1999PASP..111..861E

We present low-resolution (∼6 Å), high signal-to-noise spectropolarimetric observations obtained with the new William-Wehlau spectropolarimeter for the apparently brightest Wolf-Rayet star in the sky, the 78.5 day WR+O binary γ² Velorum. Quasi-simultaneous monitoring of all four Stokes parameters I(λ), q(λ), u(λ), and v(λ) was carried out over an interval of 31 nights centered on periastron. All emission lines in our observed wavelength interval (5200-6000 Å) show highly stochastic variations over the whole run. The phase-dependent behavior of the excess emission in the C III λ5696 line can be related to the wind-wind collision phenomenon. Varying features of Stokes q and u are seen across the strong lines, probably as a result of variable electron scattering of mainly continuum light. The spherical symmetry of the WR wind is thus broken by the presence of the O companion and clumping in the WR wind. Similar features in the extended red wing of the C III λ5696 emission line remain unexplained. No obvious circular line polarization features are seen across any emission line above the 3 σ∼0.03% instrumental level.