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Stellar to Substellar Model Atmospheres

Published online by Cambridge University Press:  23 April 2012

France Allard ,
Derek Homeier  and
Bernd Freytag
France Allard
Affiliation:
Centre de Recherche Astrophysique de Lyon, UMR 5574, CNRS, Université de Lyon, École Normale Supérieure de Lyon, 46 Allée d'Italie, F-69364 Lyon Cedex 07, France, email: france.allard@ens-lyon.fr
Derek Homeier
Affiliation:
Centre de Recherche Astrophysique de Lyon, UMR 5574, CNRS, Université de Lyon, École Normale Supérieure de Lyon, 46 Allée d'Italie, F-69364 Lyon Cedex 07, France, email: france.allard@ens-lyon.fr
Bernd Freytag
Affiliation:
Centre de Recherche Astrophysique de Lyon, UMR 5574, CNRS, Université de Lyon, École Normale Supérieure de Lyon, 46 Allée d'Italie, F-69364 Lyon Cedex 07, France, email: france.allard@ens-lyon.fr
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Abstract

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The spectral transition from Very Low Mass stars (VLMs) to brown dwarfs (BDs) and planetary mass objects (Planemos) requires model atmospheres that can treat line, molecule, and dust-cloud formation with completeness and accuracy. One of the essential problems is the determination of the surface velocity field throughout the main sequence down to the BD and planemo mass regimes. We present local 2D and 3D radiation hydrodynamic simulations using the CO5BOLD code with binned Phoenix gas opacities, forsterite dust formation (and opacities) and rotation. The resulting velocity field vs depth and Teff has been used in the general purpose model atmosphere code Phoenix, adapted in static 1D spherical symmetry for these cool atmospheres. The result is a better understanding of the spectral transition from the stellar to substellar regimes. However, problems remain in reproducing the colors of the dustiest brown dwarfs. The global properties of rotation can change the averaged spectral properties of these objects. Our project for the period 2011-2015 is therefore to develop scaled down global 3D simulations of convection, cloud formation and rotation thanks to funding by the Agence Nationale de la Recherche in France.

Keywords

starsbrown dwarfsplanetsmodel atmosphereshydrodynamic simulations
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 7 , Symposium S282: From Interacting Binaries to Exoplanets: Essential Modeling Tools , July 2011 , pp. 235 - 242
Copyright
Copyright © International Astronomical Union 2012

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