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        The Most Metal-poor Stars. I : Discovery, Data and Atmospheric Parameters

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        Author
        Norris, John
        Bessell, Michael
        Yong, David
        Christlieb, Norbert
        Barklem, Paul
        Asplund, Martin
        Murphy, Michael
        Beers, Timothy
        Frebel, Anna
        Ryan, Sean G.
        Attention
        2299/11290
        Abstract
        We report the discovery of 34 stars in the Hamburg/ESO Survey for metal-poor stars and the Sloan Digital Sky Survey that have [Fe/H] <~ -3.0. Their median and minimum abundances are [Fe/H] = -3.1 and -4.1, respectively, while 10 stars have [Fe/H] < -3.5. High-resolution, high signal-to-noise spectroscopic data—equivalent widths and radial velocities—are presented for these stars, together with an additional four objects previously reported or currently being investigated elsewhere. We have determined the atmospheric parameters, effective temperature (T eff), and surface gravity (log g), which are critical in the determination of the chemical abundances and the evolutionary status of these stars. Three techniques were used to derive these parameters. Spectrophotometric fits to model atmosphere fluxes were used to derive T eff, log g, and an estimate of E(B - V); Hα, Hβ, and Hγ profile fitting to model atmosphere results provided the second determination of T eff and log g; and finally, we used an empirical T eff-calibrated Hδ index, for the third, independent T eff determination. The three values of T eff are in good agreement, although the profile fitting may yield systematically cooler T eff values, by ~100 K. This collective data set will be analyzed in future papers in the present series to utilize the most metal-poor stars as probes of conditions in the early universe.
        Publication date
        2013-01
        Published in
        The Astrophysical Journal
        Published version
        https://doi.org/10.1088/0004-637X/762/1/25
        Other links
        http://hdl.handle.net/2299/11290
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