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

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 (ΔΠ1) of red-giant stars that ignite He burning in degenerate conditions (M ≤ 2.0 M⊙). We also compare the predictions of these models with Kepler observations. For a given Δv, ΔΠ1 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 stars and regardless of the transport processes occurring in their interiors, the observed ΔΠ1 can provide information as to their stellar luminosity, within ~10-20 per cent. In general, the trends of ΔΠ1 with respect to mass and metallicity that are observed in Kepler red-giant stars are well reproduced by the models.