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Session 78 - Stars - Young and Old, Large and Small.
Display session, Wednesday, January 15
Stellar evolutionary models for massive stars are often used to infer a mass via the star's luminosity, but empirical checks on the accuracy of the theoretical mass-luminosity relation have been lacking. There has also been a history of discrepancy between the masses inferred via atmospheric models and stellar evolutionary models, with differences as much as a factor of two. We present a mass-luminosity relationship using masses calculated from orbital solutions and luminosities determined primarily from cluster membership combined with the bolometric corrections inferred from improved spectral type classification of the components. Close to 400 spectra were obtained from the Coude feed spectrograph at KPNO between wavelength regions of 4000ÅÅand 4400ÅÅcovering 23 massive binary systems. Seven of the 23 systems (V453 Cyg, V382 Cyg, Y Cyg, DH Cep, AH Cep, HD 191201, HD 206267) exhibit well- defined orbits from the measured radial velocities. Spectral type was determined primarily from the ratio of Helium I and Helium II line intensities. We compare our results to the previous two methods and find good agreement with evolutionary model mass predictions. We also note the various methods of measuring radial velocities leading to questionable orbital parameters and offer orbital parameters based on simultaneous Gaussian fits of radial velocity lines from high resolution, high signal-to-noise CCD spectra for the seven binary systems. Based on our spectral analysis, we note the difficulties presented by the remaining sixteen systems in our study.
Program listing for Wednesday