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Astron. Astrophys. 347, 127-136 (1999)

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

J. Schweickhardt 1, W. Schmutz 2, O. Stahl 1, Th. Szeifert 1 and B. Wolf 1

1 Landessternwarte Heidelberg-Königstuhl, D-69117 Heidelberg, Germany
2 Institut für Astronomie, ETH-Zentrum, CH-8092 Zürich, Switzerland

Received 8 February 1999 / Accepted 29 April 1999


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 [FORMULA] d and a radial velocity semi-amplitude [FORMULA] 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 [FORMULA] km s-1. This leads to a mass ratio [FORMULA]. We obtain masses of [FORMULA] and [FORMULA] 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".

Key words: stars: binaries: eclipsing – stars: binaries: spectroscopic – stars: early-type – stars: fundamental parameters – stars: individual: WR 22 – stars: Wolf-Rayet

* Based on observations collected at the European Southern Observatory at La Silla, Chile. ESO proposals Nr. 56.D-327 and 57.D-517.

Send offprint requests to: (jschweickhardt@lsw.uni-heidelberg.de)

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© European Southern Observatory (ESO) 1999

Online publication: June 18, 1999