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A. Frebel, J.E. Norris (The Australian National University), N. Christlieb (Hamburger Sternwarte), T.C. Beers (Michigan State University), M. Asplund, M.S. Bessell (The Australian National University), W. Aoki (National Astronomical Observatory of Japan)
We present very recent work on bright (10 < B < 14) extremely metal-poor stars selected from the Hamburg/ESO survey. Detailed knowledge about the most metal-poor objects found in the halo of the Galaxy is crucial for a comprehensive understanding of the early Universe since they are the closest relatives to true first stars (``Population III" objects). In a sample of 1777 bright metal-poor candidate stars we identified ~ 100 star with [Fe/H] < -2.5. This sample is currently being observed with high-resolution spectroscopy to reveal any unusual abundance patterns which are of astrophysical interest (e.g. ultra metal-poor, s- or r-process enhanced). So far, we have found the bright dwarf or subgiant HE 1327-2326 which has a new low record iron abundance of [Fe/H] = -5.4. Most characteristically, this star displays huge amounts of CNO elements with respect to iron (~4 dex) as well as an enhancement of the neutron-capture element Sr. Despite its evolutinary status, no Li could be detected. The interpretation of the abundance pattern of HE 1327-2326 challenges the current theoretical understanding of the first stars. Furthermore, we are searching for stars with strong enhancement of r-process abundances. Potential abundance measurements of the the heavy elements Th and U allow the determination of stellar ages. These are independent lower limits for the age of the Universe. A.F, J.E.N., M.S.B and M.A. acknowledge funding from the Australian Research Council. N.C. acknowledges funding from Deutsche Forschungsgemeinschaft. T.C.B. acknowledges funding from the US National Science Foundation Physics and Frontiers Center/JINA: Joint Institute for Nuclear Astrophysics, awarded by the US National Science Foundation.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.