The Chemical Abundances of Stars in the Halo (CASH) Project. II. A Sample of 14 Extremely Metal-poor Stars

• Published in: The Astrophysical journal Vol. 742; no. 1; pp. 54 - jQuery1323901673583='48'
• Main Authors: Hollek, Julie K, Frebel, Anna, Roederer, Ian U, Sneden, Christopher, Shetrone, Matthew, Beers, Timothy C, Kang, Sung-ju, Thom, Christopher
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 20.11.2011; IOP
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Galaxy halo; stars: atmospheres; Data analysis; Neutron stars; methods: data analysis; Population II; Stellar abundance; Neutron capture; Be stars; r process; stars: abundances; Galaxy: halo; stars: Population II; Metallicity; Physical parameter; Abundance ratio; Metal-poor stars
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/742/1/54

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 ~1,000) and corresponding high-resolution (R ~3,000) 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.