NOAO >   Observing Info >   Approved Programs >   2015A-0289

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Program Information for 2015A-0289


PI: Courtney McGahee, Appalachian State U., mcgaheece@appstate.edu
Address: Dept of Physics and Astronomy, ASU Box 32106, Boone, NC 28608-2106 USA

CoI: Jeremy King, Clemson U.
CoI: Constantine Deliyannis, Indiana U.

Title: Abundances in M67 Red Giants: Constraints on Stellar Mixing and the Origin of Yellow Stragglers

Abstract: We propose to address fundamental challenges to our understanding of stellar evolution by obtaining high-resolution ($R{\sim}20,000$), high- S/N (${\ge}100$) spectra of a large sample of evolved stars in the old (${\sim}4$ Gyr) open cluster M67 using the {\it Hydra\/} multi-object spectrograph on the WIYN 3.5-meter telescope. The PI's recent dissertation results indicate that anomalous yellow stragglers (superluminous subgiants) that are cluster members show uniform and low Fe abundances compared to M67 turnoff and subgiant stars. The distribution of [Fe/H] values on the cluster's giant branch will chemically test the hypothesis that yellow stragglers are transitory objects that subsequently evolve to an unrecognized yellower giant branch than more numerous lower mass cluster giants. Accompanying determination of light element abundances will map stellar mixing from the cluster turnoff to the RGB tip and clump. These data will allow us to determine whether the Na,Mg,Al enhancements and large inferred $^{12}$C depletion factors (both of which conflict with standard stellar models) evinced by Hyades giants are also present in the much older M67 giants, which are likely more prone to mixing given their lower mass.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2015A):  WIYN/HYDR -- 7n on Feb 23 - Mar 01 2015


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 >   2015A-0289

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