Alteration of Chemical Abundances from Infall of Planetary Material
The study of the properties of the stars with planets reveal a clear correlation between the frequency of planets and the stellar metellicity. Two alternative explanations have been proposed: either high metallicity makes the planet formation easier (because of large dust content in the proto planetary disk) or the abundances of the star with planets are polluted by the infall of metal-rich rocky material. To test the pollution hypothesis, binary systems can be used, performing high precision differential abundance analysis.
Indeed, for pairs with similar components, such as those studied in the SARG Planet search, and stars with thin enough convective zones, it is possible to achieve sensitivities down to the abundance changes caused by the ingestion of a few Earth masses of rocky material, similar to the amount of rocky material that should have been accreted by the Sun during its main sequence lifetime.
The results of the study of about 50 pairs show that most of the pairs have abundance difference smaller than 0.03 dex. We found only one case (HD 113984) with a large (0.25 dex) abundance difference. The primary of this binary appears to be a blue straggler, and the abundance difference might be due to the peculiar evolution of the star. This suggests that phenomena of planetary pollution during main sequence lifetime of solar type stars are not common.
People: R. Gratton, S. Desidera, R. Claudi, S. Lucatello
Collaboration: G. Bonanno, R. Cosentino, S. Scuderi (INAF OA Catania), A.F. Martizez Fiorenzano (TNG)
Publications: Desidera et al. (2007) A&A 462,1039