Mass dependence of overshooting beneath convective envelopes

Abstract

Although the dependence of convective core overshooting on mass has attracted much attention, no corresponding work exists for overshooting below a convective envelope. We aim to quantify this relationship for pre-main sequence stars of intermediate mass ranging from $1.2 M_{\mathsf{sun}}$ to $6 M_{\mathsf{sun}}$. These stars have a similar thermal and density structure, making this a suitable choice to isolate the effect of changing mass. We produce a series of two-dimensional global simulations of stars using MUSIC, a fully compressible, time-implicit hydrodynamics code. The stars that we select for this study are near the end of the pre-main sequence and are convectively unstable above 80% of their stellar radius; they thus have a convective envelope that is shallower than the current sun. For this series of stellar models, a simple scaling with luminosity, with a scaling exponent of 1/4, accounts for the increasing overshooting with stellar mass. This result has interesting similarities with the scaling found by Baraffe et al. [2023] for a range of intermediate mass and massive stars at the zero-age main sequence (ZAMS) that have convective cores.