Issue |
A&A
Volume 616, August 2018
|
|
---|---|---|
Article Number | A89 | |
Number of page(s) | 12 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361/201832770 | |
Published online | 24 August 2018 |
Inelastic O+H collisions and the O I 777 nm solar centre-to-limb variation
1
Max Planck Institute für Astronomy,
Königstuhl 17,
69117
Heidelberg,
Germany
e-mail: amarsi@mpia.de
2
Research School of Astronomy and Astrophysics, Australian National University,
Canberra,
ACT 2611,
Australia
3
Theoretical Astrophysics, Department of Physics and Astronomy, Uppsala University,
Box 516,
751 20
Uppsala,
Sweden
4
Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University,
Ny Munkegade 120,
8000
Aarhus C,
Denmark
5
Department of Physics and Astronomy, Drake University,
Des Moines,
IA 50311,
USA
Received:
5
February
2018
Accepted:
27
March
2018
The O I 777 nm triplet is a key diagnostic of oxygen abundances in the atmospheres of FGK-type stars; however, it is sensitive to departures from local thermodynamic equilibrium (LTE). The accuracy of non-LTE line formation calculations has hitherto been limited by errors in the inelastic O+H collisional rate coefficients; several recent studies have used the Drawin recipe, albeit with a correction factor SH that is calibrated to the solar centre-to-limb variation of the triplet. We present a new model oxygen atom that incorporates inelastic O+H collisional rate coefficients using an asymptotic two-electron model based on linear combinations of atomic orbitals, combined with a free electron model based on the impulse approximation. Using a 3D hydrodynamic STAGGER model solar atmosphere and 3D non-LTE line formation calculations, we demonstrate that this physically motivated approach is able to reproduce the solar centre-to-limb variation of the triplet to 0.02 dex, without any calibration of the inelastic collisional rate coefficients or other free parameters. We infer log ϵO = 8.69 ± 0.03 from the triplet alone, strengthening the case for a low solar oxygen abundance.
Key words: atomic data / radiative transfer / line: formation / Sun: atmosphere / Sun: abundances / methods: numerical
© ESO 2018
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