  Exoplanets host stars present a clear metallicity excess compared to stars
without detected planets, with an average overabundance of 0.2 dex. This excess
may be primordial, in which case the stars should be overmetallic down to their
center, or it may be due to accretion in the early phases of planetary
formation, in which case the stars would be overmetallic only in their outer
layers. In the present paper, we show the differences in the internal structure
of stars, according to the chosen scenario. Namely two stars with the same
observable parameters (luminosity, effective temperature, outer chemical
composition) are completely different in their interiors according to their
past histories, which we reconstitute through the computations of their
evolutionary tracks. It may happen that stars with an initial overmetallicity
have a convective core while the stars which suffered accretion do not. We
claim that asteroseismic studies of these exoplanets host stars can give clues
about their internal structures and metallicities, which may help in
understanding planetary formation.
