Статья

THE MOST METAL-POOR STARS. II. CHEMICAL ABUNDANCES OF 190 METAL-POOR STARS INCLUDING 10 NEW STARS WITH [Fe/H] ⩽ –3.5, ,

David YongResearch School of Astronomy and Astrophysics, The Australian National University, Weston, ACT 2611, AustraliaJohn E. NorrisResearch School of Astronomy and Astrophysics, The Australian National University, Weston, ACT 2611, AustraliaM. S. BessellResearch School of Astronomy and Astrophysics, The Australian National University, Weston, ACT 2611, AustraliaN. ChristliebZentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117 Heidelberg, GermanyM. AsplundMax-Planck Institute for Astrophysics, Karl-Schwarzschild Str. 1, D-85741 Garching, GermanyTimothy C. BeersDepartment of Physics & Astronomy and JINA (Joint Institute for Nuclear Astrophysics), Michigan State University, East Lansing, MI 48824, USAP. S. BarklemDepartment of Physics and Astronomy, Uppsala University, Box 515, SE-75120 Uppsala, SwedenAnna FrebelMassachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139, USASean G. RyanCentre for Astrophysics Research, School of Physics, Astronomy & Mathematics, University of Hertfordshire, College Lane, Hatfield, Hertfordshire AL10 9AB, UK

2012en

ABI

Аннотация

We present a homogeneous chemical abundance analysis of 16 elements in 190 metal-poor Galactic halo stars (38 program and 152 literature objects). The sample includes 171 stars with [Fe/H] < -2.5, of which 86 are extremely metal poor, [Fe/H] < -3.0. Our program stars include ten new objects with [Fe/H] < -3.5. We identify a sample of "normal" metal-poor stars and measure the trends between [X/Fe] and [Fe/H], as well as the dispersion about the mean trend for this sample. Using this mean trend, we identify objects that are chemically peculiar relative to "normal" stars at the same metallicity. These chemically unusual stars include CEMP-no objects, one star with high [Si/Fe], another with high [Ba/Sr], and one with unusually low [X/Fe] for all elements heavier than Na. The Sr and Ba abundances indicate that there may be two nucleosynthetic processes at lowest metallicity that are distinct from the main r-process. Finally, for many elements, we find a significant trend between [X/Fe] versus Teff which likely reflects non-LTE and/or 3D effects. Such trends demonstrate that care must be exercised when using abundance measurements in metal-poor stars to constrain chemical evolution and/or nucleosynthesis predictions.

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Идентификаторы

DOI: 10.1088/0004-637x/762/1/26

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