NOAO >   Observing Info >   Approved Programs >   2001B-0133

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Proposal Information for 2001B-0133


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

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

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

Abstract: We propose a new, 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, based upon which estimates of the lower limit of the age of the Galaxy (and universe) have been made. CS 31082- 001, in contrast to CS 22892-052, is not carbon-enhanced, and thus permitted the first measurement of uranium abundance outside of the solar system. Based on previous high-resolution follow-up, the greatly r-process enhanced stars occur with a frequency of roughly 2-3% among [Fe/H] \le - 2.5 giants. A planned future high-resolution study of ~ 500 such stars will yield new detections of 10-15 highly r-process enhanced stars. The key to these discoveries is the identification of a sufficiently large number of [Fe/H] \le -2.5 giants, which we seek to initiate with this proposal, in collaboration with additional telescopes worldwide.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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