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Browsing by Author "Christlieb, N"

Browsing by Author "Christlieb, N"

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  • The Hamburg/ESO R-process Enhanced Star survey (HERES) VIII. The r+s star HE 1405 0822 
    Cui, W. Y; Sivarani, T; Christlieb, N (EDP Sciences, 2013-10)
    Aims. The aim of this study is a detailed abundance analysis of the newly discovered r-rich star HE 1405−0822, which has [Fe/H] = −2.40. This star shows enhancements of both r- and s-elements, [Ba/Fe] = + 1.95 and [Eu/Fe] ...
  • A high-resolution spectral analysis of three carbon-enhanced metal-poor stars 
    Goswami, A; Aoki, W; Beers, T. C; Christlieb, N; Norris, J. E; Ryan, S. G; Tsangarides, S (Blackwell Publishing, 2006-09)
    We present results of an analysis of high-resolution spectra obtained with the Subaru Telescope High Dispersion Spectrograph, of two Carbon-Enhanced Metal-Poor stars, HE 1305+0007 and HE 1152-0355, and of the classical CH ...
  • Making Good Use of Bad Weather: Finding Extremely Metal-Poor Stars in the Clouds 
    Placco, V. M; Beers, T. C; Rossi, S; Kennedy, C; Christlieb, N; Lee, Y. S; Sivarani, T (Astronomical Society of the Pacific, 2012-12)
    Current results are presented for a new survey effort to search for Extremely Metal-Poor (EMP) and Carbon Enhanced Metal-Poor (CEMP) stars from the Hamburg / ESO objective-prism survey (HES). These stars are important ...
  • The metal-poor end of the Spite plateau I. Stellar parameters, metallicities, and lithium abundances 
    Sbordone, L; Bonifacio, P; Caffau, E; Ludwig, H. -G; Behara, N. T; González Hernández, J. I; Steffen, M; Cayrel, R; Freytag, B; Van’t Veer, C; Molaro, P; Plez, B; Sivarani, T; Spite, M; Spite, F; Beers, T. C; Christlieb, N; François, P; Hill, V (EDP Sciences, 2010-11)
    Context. The primordial nature of the Spite plateau is at odds with the WMAP satellite measurements, implying a primordial Li production at least three times higher than observed. It has also been suggested that A(Li) might ...
  • The metal–poor end of the Spite plateau 
    Sbordone, L; Bonifacio, P; Caffau, E; Ludwig, H. -G; Behara, N; Gonzalez-Hernandez, J. I; Steffen, M; Cayrel, R; Freytag, B; Van't Veer, C; Molaro, P; Plez, B; Sivarani, T; Spite, M; Spite, F; Beers, T. C; Christlieb, N; François, P; Hill, V (Cambridge University Press, 2010-03)
    We present the largest sample available to date of lithium abundances in extremely metal poor (EMP) Halo dwarfs. Four Teff estimators are used, including IRFM and Hα wings fitting against 3D hydrodynamical synthetic ...
  • The metal–poor end of the Spite plateau: gravity sensitivity of the Hα wings fitting. 
    Sbordone, L; Bonifacio, P; Caffau, E; Ludwig, H. -G; Behara, N; Gonzalez-Hernandez, J. I; Steffen, M; Cayrel, R; Freytag, B; Van't Veer, C; Molaro, P; Plez, B; Sivarani, T; Spite, M; Spite, F; Beers, T. C; Christlieb, N; François, P; Hill, V (Cambridge University Press, 2010-04)
    We recently presented (Sbordone et al., 2009a) the largest sample to date of lithium abundances in extremely metal-poor (EMP) Halo dwarf and Turn-Off (TO) stars. One of the most crucial aspects in estimating Li abundances ...
  • A New Technique for Solar Imaging Spectro-polarimetry using Shack-Hartmann and Fabry-Perot 
    Placco, V. M; Beers, T. C; Rossi, S; Kennedy, C; Christlieb, N; Lee, Y. S; Sivarani, T (Astronomical Society of the Pacific, 2012-02)
    A new technique for solar imaging spectro-polarimetry is presented. Using the combination of a Shack-Hartmann (SH) and a Fabry-Pérot (FP) interferometer, high-cadence spectroscopic observations can be obtained at discrete ...
  • [O/Fe] Estimates for Carbon-enhanced Metal-poor Stars from Near-infrared Spectroscopy 
    Kennedy, C. R; Sivarani, T; Beers, T. C; Lee, Y. S; Placco, V. M; Rossi, S; Christlieb, N; Herwig, F; Plez, B (IOP Publishing, 2011-03)
    We report on oxygen abundances determined from medium-resolution near-infrared spectroscopy for a sample of 57 carbon-enhanced metal-poor (CEMP) stars selected from the Hamburg/ESO Survey. The majority of our program stars ...
  • A Search for Unrecognized Carbon-Enhanced Metal-Poor Stars 
    Placco, V. M; Kennedy, C. R; Rossi, S; Beers, T. C; Christlieb, N; Sivarani, T (Cambridge University Press, 2010-03)
    We have developed a new procedure to search for Carbon-Enhanced Metal-Poor (CEMP) stars from the Hamburg/ESO (HES) prism-survey plates. This method uses an extended line index for the CH G-band, which we demonstrate to ...
  • A search for unrecognized carbon-enhanced metal-poor stars in the galaxy 
    Placco, V. M; Kennedy, C. R; Rossi, S; Beers, T. C; Lee, Y. S; Christlieb, N; Sivarani, T; Reimers, D; Wisotzki, L (Institute of Physics, 2010-03)
    We have developed a new procedure to search for carbon-enhanced metal-poor (CEMP) stars from the Hamburg/ESO (HES) prism-survey plates. This method employs an extended line index for the CH G band, which we demonstrate to ...
  • Searches for Metal-poor Stars from the Hamburg/ESO Survey Using the CH G Band 
    Placco, V. M; Kennedy, C. R; Beers, T. C; Christlieb, N; Rossi, S; Sivarani, T; Lee, Young Sun; Reimers, D; Wisotzki, L (IOP Publishing, 2011-12)
    We describe a new method to search for metal-poor candidates from the Hamburg/ESO objective-prism survey (HES) based on identifying stars with apparently strong CH G-band strengths for their colors. The hypothesis we exploit ...

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