Stellar Evolution with Enriched Surface Convection Zones I. General Effects of Planet Consumption

Abundance analyses of stars with planets have revealed that their metallicities are enhanced relative to field stars. Such a trend was originally suggested to be due to accretion of iron-rich planetary material. Based on this assumption, we have developed a stellar evolution code to model stars with non-uniform metallicity distributions. We have calculated “polluted” stellar evolution tracks for stars with M=0.9–1.2 M⊙. Our models encompass a range of initial metal content from Z=0.01 to 0.03, and include metallicity enhancements within the stellar convection zone corresponding to ∆Z=0.005-0.03. We find that the primary effects of metal enhancement on stellar structure and evolution are expansion of the convection zone and downward shift of effective temperature. In addition, we have computed the surface metallicities expected for stars of different mass for fixed quantities of pollution; there appears to be no correlation with present observational data on the metallicities of stars known to harbor planets. Subject headings: planetary systems — stars: abundances — stars: chemically peculiar — stars:evolution — stars:individual(HD 209458)