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Chemical Separation vs Rotation in a and F-Stars

Published online by Cambridge University Press:  12 April 2016

Paul Charbonneau*
Affiliation:
High Altitude Observatory, National Center for Atmospheric Research1, P.O. Box 3000, Boulder, CO 80307, U.S.A.

Abstract

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The role played by rotationally-induced mixing in the diffusion-based models for non-magnetic chemically peculiar stars is investigated. This paper focuses on one specific rotationally controlled mixing mechanism, namely thermally-driven meridional circulation. Its effects on the time evolution of chemical abundances are illustrated by means of three specific examples. The first two concern the diffusion model for FmAm stars, where it is shown that while circulation has a determining influence on the settling of Helium, it has no significant effect on the diffusion of heavier metals once the He superficial convection zone has disappeared. The third example is concerned with the diffusion/mass loss model for λBootis stars. It is shown that the inclusion of circulation prevents the appearance of generalized underabundances at any epoch of the evolution, indicating that the diffusion/mass loss model for these objects must be abandoned.

Type
V. Theory of CP Star Photospheres
Copyright
Copyright © Astronomical Society of the Pacific 1993

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