The Effects of Metallicity on Convective Overshoot Behaviour in Models of delta Scuti Variable Stars

TL;DR

This study investigates how metallicity influences convective overshoot and pulsation properties in delta Scuti stars, revealing a metallicity-dependent relationship between pulsation constant and effective temperature.

Contribution

It extends previous models by incorporating metallicity variation, showing its impact on convective overshoot behavior and pulsation characteristics in delta Scuti stars.

Findings

Convective boundary treatment affects overshoot dependence.

Rotation and overshoot influence the slope of Q vs. Teff.

Metallicity impacts the pulsation constant Q, especially at low metallicities.

Abstract

delta Scuti variables are stars which exhibit periodic changes in their luminosity through radial and non-radial pulsations. Internally, these stars have relatively small convective cores, and convective overshoot can significantly affect the size. Recently, models of radial pulsation in delta Scuti stars found a strong correlation between the pulsation constant (Q) as a function of effective temperature and the amount of convective overshoot within the star. However, only models with metallicities of Z = 0.02 were examined, leaving the dependence of this relationship on chemical composition unknown. In this work, we have extended the models' pulsation properties using GYRE. By varying the models' mass, rotation speed, convective overshoot, and metallicity, we studied the behaviour of Q at low temperature. We found that the updated convective boundary treatment in MESA changes the overshoot dependence found previously, and the value of the slope depends on both rotation and overshoot. We also found that there is a metallicity dependence in the Q values. The lowest metallicity models in our grid reached higher temperatures than previously studied, revealing a parabolic relation between log Q and log Teff.