Effects of stratification on overshooting and waves atop the convective core of $5M_{\odot}$ main-sequence stars

TL;DR

This study uses 2D simulations to analyze how helium stratification in 5 solar mass stars affects convective overshooting and internal gravity waves, revealing that evolved stratification inhibits mixing and wave excitation.

Contribution

It provides new insights into how helium stratification impacts convective overshoot and wave dynamics in main-sequence stars, with detailed simulation results across evolutionary stages.

Findings

Helium stratification hinders convective overshoot.

Internal gravity waves are less excited in evolved stars.

Wave power decreases significantly in later evolutionary stages.

Abstract

As a massive star evolves along the main sequence, its core contracts, leaving behind a stable stratification in helium. We simulate 2D convection in the core at three different stages of evolution of a $5M_{\odot}$ star, with three different stratifications in helium atop the core. We study the propagation of internal gravity waves in the stably-stratified envelope, along with the overshooting length of convective plumes above the convective boundary. We find that the stratification in helium in evolved stars hinders radial motions and effectively shields the radiative envelope against plume penetration. This prevents convective overshooting from being an efficient mixing process in the radiative envelope. In addition, internal gravity waves are less excited in evolved models compared to the zero-age-main-sequence model, and are also more damped in the stratified region above the core. As a result, the wave power is several orders of magnitude lower in mid- and terminal-main-sequence models compared to zero-age-main-sequence stars.