Non-adiabatic study of γ Doradus stars, application to low metallicity stars and binary interactions
Loïc Fellay, University of Liège
γ Doradus stars, which span spectral types A7 to F5, exhibit g-mode instabilities driven by convective flux blocking at the base of their convective envelopes. Accurately modelling their instability strips requires non-adiabatic stellar oscillation codes that incorporate a time-dependent treatment of convection–oscillation interactions, such as MAD.
In this seminar, I will present our current understanding of their instability strips and the excitation of oscillation modes by convective flux blocking, including the effects of rotation and metallicity. I will then discuss two main applications of this knowledge in the context of non-adiabatic asteroseismology.
The first application focuses on low-metallicity γ-Doradus stars observed by Kepler in the open field. For these stars, we find significant discrepancies between the modelled and observed instability strips. I will explore possible explanations for these differences and discuss what physical constraints we can infer for such stars.
The second application concerns the interactions within binary systems through tidally excited oscillations, which drive exchanges of energy and angular momentum between the orbit and the stellar components. In this context, non-adiabatic oscillation modelling is essential. I will show how the rotational and orbital evolution of binary systems hosting γ Doradus stars is influenced by the growth and damping of tidally excited oscillations across the entire γ-Doradus main sequence.