Journal
ASTRONOMY & ASTROPHYSICS
Volume 624, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201833603
Keywords
atomic data; radiative transfer; line: formation; Sun: abundances; Sun: photosphere
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Funding
- Alexander von Humboldt Foundation
- Swedish Research Council
- project grant The New Milky Way from the Knut and Alice Wallenberg Foundation
- Danish National Research Foundation [DNRF106]
- Australian Research Council [DP150100250, FL110100012]
- Swedish National Infrastructure for Computing (SNIC) [SNIC2018-3-465]
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Carbon abundances in late-type stars are important in a variety of astrophysical contexts. However C I lines, one of the main abundance diagnostics, are sensitive to departures from local thermodynamic equilibrium (LTE). We present a model atom for non-LTE analyses of C I lines, that uses a new, physically-motivated recipe for the rates of neutral hydrogen impact excitation. We analyse C I lines in the solar spectrum, employing a three-dimensional (3D) hydrodynamic model solar atmosphere and 3D non-LTE radiative transfer. We find negative non-LTE abundance corrections for C I lines in the solar photosphere, in accordance with previous studies, reaching up to around 0.1 dex in the disk-integrated flux. We also present the first fully consistent 3D non-LTE solar carbon abundance determination: we infer log is an element of(C) = 8.44 +/- 0.02, in good agreement with the current standard value. Our models reproduce the observed solar centre-to-limb variations of various C I lines, without any adjustments to the rates of neutral hydrogen impact excitation, suggesting that the proposed recipe may be a solution to the long-standing problem of how to reliably model inelastic collisions with neutral hydrogen in late-type stellar atmospheres.
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