NOAO >   Observing Info >   Approved Programs >   2010B-0005

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Proposal Information for 2010B-0005


PI: Philip Massey, Lowell Observatory, phil.massey@lowell.edu
Address: 1400 W Mars Hill Road, Flagstaff, AZ 86001, USA

CoI: Kathryn Neugent, Lowell Observatory
CoI: Knut Olsen, NOAO
CoI: Brian Skiff, Lowell Observatory
CoI: Georges Meynet, Geneva Observatory
CoI: Andre Maeder, Geneva Observatory

Title: A Census of Yellow Supergiants in the Magellanic Clouds: Testing Massive Star Evolutionary Models

Abstract: We are proposing to continue our program to determine an accurate census of the yellow (F- and G-type) supergiants in the SMC and LMC in order to carry out a new and stringent test of the latest stellar evolutionary models. This region of the H-R diagram is heavily contaminated (80-90%) by foreground dwarfs and halo giants, but our study will use radial velocities to establish membership. Our recent study of the yellow supergiants in M31 demonstrated a serious disagreement between the evolutionary time scales for stars in this very short-lived phase. This might be connected to M31's high metallicity (~2\times solar) and its result on mass-loss during the red supergiant phase, or it may be a more generic problem with the models. We therefore propose to conduct similar tests at low metallicity. The Magellanic Clouds are ideal to further these studies, due both to their proximity and low reddening, plus our knowledge of their unevolved (O- type) and evolved (red supergiants, Wolf-Rayet star) populations. The TAC generously assigned us 5 nights for this project last October. Despite poor weather, we were able to obtain useful data on 74% of our SMC sample, but now need to finish our SMC sample and extend the work to the LMC. When our study is complete, the SMC and LMC will be the first galaxies to have their massive population characterized from one side of the HRD to the other, providing the observational database against which both current and future evolutionary models can be compared.


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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