Convective Penetration in Early-Type Stars

TL;DR

This paper applies a recent theory of convective penetration to predict mixing in early-type stars, showing it can explain observed core sizes and providing a practical formula for the extent of mixing across a wide mass range.

Contribution

It adapts and tests a new theory of convective penetration to quantify core mixing in early-type stars, aligning predictions with observational data.

Findings

Convective penetration accounts for observed core masses.

The theory matches trends in star mass and age.

A fitting formula for core mixing extent is provided.

Abstract

Observations indicate that the convective cores of stars must ingest a substantial amount of material from the overlying radiative zone, but the extent of this mixing and the mechanism which causes it remain uncertain. Recently, Anders et al. (2021) developed a theory of convective penetration and calibrated it with 3D numerical hydrodynamics simulations. Here we employ that theory to predict the extent of convective boundary mixing in early-type main-sequence stars. We find that convective penetration produces enough mixing to explain core masses inferred from asteroseismology and eclipsing binary studies, and matches observed trends in mass and age. While there are remaining uncertainties in the theory, this agreement suggests that most convective boundary mixing in early-type main-sequence stars arises from convective penetration. Finally, we provide a fitting formula for the extent of core convective penetration for main-sequence stars in the mass range from $1.1-60 M_\odot$.