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Paper: Carbon Abundances for Metal-Poor Stars Based on Medium-Resolution Spectra
Volume: 165, The Third Stromlo Symposium: The Galactic Halo
Page: 264
Authors: Rossi, Silvia; Beers, Timothy C.; Sneden, Chris
Abstract: Several recent papers have pointed out that the frequency of carbon-enhanced stars in the Galaxy appears to increase at the lowest metal abundances, which may provide an important clue to the early chemical evolution of the Milky Way. The large objective-prism survey of Beers and collaborators has discovered numerous additional carbon-rich stars at extremely low metallicity. First estimates of the carbon abundances for these stars can be obtained by application of spectral-synthesis techniques in combination with moderate-resolution spectra collected during the course of the survey. We calibrate our carbon abundance estimates by comparison with previous determinations for metal-deficient dwarf and giant stars reported in the literature. Using this approach, we are able to reproduce the literature carbon abundances with an accuracy of ~0.15 dex. We then apply this technique to estimate the abundance of carbon in a sample of 56 stars identified as carbon-rich, relative to stars of similar metal abundance, in the sample of strong G-band stars discussed by Beers, Preston, & Shectman. We combine our new measurements with other data for metal-deficient stars to study the range of carbon abundances in stars over the metallicity interval -4.0 <= feh <= 0.0.
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