NOAO >   Observing Info >   Approved Programs >   2002A-0134

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Proposal Information for 2002A-0134


PI: Timothy Beers, Michigan State University, beers@pa.msu.edu
Address: E, Lansing, MI 48824, US

CoI: Norbert Christlieb, Hamburger Sternwarte, Hamburg, Germany
CoI: Sean Ryan, Physics & Astronomy, Open University, UK
CoI: John Norris, Mount Stromlo & Siding Spring Obs., Australia
CoI: Silvia Rossi, IAG, University of Sao Paulo, Brazil
CoI: Bruce Carney, Physics/Astronomy, Univ. of North Carolina
CoI: Chris Sneden, Astronomy Dept., University of Texas, Austin
CoI: Jaehyon Rhee, Astronomy Dept., University of Virginia
CoI: Tatiana Sevastyanenko, Dept. of Physics/Astronomy, Michigan State University

Title: A ``Quick Survey'' for Halo Giants with [Fe/H] \le -2.5

Abstract: We propose an accelerated search for relatively bright giants in the halo of the Milky Way with [Fe/H] \le -2.5. Our primary motivation for this search is the recent discovery of a second ``r-process- enhanced'' star, CS 31082-001. This star is similar in many respects to the previously unique example of the phenomenon, CS 22892-052, and exhibits [r-process/Fe] elemental ratios in excess of 30-50 times solar values. Both of these stars have measurable lines of the radioactive species thorium, from which lower limits of the age of the Galaxy have been made. High-resolution spectroscopy of CS 31082-001 permitted the first meaningful measurement of uranium abundance outside of the Solar System. A second detection of uranium has recently been made in the moderately r-process-enhanced star BD+17:3248. The highly r-process-enhanced stars occur with a frequency of roughly 2-3% among [Fe/H] \le -2.5 giants. High-resolution studies of ~ 1500 such stars, already underway with the VLT and soon to begin with SUBARU and HET, will yield new detections of some 30-50 highly r-process-enhanced stars (and perhaps larger numbers of moderately r-process-enhanced stars), opening the door to detailed understanding of the r-process, as well as providing a plethora of stars useful for nucleo-cosmochronology.


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