Testing convective-core overshooting using period spacings of dipole modes in red giants

TL;DR

This paper proposes a method to test the extent of convective-core overshooting in red giants using period spacings of dipole modes, linking observable data to internal stellar mixing processes.

Contribution

It introduces a novel approach to constrain core mixing in stellar evolution by analyzing period spacings in red giants, supported by stellar models and observations.

Findings

Period spacing correlates with helium core mass.

Average period spacing depends linearly on convective core size.

Evidence suggests extra mixing during the helium-burning phase.

Abstract

Uncertainties on central mixing in main sequence (MS) and core He-burning (He-B) phases affect key predictions of stellar evolution such as late evolutionary phases, chemical enrichment, ages etc. We propose a test of the extension of extra-mixing in two relevant evolutionary phases based on period spacing Delta_P of solar-like oscillating giants. From stellar models and their corresponding adiabatic frequencies (respectively computed with ATON and LOSC codes) we provide the first predictions of the observable Delta_P for stars in the red giant branch (RGB) and in the red clump (RC). We find: i) a clear correlation between Delta_P and the mass of the helium core (M_He); the latter in intermediate-mass stars depends on the MS overshooting, hence it can be used to set constraints on extra mixing during MS when coupled with chemical composition; ii) a linear dependence of the average value of the asymptotic period spacing (<Delta_P>_a) during the He-B phase on the size of the convective core. A first comparison with the inferred asymptotic period spacing for Kepler RC stars suggests the need for extra mixing also during this phase, as evinced from other observational facts.