Probing the properties of convective cores through g modes: high-order g modes in SPB and gamma Doradus stars

TL;DR

This paper develops an analytical model for high-order g modes in main sequence stars, revealing how core chemical gradients influence their periods and offering insights for asteroseismology of SPB and gamma Doradus stars.

Contribution

It introduces an analytical approximation for high-order g modes that accounts for the mu gradient, enhancing understanding of stellar core properties and mode spectra.

Findings

Period spacing is affected by the mu gradient location and sharpness.

Chemical mixing alters g-mode spectra significantly.

The model applies to stars with 1-10 solar masses.

Abstract

In main sequence stars the periods of high-order gravity modes are sensitive probes of stellar cores and, in particular, of the chemical composition gradient that develops near the outer edge of the convective core. We present an analytical approximation of high-order g modes that takes into account the effect of the mu gradient near the core. We show that in main-sequence models, similarly to the case of white dwarfs, the periods of high-order gravity modes are accurately described by a uniform period spacing superposed to an oscillatory component. The periodicity and amplitude of such component are related, respectively, to the location and sharpness of the mu gradient. We investigate the properties of high-order gravity modes for stellar models in a mass domain between 1 and 10 Msun, and the effects of the stellar mass, evolutionary state, and extra-mixing processes on period spacing features. In particular, we show that for models of a typical SPB star, a chemical mixing that could likely be induced by the slow rotation observed in these stars, is able to significantly change the g-mode spectra of the equilibrium model. Prospects and challenges for the asteroseismology of gamma Doradus and SPB stars are also discussed.