Modeling Convective Core Overshoot and Diffusion in Procyon Constrained by Asteroseismic Data

TL;DR

This study uses asteroseismic data to refine stellar models of Procyon, revealing that including diffusion and a higher degree of core overshoot improves model accuracy and internal mixing understanding.

Contribution

It introduces a Bayesian analysis approach to constrain core overshoot and diffusion in Procyon models using asteroseismic data, highlighting the importance of model frequency type.

Findings

Most probable models include helium and metal diffusion.

Core overshoot between 0.9 and 1.5 pressure scale heights.

Models with higher overshoot better match asteroseismic data.

Abstract

We compare evolved stellar models, which match Procyons mass and position in the HR diagram, to current ground-based asteroseismic observations. Diffusion of helium and metals along with two conventional core overshoot descriptions and the Kuhfuss nonlocal theory of convection are considered. We establish that one of the two published asteroseismic data reductions for Procyon, which mainly differ in their identification of even versus odd l-values, is a significantly more probable and self-consistent match to our models than the other. The most probable models according to our Bayesian analysis have evolved to just short of turnoff, still retaining a hydrogen convective core. Our most probable models include Y and Z diffusion and have conventional core overshoot between 0.9 and 1.5 pressure scale heights, which increases the outer radius of the convective core by between 22% to 28%, respectively. We discuss the significance of this comparatively higher than expected core overshoot amount in terms of internal mixing during evolution. The parameters of our most probable models are similar regardless of whether adiabatic or nonadiabatic model p-mode frequencies are compared to the observations, although, the Bayesian probabilities are greater when the nonadiabatic model frequencies are used. All the most probable models (with or without core overshoot, adiabatic or nonadiabatic model frequencies, diffusion or no diffusion, including priors for the observed HRD location and mass or not) have masses that are within one sigma of the observed mass 1.497+/-0.037 Msun.