  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 planet's 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 planet's 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 planet's 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.
