EAS Publications Series
Volume 60, 2013Betelgeuse Workshop 2012 The Physics of Red Supergiants: Recent Advances and Open Questions
|Page(s)||137 - 144|
|Section||Atmospheric Structure and Dynamics|
|Published online||23 May 2013|
P. Kervella, T. Le Bertre and G. Perrin (eds)
EAS Publications Series, 60 (2013) 137-144
Global radiation-hydrodynamics simulations of red supergiant stars
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,
2 Laboratoire Lagrange, UMR 7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, BP. 4229, 06304 Nice Cedex 4, France
The small-scale surface granulation on cool main-sequence stars and white dwarfs influences the overall appearance of these objects only weakly. And it is only indirectly observable by analyzing e.g. line-shapes or temporal fluctuations – except for the Sun. The large-scale and high-contrast convective surface cells and accompanying sound waves on supergiants and low-gravity AGB stars on the other hand have a strong impact on the outer atmospheric layers and are directly detectable by interferometric observations.
Necessary to interpret modern observations with their high resolution in frequency, time, and/or space are detailed numerical multi-dimensional time-dependent radiation-hydrodynamical simulations. Local simulations of small patches of convective surface layers and the atmosphere of main-sequence stars have matured over three decades and have reached an impressive level of agreement with observations and also between different computational codes. However, global simulations of the entire convective surface and atmosphere of a red supergiants are considerably more demanding – and limited – and have become available only for about one decade.
Still, they show how the surface is shaped by the interaction of small surface granules, that sit on top of large envelope convection cells, and waves, that can travel as shocks into the outer atmosphere. The route to more complete future models will be discussed, that comprise the outer atmosphere of the stars and that could explain some of the little-understood phenomena like chromosphere, molsphere, or wind-formation.
© EAS, EDP Sciences 2013