Wind Inhomogeneities in Wolf-Rayet Stars. III. Unusual Emission-Line Profile Variations in gamma^2 Velorum

Details Wind Inhomogeneities in Wolf-Rayet Stars. III. Unusual Emission-Line Profile Variations in gamma^2 Velorum Wind Inhomogeneities in Wolf-Rayet Stars. III. Unusual Emission-Line Profile Variations in gamma^2 Velorum

Mar 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aj....117.1441l&link_type=abstract

The Astronomical Journal, Volume 117, Issue 3, pp. 1441-1453.

Astronomy and Astrophysics

Astronomy

15

Methods: Data Analysis, Stars: Individual (Gamma^2 Velorum), Stars: Wolf-Rayet

Scientific paper

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 lambda5696 emission line in gamma^2 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 sigma_xi~=80 km s^-1, and (2) broad-moving subpeaks with sigma_xi~=200 km s^-1. Both narrow and broad subpeak components are seen to move systematically in a direction from the line center (xi=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 gamma^2 Vel, we find no evidence for a recurrent behavior. We investigate the possibility that, in gamma^2 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.

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