Hostname: page-component-77c89778f8-gvh9x Total loading time: 0 Render date: 2024-07-21T23:19:45.418Z Has data issue: false hasContentIssue false
  • English
  • Français

Dynamics and variability of winds from single Wolf-Rayet stars

Published online by Cambridge University Press:  25 May 2016

Stanley P. Owocki  and
Kenneth G. Gayley
Stanley P. Owocki
Affiliation:
Bartol Research Institute, University of Delaware, Newark, DE 19350, USA
Kenneth G. Gayley
Affiliation:
Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52245, USA

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We review the dynamics of winds from single Wolf-Rayet stars, with emphasis on the following specific points:

  1. (a) The classical “momentum problem” (to explain the large inferred ratio of wind to radiative momentum, η Mv∞/(L/c) ≫ 1) is in principle readily solved through multiple scattering of radiation by an opacity that is sufficiently “gray” in its spectral distribution. In this case, one simply obtains η ≃ τ, where τ is the wind optical depth;

  2. (b) Lines with a Poisson spectral distribution yield an “effectively gray” cumulative opacity, with multi-line scattering occuring when the velocity separation between thick lines Δv is less than the wind terminal speed v∞. In this case, one obtains η ≃ v∞/Δv;

  3. (c) However, realistic line lists are not gray, and leakage through gaps in the line spectral distribution tends to limit the effective scattering to η ≲ 1;

  4. (d) In WR winds, ionization stratification helps spread line-bunches and so fill in gaps, allowing for more effective global trapping of radiation, and thus η > 1;

  5. (e) However, photon thermalization can reduce the local effectiveness of line-driving near the stellar core, making it difficult for radiation alone to initiate the wind;

  6. (f) The relative complexity of WR wind initiation may be associated with the extensive turbulent structure inferred from observed variabililty in WR wind emission lines;

  7. (g) Overall, the understanding of WR winds is perhaps best viewed as an “opacity problem”, i.e., identifying the enhanced opacity that can adequately block the radiation flux throughout the wind, and thus drive a WR mass loss that is much greater than from OB stars of comparable luminosity.

Type
Part 2. Models for single star evolution of massive stars: wind + atmosphere + interior
Information
Symposium - International Astronomical Union , Volume 193: Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies , 1999 , pp. 157 - 167
Copyright
Copyright © Astronomical Society of the Pacific 1999 

References

Abbott, D.C., Lucy, L.B. 1985, ApJ 679, 693 Google Scholar
Beals, C.S. 1941, in: Shaler, A. (ed.), Observation des Novae (Paris: Hermann)Google Scholar
Castor, J.I., Abbott, D.C., Klein, R.I. 1975, ApJ 195, 157 (CAK) CrossRefGoogle Scholar
Friend, D.B., Castor, J.I. 1983, ApJ 272, 259 CrossRefGoogle Scholar
Gayley, K.G. 1995, ApJ 454, 410 CrossRefGoogle Scholar
Gayley, K.G., Owocki, S.P., Cranmer, S.R. 1994, ApJ 442, 296 CrossRefGoogle Scholar
Glatzel, W., Kiriakidis, M., Fricke, K.J. 1993, MNRAS 262, 7 CrossRefGoogle Scholar
Hamann, W.-R., Koesterke, L., Wessolowski, U. 1995, A&A 299, 151 Google Scholar
Hillier, D.J. 1991, A&A 247, 455 Google Scholar
Hillier, D.J., Millier, D.L. 1998, ApJ 496, 407 CrossRefGoogle Scholar
Kato, M., Iben, I. 1992, ApJ 394, 305 CrossRefGoogle Scholar
Kudritzki, R.-P., Lennon, D., Puls, J. 1995, in: Walsh, J. & Danziger, I. (eds.), Science with the Very Large Telescope , (ESO: Garching)Google Scholar
Netzer, N., Elitzur, M. 1993, ApJ 410, 701 CrossRefGoogle Scholar
Lépine, S. 1998, PhD Thesis, Université de Montréal Google Scholar
Lucy, L.B., Abbott, D.C. 1993, ApJ 405, 738 CrossRefGoogle Scholar
Owocki, S.P. 1994, in: Moffat, A.F.J., Owocki, S. P., Fullerton, A. W. & St-Louis, N. (eds.), Instability and Variability of Hot-Star Winds, ApSS 221, 3 Google Scholar
Owocki, S.P., Gayley, K.G. 1995, in: van der Hucht, K.A. and Williams, P.M. (eds.), Wolf-Rayet Stars: Binaries, Colliding Winds, Evolution, Proc. IAU Symp. No. 163 (Dordrecht: Kluwer), p. 138 CrossRefGoogle Scholar
Puls, J., Kudritzki, R.-P., Herrero, A. et al. 1996, A&A 305, 171 Google Scholar
Robert, C. 1991, PhD Thesis, Université de Montréal Google Scholar
Schmutz, W., Hamann, W.-R., Wessolowski, U. 1989, A&A 210, 236 Google Scholar
Schmutz, W. 1997, A&A 321, 268 Google Scholar
Schulte-Ladbeck, R.E., Eenens, P., Davis, K. 1995, ApJ 454, 917 CrossRefGoogle Scholar
Springmann, U. 1994, A&A 289, 505 Google Scholar
Springmann, U., Puls, J. 1997, in: Howarth, I. (ed.), Boulder-Munich II: Properties of Hot, Luminous Stars, ASP-CS 131, 286 Google Scholar
Springmann, U. 1998, Ph.D. Thesis, University of Munich Google Scholar
Willis, A. J. 1991, in: van der Hucht, K.A & Hidayat, B. (eds.), Wolf-Rayet Stars and Interrelations with Other Massive Stars in Galaxies, Proc. IAU Symp. No. 143, (Dordrecht: Kluwer), p. 265 CrossRefGoogle Scholar
Willson, L. 1987, in: Late Stages of Stellar Evolution (Dordrecht: Reidel), p. 253 CrossRefGoogle Scholar