| Issue |
A&A
Volume 486, Number 1, July IV 2008
|
|
|---|---|---|
| Page(s) | 303 - 310 | |
| Section | Stellar atmospheres | |
| DOI | https://doi.org/10.1051/0004-6361:200809452 | |
| Published online | 15 May 2008 | |
Statistical equilibrium of silicon in the solar atmosphere*
1
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China e-mail: sjr@bao.ac.cn
2
Institut für Astronomie und Astrophysik der Universität München, Scheinerstr. 1, 81679 München, Germany
3
Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya Str. 48, Moscow, Russia 109017, Russia
Received:
25
January
2008
Accepted:
23
April
2008
Aims. The statistical equilibrium of neutral and ionised silicon in the solar photosphere is investigated. Line formation is discussed and the solar silicon abundance determined.
Methods. High-resolution solar spectra were used to determine solar 
values by comparison with Si line synthesis
based on LTE and NLTE level populations. The results will be used in
a forthcoming paper for differential abundance analyses of
metal-poor stars. A detailed analysis of silicon line spectra leads
to setting up realistic model atoms, which are exposed to
interactions in plane-parallel solar atmospheric models. The
resulting departure coefficients are entered into a line-by-line
analysis of the visible and near-infrared solar silicon spectrum.
Results. The statistical equilibrium of Si I turns out to depend marginally on bound-free interaction processes, both radiative and collisional. Bound-bound interaction processes do not play a significant role either, except for hydrogen collisions, which have to be chosen adequately for fitting the cores of the near-infrared lines. Except for some near-infrared lines, the NLTE influence on the abundances is weak.
Conclusions. Taking the deviations from LTE in silicon into account, it is
possible to calculate the ionisation equilibrium from neutral and
ionised lines. The solar abundance based on the experimental
f-values of Garz corrected for the Becker et al.'s measurement is
7.52 ± 0.05. Combined with an extended line sample with selected
NIST f-values, the solar abundance is 7.52 ± 0.06, with a
nearly perfect ionisation equilibrium of
(Si II/Si I) = -0.01.
Key words: line: formation / line: profiles / stars: abundances / stars: late-type / Sun: abundances
© ESO, 2008
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