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An Update on the 0Z Project

Cohen, J. G. and Christlieb, N. and McWilliam, A. and Shectman, S. and Thompson, I. (2008) An Update on the 0Z Project. In: First stars III : Santa Fe, New Mexico, 15-20 July 2007. AIP Conference Proceedings. No.990. American Institute of Physics , Melville, NY, pp. 118-121. ISBN 978-0-7354-0509-7.

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We give an update on our 0Z Survey to find more extremely metal poor (EMP) stars with [Fe/H]<−3 dex through mining the database of the Hamburg/ESO Survey. We present the most extreme such stars we have found from ~1550 moderate resolution follow up spectra. One of these, HE1424–0241, has highly anomalous abundance ratios not seen in any previously known halo giant, with very deficient Si, moderately deficient Ca and Ti, highly enhanced Mn and Co, and low C, all with respect to Fe. We suggest a SNII where the nucleosynthetic yield for explosive α–burning nuclei was very low compared to that for the hydrostatic α–burning element Mg, which is normal in this star relative to Fe. A second, less extreme, outlier star with high [Sc/Fe] has also been found.We examine the extremely metal-poor tail of the HES metallicity distribution function (MDF). We suggest on the basis of comparison of our high resolution detailed abundance analyses with [Fe/H](HES) for stars in our sample that the MDF inferred from follow up spectra of the HES sample of candidate EMP stars is heavily contaminated for [Fe/H](HES) <−3 dex; many of the supposed EMP stars below that metallicity are of substantially higher Fe-metallicity, including most of the very C-rich stars, or are spurious objects.

Item Type:Book Section
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URLURL TypeDescription DOIArticle Paper
Cohen, J. G.0000-0002-8039-4673
Christlieb, N.0000-0002-4043-2727
Additional Information:© 2008 American Institute of Physics. Issue Date: 11 March 2008. This work is based in part on observations obtained at the WM. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. Some of the data presented herein were obtained at the Palomar Observatory. We are grateful to the many people who have worked to make the Keck Telescope and HIRES a reality and to operate and maintain the Keck Observatory. J.G.C. is grateful to NSF grant AST-0507219 for partial support. N.C. is a Research Fellow of the Royal Swedish Academy of Sciences supported by a grant from the Knut and Alice Wallenberg Foundation. He also acknowledges financial support from Deutsche Forschungsgemeinschaft through grants Ch 214/3 and Re 353/44. We thank Tim Beers for providing us with [Fe/H] (HES) values using the most recent version of his codes.
Funding AgencyGrant Number
Knut and Alice Wallenberg FoundationUNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)Ch 214/3
Deutsche Forschungsgemeinschaft (DFG)Re 353/44
Subject Keywords:astronomical atlases, dwarf stars, chemical analysis, galaxies
Series Name:AIP Conference Proceedings
Issue or Number:990
Classification Code:PACS: 95.80.+p; 97.20.Tr; 97.10.Tk; 98.35.Gi
Record Number:CaltechAUTHORS:20100707-132658295
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Official Citation:An Update on the 0Z Project J. G. Cohen, N. Christlieb, A. McWilliam, S. Shectman, and I. Thompson, AIP Conf. Proc. 990, 118 (2008), DOI:10.1063/1.2905516
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18926
Deposited By: Tony Diaz
Deposited On:06 Aug 2010 21:55
Last Modified:09 Mar 2020 13:18

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