Luminosity to the Eddington luminosity ratio in AGN

Abstract

We discuss the optical/UV/Xray spectra of AGN within the frame of the corona model of Witt, Czerny and Zycki (1996). In this model both the disk and the corona accrete and release energy through the viscosity. The relative strength the the disk and the corona is therefore determined by the model. Translated into the spectra, this model allows to predict the spectral index alpha_{ox}, measuring the relative strenth of the big blue bump with respect to the hard X-ray power law. Comparison of the predicted and observed distributions of alpha_{ox} allow us to conclude that the luminosity to the Eddington luminosity ratio in quasars cover typically the range 0.01 - 0.1 and it is broader in Seyferts, 0.001 - 0.3, or even higher. We identify Narrow Line Seyfert galaxies as objects having high luminosity to the Eddington luminosity ratio although, in principle, the second branch of high big blue bump objects for this ratio being below 0.001 is also predicted.