Astrophys. J., 742, 54 (2011/November-3)
The Chemical Abundances of Stars in the Halo (CASH) project. II. A sample of 14 extremely metal-poor stars.
HOLLEK J.K., FREBEL A., ROEDERER I.U., SNEDEN C., SHETRONE M., BEERS T.C., KANG S.-J. and THOM C.
Abstract (from CDS):
We present a comprehensive abundance analysis of 20 elements for 16 new low-metallicity stars from the Chemical Abundances of Stars in the Halo (CASH) project. The abundances have been derived from both Hobby-Eberly Telescope High Resolution Spectrograph snapshot spectra (R ∼15, 000) and corresponding high-resolution (R ∼35, 000) Magellan Inamori Kyocera Echelle spectra. The stars span a metallicity range from [Fe/H] from -2.9 to -3.9, including four new stars with [Fe/H] < -3.7. We find four stars to be carbon-enhanced metal-poor (CEMP) stars, confirming the trend of increasing [C/Fe] abundance ratios with decreasing metallicity. Two of these objects can be classified as CEMP-no stars, adding to the growing number of these objects at [Fe/H]< - 3. We also find four neutron-capture-enhanced stars in the sample, one of which has [Eu/Fe] of 0.8 with clear r-process signatures. These pilot sample stars are the most metal-poor ([Fe/H] ≲ -3.0) of the brightest stars included in CASH and are used to calibrate a newly developed, automated stellar parameter and abundance determination pipeline. This code will be used for the entire ∼500 star CASH snapshot sample. We find that the pipeline results are statistically identical for snapshot spectra when compared to a traditional, manual analysis from a high-resolution spectrum.
Galaxy: halo - methods: data analysis - stars: abundances - stars: atmospheres - stars: Population II
VizieR on-line data:
<Available at CDS (J/ApJ/742/54): table1.dat table2.dat table5.dat table6.dat>
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