title: Two families of exocomets in the β Pictoris system.
abstract: The young planetary system surrounding the star β Pictoris harbours active minor bodies. These asteroids and comets produce a large amount of dust and gas through collisions and evaporation, as happened early in the history of our Solar System. Spectroscopic observations of β Pictoris reveal a high rate of transits of small evaporating bodies, that is, exocomets. Here we report an analysis of more than 1,000 archival spectra gathered between 2003 and 2011, which provides a sample of about 6,000 variable absorption signatures arising from exocomets transiting the disk of the parent star. Statistical analysis of the observed properties of these exocomets allows us to identify two populations with different physical properties. One family consists of exocomets producing shallow absorption lines, which can be attributed to old exhausted (that is, strongly depleted in volatiles) comets trapped in a mean motion resonance with a massive planet. Another family consists of exocomets producing deep absorption lines, which may be related to the recent fragmentation of one or a few parent bodies. Our results show that the evaporating bodies observed for decades in the β Pictoris system are analogous to the comets in our own Solar System.
authors.affiliation: 1] Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France [2] Université Pierre et Marie Curie, UMR 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France [3] School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: F
authors.initials: F
authors.lastname: Kiefer
authors.affiliation: 1] Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France [2] Université Pierre et Marie Curie, UMR 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France.
authors.forename: A Lecavelier
authors.initials: AL
authors.lastname: des Etangs
authors.affiliation: Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France.
authors.forename: J
authors.initials: J
authors.lastname: Boissier
authors.affiliation: 1] Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France [2] Université Pierre et Marie Curie, UMR 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France.
authors.forename: A
authors.initials: A
authors.lastname: Vidal-Madjar
authors.affiliation: Université Joseph Fourier-Grenoble 1/CNRS- Institut National des Sciences de l'Univers, Institut de Planétologie et d'Astrophysique de Grenoble, UMR 5274, 414 Rue de la Piscine, 38400 St-Martin d'Hères, France.
authors.forename: H
authors.initials: H
authors.lastname: Beust
authors.affiliation: Université Joseph Fourier-Grenoble 1/CNRS- Institut National des Sciences de l'Univers, Institut de Planétologie et d'Astrophysique de Grenoble, UMR 5274, 414 Rue de la Piscine, 38400 St-Martin d'Hères, France.
authors.forename: A-M
authors.initials: AM
authors.lastname: Lagrange
authors.affiliation: 1] Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France [2] Université Pierre et Marie Curie, UMR 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France.
authors.forename: G
authors.initials: G
authors.lastname: Hébrard
authors.affiliation: 1] Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France [2] Université Pierre et Marie Curie, UMR 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, F-75014 Paris, France.
authors.forename: R
authors.initials: R
authors.lastname: Ferlet