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Bright metal-poor stars from the Hamburg/ESO survey. I. Selection and follow-up observations from 329 fields

Frebel, Anna and Christlieb, Norbert and Norris, John E. and Beers, Timothy C. and Bessell, Michael S. and Rhee, Jaehon and Fechner, Cora and Marsteller, Brian and Rossi, Silvia and Thom, Christopher and Wisotzki, Lutz and Reimers, Dieter (2006) Bright metal-poor stars from the Hamburg/ESO survey. I. Selection and follow-up observations from 329 fields. Astrophysical Journal, 652 (2). pp. 1585-1603. ISSN 0004-637X.

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We present a sample of 1777 bright (9 < B < 14) metal-poor candidates selected from the Hamburg/ESO Survey (HES). Despite saturation effects present in the red portion of the HES objective-prism spectra, the data were recoverable and quantitative selection criteria could be applied to select the sample. Analyses of medium-resolution (~2 Å) follow-up spectroscopy of the entire sample, obtained with several 2–4 m class telescopes, yielded 145 new metal-poor stars with metallicity [Fe/H] < -2.0, of which 79 have [Fe/H] < -2.5 and 17 have [Fe/H] < -3.0. We also obtained C/Fe estimates for all of these stars. From this, we find a frequency of C-enhanced ([C/Fe] > 1.0) metal-poor ([Fe/H] < -2.0) giants of 9% ± 2%, which is lower than previously reported. However, the frequency rises to similar (>20%) and higher values with increasing distance from the Galactic plane. Although the numbers of stars at low metallicity are falling rapidly at the lowest metallicities, there is evidence that the fraction of carbon-enhanced metal-poor stars is increasing rapidly as a function of declining metallicity. For ~60 objects, high-resolution data have already been obtained; one of these, HE 1327-2326, is the new record holder for the most iron-deficient star known.

Item Type:Article
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Frebel, Anna0000-0002-2139-7145
Christlieb, Norbert0000-0002-4043-2727
Beers, Timothy C.0000-0003-4573-6233
Additional Information:© 2006 The American Astronomical Society. Received 2006 June 13; accepted 2006 August 14. We thank S. Tsangarides and J.D. Tanner for reducing the AAT data and E. Westra for useful comments on earlier versions of the manuscript. A.F., J.E.N., and M.S.B. acknowledge support from the Australian Research Council under grants DP0342613 and DP0663562. N.C. and D.R. acknowledge support from Deutsche Forschungsgemeinschaft under grants Ch 214/3 and Re 353/44. T.C.B. acknowledges support from grants AST 04-06784 and PHY 02-16783, Physics Frontier Centers/Joint Institute for Nuclear Astrophysics, awarded by the US National Science Foundation. S.R. thanks FAPESP, CNPq, and Capes for partial financial support. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. It makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.
Subject Keywords:catalogs—Galaxy: abundances—Galaxy: halo—Galaxy: stellar content—stars: abundances—stars: carbon—stars: Population II—techniques: spectroscopic
Issue or Number:2
Record Number:CaltechAUTHORS:FREapj06
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7107
Deposited By: Lindsay Cleary
Deposited On:09 Jan 2007
Last Modified:09 Mar 2020 13:18

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