Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999apj...514..909l&link_type=abstract
The Astrophysical Journal, Volume 514, Issue 2, pp. 909-931.
Astronomy and Astrophysics
Astronomy
119
Instabilities, Line: Profiles, Stars: Mass Loss, Stars: Wolf-Rayet, Turbulence
Scientific paper
We present high-resolution spectroscopic monitoring of the line-profile variations (LPVs) in the He II lambda5411 emission line of four Wolf-Rayet (WR) stars of the WN sequence (HD 96548, HD 191765, HD 192163, and HD 193077) and in the C III lambda5696 emission line of five WR stars of the WC sequence (HD 164270, HD 165763, HD 192103, HD 192641, and HD 193793). The LPVs are shown to present systematic patterns: they all consist of a number of relatively narrow emission subpeaks that tend to move from the line centers toward the line edges. We introduce a phenomenological model that depicts WR winds as being made up of a large number of randomly distributed, radially propagating, discrete wind emission elements (DWEEs). This working model is used to simulate LPV patterns in emission lines from a clumped wind. General properties of the LPV patterns are analyzed with the help of novel numerical tools (based on multiscale, wavelet analysis), and simulations are compared to the data. We investigate the effects on the LPVs of local velocity gradients, optical depths, various numbers of discrete wind elements, and a statistical distribution in the line flux from individual elements. We also investigate how the LPV patterns are affected by the velocity structure of the wind and by the extension of the line-emission region (LER). Eight of the stars in our sample are shown to possess strong similarities in their LPV patterns, which can all be explained in terms of our simple model of local wind inhomogeneities. We find, however, that a very large number (>~10^4) of DWEEs must be used to account for the LPV. Large velocity dispersions must occur within DWEEs, which give rise to the sigma_xi ~100 km s^-1 line-of-sight velocity dispersions. We find evidence for anisotropy in the velocity dispersion within DWEEs with sigma_v_r ~4sigma_v_theta, where sigma_v_r and sigma_v_theta are the velocity dispersions in the radial and azimuthal directions, respectively. We find marginal evidence for optical depth effects within inhomogeneous features, with the escape probability being slightly smaller in the radial direction. The kinematics of the variable features reveals lower than expected radial accelerations, with 20
Lepine Sebastien
Moffat Anthony F. J.
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