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Issue A&A
Volume 399, Number 1, February III 2003
Page(s) 263 - 269
Section Stellar atmospheres
DOI 10.1051/0004-6361:20021731



A&A 399, 263-269 (2003)
DOI: 10.1051/0004-6361:20021731

Stellar rotation: Evidence for a large horizontal turbulence and its effects on evolution

A. Maeder

Geneva Observatory, 1290 Sauverny, Switzerland
(Received 2 May 2002 / Accepted 21 November 2002)

Abstract
We derive a new expression for the coefficient $D_{{\rm h}}$ of diffusion by horizontal turbulence in rotating stars. This new estimate can be up to two orders of magnitude larger than that given by a previous expression. As a consequence the differential rotation on an equipotential is found to be very small, which reinforces Zahn's hypothesis of shellular rotation. The role of the so-called $\mu$-currents, as well as the driving of circulation, are reduced by the large horizontal turbulence. Stellar evolutionary models for a 20  $M{\odot}$ star are calculated with the new coefficient. The new and large $D_{{\rm h}}$ tends to limit the size of the convective core and at the same time it largely favours the diffusion of helium and nitrogen to the surface of rotating OB stars, a feature supported by recent observations.


Key words: turbulence -- stars: evolution -- stars: rotation




© ESO 2003


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