Rotation and its interaction with pulsations in stars
Institut d'Astrophysique et de Géophysique, Université de Liège
Stellar rotation plays a key role in the evolution of stars. It causes mixing of chemical elements and transport of angular momentum inside the star which will strongly determine the star's history. Asteroseismology is the most efficient observational mean to get information about stellar interiors. But rotation also impacts these seismic pulsations: the centrifugal force distorts the resonant cavity while the Coriolis force modifies the fluid dynamics. Therefore, in order to get relevant information about the stellar structure from asteroseismology, one should reach a good understanding of the rotational effect on stellar pulsations.
On the one hand, when rotation velocity is small, a perturbative approach gives satisfying results for the computations of the rotational impact on oscillations. This is the case for solar-like stars, for instance. Based on the perturbative treatment, I will show how, given two indicators of rotation in photometric light curves, I was able to determine possible rotation profiles in two stars observed by CoRoT.
However, when the perturbative approach is no longer relevant, for rapid rotators, I built a non-perturbative, two-dimensional code which fully takes into account both centrifugal distorsion and Coriolis force. The code has been validated, and it is now operational. After a short presentation of the ACOR code, I will tackle its applications in two different seismic situations: stars with high surface velocities, and which oscillate in acoustic modes probing the centrifugally distorted outer layers, such as δScuti stars, and cooler stars with very low surface velocities, but rapidly rotating cores, and which oscillate in mixed modes (gravito-acoustic modes) located both in the core and the envelop such as in sub-giant or red giant stars.
14 junho 2012, 13:30
Centro de Astrofísica
Rua das Estrelas