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Paper: Fundamental Parameters of Intermediate and High Mass Stars
Volume: 318, Spectroscopically and Spatially Resolving the Components of Close Binary Stars
Page: 222
Authors: Bennett, P.D.; Brown, A.; Fawcett, S.M.; Yang, S.; Bauer, W.H.
Abstract: Knowledge of the fundamental stellar properties: mass, radius, effective temperature and wind mass-loss rate are essential for constraining models of the late stages of evolution. The only accurate, fundamental method is to determine these parameters from binary stars but this has been done for few binaries—and no red supergiants—to the accuracy needed to significantly constrain models. We seek to determine the masses of red supergiant (RSG) stars in massive binaries accurate to 1%. In detached RSG binaries, the component stars evolve independently and the (lower mass) companions are still on the main sequence as B or A stars. To determine accurate orbits of the supergiant primaries, radial velocity observations of ∼50 detached RSG binaries have been carried out at the DAO 1.2m McKellar Telescope over the past decade. The early-type spectra of the companions are nearly featureless in the optical, and furthermore, these spectra must be separated from those of the brighter RSG primary. Therefore, it is advantageous to use the companion's spectrum in the ultraviolet (UV) to determine radial velocity shifts. Eclipsing binaries are especially useful because stellar masses can be found from analyses of the eclipse light curve and spectroscopy alone. We present preliminary analyses of fundamental parameters of three red supergiant eclipsing binary systems for which HST/GHRS and STIS high-resolution UV spectroscopy is available: ζ Aur, HR 2554, and VV Cep.
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