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C. Sneden (U. Texas)
Descriptions of Galactic chemical evolution are deduced from the chemical compositions of stars over a wide metallicity range. Accurate determinations of the compositions of very metal-poor halo stars are critical in this endeavor, since such stars exhibit the nucleosynthetic output of few (in rare cases, perhaps one) preceding stellar generations.
Comparison of nucleosynthesis predictions with observed stellar abundances can be no better than the atomic transition data (oscillator strengths, hyperfine/isotopic structure information) that enter into the chemical composition analyses. In the past decade several atomic physics groups have made significant progress in producing transition data for neutron-capture elements (Z>30) of relevance to halo-star spectroscopic analyses. In this brief review, examples of stars with unusual neutron-capture abundance ratios will be shown, highlighting recent advances from lab transition probability studies. Suggestions for future lab investigations will be given.
This work has been supported by US federal grants, most recently by NSF AST03-07495 and by NASA STScI GO-8111 and GO-8342.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.