Metallicity estimates for A-, F-, and G-type stars from the Edinburgh–Cape Blue Object Survey |
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| Authors: | T C Beers S Rossi D O'Donoghue D Kilkenny R S Stobie C Koen R Wilhelm |
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| Institution: | Department of Physics and Astronomy, Michigan State University, E. Lansing, MI 48824, USA;Instituto Astronômico e Geofísico, Universidade de São Paulo, Av. Miguel Stefano 4200, 04301-904, São Paulo, Brazil;South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa;McDonald Observatory, University of Texas, Austin, TX 78712, USA |
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| Abstract: | The Edinburgh–Cape Blue Object Survey is an ongoing project to identify and analyse a large sample of hot stars selected initially on the basis of photographic colours (down to a magnitude limit  over the entire high-Galactic-latitude southern sky, and then studied with broad-band UBV photometry and medium-resolution spectroscopy. Due to unavoidable errors in the initial candidate selection, stars that are likely metal-deficient dwarfs and giants of the halo and thick-disc populations are inadvertently included, yet are of interest in their own right. In this paper we discuss a total of 206 candidate metal-deficient dwarfs, subgiants, giants, and horizontal-branch stars with photoelectric colours redder than  and with available spectroscopy. Radial velocities, accurate to ～10–15 km s?1, are presented for all of these stars. Spectroscopic metallicity estimates for these stars are obtained using a recently recalibrated relation between Ca ii K-line strength and  colour. The identification of metal-poor stars from this colour-selection technique is remarkably efficient, and competitive with previous survey methods. An additional sample of 186 EC stars with photoelectric colours in the range  composed primarily of field horizontal-branch stars and other, higher gravity, A- and B-type stars, is also analysed. Estimates of the physical parameters T eff, log g , and Fe/H] are obtained for cooler members of this subsample, and a number of candidate RR Lyrae variables are identified. |
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| Keywords: | surveys stars: Population II Galaxy: abundances Galaxy: halo |
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