Wolf-Rayet Stars: Observations, Physics, Evolution

Volume 99 of the series International Astronomical Union/Union Astronomique Internationale pp 387-392

The Wo Wolf-Rayet Stars

  • M. J. BarlowAffiliated withDept. of Physics and Astronomy, University College London
  • , D. G. HummerAffiliated withJoint Institute for Laboratory Astrophysics, University of Colorado and National Bureau of Standards

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Sanduleak (1971) has listed five stars, not apparently associated with planetary nebulae, which show very strong O VI 3811,34 Å emission. He pointed out that two of them are in the Magellanic Clouds and have absolute magnitudes comparable to those of classical (Population I) Wolf-Rayet stars. O VI emission is know to occur in some classical Wolf-Rayet stars, but not with the extreme strength shown by the Sanduleak stars. We have obtained absolute optical spectrophotometry (3100 – 7400Å) of all five of these stars, using the UCL Image Photon Counting System and RGO Spectrograph on the Anglo- Australian Telescope. Figure 1 shows their relative flux distributions. Inspection shows that Sand 1 is very lightly reddened, Sand 2 and 3 have intermediate reddening, and Sand 4 and 5 are heavily reddened. IUE ultraviolet spectrophotometry has been obtained of the first three stars; Sand 4 and 5 are too heavily reddened for IUE spectra to be feasible.