Disk/corona model of the mean spectra of radio-quiet and radio-loud QSO

Abstract

We test the disk/corona model of Janiuk et al. (2000) against the composite mean optical/UV/soft X-ray spectrum of radio loud and radio quiet quasars from Laor et al. (1997) which applies to faint quasars. The model well represents the optical/UV continuum if the hardening of the locally emitted spectrum is included, with the color to effective temperature ratio $f \sim 2$ in the inner 20-30 Schwarzschild radii. Comptonization seen in the soft X-ray band is well explained by the adopted corona model in the case of radio loud objects. However, this Comptonization is much stronger in radio quiet objects and additional ad hoc assumed Comptonizing medium must be present. We speculate that perhaps in both types of quasars there is a strong outflow of the hot plasma; this plasma is collimated in radio loud objects but not collimated in the radio quiet objects so it is present along the line of sight, serving as the required Comptonizing medium. Hard X-ray power law is not explained by the model and it may come from non-thermal component of electron plasma, as it is the case for galactic black holes in their soft states.