Work

From core to envelope: Revealing the deep dynamics of stars with two convective zones

Year: 2026

Type: article

Abstract: On the Hertzsprung-Russell diagram, F-type solar pulsators connect the Sun to intermediate-mass stars located on the instability strip. With respect to lower-mass stars, they are structurally peculiar in the sense that they are constituted of three distinct dynamical layers: a small convective core, a deep radiative interior, and a shallow convective envelope. Current asteroseismic techniques only provide limited information on the interior dynamics of these stars. Indeed only gravity modes ( g modes), for which unambiguous characterisation is lacking, are able to probe the deep stellar layers. A better understanding of the excitation and behaviour in F-type solar pulsators is therefore necessary in order to consider their detection. In this work, we simulate the global stellar structure of an F-type star (core, radiative interior, envelope) for the first time. We show that the contribution of the core strongly affects the spectrum of excited g modes, with low-order high-degree modes unable to form due to their interaction with the turbulent convection of the core. Finally, by computing the disc-integrated signature of the modes, we are able to demonstrate that they preserve their integrity up to the top of the convective envelope, which is a strong argument in favour of their detectability with space-borne photometry.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202659634

Authors: S. N. Breton, A. S. Brun, R. A. García