The photospheres of stars hosting planets have larger metallicity than stars lacking planets. In the present work we study the possibility of an earlier metal enrichment of the photospheres by means of impacting planetesimals during the first 20-30Myr. Here we explore this contamination process by simulating the interactions of an inward migrating planet with a disc of planetesimal interior to its orbit. The results show the percentage of planetesimals that fall on the star. We identified the dependence of the planets eccentricity ($e_p$) and time scale of migration ($tau$) on the rate of infalling planetesimals. For very fast migrations ($tau=10^2$yr and $tau=10^3$yr) there is no capture in mean motion resonances, independently of the value of $e_p$. Then, due to the planets migration the planetesimals suffer close approaches with the planet and more than 80% of them are ejected from the system. For slow migrations ($tau=10^5$yr and $tau=10^6$yr) the percentage of collisions with the planet decrease with the increase of the planets eccentricity. For $e_p=0$ and $e_p=0.1$ most of the planetesimals were captured in the 2:1 resonance and more than 65% of them collided with the star. Whereas migration of a Jupiter mass planet to very short pericentric distances requires unrealistic high disc masses, these requirements are much smaller for smaller migrating planets. Our simulations for a slowly migrating 0.1 $M_{rm Jupiter}$ planet, even demanding a possible primitive disc three times more massive than a primitive solar nebula, produces maximum [Fe/H] enrichments of the order of 0.18 dex. These calculations open possibilities to explain hot Jupiters exoplanets metallicities.
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