NOAO >   Observing Info >   Approved Programs >   2010B-0312

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Proposal Information for 2010B-0312


PI: Barbara J. Anthony-Twarog, University of Kansas, bjat@ku.edu
Address: Physics Department, 1251 Wescoe Hall Dr., Lawrence, KS 66045-7582, USA

CoI: Constantine P. Deliyannis, Indiana University
CoI: Bruce A. Twarog, University of Kansas

Title: Probing Stellar Structure and Evolution via Li Abundances

Abstract: Tests of sub-photospheric stellar structure and its evolution are few and far between. In addition to asteroseismology, color-magnitude diagram (CMD) morphology, and abundance anomalies among evolved stars, an increasingly valuable probe of stellar structure for lower mass main sequence and post-main-sequence stars is the Li abundance. Building upon our recent analysis of stars in the open clusters NGC 3680, NGC 752, IC 4651, and NGC 6253, we propose to obtain high-dispersion spectra in the Li 6708 A region for 150-350 stars from the tip of the giant branch to below the main sequence turnoff in each of 3 northern open clusters, NGC 2158, NGC 6819, and NGC 7789. The observations will (a) supply definitive spectroscopic metallicity estimates for a comprehensive sample of evolved and unevolved stars in each cluster, (b) allow mapping of the impact of convection on Li-evolution from the turnoff region through the subgiant branch and along the giant branch for stars near the He-degenerate core boundary, and (c) test the possibility of Li-enhancement due to mixing coupled to rotation for stars on the blue side of the Li-dip as they leave the main sequence. The HYDRA run requested for Fall 2010 will be used to obtain spectroscopy of an extensive sample of stars in NGC 6819 and NGC 7789. Indiana WIYN time on the 0.9m in November will be used to obtain intermediate-band photometry in NGC 7789 and NGC 2158 to aid in reddening, temperature, and membership determination.


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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