PI: Bruce A Twarog, U. of Kansas, firstname.lastname@example.org
Address: Dept. of Physics & Astronomy, 1251 Wescoe Hall Dr., Lawrence, KS 66045 USA
CoI: Constantine Deliyannis, Indiana U.
CoI: Barbara Anthony-Twarog, U. of Kansas
Title: Constraining the Origin and Stellar Evolution of Li Using Giants in M92 and NGC 2506
Abstract: Based upon our results in NGC 3680 and NGC 6253, we began a comprehensive program focused on the collection and analysis of high- dispersion spectra in the Li 6708 \AA\ region for 150-330 stars per cluster from the tip of the RGB to below the MS-turnoff in each of the open clusters NGC 2158, NGC 2204, NGC 6811, NGC 6819, and NGC 7789. Combined intermediate-band photometry and spectroscopy allows us to map the main sequence and post-main sequence evolution of Li with age and metallicity. Our success in these clusters leads us to push the study limits to a moderately metal-poor cluster (NGC 2506, [Fe/H] = --0.4) and an exceptionally low-metallicity globular cluster (M92, [Fe/H] = --2.7) by probing the evolution of stars on their giant/subgiant branches. With $\sim$150 stars to below the HB in M92 and $\sim$100 stars to the base of the giant branch and subgiant branch in NGC 2506, we will (a) test the degree to which standard theory correctly predicts subgiant dilution, (b) search for Li-rich stars and empirically constrain the non- standard mixing mechanisms known to be at work on the RGB, and differentiate among proposed models, (c) test the impact of intracluster population inhomogeneities on the dispersion in Li, and (d) constrain the Big Bang Li abundance.
Program Type: Standard/Galactic
Run 2 (2015A): WIYN/HYDR -- 4n on May 22 - May 23 2015, Jun 20 - Jun 21 2015
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360