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Observational Evidence for the Stratification of Chemical Abundances in Stellar Atmospheres

Published online by Cambridge University Press:  26 May 2016

T. Ryabchikova ,
G. A. Wade  and
F. Leblanc
T. Ryabchikova
Affiliation:
Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, 119017 Moscow, Russia Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
G. A. Wade
Affiliation:
Department of Physics, Royal Military College of Canada, PO Box 17000, Station “Forces” Kingston, Ontario, K7K 7B4, Canada
F. Leblanc
Affiliation:
Département de physique et d'astronomie, Université de Moncton, Moncton, New Brunswick, E1A 3E9, Canada

Abstract

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We present spectroscopic and photometric observational evidence for abundance stratification in stellar atmospheres. Attention is given to chemically peculiar (Ap) stars in which magnetic fields stabilize the atmosphere, allowing diffusion processes to establish abundance stratification during the early stages of star's life. The results of recent empirical modelling of chemically stratified atmospheres are briefly discussed, and a comparison is given with the predictions of self-consistent atmospheric models which include radiative diffusion.

The importance of abundance stratification analysis is demonstrated for rapidly oscillating (roAp) stars in which the amplitudes of the radial velocity pulsations are different for the lines of different elements in different ionization stages. We also demonstrate that chemical stratification has important effects on the Zeeman Stokes IQUV profiles of Ap stars, indicating that stratification must be taken into account in detailed modelling of their magnetic fields.

Type
Session E. Comparison with Observations
Information
Symposium - International Astronomical Union , Volume 210: Modelling of Stellar Atmospheres , 2003 , pp. 301 - 312
Copyright
Copyright © Astronomical Society of the Pacific 2003 

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