Issue |
A&A
Volume 387, Number 1, May III 2002
|
|
---|---|---|
Page(s) | 271 - 284 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20020381 | |
Published online | 15 May 2002 |
Radiative accelerations in stars: The effect of Zeeman splitting
1
DAEC/LUTH (Observatoire de Paris – CNRS), Observatoire de Meudon, 92195 Meudon Cedex, France
2
Institut für Astronomie (IfA), Universität Wien, Türkenschanzstrasse 17, 1180 Wien, Austria e-mail: stift@astro.univie.ac.at
Corresponding author: G. Alecian, georges.alecian@obspm.fr
Received:
21
December
2001
Accepted:
8
March
2002
The influence of Zeeman splitting on radiative accelerations
of chemical elements in stellar atmospheres permeated by
magnetic fields with strengths of up to a few Tesla has for
the first time been investigated in detail taking into account
magneto-optical effects and line blending. The work is based
on the newly developed object-oriented and parallel code CARAT
(which is presented in some detail), on extensive atomic data
taken from the VALD database and on a 12 000 K,
Kurucz atmosphere with solar abundances. The calculations show
that magnetically induced spectral line desaturation can lead
to unexpectedly large amplifications of accelerations – relative
to the zero-field case – in a number of atomic species. These
amplifications are found to be strongly dependent both on field
strength and on field orientation, reaching a pronounced maximum
near the inclination of
between field vector and
vertical with values sometimes in excess of 1.5 dex. Horizontal
accelerations, a consequence of polarised radiative transfer,
turn out to remain fairly small and will probably not have any
important effect on the diffusion velocity vector.
This first study on a large scale of how radiative accelerations
are affected by Zeeman splitting is completed by a discussion
of the importance of complete atomic line lists, in particular
line lists with correct Landé factors; it must also
be accepted that magneto-optical effects can by no means be
neglected. Finally, it appears that the “canonical” picture
of abundance inhomogeneities may have to be revised: instead
of being tied to regions with predominantly vertical or
horizontal magnetic fields, abundance patches could show
up as contours about the curves tracing the field vector
inclination of ≈
.
Key words: diffusion / stars: abundances / stars: chemically peculiar / stars: magnetic fields / polarization
© ESO, 2002
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