Carbon Abundances of Metal-Poor Star Determined from the C I 1.068-1.069 micron Lines

Abstract

A non-LTE analysis of C I lines at 1.068-1.069 micron was carried out for selected 46 halo/disk stars covering a wide metallicity range (-3.7 <[Fe/H]< +0.3), based on the spectral data collected with IRCS+AO188 of the Subaru Telescope, in order to examine whether and how these strong neutral carbon lines of multiplet 1 can be exploited for establishing stellar carbon abundances, especially for very metal-poor stars where CH molecular lines have been commonly used. These C I lines were confirmed to be clearly visible for all stars down to [Fe/H] ~ -3.7, from which C abundances could be successfully determined. The resulting [C/Fe] vs. [Fe/H] diagram revealed almost the same trend established from previous studies. When the results for individual stars are compared with the published data collected from various literature, while a reasonable agreement is seen as a whole, a tendency is observed that our abundances are appreciably higher than those from CH lines especially for very metal-poor giants of low gravity. Since the abundances of these C I lines are subject to rather large non-LTE corrections (typically by several tenths dex) whose importance progressively grows as the metallicity is lowered, attention should be paid to how the collisional rates (especially due to neutral hydrogen) are treated in non-LTE calculations.

16 pages, 8 figures, 3 tables and 2 electronic tables; accepted for publication in Publ. Astron. Soc. Japan (Vol.65, No. 4)

References in corpus (8)

• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• Near-UV Observations of HD221170: New Insights into the Nature of r-Process-Rich Stars
• Fundamental Parameters and Chemical Composition of Arcturus
• 3D Hydrodynamical Simulations of Surface Convection in Red Giant Stars. Impact on spectral line formation and abundance analysis
• First stars IX -Mixing in extremely metal-poor giants. Variation of the 12C/13C, [Na/Mg] and [Al/Mg] ratios
• Carbon and Strontium Abundances of Metal-Poor Stars
• The non-LTE line formation of neutral carbon in late-type stars
• Behavior of [S/Fe] in Very Metal-Poor Stars from the S I 1.046 micron Lines Revisited

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