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CI non–LTE spectral line formation in late-type stars

Published online by Cambridge University Press:  23 December 2005

D. Fabbian
Affiliation:
RSAA, The Australian National University, Mt. Stromlo Observatory, Cotter Rd., Weston ACT 2611, Australia email: damian@mso.anu.edu.au
M. Asplund
Affiliation:
RSAA, The Australian National University, Mt. Stromlo Observatory, Cotter Rd., Weston ACT 2611, Australia email: damian@mso.anu.edu.au
M. Carlsson
Affiliation:
Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, N-0315 Oslo, Norway
D. Kiselman
Affiliation:
The Institute for Solar Physics of the Royal Swedish Academy of Sciences, AlbaNova University Centre, 106 91 Stockholm, Sweden
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Abstract

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We present non–Local Thermodynamic Equilibrium (non–LTE) calculations for neutral carbon spectral line formation, carried out for a grid of model atmospheres covering the range of late-type stars. The results of our detailed calculations suggest that the carbon non–LTE corrections in these stars are higher than usually adopted, remaining substantial even at low metallicity. For the most metal-poor stars in the sample of Akerman et al (2004), the effects are of the order of $\Delta\log\epsilon_{\rm C} \simeq -0.35\ldots-0.45$ (when neglecting H collisions). Applying our results to those observations, the apparent [C/O] upturn seen in their LTE analysis is no longer present, thus revealing no need to invoke contributions from Pop. III stars to the carbon nucleosynthesis.

Type
Contributed Papers
Copyright
© 2005 International Astronomical Union