Inelastic O plus H collisions and the O I 777 nm solar centre-to-limb variation

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    A. M. Amarsi, Australian Natl Univ, Australian National University, Res Sch Astron & Astrophys, P. S. Barklem, Uppsala Univ, Uppsala University, Dept Phys & Astron, Theoret Astrophys, M. Asplund, Australian Natl Univ, Australian National University, Res Sch Astron & Astrophys,
  • R. Collet
  • O. Zatsarinny, Drake Univ, Dept Phys & Astron

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.

Original languageEnglish
Article number89
JournalAstronomy & Astrophysics
Volume616
Number of pages12
ISSN1432-0746
DOIs
Publication statusPublished - 24 Aug 2018

    Research areas

  • atomic data, radiative transfer, line: formation, Sun: atmosphere, Sun: abundances, methods: numerical, SPECTRAL-LINE-FORMATION, LATE-TYPE STARS, MODEL STELLAR ATMOSPHERES, NEUTRAL HYDROGEN-ATOMS, OXYGEN ABUNDANCE, CROSS-SECTIONS, RADIATIVE-TRANSFER, GIANT STARS, LTE, 3D

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