Absolute Magnitudes and Intrinsic Colours of Wolf-Rayet Stars

Results of five-colour narrow band photoelectric observations are given for forty-three Wolf-Rayet (WR) stars in the Magellanic Clouds and for seventy-seven WR stars in the Galaxy. Photometric classification criteria are established and most WR stars in the Magellanic Clouds are classified. Absolute magnitudes are found to be correlated with spectral subclass; among the WN stars, those in the lowest excitation subclasses are the most luminous. It is found that the WR stars in the Large Magellanic Cloud are very similar to stars of the same spectral subclass in the Galaxy. However, subclasses WC6, WC7, WC8 and WC9 are completely absent from the Magellanic Clouds, and WN6 stars are rare. The relationship between absolute magnitude and spectral appearance of the WC5 + OB stars and the WN4 + OB stars is consistent with the hypothesis that these are binary systems in which WR stars, similar to single stars of the same type, are associated with O or B stars.