Examinando por Autor "Keller, S.C."

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    The Gaia-ESO Survey: the most metal-poor stars in the galactic bulge
    (Oxford University Press, 2014-09) Howes, L.M.; Asplund, M.; Casey, A.R.; Keller, S.C.; Yong, D.; Gilmore, G.; Lind, K.; Worley, C.; Bessell, M.S.; Casagrande, L.; Marino, A.F.; Nataf, D.M.; Owen, C.I.; Da Costa, G.S.; Schmidt, B.P.; Tisserand, P.; Randich, S.; Feltzing, S.; Vallenari, A.; Allende Prieto, C.; Bensby, T.; Flaccomio, E.; Korn, A.J.; Pancino, E.; Recio-Blanco, A.; Smiljanic, R.; Bergemann, M.; Costado, M.T.; Damiani, F.; Heiter, U.; Hill, V.; Hourihane, A.; Jofré, P.; Lardo, C.; de Laverny, P.; Magrini, L.; Maiorca, E.; Masseron, T.; Morbidelli, L.; Sacco, G.G.; Minniti, D.; Zoccali, M.
    We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilizes SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe the discovery and analysis of four bulge giants with −2.72 ≤ [Fe/H] ≤ −2.48, the lowest metallicity bulge stars studied with high-resolution spectroscopy to date. Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived abundances of twelve elements. Given the uncertainties, we find a chemical similarity between these bulge stars and halo stars of the same metallicity, although the abundance scatter may be larger, with some of the stars showing unusual [α/Fe] ratios.
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    The Gaia-ESO Survey: The most metal-poor stars in the Galactic bulge
    (2014) Howes, L.M.; Asplund, M.; Casey, A.R.; Keller, S.C.; Yong, D.; Gilmore, G.; Lind, K.; Worley, C.; Bessell, M.S.; Casagrande, L.; Marino, A.F.; Nataf, D.M.
    We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilizes SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe the discovery and analysis of four bulge giants with -2.72 = [Fe/H] = -2.48, the lowest metallicity bulge stars studied with high-resolution spectroscopy to date. Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived abundances of twelve elements. Given the uncertainties, we find a chemical similarity between these bulge stars and halo stars of the same metallicity, although the abundance scatter may be larger, with some of the stars showing unusual [a/Fe] ratios. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.