Abstract:

We present new multimode data collected since 1987 for the peculiar Wolf-Rayet star EZ CMa. The continuum photometry and polarimetry show periodic variations consistent with the previously known 3.766 day period. As before, the shapes of the light and polarization curves change from one epoch to another. A periodicity search was carried out on the amplitude of the light curves in an attempt to understand the epoch-toepoch changes. The result was inconclusive. Linear polarization data were well fitted with an eccentric binary model where an additional free parameter was included to allow for epoch-dependent changes of the geometrical electron distribution in the W-R envelope. This yielded a set of basic parameters including the eccentricity, e = 0.39 ± 0.02, and the orbital inclination, i = 114° ±3°, which appear to remain constant within their errors for most data sets. The spectroscopic data show global profile variations for all three observed strong emission lines He II λ5412, C iv λ5807, and He I λ5876. Periodicity of these variations was not obvious. Radial velocities of the lines vary with the 3.766 day period. Nevertheless, it is not clear whether these are strictly due to systematic line motion as expected in a binary system. Radially expanding inhomogeneities are also seen superposed on the line profiles. Variable polarization in the lines is also observed. We searched for a correlation in the variability seen in different modes of observation; the situation is confused by a lack of sufficient simultaneity. Finally, we discuss all the results from two points of view: a W-R +c binars system and a rotating single star.