Revised mass determination of the super massive Wolf-Rayet star WR 22

We analyze the orbital motion of the WN 7+abs + O binary WR 22 based on 88 high resolution optical spectra obtained in 1996. We determine a period of P=80.336 +/- 0.0013 d and a radial velocity semi-amplitude K_WR = 70.6 +/- 0.8 km s^{-1} for the Wolf-Rayet star. By averaging six He i lines it is possible to detect the weak absorptions of the O companion. The spectral class of the O star is O 9 III (O 8-O 9.5) but the luminosity class is uncertain and brightness arguments indicate a luminosity class V. For the orbit of the O companion we derive K_O = 190 +/- 10 km s^{-1}. This leads to a mass ratio q = M_WR/M_O = 2.69 +/- 0.14. We obtain masses of 55.3 +/- 7.3: M_{\odot} and 20.6 +/- 1.7: M_{\odot} for the WR and for the O star, respectively. Our mass determination revises down considerably the last published value for the mass of the Wolf-Rayet component but even with the new mass WR 22 remains ``the most massive Wolf-Rayet star ever weighed''. Based on observations collected at the European Southern Observatory at La Silla, Chile. ESO proposals Nr. 56.D-327 and 57.D-517.