Accretion-disk modelling of the optical-UV spectrum of quasars

  • Amri Wandel
  • Vahé Petrosian
VI. Theories of the Continuum
Part of the Lecture Notes in Physics book series (LNP, volume 307)


The thin accretion-disk spectrum, including the effect of electron scattering , is calculated for a grid of the accretion parameters (black hole mass and accretion rate). It is shown that the luminosity and spectral slope in the UV and optical bands are uniquely determined by these parameters and depend only weakly on the viscosity parameter. The model calculations are compared with data from IUE and ground based observations for a sample of ∼70 quasars and Seyfert 1 nuclei, with UV spectra and fluxes in the 912-1450A band. It is found that the black hole mass is in the range 108 – 109.5M for the quasars, and 107.5 – 108.5M for the Seyferts in the sample, and that the ratio of UV to Eddington luminosities varies from ∼ 1 for luminous, high redshift quasars, to ≪ 0.01 for low luminosity objects. The optical (4200-7500A) band gives similar results. The correlation between the spectral slope and luminosity of quasars in the UV and optical bands can be explained by evolution along curves of constant black hole mass and decreasing accretion rate. The relation between the spectrum and the accretion parameters can be used to constrain the cosmological evolution of the objects.


Black Hole Spectral Index Accretion Disk Accretion Rate Black Hole Mass 
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  1. Bechtold, J., Czerny, B., Elvis, M., Fabbiano, G., and Green, R. 1986, Ap. J., 314, 699.Google Scholar
  2. Cheng, F.H., and Fang, L.Z. 1987, preprint.Google Scholar
  3. Czerney, B., and Elvis, M. 1987, Ap. J.,, in press.Google Scholar
  4. Edelson, R.A. and Malkan, M.A. 1987, Ap. J., 308, 59.Google Scholar
  5. Kinney, A.L., Huggins, P.J., Bregman, J.N. and Glassgold, A.E., 1985, Ap. J., 291, 128.Google Scholar
  6. Malkan, M.A. 1983, Ap. J., 268, 582.Google Scholar
  7. Neugebauer, G., Green, R.J., Matthews, K., Schmidt, M., Soifer, B.T., and Bennett, J. 1987, Ap. J. Sup., 63, 615.Google Scholar
  8. O'Dell, S.L., Scott, H.A., and Stein, W.A. 1987 Ap. J. Google Scholar
  9. Osmer, P.S. and Smith, M.G. 1977, Ap. J., 213, 607.Google Scholar
  10. -1980, Ap. J. Sup., 42, 333.Google Scholar
  11. Sakura, N.I. and Sunyaev, R.A. 1973, Asir. Ap., 24, 337.Google Scholar
  12. Wandel, A. 1987, Ap. J. (Letters), 316, L55.Google Scholar
  13. Wandel, A., and Yahil, A. 1985, Ap. J. (Letters), 295, L1.Google Scholar
  14. Wandel, A., and Mushotzky, R.F. 1986, Ap. J. (Letters), 306, L61.Google Scholar
  15. Wandel, A., and Petrosian 1987, Ap. J. (Letters),, L(in press).Google Scholar

Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • Amri Wandel
    • 1
  • Vahé Petrosian
    • 1
  1. 1.Center of Space Science and Astrophysics Stanford UniversityStanfordUSA

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