4 Conclusions

The results presented here show that the accretion of planetary material by a solar-type star will produce an enhancement of the stellar surface abundance of lithium which could be observable during a large fraction of the main sequence lifetime. Within the framework of the standard model, the $T_{\rm eff}$ range where the ingested $^6{\rm Li}$ could be detected is 5900-6400 K. The upper limit is imposed by observational evidence given by the Li-Gap in the Hyades (Boesgaard & Tripicco 1986). The lower limit is the result of direct convective mixing and should increase about 100 or 200 K when extra-mixing processes are considered. The $T_{\rm eff}$ range where $^7{\rm Li}$ would survive is larger. Therefore, a very valuable test for planetary migration/accretion scenarios can be provided by high-resolution spectroscopic observations of ^6,7Li in planet host stars.