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Diffusion Models for Magnetic Ap Stars

Published online by Cambridge University Press:  12 April 2016

J. Babel
J. Babel*
Affiliation:
Institut d’Astronomie de l’Université de Lausanne, CH-1290 Chavannesdes-Bois, Switzerland

Abstract

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Progress made in spectroscopy and in the diffusion theory permits now to make severe comparisons, based on line profiles, between theory and observation.

We first review transport processes which are present in the atmospheric layers of Ap stars and discuss their relative importance. We then show that mass loss could play a key role for the creation of abundance maps. A mass loss model is proposed for 53 Cam and is compared, by spectrum synthesis, with visible and IUE high resolutions observations. The model accounts well for the line profiles of several elements with an exception for Ti. Furthermore, the abundance stratification predicted by this model gives close agreement with the large variation of the abundances of Cr and Fe found between the visible and UV domains. The diffusion-mass loss model finally permits to give a simple interpretation of the peculiar Ca II K lines observed in many Ap SrCrEu stars and in particular in 53 Cam, β CrB and HD 191742.

Type
V. Theory of CP Star Photospheres
Information
International Astronomical Union Colloquium , Volume 138: Peculiar versus Normal Phenomena in A-Type and Related Stars , 1993 , pp. 458 - 472
Copyright
Copyright © Astronomical Society of the Pacific 1993

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