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Discovery of an "alpha" Element-Poor Halo Star in a Search for Very Low- Metallicity Disk Stars
We report [Fe/H] results for a sample of five high-velocity metal-poorhalo population stars and five comparably metal-poor stars thought tohave kinematics typical of an older, hotter disk population. We alsoderive abundances of lithium, oxygen, magnesium, silicon, calcium,titanium, and barium for many of the stars. Four of the candidate diskpopulation stars are found to be subgiants, and a re-evaluation of theirkinematics show that they have kinematics typical of the halopopulation. One star, G190-15, is confirmed to be a dwarf with disk-likekinematics: U = -10, V = -80, W = -90 \kms. It is indistinguishable in[X/Fe] from other metal-poor stars with higher velocities, however. Themost interesting star is the high-velocity subgiant BD+80° 245,which is found to have <[``alpha "/Fe]> = -0.29+/-0.02 despite itslow metallicity, [Fe/H] = -1.86. It is also extremely deficient inbarium, [Ba/Fe] ~ -1.8, and has a large apogalacticon distance, over 20kpc. It has experienced a very different chemical history than haveother metal-poor stars found in the solar neighborhood.
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