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Atmospheric Diagnostics of Wolf-Rayet Stars

Published online by Cambridge University Press:  12 April 2016

C. Doom
C. Doom*
Affiliation:
Astrophysical Insitute, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium

Extract

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Wolf-Rayet (WR) stars are the descendants of massive stars that have lost their hydrogen rich envelope. Recently more accurate data on WR stars have become available: mass-loss rates (van der Hucht et al. 1986), radii and luminosities (Underhill 1983, Nussbaumer et al. 1982).

It may therefore be worthwhile to investigate if combinations of observed parameters shed some light on the structure of the extended stellar wind of WR stars.

In many WR stars the photosphere is situated in the stellar wind. We assume that the wind is stationary and isotropic. Further we assume a velocity law v(r)=v∞(1−Rs/r)β where v∞ is the terminal velocity of the wind in km/s, Rs is the radius where the wind acceleration starts and β > 0 is a free parameter. We can then easily compute the level R in the wind where the photosphere is located (de Loore et al. 1982): R is the solution of the equation 6.27 10−9 τat R v∞/ = fβ(Rs/R) where τat is the optical depth at the photosphere (2/3 or 1), (>0) is the mass loss rate in M⊙/yr and fβ > 1 is a slowly varying function (Doom 1987).

Type
Part II. Mass-Losing Stars in Different Stages of Evolution
Information
International Astronomical Union Colloquium , Volume 108: Atmospherics Diagnostics of Stellar Evolution: Chemical Peculiarity, Mass Loss, and Explosion , 1988 , pp. 148 - 149
Copyright
Copyright © Springer-Verlag 1988

References

de Loore, C., Hellings, P., Lamers, H.J.G.L.M., 1982: in de Loore, C.W.H. and Willis, A.J. (eds.) Wolf-Rayet stars, observtions, physics, evolution, Proc IAU Symp. 99 (D. Reidel, Dordrecht), p53 Google Scholar
Doom, C., 1987: Rep. Prog. Phys. (in press)Google Scholar
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Doom, C., de Greve, J.P., de Loore, C., 1986: Astrophys. J. 303, 136 Google Scholar
Nussbaumer, H., Schmutz, W., Smith, L.J., Willis, A.J., 1982: Astron. Astrophys. Suppl. 47, 257 Google Scholar
Schmutz, W., 1988: this volumeGoogle Scholar
van der Hucht, K.A., Cassinelli, J.P., Williams, P.M., 1986: Astron. Astrophys. 168, 111 Google Scholar