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Sökning: WFRF:(Menard Franois)

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1.
  • Boccaletti, Anthony, et al. (författare)
  • Fast-moving features in the debris disk around AU Microscopii
  • 2015
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 526:7572, s. 230-
  • Tidskriftsartikel (refereegranskat)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(1). 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 beta Pictoris system, in which the known planet generates an observable warp in the disk(2-5). 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(6-9). 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.
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2.
  • Kooistra, Robin, et al. (författare)
  • Radial decoupling of small and large dust grains in the transitional disk RX J1615.3-3255
  • 2017
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 597
  • Tidskriftsartikel (refereegranskat)abstract
    • We present H-band (1.6 mu m) scattered light observations of the transitional disk RX J1615.3-3255, located in the similar to 1 Myr old Lupus association. From a polarized intensity image, taken with the HiCIAO instrument of the Subaru Telescope, we deduce the position angle and the inclination angle of the disk. The disk is found to extend out to 68 +/- 12 AU in scattered light and no clear structure is observed. Our inner working angle of 24 AU does not allow us to detect a central decrease in intensity similar to that seen at 30 AU in the 880 mu m continuum observations. We compare the observations with multiple disk models based on the spectral energy distribution (SED) and submm interferometry and find that an inner rim of the outer disk at 30 AU containing small silicate grains produces a polarized intensity signal which is an order of magnitude larger than observed. We show that a model in which the small dust grains extend smoothly into the cavity found for large grains is closer to the actual H-band observations. A comparison of models with di ff erent dust size distributions suggests that the dust in the disk might have undergone significant processing compared to the interstellar medium.
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