Possible stellar metallicity enhancements from the accretion of planets

A number of recently discovered extrasolar planet candidates have surprisingly small orbits, which may indicate that considerable orbital migration takes place in protoplanetary systems. A natural consequence of orbital migration is for a series of planets to be accreted, destroyed, and then thoroughly mixed into the convective envelope of the central star: We study the ramifications of planet accretion for the final main-sequence metallicity of the star. If maximum disk lifetimes are on the order of similar to 10 Myr, stars with masses near 1.0 M-circle dot are predicted to have virtually no metallicity enhancement. On the other hand, early F-and late A-type stars with masses M-* approximate to 1.5-2.0 M circle dot can experience significant metallicity enhancements due to their considerably smaller convection zones during the first 10 Myr of pre-main-sequence evolution. We show that the metallicities of an aggregate of unevolved F stars are consistent with an average star accreting similar to 2 Jupiter-mass planets from a protoplanetary disk having a 10 Myr dispersal time.