COMETARY-LIKE BODIES IN THE PROTOPLANETARY DISK AROUND BETA-PICTORIS

Repeated spectroscopic observations of beta Pictoris have been performed since 1985 and revealed the presence, in many metallic lines like Ca II, Mg II, Fe II, ..., of strong sporadic circumstellar absorption, redshifted by tens to hundreds of km s-1 with respect to the star and highly time-variable (time-scales of days or hours). We have tentatively interpreted these variable events as the spectral signature of infalling cometary-like bodies, when evaporating in the vicinity of the star. This scenario has been furthermore theoretically studied, and we showed that it could indeed explain correctly the observations with their peculiar characteristics, like (1) the behavior difference between visible and UV lines, (2) the unusual line ratios, (3) the surprising presence of Al III absorption lines. Constraints deduced from both observational data and theoretical study allowed us to suggest that a planet within the disk could be responsible, by perturbations, of this high rate infall of small bodies towards the star (> 100 per year).