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Inelastic O plus H collisions and the O I 777 nm solar centre-to-limb variation
Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
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2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 616, article id A89Article in journal (Refereed) Published
Abstract [en]

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 S-H 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 epsilon(O) = 8.69 +/- 0.03 from the triplet alone, strengthening the case for a low solar oxygen abundance.

Place, publisher, year, edition, pages
EDP SCIENCES S A , 2018. Vol. 616, article id A89
Keywords [en]
atomic data, radiative transfer, line: formation, Sun: atmosphere, Sun: abundances, methods: numerical
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-362494DOI: 10.1051/0004-6361/201832770ISI: 000442550000003OAI: oai:DiVA.org:uu-362494DiVA, id: diva2:1253655
Funder
Australian Research Council, FL110100012Australian Research Council, DP150100250Swedish Research CouncilKnut and Alice Wallenberg FoundationAvailable from: 2018-10-05 Created: 2018-10-05 Last updated: 2018-10-05Bibliographically approved

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Barklem, Paul

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