title: Fast-moving features in the debris disk around AU Microscopii.
abstract: In the 1980s, excess infrared emission was discovered around main-sequence stars; subsequent direct-imaging observations revealed orbiting disks of cold dust to be the source. These 'debris disks' were thought to be by-products of planet formation because they often exhibited morphological and brightness asymmetries that may result from gravitational perturbation by planets. This was proved to be true for the β Pictoris system, in which the known planet generates an observable warp in the disk. The nearby, young, unusually active late-type star AU Microscopii hosts a well-studied edge-on debris disk; earlier observations in the visible and near-infrared found asymmetric localized structures in the form of intensity variations along the midplane of the disk beyond a distance of 20 astronomical units. Here we report high-contrast imaging that reveals a series of five large-scale features in the southeast side of the disk, at projected separations of 10-60 astronomical units, persisting over intervals of 1-4 years. All these features appear to move away from the star at projected speeds of 4-10 kilometres per second, suggesting highly eccentric or unbound trajectories if they are associated with physical entities. The origin, localization, morphology and rapid evolution of these features are difficult to reconcile with current theories.
authors.affiliation: LESIA, Observatoire de Paris, CNRS, Université Paris Diderot, Université Pierre et Marie Curie, 5 place Jules Janssen, 92190 Meudon, France.
authors.forename: Anthony
authors.initials: A
authors.lastname: Boccaletti
authors.affiliation: ETH Zürich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Thalmann
authors.affiliation: Université Grenoble Alpes, IPAG, F-38000 Grenoble, France.|CNRS, IPAG, F-38000 Grenoble, France.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Lagrange
authors.affiliation: Department of Astronomy, Stockholm University, SE-106 91 Stockholm, Sweden.|Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Janson
authors.affiliation: Université Grenoble Alpes, IPAG, F-38000 Grenoble, France.|CNRS, IPAG, F-38000 Grenoble, France.
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Augereau
authors.affiliation: Steward Observatory, 933 North Cherry Avenue, The University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Glenn
authors.initials: G
authors.lastname: Schneider
authors.affiliation: CNRS, IPAG, F-38000 Grenoble, France.|European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile.
authors.forename: Julien
authors.initials: J
authors.lastname: Milli
authors.affiliation: Eureka Scientific, 2452 Delmer, Suite 100, Oakland, California 96002, USA.
authors.forename: Carol
authors.initials: C
authors.lastname: Grady
authors.affiliation: Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA.
authors.forename: John
authors.initials: J
authors.lastname: Debes
authors.affiliation: Centre de Recherche Astrophysique de Lyon, (CNRS/ENS-L/Université Lyon 1), 9 avenue Charles André, 69561 Saint-Genis-Laval, France.|Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France.
authors.forename: Maud
authors.initials: M
authors.lastname: Langlois
authors.affiliation: Université Grenoble Alpes, IPAG, F-38000 Grenoble, France.|CNRS, IPAG, F-38000 Grenoble, France.
authors.forename: David
authors.initials: D
authors.lastname: Mouillet
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Henning
authors.affiliation: University of Amsterdam, Anton Pannekoek Institute for Astronomy, Science Park 904 1098 XH Amsterdam, The Netherlands.
authors.forename: Carsten
authors.initials: C
authors.lastname: Dominik
authors.affiliation: INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy.
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Maire
authors.affiliation: Université Grenoble Alpes, IPAG, F-38000 Grenoble, France.|CNRS, IPAG, F-38000 Grenoble, France.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Beuzit
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.|Department of Physics and Astronomy, College of Charleston, South Carolina, 29424, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Carson
authors.affiliation: Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France.
authors.forename: Kjetil
authors.initials: K
authors.lastname: Dohlen
authors.affiliation: ETH Zürich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland.
authors.forename: Natalia
authors.initials: N
authors.lastname: Engler
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Feldt
authors.affiliation: Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France.|ONERA-The French Aerospace Laboratory, 92322 Châtillon, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Fusco
authors.affiliation: Sterrewacht Leiden, PO Box 9513, Niels Bohrweg 2, NL-2300RA Leiden, The Netherlands.
authors.forename: Christian
authors.initials: C
authors.lastname: Ginski
authors.affiliation: CNRS, IPAG, F-38000 Grenoble, France.|European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile.
authors.forename: Julien H
authors.initials: JH
authors.lastname: Girard
authors.affiliation: Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA.
authors.forename: Dean
authors.initials: D
authors.lastname: Hines
authors.affiliation: CNRS, IPAG, F-38000 Grenoble, France.|European Southern Observatory (ESO), Karl Schwarzschild Strasse 2, 85748 Garching bei München, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Kasper
authors.affiliation: Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, California 91125, USA.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Mawet
authors.affiliation: UMI-FCA, CNRS/INSU France (UMI 3386), and Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Correo Central, Santiago, Chile.
authors.forename: François
authors.initials: F
authors.lastname: Ménard
authors.affiliation: ETH Zürich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Meyer
authors.affiliation: Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Moutou
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.
authors.forename: Johan
authors.initials: J
authors.lastname: Olofsson
authors.affiliation: Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington DC 20015, USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Rodigas
authors.affiliation: Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France.|ONERA-The French Aerospace Laboratory, 92322 Châtillon, France.
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Sauvage
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.|NASA Ames Research Center, Space Science and Astrobiology Division, MS 245-6, Moffett Field, California 94035, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Schlieder
authors.affiliation: ETH Zürich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland.
authors.forename: Hans Martin
authors.initials: HM
authors.lastname: Schmid
authors.affiliation: INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Turatto
authors.affiliation: Observatoire de Genève, University of Geneva, 51 Chemin des Maillettes, 1290 Versoix, Switzerland.
authors.forename: Stephane
authors.initials: S
authors.lastname: Udry
authors.affiliation: Laboratoire J.-L. Lagrange, Observatoire de la Côte d'Azur (OCA), Université de Nice-Sophia Antipolis (UNS), CNRS, Campus Valrose, 06108 Nice Cedex 2, France.
authors.forename: Farrokh
authors.initials: F
authors.lastname: Vakili
authors.affiliation: European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile.|Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France.
authors.forename: Arthur
authors.initials: A
authors.lastname: Vigan
authors.affiliation: European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile.|Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France.
authors.forename: Zahed
authors.initials: Z
authors.lastname: Wahhaj
authors.affiliation: Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, Oklahoma 73019, USA.
authors.forename: John
authors.initials: J
authors.lastname: Wisniewski