EDP Sciences
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Volume 384, Number 3, March IV 2002
Page(s) 1012 - 1022
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020085

A&A 384, 1012-1022 (2002)
DOI: 10.1051/0004-6361:20020085

On the variability of the visual binary WR 86

WC7 with a $\beta$-Cephei companion
S. J. Paardekooper1, P. M. Veen1, A. M. van Genderen1 and K. A. van der Hucht2

1  Leiden Observatory, Postbus 9513, 2300 RA Leiden, The Netherlands
2  SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

(Received 30 August 2001 / Accepted 15 January 2002)

We discuss the variability of WR 86 (WC7 (+B0 III)), a known visual binary, confirmed by Hubble Space Telescope observations (Niemela et al. 1998). Photometric observations show a fairly smooth light curve with a time scale of ~3.5 h and a light amplitude of ${\sim}0\fm 01$. Because of the spectral classification of the visual companion (B0 III) it might well be a $\beta$-Cephei star. From observations taken in 1989, 1990 and 1995 we derive two photometric frequencies, $6.914\: \rm {cd^{-1}}$ and $7.236\: \rm {cd^{-1}}$, where only the latter is given in the recent VIIth catalogue of galactic Wolf-Rayet stars (van der Hucht 2001). Our spectroscopy reveals a slightly variable WR star and almost certainly a pulsating companion. Comparison with stellar models suggests that WR 86 consists of a $20~{M_\odot}$ $\beta$-Cephei star in combination with a WR star of initial mass $40~{M_\odot}$, at Z=0.04. We derive a distance to WR 86 of $2.1 \pm 0.8$ kpc.

Key words: stars: binaries: general -- stars: Wolf-Rayet -- stars: individual: WR 86

Offprint request: A. M. van Genderen, genderen@strw.leidenuniv.nl

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