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arXiv · 1703.04027

Non-LTE line formation of Fe in late-type stars IV: Modelling of the solar centre-to-limb variation in 3D

K. Lind·A. M. Amarsi·M. Asplund·P. S. Barklem·M. Bautista·M. Bergemann·R. Collet·D. Kiselman·J. Leenaarts·T. M. D. Pereira
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Abstract

Our ability to model the shapes and strengths of iron lines in the solar spectrum is a critical test of the accuracy of the solar iron abundance, which sets the absolute zero-point of all stellar metallicities. We use an extensive 463-level Fe atom with new photoionisation cross-sections for FeI as well as quantum mechanical calculations of collisional excitation and charge transfer with neutral hydrogen; the latter effectively remove a free parameter that has hampered all previous line formation studies of Fe in non-local thermodynamic equilibrium (NLTE). For the first time, we use realistic 3D NLTE calculations of Fe for a quantitative comparison to solar observations. We confront our theoretical line profiles with observations taken at different viewing angles across the solar disk with the Swedish 1-m Solar Telescope. We find that 3D modelling well reproduces the observed centre-to-limb behaviour of spectral lines overall, but highlight aspects that may require further work, especially cross-sections for inelastic collisions with electrons. Our inferred solar iron abundance is log(eps(Fe))=7.48+-0.04.

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K. Lind, A. M. Amarsi, M. Asplund, P. S. Barklem, M. Bautista, M. Bergemann, R. Collet, D. Kiselman, J. Leenaarts, T. M. D. Pereira. 2017-03-11. Non-LTE line formation of Fe in late-type stars IV: Modelling of the solar centre-to-limb variation in 3D. https://doi.org/10.1093/mnras/stx673

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