Journal ArticleDOI
Wind Inhomogeneities in Wolf-Rayet Stars. II. Investigation of Emission-Line Profile Variations
TLDR
In this article, a phenomenological model was introduced to simulate line-profile variations (LPVs) in emission lines from a clumped wind, and the authors investigated 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.Abstract:
We present high-resolution spectroscopic monitoring of the line-profile variations (LPVs) in the He II λ5411 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 λ5696 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 (104) of DWEEs must be used to account for the LPV. Large velocity dispersions must occur within DWEEs, which give rise to the ξ~100 km s-1 line-of-sight velocity dispersions. We find evidence for anisotropy in the velocity dispersion within DWEEs with σvr~4σvθ, where σvr and σvθ 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 r−1)β, with v∞ the terminal wind velocity. The mean duration of subpeak events, interpreted as the crossing time of DWEEs through the LER, is found to be consistent with a relatively thin LER. As a consequence, the large emission-line broadening cannot be accounted for by the systematic radial velocity gradient from the accelerating wind. Rather, emission-line broadening must be dominated by the large "turbulent" velocity dispersion σvr suggested by the LPV patterns. The remaining WR star in our sample (HD 191765) is shown to present significant differences from the others in its LPV pattern. In particular, the associated mean velocity dispersion is found to be especially large (ξ~350 km s-1, compared to ξ~100 km s-1 in other stars). Accordingly, the LPV patterns in HD 191765 cannot be satisfactorily accounted for with our model, requiring a different origin.read more
Citations
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Journal ArticleDOI
The photometric variability of the WC9-type Wolf-Rayet star WR 103
TL;DR: In this article, a collection of archival multi-colour photometric data of the variable WC9-type Wolf-Rayet star WR103 was used to search for periodicity and to disentangle continuum and line emission variations.
Journal ArticleDOI
On the Baldwin effect of He ii emission lines in WR (WN) stars
TL;DR: In this article, the relation between the equivalent width of He ii emission lines and the monochromatic continuum luminosity at the line wavelength in the spectra of Wolf-Rayet stars was investigated.
Journal ArticleDOI
OUP accepted manuscript
TL;DR: In this article , a series of XMM-Newton RGS data of the binary Wolf-Rayet star WR140 was analyzed, and it was shown that the temperature of the plasma producing Ne emission lines is 0.4-0.8 keV, using the intensity ratio of Kα lines from He-like and H-like Ne.
Journal ArticleDOI
Pulsations in Wolf-Rayet stars: observations with MOST
A.-N. Chené,Anthony F. J. Moffat +1 more
TL;DR: In this article, the first clear detection of a pulsation period of P = 9.8h in Wolf-Rayet stars was reported, and two other stars showed periods of a few days, which must be related to stellar pulsations.
Journal ArticleDOI
Direct spectroscopic observations of clumping in O-star winds
TL;DR: In this paper, transient substructures in the radiation-driven winds of five massive, hot stars in different evolutionary stages are detected as variable, narrow subpeaks superposed on their wide, wind-broadened (optical) emission lines.
References
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Journal ArticleDOI
The Treatment of Non-LTE Line Blanketing in Spherically Expanding Outflows
TL;DR: In this article, the authors proposed to use the idea of super levels first pioneered by Anderson to improve the performance of the non-LTE radiative transfer code of Hillier stars with stellar winds.
Journal ArticleDOI
Time-dependent models of radiatively driven stellar winds. I - Nonlinear evolution of instabilities for a pure absorption model
TL;DR: In this paper, numerical radiation-hydrodynamics simulations of the nonlinear evolution of instabilities in radiatively driven stellar winds have been performed and the results show a strong tendency for the unstable flow to form rather sharp rarefactions in which the highest speed material has very low density.
Journal ArticleDOI
Terminal velocities for a large sample of O stars, B supergiants, and Wolf-Rayet stars
TL;DR: In this article, it is argued that easily measured, reliable estimates of terminal velocities for early-type stars are provided by the central velocity asymptotically approached by narrow absorption features and by the violet limit of zero residual intensity in saturated P Cygni profiles.