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Instabilities in the Envelopes and Winds of Very Massive Stars

  • Stanley P. OwockiEmail author
Chapter
Part of the Astrophysics and Space Science Library book series (ASSL, volume 412)

Abstract

The high luminosity of Very Massive Stars (VMS) means that radiative forces play an important, dynamical role both in the structure and stability of their stellar envelope, and in driving strong stellar-wind mass loss. Focusing on the interplay of radiative flux and opacity, with emphasis on key distinctions between continuum vs. line opacity, this chapter reviews instabilities in the envelopes and winds of VMS. Specifically, we discuss how: (1) the iron opacity bump can induce an extensive inflation of the stellar envelope; (2) the density dependence of mean opacity leads to strange mode instabilities in the outer envelope; (3) desaturation of line-opacity by acceleration of near-surface layers initiates and sustains a line-driven stellar wind outflow; (4) an associated line-deshadowing instability leads to extensive small-scale structure in the outer regions of such line-driven winds; (5) a star with super-Eddington luminosity can develop extensive atmospheric structure from photon bubble instabilities, or from stagnation of flow that exceeds the “photon tiring” limit; (6) the associated porosity leads to a reduction in opacity that can regulate the extreme mass loss of such continuum-driven winds. Two overall themes are the potential links of such instabilities to Luminous Blue Variable (LBV) stars, and the potential role of radiation forces in establishing the upper mass limit of VMS.

Keywords

Mass Loss Rate Radiative Force Sonic Point Stellar Envelope Eddington Limit 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgements

This work was supported in part by NASA ATP grant NNX11AC40G, NASA Chandra grant TM3-14001A, and NSF grant 1312898 to the University of Delaware. I thank M. Giannotti for sharing his Mathematica notebook for the OPAL opacity tables, and N. Shaviv for many helpful discussions and for providing Fig. 5.12. I also acknowledge numerous discussions with G. Graefener, N. Smith, J. Sundqvist, J. Vink and A.J. van Marle.

