Issue |
A&A
Volume 398, Number 3, February II 2003
|
|
---|---|---|
Page(s) | 1029 - 1039 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20021632 | |
Published online | 28 January 2003 |
Mineral formation in stellar winds
IV. Formation of magnesiowüstite
Institut für Theoretische Astrophysik, Universität Heidelberg, Tiergartenstraße 15, 69121 Heidelberg, Germany
Corresponding author: H.-P. Gail, gail@ita.uni-heidelberg.de
Received:
2
August
2002
Accepted:
7
November
2002
The possible formation of iron-magnesium-oxides in stellar outflows from
cool stars with oxygen rich element mixture is discussed. Chemical equilibrium
calculations for the non-ideal solid solution magnesiowüstite with composition
MgxFeO show that this oxide may be formed under conditions of
imperfect equilibrium condensation. A model is developed for calculating the
condensation of magnesiowüstite under non equilibrium conditions in stellar
outflows and numerical models for multi-component dust condensation
including magnesiowüstite in oxygen rich stellar outflows from cool stars are
calculated. It is found that magnesiowüstite should be formed in small but
probably detectable quantities in outflows from oxygen rich AGB-stars with
mass-loss rates
yr-1. It forms a
feature in the spectrum which seems to correspond to a not yet identified feature
seen in some circumstellar dust shells. For higher mass-loss rates condensation of
magnesiowüstite is suppressed by early massive condensation of silicates.
Key words: circumstellar matter / dust, extinction / stars: mass-loss / stars: winds, outflows / stars: AGB and post-AGB
© ESO, 2003
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