The first linear polarization spectra of Wolf-Rayet stars in the ultraviolet: EZ canis majoris and θ muscae
During the 1990 December Astro-1 space shuttle mission we conducted spectropolarimetry in the wave-length region from 1400 to 3200 Å of the Wolf-Rayet stars EZ CMa (WN5) and θ Mus (WC6 + O9.5I) with the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE). The UV polarization of EZ CMa displays features which correspond to emission lines. This indicates a large, ∼0.8%, intrinsic UV-continuum polarization, and provides further evidence that the wind of EZ CMa is highly distorted. The polarization of θ Mus does not change across emission lines, or the strong interstellar 2200 Å feature. The polarization decreases smoothly to shorter wavelengths, at constant position angle. The combined UV-optical polarization spectrum of θ Mus can be described well with interstellar polarization following a Serkowski law.