References

  1. Abbott, D. C. (1980). The theory of radiatively driven stellar winds. I - A physical interpretation. Astrophysical Journal, 242, 1183.Google Scholar
  2. Abbott, D. C. (1982). The theory of radiatively driven stellar winds. II - The line acceleration. Astrophysical Journal, 259, 282.Google Scholar
  3. Arons, J. (1992). Photon bubbles - Overstability in a magnetized atmosphere. Astrophysical Journal, 388, 561.CrossRefADSGoogle Scholar
  4. Begelman, M. C. (2002). Super-eddington fluxes from thin accretion disks? Astrophysical Journal Letters, 568, L97.CrossRefADSGoogle Scholar
  5. Belyanin, A. A. (1999). Optically thick super-Eddington winds in galactic superluminal sources. Astronomy and Astrophysics, 344, 199.ADSGoogle Scholar
  6. Blaes, O., & Socrates, A. (2003). Local radiative hydrodynamic and magnetohydrodynamic instabilities in optically thick media. Astrophysical Journal, 596, 509.CrossRefADSGoogle Scholar
  7. Castor, J. I., Abbott, D. C., & Klein, R. I. (1975). Radiation-driven winds in of stars. Astrophysical Journal, 195, 157.CrossRefADSGoogle Scholar
  8. Cohen, D. H., Leutenegger, M. A., Wollman, E. E., Zsargó, J., Hillier, D. J., Townsend, R. H. D., & Owocki, S. P. (2010). A mass-loss rate determination for ζ Puppis from the quantitative analysis of X-ray emission-line profiles. Monthly Notices of the Royal Astronomical Society, 405, 2391.ADSGoogle Scholar
  9. Crowther, P. A. (2012). In Death of massive stars: Supernovae and gamma-ray bursts (Volume 279 of IAU symposium, Environments of massive stars and the upper mass limit, pp. 9–17), Nikkon.Google Scholar
  10. Crowther, P. A., Schnurr, O., Hirschi, R., Yusof, N., Parker, R. J., Goodwin, S. P., & Kassim, H. A. (2010). The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150Msolar stellar mass limit. Monthy Notices of the Royal Astronomical Society, 408, 731.CrossRefADSGoogle Scholar
  11. Dessart, L., & Owocki, S. P. (2003). Two-dimensional simulations of the line-driven instability in hot-star winds. Astronomy and Astrophysics, 406, L1.CrossRefADSGoogle Scholar
  12. Dessart, L., & Owocki, S. P. (2005). 2D simulations of the line-driven instability in hot-star winds. II. Approximations for the 2D radiation force. Astronomy and Astrophysics, 437, 657.Google Scholar
  13. Eddington, A. S. (1926). The internal constitution of the stars. Cambridge: Cambridge University Press.zbMATHGoogle Scholar
  14. Feldmeier, A. (1995). Time-dependent structure and energy transfer in hot star winds. Astronomy and Astrophysics, 299, 523.ADSGoogle Scholar
  15. Feldmeier, A., Puls, J., & Pauldrach, A. W. A. (1997). The X-ray emission from shock cooling zones in O star winds. Astronomy and Astrophysics, 322, 878.ADSGoogle Scholar
  16. Figer, D. F. (2005). An upper limit to the masses of stars. Nature, 434, 192.CrossRefADSGoogle Scholar
  17. Friend, D. B., & Abbott, D. C. (1986). The theory of radiatively driven stellar winds. III - Wind models with finite disk correction and rotation. Astrophysical Journal, 311, 701.Google Scholar
  18. Fullerton, A. W., Massa, D. L., & Prinja, R. K. (2006). The discordance of mass-loss estimates for galactic O-type stars. Astrophysical Journal, 637, 1025.CrossRefADSGoogle Scholar
  19. Gammie, C. F. (1998). Photon bubbles in accretion discs. Monthy Notices of the Royal Astronomical Society, 297, 929.CrossRefADSGoogle Scholar
  20. Gayley, K. G. (1995). An improved line-strength parameterization in hot-star winds. Astrophysical Journal, 454, 410.CrossRefADSGoogle Scholar
  21. Glatzel, W. (1994). On the origin of strange modes and the mechanism of related instabilities. Monthy Notices of the Royal Astronomical Society, 271, 66.CrossRefADSGoogle Scholar
  22. Glatzel, W. (2005). In R. Humphreys & K. Stanek (Eds.) The fate of the most massive stars (Volume 332 of Astronomical Society of the Pacific conference series, Instabilities in the most massive evolved stars, p. 22), Jackson Hole, WY.Google Scholar
  23. Glatzel, W., & Kiriakidis, M. (1993). Stability of massive stars and the humphreys / davidson limit. Monthy Notices of the Royal Astronomical Society, 263, 375.CrossRefADSGoogle Scholar
  24. Gräfener, G., Owocki, S. P., & Vink, J. S. (2012). Stellar envelope inflation near the Eddington limit. Implications for the radii of Wolf-Rayet stars and luminous blue variables. Astronomy and Astrophysics, 538, A40.Google Scholar
