Other
Scientific paper
Mar 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aipc..990..175g&link_type=abstract
FIRST STARS III: First Stars II Conference. AIP Conference Proceedings, Volume 990, pp. 175-177 (2008).
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1
Dwarf Stars, Chemical Analysis, Astronomical Spectra, Star Formation, Stellar Atmospheres, Galaxies
Scientific paper
Unevolved extremely metal-poor stars offer us a unique tool to infer knowledge of the first generation of stars. We have analysed UVES high-resolution spectra of the double-lined spectroscopic binary CS 22876-032 which comprises the two most metal-poor dwarfs currently known. In particular, we determine the oxygen (from OH lines in the near-UV) and lithium abundances taking into account 3D effects.
The long-time baseline radial velocity measurements and photometric data available allowed us to determine the orbital elements as well as stellar parameters of both components. We use OSMARCS 1D models and the TURBOSPECTRUM spectral synthesis code to determine the abundances of Li, O, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Fe, Co and Ni. We also use the CO5 BOLD 3D model atmosphere code to predict the 3D abundance corrections, mainly for Li, O and Fe.
We find a metallicity of [Fe/H]~-3.6 for both stars using 1D models with 3D corrections of ~-0.1 dex from horizontal and temporal averaged 3D models. The [α/Fe] ratios are consistent with those found for metal-poor giants with similar [Fe/H], although Ca and Si are rather low, [X/Fe]~=0. The 1D O abundance, [O/Fe]~2 for both stars, is very large, but 3D models predict abundance corrections of roughly -1.0 dex and -1.5 dex for the secondary and primary stars, respectively. These 3D corrections bring the O abundances derived from near-UV OH bands in these two dwarfs closer to other high-quality measurements from the forbidden [OI] 630 nm line in metal-poor giants. The Li abundance is consistent with the Spite plateau, although the secondary star shows a lower abundance.
Andersen Jeppe J.
Barbuy Batriz
Beers Timothy C.
Bonifacio Piercarlo
Caffau Elisabetta
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