Testing the cores of first ascent red-giant stars using the period spacing of g modes

TL;DR

This study investigates how rotation and core overshooting influence the period spacing of gravity modes in red-giant stars, using models and Kepler data to improve stellar property determinations.

Contribution

It demonstrates that the asymptotic period spacing of g modes can reveal stellar luminosity and core properties, accounting for mixing processes and observational data.

Findings

Observed $\Delta \Pi_1$ correlates with stellar luminosity within 10-20%.

Models reproduce the observed trends of $\Delta \Pi_1$ with mass and metallicity.

Rotation and overshooting effects are significant in interpreting asteroseismic data.

Abstract

In the context of the determination of stellar properties using asteroseismology, we study the influence of rotation and convective-core overshooting on the properties of red-giant stars. We used models in order to investigate the effects of these mechanisms on the asymptotic period spacing of gravity modes ($\Delta \Pi_1$) of red-giant stars that ignite He burning in degenerate conditions (M$\lesssim$2.0 M$_{\odot}$). We also compare the predictions of these models with Kepler observations. For a given $\Delta\nu$, $\Delta \Pi_1$ depends not only on the stellar mass, but also on mixing processes that can affect the structure of the core. We find that in the case of more evolved red-giant-branch (RGB) stars and regardless of the transport processes occurring in their interiors, the observed $\Delta \Pi_1$ can provide information as to their stellar luminosity, within ~10-20%. In general, the trends of $\Delta \Pi_1$ with respect to mass and metallicity that are observed in Kepler red-giant stars are well reproduced by the models.