The effects of metallicity on convective overshoot behaviour in models of (delta) Scuti stars

Abstract

Delta Scuti variables are stars which exhibit periodic changes in their luminosity through radial and non-radial pulsations of their surfaces. The aim of this research is to gain a better understanding of those stars' behaviours through an expansion of the findings of Lovekin and Guzik, which found a strong correlation between Delta Scuti stars' 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, prompting the question of if this relation is dependent on chemical composition. I collected the data in this research through creation of a grid of stellar models using the open-source coding language MESA, and analyzed the models pulsation properties using the complementary coding language GYRE. By varying the models mass, rotation speed, convective overshoot, and metallicity it was determined that the relationship found by Lovekin and Guzik does hold for stars of other metal compositions and may have a quantifiable metallicity dependence, although statistically weak. In addition, a second relation between Q as a function of effective temperature and convective overshoot was discovered at higher effective temperatures as well. The cause of this new relation was found to be due to the deepest surface convection zone depth of the models.