THE CHEMICAL ABUNDANCES OF STARS IN THE HALO (CASH) PROJECT. II. A SAMPLE OF 14 EXTREMELY METAL-POOR STARS ,

Journal Article · Sun Nov 20 00:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/742/1/54; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21612627

Hollek, Julie K; Sneden, Christopher; Shetrone, Matthew ^[1]; Frebel, Anna ^[2]; Roederer, Ian U ^[3]; Beers, Timothy C ^[4]; Kang, Sung-ju ^[5]; Thom, Christopher ^[6]

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1. Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States)
2. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
3. Carnegie Observatories, Pasadena, CA 91101 (United States)
4. Department of Physics and Astronomy, and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States)
5. Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)
6. Space Telescope Science Institute, Baltimore, MD 21218 (United States)

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 {approx}15, 000) and corresponding high-resolution (R {approx}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] {approx}< -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 {approx}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.

• OSTI ID: 21612627
• Journal Information: Astrophysical Journal, Vol. 742, Issue 1; Other Information: DOI: 10.1088/0004-637X/742/1/54; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
DATA ANALYSIS
GALAXIES
METALS
NEUTRON REACTIONS
R PROCESS
STARS
STELLAR ATMOSPHERES
TELESCOPES
TRITIUM
ATMOSPHERES
BARYON REACTIONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
ELEMENTS
EVOLUTION
HADRON REACTIONS
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
ODD-EVEN NUCLEI
RADIOISOTOPES
STAR EVOLUTION
YEARS LIVING RADIOISOTOPES