The Power of Optical/IR Interferometry: Recent Scientific Results and 2nd Generation Instrumentation

Part of the series Eso Astrophysics Symposia pp 71-82

Limb Darkening: Getting Warmer

  • J. P. AufdenbergAffiliated withNational Optical Astronomy Observatory
  • , H.-G. LudwigAffiliated withLund Observatory, Lund University
  • , P. KervellaAffiliated withObservatorie de Paris-Meudon, LESIA, UMR 8109
  • , A. MérandAffiliated withObservatorie de Paris-Meudon, LESIA, UMR 8109
  • , S. T. RidgwayAffiliated withNational Optical Astronomy ObservatoryObservatorie de Paris-Meudon, LESIA, UMR 8109
  • , V. Coudé du ForestoAffiliated withObservatorie de Paris-Meudon, LESIA, UMR 8109
  • , T. A. ten BrummelaarAffiliated withMt. Wilson Observatory, The CHARA Array
  • , D. H. BergerAffiliated withMt. Wilson Observatory, The CHARA Array
  • , J. SturmannAffiliated withMt. Wilson Observatory, The CHARA Array
    • , N. H. TurnerAffiliated withMt. Wilson Observatory, The CHARA Array

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We present interferometric observations and model atmosphere analyses of three stars: the F-type subgiant Procyon, the A-type supergiant Deneb, and the B-type supergiant Rigel. We use VLTI/VINCI and Mark III observations of Procyon to test recent multiwavelength limb-darkening predictions from 3-D hydrodynamic atmosphere simulations with no free parameters for convection. We also investigate the effects of different 1-D atmospheric convection treatments on limb-darkening predictions. We show that the 3-D model predictions are confirmed and we find that 1-D models fail to reproduce Procyon’s UV spectral energy distribution, a result consistent with models of granulation for Procyon’s surface. We use observations employing the longest baselines of the CHARA Array together with the FLUOR beam combiner to determine precise angular diameters for the two early-type supergiants and test limb-darkening predictions from expanding atmosphere models of these tars’ stellar winds. For Deneb, we derive angular diameters consistent with previous measurements, but which vary with position angle at the ≃3% level. Observations of the 2nd lobe of Deneb’s visibility curve are more consistent with expanding atmosphere predictions than hydrostatic atmosphere predictions. For Rigel, we derive from the CHARA/FLUOR observations a limb-darkened angular diameter consistent with a recent VLTI/IONIC measurement and 8% larger than reported from the Intensity Interferometer.