NOAO >   Observing Info >   Approved Programs >   2009B-0034

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Proposal Information for 2009B-0034


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

CoI: Maria Drout, University of Iowa
CoI: Knut Olsen, NOAO
CoI: Brian Skiff, Lowell Observatory
CoI: Norbert Przybilla, Univ Erlangen-Nurnberg, Bamberg, Germany
CoI: Georges Meynet, Geneva Observatory
CoI: Andre Maeder, Geneva Observatory

Title: A Census of Yellow Supergiants in the SMC: Testing Massive Star Evolutionary Models at Low Metallicities

Abstract: We are proposing to determine an accurate census of the yellow (F- and G-type) supergiants in the SMC 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 both radial velocities and standard spectral luminosity indicators 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 (~2\times solar) metallicity 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 a similar test at low metallicity. The SMC is the ideal place to further these studies, due both to its proximity and low reddening, plus our knowledge of the unevolved (O-type) and evolved (red supergiants, Wolf-Rayet star) populations. When our study is complete, the SMC will be the first galaxy to have its 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.


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