Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994ap%26ss.216...55m&link_type=abstract
Astrophysics and Space Science, vol. 216, no. 1-2, p. 55-65
Astronomy and Astrophysics
Astrophysics
25
Emission Spectra, Hot Stars, Interstellar Matter, Line Spectra, Magnetohydrodynamic Flow, Mass Spectra, Plasma Turbulence, Stellar Models, Stellar Spectra, Stellar Winds, Wavelet Analysis, Wolf-Rayet Stars, Compressible Flow, Power Series, Power Spectra, Scaling Laws, Stellar Mass, Supersonic Flow, Turbulent Flow
Scientific paper
The quantification of stochastic substructures seen propagating away from the centers of emission lines of Wolf-Rayet (WR) stars is extended using the powerful, objective technique of wavelet analysis. Results for the substructures in one WR star so far show that the scaling laws between (a) flux and velocity dispersion and (b) lifetime and flux, combined with (c) their mass spectrum, strongly support the hypothesis that we are seeing the high mass tail-end distribution of full-scale supersonic compressible turbulence in the winds. This turbulence sets in beyond a critical radius from the star and shows remarkable similarity to the hierarchy of cloudlets seen in giant molecular clouds and other components of the Interstellar Medium (ISM). The velocity dispersion is larger on average for substructures (interpreted as density enhanced turbulent eddies) propagating towards or away from the observer, suggesting that the turbulence is anisotropic. This is not surprising, since the most likely force which drives the wind and the ensuing turbulence alike, radiation pressure, is directed outwards in all directions from the star. It is likely that a similar kind of turbulence prevails in the winds of all hot stars, of which those of WR stars are the most extreme. The consequences of clumping in winds are numerous. One of the most important is the necessary reduction in the estimate of the mass-loss rates compared to smooth outflow models.
Henriksen Richard N.
Lepine Sebastien
Moffat Anthony F. J.
Robert Carmelle
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