Stellar interiors revealed by internal waves and mixed modes

The principle of asteroseismology is to use stellar oscillations as seismic waves to reveal the properties of deep stellar interiors. This method is certainly the most efficient and elegant to sound the invisible regions of a star. The field of asteroseismology has undergone a revolution thanks to space missions which provide high quality observations of oscillation modes at the surface of stars.

These oscillations reveal the complexity of stellar interiors and provide constraints on key physical processes, such as convection, mixing, rotation or magnetic fields. Many questions, however, remain regarding the physical properties of waves propagating in the deep interior and their interpretation when detected at the stellar surface.

In this project, we propose a study based on innovative multi-dimensional hydrodynamical simulations of waves excited by convection and used by asteroseismology to reveal the properties of the deepest layers in stars. The proposal is divided into two complementary studies. We first plan to study internal gravity waves and mixed modes in evolved low mass stars.

Mixed modes play an important role on the rotation of the cores of these stars and provide information on the rotational properties of their cores. We plan to describe the properties of these waves in the deep interior thanks to numerical simulations, in order to advance their theoretical understanding.

We also plan to study internal gravity waves in massive stars which are excited deep in the deep interior by convective motions and propagate towards the surface where they could be detected. We plan to perform challenging numerical simulations extending close to the stellar surface in order to confirm whether these waves can reach the stellar surface and explain the observed variability of these stars.

As the two studies are performed within the same numerical framework, this project will contribute to the general understanding of internal waves under various stellar contexts. We propose unique and challenging numerical simulations of mixed modes, which have never been performed so far and which will provide a breakthrough in the field.