs from gravity-mode asteroseismology

TL;DR

This study uses asteroseismology to analyze internal mixing profiles and helium core masses of 26 B-type pulsating stars, revealing the diversity and uncertainties in stellar interior models and their impact on stellar evolution predictions.

Contribution

It provides the first detailed comparison of mixing profiles in B-type stars using Kepler data, highlighting the degeneracy and preferred mixing mechanisms in stellar interiors.

Findings

Unambiguous mixing profiles for 5 stars.

Convective penetration favored in ~55% of cases.

Helium core mass estimates are highly sensitive to envelope mixing.

Abstract

The chemical evolution of the Galaxy is largely guided by the yields from massive stars. Their evolution is heavily influenced by their internal mixing, allowing the stars to live longer and yield a more massive helium core at the end of their main-sequence evolution. Asteroseismology is a powerful tool for studying stellar interiors by providing direct probes of the interior physics of the oscillating stars. This work revisits the recently derived internal mixing profiles of 26 slowly pulsating B stars observed by the Kepler space telescope, in order to investigate how well the mixing profiles can in fact be distinguished from one another as well as provide predictions for the expected helium core masses obtained at the end of the main-sequence evolution. We find that for five of these stars the mixing profile is derived unambiguously, while the remaining stars have at least one other mixing profile which explains the oscillations equally well. Convective penetration is preferred over exponential diffusive overshoot for ~55% of the stars, while stratified mixing is preferred in the envelope (~39%). We estimate the expected helium core masses obtained at the end of the main-sequence evolution and find them to be highly influenced by the estimated amount of mixing occurring in the envelopes of the stars.