Free Access
Astron. Astrophys. Suppl. Ser.
Volume 119, Number 1, October_I 1996
Page(s) 37 - 53
Published online 15 October 1996
Multi-colour photometric and spectroscopic monitoring of the WN5 star EZ Canis Majoris DOI: 10.1051/aas:1996226

Astronomy and Astrophysics Supplement Series, Vol. 119, October I 1996, 37-53

Multi-colour photometric and spectroscopic monitoring of the WN5 star EZ Canis Majoris gif

M.F.J. Duijsens , K.A. van der Hucht , A.M. van Genderen , H.E. Schwarz , H.P.J. Linders and O.M. Kolkman

Send offprint requests to: A.M. van Genderen

Leiden Observatory, Postbus 9513, NL-2300 RA Leiden, The Netherlands
Space Research Organisation Netherlands, Sorbonnelaan 2, NL-3584 CA Utrecht, The Netherlands
Nordic Optical Telescope, Apartado 474, E-38700 Sta. Cruz de La Palma, Canarias, Spain
Kapteyn Laboratory, Postbus 800, 9700 AV Groningen, The Netherlands

Received December 6, 1995; accepted February 21, 1996


We present and analyse photometric and spectroscopic observations of the WN5 star EZ Canis Majoris obtained over a period of 7 years. We discuss the changing light curve, the shift in phase of the maxima and point to flare type variability seen in one night. Small amplitude variations are reported in another night. We have investigated the change of the average visual magnitude over a time span of 18 years and found a tentative cyclic variation with a time scale of (6.6 yr) with a range of . This, of course, should be verified. If true, a precession phenomenon may offer an explanation. The trend of the maximum light amplitude of the cycle is also investigated and it shows a saw-tooth character with a timescale of . A possible relation with the magnetic activity of the star is discussed. We conclude that the line emission variability can be caused by both a single star model with an ever-changing wind and a binary (WN+NS) model.

Key words: stars: Wolf-Rayet --- stars: individual: WR 6 = HD 50896 = EZ CMa --- stars: variable --- binaries: close

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