  25. Grevesse, N., & Noels, A. (1993). Atomic data and the spectrum of the solar photosphere. Physica Scripta T47, 133.CrossRefADSGoogle Scholar
  26. Humphreys, R. M., Davidson, K. (1979). Studies of luminous stars in nearby galaxies. III - Comments on the evolution of the most massive stars in the milky way and the large magellanic cloud. Astrophysical Journal, 232, 409.Google Scholar
  27. Iglesias, C. A., & Rogers, F. J. (1996). Updated opal opacities. Astrophysical Journal, 464, 943.CrossRefADSGoogle Scholar
  28. Joss, P. C., Salpeter, E. E., & Ostriker, J. P. (1973). On the “critical luminosity” in stellar interiors and stellar surface boundary conditions. Astrophysical Journal, 181, 429.CrossRefADSGoogle Scholar
  29. Kee, N. D., Owocki, S., & ud-Doula, A. (2014). Suppression of X-rays from radiative shocks by their thin-shell instability. Monthy Notices of the Royal Astronomical Society, 438, 3557.Google Scholar
  30. Kippenhahn, R., Weigert, A., & Weiss, A. (2013). Stellar structure and evolution: Astronomy and astrophysics library. Berlin/Heidelberg: Springer.Google Scholar
  31. Kudritzki, R. P., Puls, J., Lennon, D. J., Venn, K. A., Reetz, J., Najarro, F., McCarthy, J. K., & Herrero, A. (1999). The wind momentum-luminosity relationship of galactic A- and B-supergiants. Astronomy and Astrophysics, 350, 970.ADSGoogle Scholar
  32. Levermore, C. D., Pomraning, G. C., Sanzo, D. L., & Wong, J. (1986). Linear transport theory in a random medium. Journal of Mathematical Physics, 27, 2526.MathSciNetCrossRefzbMATHADSGoogle Scholar
  33. Lucy, L. B. (1984). Wave amplification in line-driven winds. Astrophysical Journal, 284, 351.CrossRefADSGoogle Scholar
  34. Lucy, L. B., & Solomon, P. M. (1970). Mass loss by hot stars. Astrophysical Journal, 159, 879.CrossRefADSGoogle Scholar
  35. MacGregor, K. B., Hartmann, L., & Raymond, J. C. (1979). Radiative amplification of sound waves in the winds of O and B stars. Astrophysical Journal, 231, 514.CrossRefADSGoogle Scholar
  36. Nugis, T., & Lamers, H. J. G. L. M. (2002). The mass-loss rates of Wolf-Rayet stars explained by optically thick radiation driven wind models. Astronomy and Astrophysics, 389, 162.Google Scholar
  37. Oey, M. S., & Clarke, C. J. (2005). Statistical confirmation of a stellar upper mass limit. Astrophysical Journal Letters, 620, L43.CrossRefADSGoogle Scholar
  38. Oskinova, L. M., Hamann, W.-R., & Feldmeier, A. (2007). Neglecting the porosity of hot-star winds can lead to underestimating mass-loss rates. Astronomy and Astrophysics, 476, 1331.CrossRefADSGoogle Scholar
  39. Owocki, S. P. (1991). In: L. Crivellari, I. Hubeny, & D. G. Hummer (Eds.) NATO ASIC proceedings 341: Stellar atmospheres – beyond classical models (A smooth source function method for including scattering in radiatively driven wind simulations, p. 235), Trieste.Google Scholar
  40. Owocki, S. P. (2008). In W.-R. Hamann, A. Feldmeier, L. M. Oskinova (Eds.), Clumping in hot-star winds (Dynamical simulation of the “velocity-porosity” reduction in observed strength of stellar wind lines, p. 121). Germany: Universitätsverlag Potsdam.Google Scholar
  41. Owocki, S. P. (2013). In T. D. Oswalt & M. A. Barstow (Eds.), Planets, stars and stellar systems. (Volume 4 of Stellar structure and evolution stellar winds, p. 735). Dordrecht/New York: Springer.Google Scholar
  42. Owocki, S. P., Castor, J. I., & Rybicki, G. B. (1988). Time-dependent models of radiatively driven stellar winds. I - Nonlinear evolution of instabilities for a pure absorption model. Astrophysical Journal, 335, 914.Google Scholar
  43. Owocki, S. P., & Cohen, D. H. (2006). The effect of porosity on X-ray emission-line profiles from hot-star winds. Astrophysical Journal, 648, 565.CrossRefADSGoogle Scholar
  44. Owocki, S. P., Gayley, K. G., & Shaviv, N. J. (2004). A porosity-length formalism for photon-tiring-limited mass loss from stars above the eddington limit. Astrophysical Journal, 616, 525.CrossRefADSGoogle Scholar
  45. Owocki, S. P., & Puls, J. (1996). Nonlocal escape-integral approximations for the line force in structured line-driven stellar winds. Astrophysical Journal, 462, 894.CrossRefADSGoogle Scholar
  46. Owocki, S. P., & Puls, J. (1999). Line-driven stellar winds: The dynamical role of diffuse radiation gradients and limitations to the sobolev approach. Astrophysical Journal, 510, 355.CrossRefADSGoogle Scholar
  47. Owocki, S. P., & Rybicki, G. B. (1984). Instabilities in line-driven stellar winds. I - Dependence on perturbation wavelength. Astrophysical Journal, 284, 337.Google Scholar
