Wednesday, March 13, 2013

1303.2984 (Barbara J. Anthony-Twarog et al.)

A Lithium-Rich Red Giant Below the Clump in the Kepler Cluster, NGC 6819    [PDF]

Barbara J. Anthony-Twarog, Constantine P. Deliyannis, Evan Rich, Bruce A. Twarog
WIYN/HYDRA spectra in the Li 6708 Angstrom region have been obtained for 332 probable members of the old open cluster, NGC 6819. Preliminary analysis shows a pattern of Li depletion from the top of the turnoff to the base of the giant branch. Starting one magnitude below the level of the clump, all brighter giants have A(Li) below 1.0, with most having upper limits below 0.5. Star W007017, located BELOW the first-ascent red giant bump is Li-rich with A(Li) = 2.3. As a highly probable single-star astrometric and radial-velocity cluster member, its discrepant asteroseismic membership could be a by-product of the processes that triggered Li-enhancement. Its color-magnitude diagram location is consistent with only one proposed enhanced mixing process among first-ascent red giants.
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