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Carbon, oxygen, and iron abundances in disk and halo stars. Implications of 3D non-LTE spectral line formation

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  • A. M. Amarsi, Max Planck Institute für Astronomy, Tyskland
  • P. E. Nissen
  • Á. Skúladóttir
The abundances of carbon, oxygen, and iron in late-type stars are important parameters in exoplanetary and stellar physics, as well as key tracers of stellar populations and Galactic chemical evolution. We carry out 3D non-LTE radiative transfer calculations for CI and OI, and 3D LTE radiative transfer calculations for FeII, across the STAGGER-grid of 3D hydrodynamic model atmospheres. The absolute 3D non-LTE versus 1D LTE abundance corrections can be as severe as $-0.3$ dex for CI lines in low-metallicity F dwarfs, and $-0.6$ dex for OI lines in high-metallicity F dwarfs. The 3D LTE versus 1D LTE abundance corrections for FeII lines are less severe, typically less than $+0.15$ dex. We use the corrections in a re-analysis of carbon, oxygen, and iron in $187$ F and G dwarfs in the Galactic disk and halo. Applying the differential 3D non-LTE corrections to 1D LTE abundances visibly reduces the scatter in the abundance plots. The thick disk and high-$\alpha$ halo population rise in carbon and oxygen with decreasing metallicity, reaching a maximum of [C/Fe]$\approx0.2$ and a plateau of [O/Fe]$\approx0.6$ at [Fe/H]$\approx-1.0$. The low-$\alpha$ halo population is qualitatively similar, albeit offset towards lower metallicities and with larger scatter. Nevertheless, these populations overlap in the [C/O] versus [O/H] plane, decreasing to a plateau of [C/O]$\approx-0.6$ below [O/H]$\approx-1.0$. In the thin-disk, stars having confirmed planet detections tend to have higher values of C/O at given [O/H]; this potential signature of planet formation is only apparent after applying the abundance corrections to the 1D LTE results. Our grids of line-by-line abundance corrections are publicly available and can readily be used to improve the accuracy of spectroscopic analyses of late-type stars.
OriginalsprogEngelsk
ArtikelnummerA104
TidsskriftAstronomy & Astrophysics
Vol/bind630
Antal sider19
ISSN1432-0746
DOI
StatusUdgivet - 2019

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