Nonequilibrium Chemistry in Circumstellar Shells

  • A. Goeres
  • R. Henkel
  • E. Sedlmayr
  • H.-P. Gail
Conference paper
Part of the Reviews in Modern Astronomy book series (MOD.ASTRONOMY, volume 1)

Abstract

The effects of UV radiation and velocity fields on the chemistry of circumstellar shells around late type stars are investigated. A discussion of the relevant time scales shows that nonequilibrium effects have to be taken into account. In order to demonstrate these non-equilibrium effects, the detailed chemical structure of the shell of α-Ori has been calculated with the physical and chemical parameters taken from CLEGG et al.[1]. The corresponding system of rate equations is solved numerically for a spherically expanding stationary flow. The departure from chemical equilibrium and from kinetic equilibrium is studied both for the wind and the periodic conditions around α-Ori. It is found that, due to UV radiation, most chemical reactions are far from chemical equilibrium, even in the case of a pure photospheric UV field. Photo-ions determine the evolution of the local chemistry. For a constant outflow velocity of 10 km/s, the H2 concentration shows the most pronounced departure from kinetic equilibrium caused by the specific temperature-dependence of the main H2-forming reactions and by wind effects. Periodic oscillations of UV radiation and temperature cause a significant departure of the SiO concentration from kinetic equilibrium.

Keywords

Dust Recombination Stein Supersaturation 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Clegg, R.E.S., van Ijzendoorn, L.J., and Allamandola, L.J.: 1983, Mon. Not. R. astr. Soc. 203, 125ADSGoogle Scholar
  2. 2.
    Honeycutt, R.K., Bernat, A.P., Kephard, J.E., Gow, CE., Sandford, M.T., and Lambert, D.L.: 1980, Astrophys. J. 239, 565CrossRefADSGoogle Scholar
  3. 3.
    Hagen, W., Stencel, R.E., and Dickinson, D.F.: 1983, Astrophys. J. 274, 186CrossRefADSGoogle Scholar
  4. 4.
    Mauron, N., Fort, B., Querci, F., Dreux, M., Fauconnier, T., and Lamy, P.: 1984, Astron. Astrophys. 130, 341ADSGoogle Scholar
  5. 5.
    Knapp, G.R., Phillips, T.G., and Huggins, P.J.: 1980, Astrophys. J. 242, L25CrossRefADSGoogle Scholar
  6. 6.
    Huggins, P.J.: 1985, in; Mass Loss from Red Giants, eds. M. Morris and B. Zuckerman, D. Reidel, Dordrecht, p. 161CrossRefGoogle Scholar
  7. 7.
    Hagen, W.: 1978, Astrophys. J. Suppl. 38, 1CrossRefADSGoogle Scholar
  8. 8.
    Bernat, A.P.: 1977, Astrophys. J. 213, 756CrossRefADSGoogle Scholar
  9. 9.
    Newell, R.T., Hjellming, R.M.: 1982, Astron. Astrophys. Suppl. 43, 1Google Scholar
  10. 10.
    Carpenter, K.G.: 1984, Astrophys. J. 285, 181CrossRefADSGoogle Scholar
  11. 11.
    Brown, A., Carpenter, K.G.: 1984, Astrophys. J. 287, L 43CrossRefADSGoogle Scholar
  12. 12.
    Carpenter, K.G., Brown, A., Stencel, R.E.: 1985, in: Mass Loss from Red Giants, eds. M. Morris and B. Zuckerman, D. Reidel, Dordrecht, p. 55CrossRefGoogle Scholar
  13. 13.
    Sutton, E.C., Storay, J.W.V., Betz, A.L., Townes, C.H., and Spears, D.L.: 1977, Astrophys. J. 217, L97CrossRefADSGoogle Scholar
  14. 14.
    Forrest, W.J., McCarthy, J.F., and Houk, J.R.: 1979, Astrophys. J. 233, 611CrossRefADSGoogle Scholar
  15. 15.
    Sopka, R.J., Hildebrand, R., Jaffe, D.J., Gatley, L., Roellig, T., Werner, M.W., Jura, M., and Zuckerman, B.: 1985, Astrophys. J. 294, 242CrossRefADSGoogle Scholar
  16. 16.
    McMillan, R.S., Tapia, S.: 1978, Astrophys. J. 266, L87CrossRefADSGoogle Scholar
  17. 17.
    Scalo, J.M., Slavsky, D.B.: 1980, Astrophys. J. 239, L73CrossRefADSGoogle Scholar
  18. 18.
    Glassgold, A.E., Huggins, P.J.: 1986, Astrophys. J. 306, 605CrossRefADSGoogle Scholar
  19. 19.
    Jordan-Engeln, G., Reutter, F.: 1976, Formelsammlung zur numerischen Mathematik, Bibliogr. Inst., MannheimGoogle Scholar
  20. 20.
    Thompson, G.I., Nandy, K., Jamar, C, Monfils, A., Houziaux, L., Carnochan, D.J., and Wilson, R.: 1978, Catalogue of Stellar UV Fluxes, UK Science Research CouncilGoogle Scholar
  21. 21.
    van Duinen, R.J., Aalders, J.W.G., Wesselius, P.W.P., Wildemann, K.J., Wu, C.C., Luinge, W., and Snel, D.: 1975, Astron. Astrophys. 39, 159ADSGoogle Scholar
  22. 22.
    Basri, G.S., Linsky, J.L., and Erikson, K.: 1981, Astrophys. J. 233, L135Google Scholar
  23. 23.
    Bernât, A.P., Hall, D.N.B., Hinkle, K.H., and Ridgway, S.: 1979, Astrophys. J. 233, L135CrossRefADSGoogle Scholar
  24. 24.
    Goldreich, P., Scoville, N.Z.: 1976, Astrophys. J. 205, 144CrossRefADSGoogle Scholar
  25. 25.
    Stull, D.R., Prophet, H.: 1971, JANAF-Tables, NSRDS-NBS-37, US Govern. Print. Off., Washington, D.C.Google Scholar
  26. 26.
    Gail, H.-P., Sedlmayr, E.: 1986, Astron. Astrophys. 166, 225ADSGoogle Scholar
  27. 27.
    Merrill, K.M., and Stein, W.A.: 1976, Publ. Astr. Soc. Pacific 88, 285CrossRefADSGoogle Scholar
  28. 28.
    Zuckerman, B.: 1980, Ann. Rev. Astron. Astrophys. 18, 263CrossRefADSGoogle Scholar
  29. 29.
    Dupree, A.K., Baliunas, S.L., Guinan, E.F., Hartmann, L., Nassiopoulos, G.E., and Sonneborn, G.: 1987, Astrophys. J. 317, L85CrossRefADSGoogle Scholar
  30. 30.
    Bertschinger, E., Chevalier, R.A.: 1985, Astrophys. J. 299, 167CrossRefADSGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1988

Authors and Affiliations

  • A. Goeres
    • 1
  • R. Henkel
    • 1
  • E. Sedlmayr
    • 1
  • H.-P. Gail
    • 2
  1. 1.Institut für Astronomie und AstrophysikTechnischen Universität BerlinGermany
  2. 2.Institut für Theoretische AstrophysikUniversität HeidelbergGermany

Personalised recommendations