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3D MHD simulations of subsurface convection in OB stars

Published online by Cambridge University Press:  12 July 2011

Matteo Cantiello ,
Jonathan Braithwaite ,
Axel Brandenburg ,
Fabio Del Sordo ,
Petri Käpylä  and
Norbert Langer
Matteo Cantiello
Affiliation:
Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, D–53121 Bonn, Germany email: cantiello@astro.uni-bonn.de
Jonathan Braithwaite
Affiliation:
Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, D–53121 Bonn, Germany email: cantiello@astro.uni-bonn.de
Axel Brandenburg
Affiliation:
NORDITA, AlbaNova University Center, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden Department of Astronomy, AlbaNova University Center, Stockholm University, SE–10691 Stockholm, Sweden
Fabio Del Sordo
Affiliation:
NORDITA, AlbaNova University Center, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden Department of Astronomy, AlbaNova University Center, Stockholm University, SE–10691 Stockholm, Sweden
Petri Käpylä
Affiliation:
NORDITA, AlbaNova University Center, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden Department of Physics, Gustaf Hällströmin katu 2a (PO Box 64), FI-00014, University of Helsinki, Finland
Norbert Langer
Affiliation:
Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, D–53121 Bonn, Germany email: cantiello@astro.uni-bonn.de
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Abstract

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During their main sequence evolution, massive stars can develop convective regions very close to their surface. These regions are caused by an opacity peak associated with iron ionization. Cantiello et al. (2009) found a possible connection between the presence of sub-photospheric convective motions and small scale stochastic velocities in the photosphere of early-type stars. This supports a physical mechanism where microturbulence is caused by waves that are triggered by subsurface convection zones. They further suggest that clumping in the inner parts of the winds of OB stars could be related to subsurface convection, and that the convective layers may also be responsible for stochastic excitation of non-radial pulsations. Furthermore, magnetic fields produced in the iron convection zone could appear at the surface of such massive stars. Therefore subsurface convection could be responsible for the occurrence of observable phenomena such as line profile variability and discrete absorption components. These phenomena have been observed for decades, but still evade a clear theoretical explanation. Here we present preliminary results from 3D MHD simulations of such subsurface convection.

Keywords

convectionhydrodynamicswavesstars: activitystars: atmospheresstars: evolutionstars: magnetic fieldsstars: spotsstars: windsoutflows
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S272: Active OB stars: structure, evolution, mass loss, and critical limits , July 2010 , pp. 32 - 37
Copyright
Copyright © International Astronomical Union 2011

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