  48. Owocki, S. P., & Rybicki, G. B. (1985). Instabilities in line-driven stellar winds. II - Effect of scattering. Astrophysical Journal, 299, 265.Google Scholar
  49. Owocki, S. P., & ud-Doula, A. (2004). The effect of magnetic field tilt and divergence on the mass flux and flow speed in a line-driven stellar wind. Astrophysical Journal, 600, 1004.Google Scholar
  50. Papaloizou, J. C. B., Alberts, F., Pringle, J. E., & Savonije, G. J. (1997). On the nature of strange modes in massive stars. Monthy Notices of the Royal Astronomical Society, 284, 821.CrossRefADSGoogle Scholar
  51. Pauldrach, A., Puls, J., & Kudritzki, R. P. (1986). Radiation-driven winds of hot luminous stars - Improvements of the theory and first results. Astronomy and Astrophysics, 164, 86.zbMATHADSGoogle Scholar
  52. Petrovic, J., Pols, O., & Langer, N. (2006). Are luminous and metal-rich Wolf-Rayet stars inflated? Astronomy and Astrophysics, 450, 219.CrossRefADSGoogle Scholar
  53. Pomraning, G. C. (1991). Linear kinetic theory and particle transport in stochastic mixtures. Singapore/New Jersey: World Scientific.zbMATHGoogle Scholar
  54. Quinn, T., & Paczynski, B. (1985). Stellar winds driven by super-Eddington luminosities. Astrophysical Journal, 289, 634.CrossRefADSGoogle Scholar
  55. Runacres, M. C., & Owocki, S. P. (2002). The outer evolution of instability-generated structure in radiatively driven stellar winds. Astronomy and Astrophysics, 381, 1015.CrossRefADSGoogle Scholar
  56. Rybicki, G. B., Owocki, S. P., & Castor, J. I. (1990). Instabilities in line-driven stellar winds. IV - Linear perturbations in three dimensions. Astrophysical Journal, 349, 274.Google Scholar
  57. Shaviv, N. J. (1998). The eddington luminosity limit for multiphased media. Astrophysical Journal Letters, 494, L193.CrossRefADSGoogle Scholar
  58. Shaviv, N. J. (2000). The porous atmosphere of η carinae. Astrophysical Journal Letters, 532, L137.CrossRefADSGoogle Scholar
  59. Shaviv, N. J. (2001). The nature of the radiative hydrodynamic instabilities in radiatively supported thomson atmospheres. Astrophysical Journal, 549, 1093.CrossRefADSGoogle Scholar
  60. Smith, N. (2002). Dissecting the Homunculus nebula around Eta Carinae with spatially resolved near-infrared spectroscopy. Monthy Notices of the Royal Astronomical Society, 337, 1252.CrossRefADSGoogle Scholar
  61. Smith, N., Davidson, K., Gull, T. R., Ishibashi, K., & Hillier, D. J. (2003). Astrophysical Journal, 586, 432.CrossRefADSGoogle Scholar
  62. Smith, N., & Owocki, S. P. (2006). Latitude-dependent effects in the stellar wind of η Carinae. Astrophysical Journal Letters, 645, L45.CrossRefADSGoogle Scholar
  63. Sobolev, V. V. (1960). Moving envelopes of stars. Cambridge: Harvard University Press.CrossRefGoogle Scholar
  64. Spiegel, E. A. (1976). In: R. Cayrel & M. Steinberg (Eds.) Physique des Mouvements dans les Atmospheres (Photohydrodynamic instabilities of hot stellar atmospheres, p. 19). Paris: Editions du Centre National de la Recherche Scientifique.Google Scholar
  65. Spiegel, E. A. (1977). In: E. A. Spiegel & J.-P. Zahn (Eds.) Problems of Stellar Convection (Volume 71 of Lecture Notes in Physics; Photoconvection, pp. 267–283). Berlin: Springer.Google Scholar
  66. Spiegel, E. A., & Tao, L. (1999). Photofluid instabilities of hot stellar envelopes. Physics Reports, 311, 163.CrossRefADSGoogle Scholar
  67. Sundqvist, J. O., Owocki, S. P., Cohen, D. H., Leutenegger, M. A., & Townsend, R. H. D. (2012). A generalized porosity formalism for isotropic and anisotropic effective opacity and its effects on X-ray line attenuation in clumped O star winds. Monthy Notices of the Royal Astronomical Society, 420, 1553.CrossRefADSGoogle Scholar
  68. Sundqvist, J. O., Puls, J., Feldmeier, A., & Owocki, S. P. (2011). The nature and consequences of clumping in hot, massive star winds. Astronomy and Astrophysics, 528, A64.CrossRefADSGoogle Scholar
  69. van Marle, A. J., Owocki, S. P., & Shaviv, N. J. (2009). On the behaviour of stellar winds that exceed the photon-tiring limit. Monthy Notices of the Royal Astronomical Society, 394, 595.CrossRefADSGoogle Scholar
  70. Vishniac, E. T. (1994). Nonlinear instabilities in shock-bounded slabs. Astrophysical Journal, 428, 186.CrossRefADSGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  1. 1.Department of Physics & AstronomyUniversity of DelawareNewarkUSA

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