Tidal interaction between an extrasolar planet and its host star

Some of the extrasolar planets that have been detected in the last 20 years are on an orbit which is very close to their host star. Tidal interaction between the planet and the star may then induce oscillations at the surface of the star. Such oscillations would produce an observational signal that could be misinterpreted as being due to an additional planet. This project aims at calculating the characteristics of those tidal oscillations for a variety of planets, and at studying whether they could affect the indirect observation of planets.

The project will focus on A-type stars, as they have a radiative envelope. Gravity modes excited in such a star by a close planetary companion have a larger amplitude at the surface than in a less massive star with a convective envelope. The gravity modes forced in a A-type star by a close planet will be calculated, and this signal will then be added to that produced by the motion of the star around the centre of mass of the system. Given this total signal, it will be calculated whether the characteristics of the planet present around the star can be recovered, or whether false information is induced.