A SEARCH FOR STARS OF VERY LOW METAL ABUNDANCE. VI. DETAILED ABUNDANCES OF 313 METAL-POOR STARS

We present radial velocities, equivalent widths, model atmosphere parameters, and abundances or upper limits for 53 species of 48 elements derived from high resolution optical spectroscopy of 313 metal-poor stars. A majority of these stars were selected from the metal-poor candidates of the HK Survey of Beers, Preston, and Shectman. We derive detailed abundances for 61% of these stars for the first time. Spectra were obtained during a 10 yr observing campaign using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Telescopes at Las Campanas Observatory, theRobertG. TullCoude Spectrograph on theHarlan J. Smith Telescope at McDonaldObservatory, and theHighResolution Spectrograph on theHobby-Eberly Telescope at McDonaldObservatory.We perform a standard LTE abundance analysis using MARCS model atmospheres, and we apply line-by-line statistical corrections to minimize systematic abundance differences arisingwhen different sets of lines are available for analysis.We identify several abundance correlations with effective temperature. A comparison with previous abundance analyses reveals significant differences in stellar parameters, which we investigate in detail. Our metallicities are, on average, lower by approximately 0.25 dex for red giants and approximately 0.04 dex for subgiants. Our sample contains 19 stars with [Fe/H] [< or =, slant] -3.5, 84 stars with [Fe/H] [< or =, slant] -3.0, and 210 stars with [Fe/H] [< or =, slant] -2.5. Detailed abundances are presented here or elsewhere for 91% of the 209 stars with [Fe/H] [< or =, slant] -2.5 as estimated from medium resolution spectroscopy by Beers, Preston, and Shectman. We will discuss the interpretation of these abundances in subsequent papers.