Carbon Abundances Of Three Cemp Stars From High-resolution Gemini-s/bHROS Spectra Of The [c I] Forbidden Line

Details Carbon Abundances Of Three Cemp Stars From High-resolution Gemini-s/bHROS Spectra Of The [c I] Forbidden Line Carbon Abundances Of Three Cemp Stars From High-resolution Gemini-s/bHROS Spectra Of The [c I] Forbidden Line

Jan 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21340608s&link_type=abstract

American Astronomical Society, AAS Meeting #213, #406.08; Bulletin of the American Astronomical Society, Vol. 41, p.199

Astronomy and Astrophysics

Astrophysics

Scientific paper

We present the results from a LTE analysis of the [C I] Forbidden line at 8727 angstroms in high-resolution Gemini-S/bHROS spectra of three Carbon-Enhanced Metal-Poor (CEMP) stars. Carbon abundances of CEMP stars are primarily derived from CH and C2 features, lines that are expected to be highly sensitive to photospheric temperature inhomogeneities, the so-called 3D effects. We find the [C/Fe] ratios based on the [C I] abundances of the two most Fe-rich stars in our sample (HE 0506-1653: [Fe/H] = -1.42 and HE 0054-2542: [Fe/H] = -2.66) to be in good agreement with previously determined molecular line-based values. The [C/Fe] ratio of the most Fe-poor star in our sample (HE 1005-1439: [Fe/H] = -3.08), however, is 0.34 dex lower than the published molecular line-based abundance. This result is in line with expectations that 3D effects on the molecular lines become more severe toward lower metallicities. We have carried out 3D LTE calculations for [C I], and the resulting corrections for all three stars are found to be modest, suggesting the discrepancy between the [C I] line and molecular line-based abundances of HE 1005-1439 is due to more severe 3D effects on the molecular lines.
S.C.S. is supported by the NOAO Leo Goldberg Fellowship; NOAO is operated by the Association of Universities for Research Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation (NSF). V.V.S. and K.C. gratefully acknowledge support from the NSF under grant AST 06-46790. T.C.B. and T.S. acknowledge partial support for this work from the NSF under grants AST 04-06784, AST 07-07776, and PHY 02-16783; Physics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA).

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