Abstract
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 – 109.5 M ⊙ for the quasars, and 107.5 – 108.5 M ⊙ 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.
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© 1988 Springer-Verlag
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Wandel, A., Petrosian, V. (1988). Accretion-disk modelling of the optical-UV spectrum of quasars. In: Miller, H.R., Wiita, P.J. (eds) Active Galactic Nuclei. Lecture Notes in Physics, vol 307. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-19492-4_200
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DOI: https://doi.org/10.1007/3-540-19492-4_200
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