M411_10b 166..170

tional settling or meridional circulation). Cosmic-ray nucleosynthesis models and observations of interstellar clouds indicate that the primordial ratio, f(Li), in the protoplanetary matter could have been as high as 0.3±0.5, which in turn would allow either the possibility of some Li depletion in the star or the ingestion of planets with even smaller mass. In this scenario we have assumed that the planet(s) was (were) ingested after the stellar convective envelope had shrunk, 10±30 Myr after stellar birth, and had reached its current mass and depth. The timescale is comparable to the lifetime of protoplanetary disks (10±20 Myr) and planetary migration. Our results favour a scenario in which a planet was engulfed owing to the multi-body interactions in the system that can take place over a timescale of 100 Myr. This is strongly supported by the highly eccentric orbit of the planetary companion of HD82943 (about 0.6). However, we hesitate to generalize it to explain the metal-rich nature of other stars hosting planets. Further Li isotopic ratio studies of a large sample of planet-bearing stars can help to put additional constraints on this scenario. Note added in proof: A second planet with a minimum mass of 0.88MJ has been discovered orbiting HD82943, with a period of 220 days (M. Mayor, personal communication). This detection has been done with the CORALIE spectrograph at the ESO La Silla Observatory. M