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Astron. Astrophys. 347, 583-589 (1999)

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Long-term coherent variations in the WR system EZ Canis Majoris: the binary scenario revisited *

L.N. Georgiev 1, G. Koenigsberger 1, M.M. Ivanov 2, N. St.-Louis 3 and O. Cardona 4

1 Instituto de Astronomía, Universidad Nacional Autonóma de México, Apdo. Postal 70-264, 04510 México D.F., México
2 Department of Astronomy, Sofia University, 5 James Bourchier Str., BG-1126 Sofia, Bulgaria
3 Departement de Physique, U. de Montreal, Canada
4 Instituto Nacional de Astrofísica, Optica y Electrónica, Apdo. Postal 75 y 216, 72000, Pue., México

Received 6 October 1997 / Accepted 15 April 1999

Abstract

An analysis of seven different spectroscopic and eight photometric sets of observations of the WN5 star HD 50896=EZ CMa, distributed over more than 15 years is used to refine the known 3.76 days period. The value of [FORMULA] yields variations which have coherent phase-dependence. Although not conclusive, this coherence in the 3.7650 day periodic variations over such a long time revives scenarios in which HD 50896 consists of a binary system, a hypothesis that had been nearly completely discarded over the past few years. A binary scenario is not in contradiction with the presence of a non-spherically symmetric wind distribution or instabilities in the WR star's wind and, in fact, mechanisms such as these are probably responsible for the difficulty in having until now obtained a period which yields coherent variations. The low X-ray fluxes suggest that the possible companion may not be a collapsed object, or that the accretion process is inhibited.

Key words: stars: binaries: spectroscopic – stars: Wolf-Rayet – stars: variables: general – stars: individual: HD 50896 = EZ CMa = WR6

* Table 3 available in electronic form only at the CDS via anonymous ftp to: cdsarc.u-strasbg.fr (130.79.128.5) (ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/347/583 ) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/347/583

Send offprint requests to: L. Georgiev (georgiev@astroscu.unam.mx)

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© European Southern Observatory (ESO) 1999

Online publication: June 30, 1999
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