Abstract

Massive stars are the main contributors of the interstellar medium enrichment. These stars are usually fast rotators, with a radiative envelope in which the interaction between stratification and rotation gives rise to a differential rotation. Besides, many of these stars are classical pulsators.

I will present quickly an attempt at modelling a well-described fast rotator, in two dimensions, using asteroseismic constraints. Even though this first approach was unsuccessful, it highlighted the need of a better understanding of the oscillations’ properties.

Our work focuses therefore on the impact of a differential rotation on the low-frequency oscillation spectrum which contains gravito-inertial modes. These modes are restored by the combination of buoyancy and Coriolis force. They probe deep layers of stars. We study them using two methods: we compute the paths of characteristics in the non-dissipative limit, and solve the fully-dissipative eigenvalue problem numerically using a spectral method. We find various singularities (attractors, critical latitudes, corotation resonances) and regular modes. Some of these modes are excited by baroclinic instabilities that may saturate through non-linear effects. If so, we have discovered a new excitation mechanism for these modes, driven by differential rotation.