Studying the internal structure of exoplanet-host stars compared to that of similar stars 
without detected planets is particularly important for the understanding of planetary 
formation and evolution. The observed overmetallicity of stars around which planets have 
been detected (which means that they have migrated from their initial location) may be a 
hint in that respect. 
Asteroseismic studies represent an excellent tool to determine the internal structure of 
exoplanet-host stars. It also leads to constraints on their external parameters (gravity, 
effective temperature, metallicity) more precise than obtained from spectroscopy. The 
determination of the mass and age of the star is also better constrained. 
After a general discussion on this subject, I will present the special cases of three 
different stars: $\mu$ Arae, observed with the HARPS spectrograph in June 2004 for 
asteroseismology, which also lead to the detection of a low-mass planet, $\iota$ Horologii, 
which we have precisely modelised and observed with HARPS in November 2006, and HD 52265, 
one of the main targets of the COROT mission, an exoplanet-host star which will be observed 
with the COROT satellite during five consecutive months.


Recent papers :
- Laymand, M ; Vauclair, S. 2006, Asteroseismology of exoplanets host stars: the special 
case of $\iota$ Horologii (HD17051, )A&A, in presse (astro-ph/0610501)
- Bazot, M.; Vauclair, S.; Bouchy, F.; Santos, N. C. 2005, Seismic analysis of the 
planet-hosting star μ Arae,  A&A, 440, 615
- Bouchy, F.; Bazot, M.; Santos, N. C.; Vauclair, S.; Sosnowska, D. 2005, Asteroseismology 
of the planet-hosting star μ Arae.  The acoustic spectrum,  A&A, 440, 609
- Bazot, M.; Vauclair, S. 2004, Asteroseismology of exoplanets hosts stars: Tests of 
internal metallicity,   A&A, 427, 965
- Santos, N. C.; Bouchy, F…… Vauclair,S. 2004,  The HARPS survey for southern extra-solar 
planets. II. A 14 Earth-masses exoplanet around μ Arae,  A&A, 426L, 19