1999AJ....117.1441L

We present very high resolution, very high signal-to-noise ratio spectra from the 3.6 m Canada-France-Hawaii telescope for the strong C III λ5696 emission line in γ² Velorum, the brightest Wolf-Rayet (WR) star in the sky. From two nights of spectroscopic monitoring, we have detected line profile variations (LPVs) in the form of moving emission features (subpeaks) on the broad, ``flat-topped'' underlying profile. We use the working model from the previous paper in this series to study these LPVs in terms of inhomogeneities in the radially expanding stellar wind. A comparison between simulations and the data suggests the variable subpeaks to consist of a superposition of two distinct components: (1) narrow-moving subpeaks with a mean line-of-sight velocity dispersion σ_ξ≃80 km.s^–1, and (2) broad-moving subpeaks with σ_ξ≃200 km.s^–1. Both narrow and broad subpeak components are seen to move systematically in a direction from the line center (ξ=0) toward the line edges. This motion is found to be consistent with a radial wind expansion at a mean acceleration rate a_r=13±3 m.s^–2. The narrow subpeaks are found to be similar to the stochastic subpeaks seen in the LPVs from several single and long-period binary WR stars. On the other hand, the broad features are reminiscent of the recurrent subpeaks observed in the LPVs from a few peculiar WR stars (HD 4004, HD 191765, and EZ CMa), although in γ² Vel, we find no evidence for a recurrent behavior.

We investigate the possibility that, in γ² Vel, these broad variable subpeaks arise from the shock-cone region, at the interface where the wind from the WR star collides with that of its O companion. We find no convincing evidence to support this hypothesis, although we suspect that there could be a relation between the existence of broad LPV subpeaks and the presence of the more massive O companion.