Granulation properties of giants, dwarfs, and white dwarfs from the CIFIST 3D model atmosphere grid^⋆

¹ Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117 Heidelberg, Germany
e-mail: ptremblay@lsw.uni-heidelberg.de; hludwig@lsw.uni-heidelberg.de; ecaffau@lsw.uni-heidelberg.de
² Centre de Recherche Astrophysique de Lyon, UMR 5574: CNRS, Université de Lyon, École Normale Supérieure de Lyon, 46 allée d’Italie, 69364 Lyon Cedex 07, France
e-mail: Bernd.Freytag@ens-lyon.fr
³ Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: msteffen@aip.de
⁴ GEPI, Observatoire de Paris, CNRS, Univ. Paris Diderot, Place Jules Janssen, 92190 Meudon, France

Received: 11 May 2013
Accepted: 5 July 2013

Abstract

Three-dimensional model atmospheres for giants, dwarfs, and white dwarfs, computed with the CO5BOLD code and part of the CIFIST grid, have been used for spectroscopic and asteroseismic studies. Unlike existing plane-parallel 1D structures, these simulations predict the spatially and temporally resolved emergent intensity so that granulation can be analysed, which provides insights on how convective energy transfer operates in stars. The wide range of atmospheric parameters of the CIFIST 3D simulations (3600 < T_eff (K) < 13 000 and 1 < log    g < 9) allows the comparison of convective processes in significantly different environments. We show that the relative intensity contrast is correlated with both the Mach and Péclet numbers in the photosphere. The horizontal size of granules varies between 3 and 10 times the local pressure scale height, with a tight correlation between the factor and the Mach number of the flow. Given that convective giants, dwarfs, and white dwarfs cover the same range of Mach and Péclet numbers, we conclude that photospheric convection operates in a very similar way in those objects.