Abundances of Extremely Metal-Poor Star Candidates

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Abundances of Extremely Metal-Poor Star Candidates 1David f68fa00016fc700abb68fcbdi,Michael Bolte,Jennifer A.Johnson 2,and Sara Lucatello 3UCO/Lick Observatory,University of California,Santa Cruz,CA 95064david@f68fa00016fc700abb68fcbd,bolte@f68fa00016fc700abb68fcbd,Jennifer.Johnson@nrc-cnrc.gc.ca,lucatello@pd.astro.it ABSTRACT We present chemical abundances for 110stars identi?ed in objective-prism surveys as candidates to be very metal-poor.The abundances are derived from high S/N,intermediate-resolution spectra obtained with the Keck Observatory Echelle Spectrom-eter and Imager.An additional 25stars with well-determined abundances ranging from [Fe/H]=?1.5and ?3.2were observed and the results used to help calibrate our anal-ysis and determine the accuracy of our abundance determinations.Abundances for the program stars were measured for Fe,Mg,Ca,Ti,Cr and Ba with an accuracy of approximately 0.3dex.53of the stars in our sample have [Fe/H]≤?2,22have [Fe/H]≤?2.5and 13stars have [Fe/H]≤?2.9.Surprisingly,approximately one third of the sample is relatively metal rich with [Fe/H]>?1.5.In addition to identifying a number of extremely metal-poor stars,this study also shows that moderate-resolution spectra obtained with the Keck Echelle Spectrometer and Imager yield relatively accu-rate abundances for stars as faint as V =14in modest exposure time (～20minutes).This capability will prove useful if the so-far elusive stars at [Fe/H]

1.Introduction

In the last decade the number of identi?ed extremely metal-poor (EMP)stars with [Fe/H]

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