NOAO >   Observing Info >   Approved Programs >   2012B-0096

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Proposal Information for 2012B-0096


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

CoI: Bruce Twarog, University of Kansas
CoI: Con Deliyannis, Indiana University

Title: Constraining the Evolution of Li via the Turnoff Structure of NGC 7789

Abstract: Two years ago we began a comprehensive program focused on the collection and analysis of high-dispersion spectra in the Li 6708 \AA\ region for 150-300 stars from the tip of the RGB to below the MS-turnoff in each of the open clusters, NGC 2158, NGC 6819, and NGC 7789. Our combined photometry and spectroscopy (a) supplies definitive reddening and metallicity estimates, (b) allows mapping of the impact of convection on Li from the turnoff through the subgiant/giant branch up to the He-degenerate-core boundary, (c) defines the temporal and metallicity dependence of the Li-dip, (d) tests for Li-depletion due to rotation-induced mixing for stars on the blue side of the Li-dip leaving the MS, and (e) discriminates between diffusion and planetesimal accretion as the cause of a Li peak near 7000K. Our observations have produced some unexpected but potentially critical results that may, for the first time, supply direct constraints on the nature of the Li-dip mechanism. Here, we'll obtain HYDRA spectra of NGC 7789 members from the top of the turnoff to the cool side of the Li-dip.


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



NOAO >   Observing Info >   Approved Programs >   2012B-0096

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