ACCRETION DISCS WITH ACCRETING CORONAE IN ACTIVE GALACTIC NUCLEI .2. THE NUCLEAR WIND

We study an accretion disc with a hot continuous corona. We assume tha t the corona itself accretes and that therefore it is powered directly by the release of the gravitational energy and cooled by radiative in teraction with the disc. We consider the vertical structure of such a corona, and show that the radial infall is accompanied by strong verti cal outflow. Such a model has two important consequences: (i) at a giv en radius the corona forms only for accretion rates larger than the li miting value, and the fraction of the energy dissipated in the corona decreases with increasing accretion rate; and (ii) the disc spectra ar e significantly softer in the optical/UV band in comparison with the p redictions for standard accretion discs, due to the mass loss and the decrease of internal dissipation in the disc. Both trends correspond w ell to the mean spectra of radio-quiet AGN and observed luminosity sta tes in galactic black hole candidates.