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A&A 417, 751-768 (2004)
DOI: 10.1051/0004-6361:20034328

Line formation in solar granulation

IV. [O I], O I and OH lines and the photospheric O abundance
M. Asplund1, N. Grevesse2, 3, A. J. Sauval4, C. Allende Prieto5 and D. Kiselman6

1  Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory, Cotter Rd., Weston, ACT 2611, Australia
2  Centre Spatial de Liège, Université de Liège, avenue Pré Aily, 4031 Angleur-Liège, Belgium
3  Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 août, 17, B5C, 4000 Liège, Belgium
4  Observatoire Royal de Belgique, avenue circulaire, 3, 1180 Bruxelles, Belgium
5  McDonald Observatory and Department of Astronomy, University of Texas, Austin, TX 78712-1083, USA
6  The Institute for Solar Physics of the Royal Swedish Academy of Sciences, AlbaNova University Centre, 106 91 Stockholm, Sweden

(Received 17 September 2003 / Accepted 2 December 2003 )

Abstract
The solar photospheric oxygen abundance has been determined from [O I], O I, OH vibration-rotation and OH pure rotation lines by means of a realistic time-dependent, 3D, hydrodynamical model of the solar atmosphere. In the case of the O I lines, 3D non-LTE calculations have been performed, revealing significant departures from LTE as a result of photon losses in the lines. We derive a solar oxygen abundance of log $\epsilon_{\rm O} = 8.66 \pm 0.05$. All oxygen diagnostics yield highly consistent abundances, in sharp contrast with the results of classical 1D model atmospheres. This low value is in good agreement with measurements of the local interstellar medium and nearby B stars. This low abundance is also supported by the excellent correspondence between lines of very different line formation sensitivities, and between the observed and predicted line shapes and center-to-limb variations. Together with the corresponding down-ward revisions of the solar carbon, nitrogen and neon abundances, the resulting significant decrease in solar metal mass fraction to Z = 0.0126 can, however, potentially spoil the impressive agreement between predicted and observed sound speed in the solar interior determined from helioseismology.


Key words: convection -- line: formation -- Sun: abundances -- Sun: granulation -- Sun: photosphere

Offprint request: M. Asplund, martin@mso.anu.edu.au




© ESO 2004


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