TITLE: Exocomets in the circumstellar gas disk of Beta Pictoris
ABSTRACT: The young planetary system surrounding Beta Pictoris harbors active minor bodies. Spectroscopic observations of Beta Pictoris reveal a high rate of transits of small evaporating bodies, i.e. exo-comets (Kiefer et al. 2014). I will report the analysis of more than thousand spectra collected with HARPS between 2003 and 2011, providing a sample of about 6000 variable absorption signatures due to transiting exocomets. Statistical analysis of the observed properties of these exocomets reveals that they belong to two distinct populations with highly different physical properties. A first family, producing shallow absorption lines, can be attributed to old exhausted comets, possibly trapped in a mean motion resonance with a massive planet; while a second family, producing deep absorption lines, is possibly related to the recent fragmentation of a few parent bodies.
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