adient. For a fixed column density corresponding to the total Thomson scattering depth of 1000, the peak of the emission spectrum moves from ultraviolet to soft X-ray range as the accretion rate increases. An inversion in the temperature distribution appears for an accretion rate higher than 10% of the Eddington luminosity. For a lower column density at high accretion rates, we found an optically thin, two-temperature and Comptonized bremsstrahlung dominated but still radiation pressure dominated disk.22:T45c,Emission spectrum from an accretion disk for active galactic nuclei is obtained by solving the vertical structure and radiative transfer self-consistently and by integrating the local spectrum over radii. We found that even for moderate accretion rates, disks emit a significant portion of the total luminosity in UV through soft X-ray range; for the accretion rate close to the Eddington limit, soft X-ray luminosity for a 0.1-2.0 keV range amounts to 57%, 43%, and 33% of the total luminosity for a black hole mass of 10⁷, 10⁸, and 10⁹ M_sun, respectively. We compared our numerical results with lUE, Einstein, EXOSAT, and ROSAT observations of low-redshift quasars and Seyfert 1 galaxies and found that our results can statistically account for observations of the UV bump and soft X-ray excess simultaneously without exceeding the Eddington limit. We also performed a detailed spectral fit to the quasar H1821 + 643, for which the estimated values of the black hole mass and accretion rate are 1.5 × 10⁹ M_sun and 0.7L_Edd, respectively.23:T477,The vertical structure and the emission spectrum of slim accretion discs around massive black holes are investigated for super-critical accretion states. A key process is the effect of photon trapping, which is included in the radiative transfer equation. It is found that the local radiation spectrum emitted from the inner region has a typical Comptonized bremsstrahlung form, and deviates significantly from the blackbody and the modified blackbody spectrum. The spectral hardening factor of the local spectrum has a large radial dependence: it takes a value of 10 4 (inner region) and 3 (outer region). Owing to the effect of photon trapping, the emergent luminosity becomes small compared with the gravitational energy released through viscosity. The effect is remarkable for a large accretion rate and a spin parameter close to unity. In particular, for an extreme Kerr case with an accretion rate of 100L Edd /c 2 , where L Edd is the Eddington luminosity, the emergent luminosity is approximately 2 per cent of the released energy. A comparison with the standard model is also discussed for an accretion rate under the Eddington limit.24:T4fe,We study a composite disk-corona structure in active galactic nuclei by solving for radiative transfer, hydrostatic balance, and energy balance at each layer with a different vertical height. A key assumption is that a fraction f of total energy is dissipated in a corona with a Thomson optical depth of τ_C_, and a remaining fraction, 1 - f within a main body of the disk. As f increases, a two-phased structure grows with an abrupt temperature jump at the interface. As a result, the emergent spectrum varies from a blackbody-like spectrum to a power-law spectrum with a high-energy cutoff. The power-law index is insensitive to a mass of a central black hole, accretion rate, and τ_C_ and decreases with an increase of f reaching ~0.9 for f ~ 1. The cutoff energy (E_cutoff_) is, on the other hand, related to τ_C_ as τ_C_ E_cutoff_ ~ 90 keV. The radiation field is a blackbody at the midplane of the disk, but has a power-law energy distribution near the surface due to a reflection of high-energy photons emanating from the corona. The resultant spectra thus produce litle UV bumps. To account for the observed AGN spectra, therefore, we should consider more complicated situations such as a partial coverage of hot corona and an effect of absorption by heavy elements.

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