Emergent Spectra from Slim Accretion Disks in Active Galactic Nuclei

Abstract

Recently the vertical structure of accretion disks has received much attention because of the available comparison with observations of the big blue bump, but all the calculations are based on the standard accretion disk model. In this paper we calculate the vertical structure and the emergent spectrum based on the radial structure of slim disks from the height-averaged equations. With the α-prescription of energy generation, we obtain the density profile as a Gaussian distribution, then solve the energy transfer problem in the z-direction. We find that the sub-Keplerian rotation affects the density profile in the z-direction. The advection process plays significant roles in the emergent spectrum, especially for high accretion rates. We show that there are two prominent characteristics of the spectrum: the presence of a maximum frequency in the emergent spectrum, which is very weakly dependent on the accretion rate, and a flattened component. These results are beyond the scope of explanation of the standard model of accretion disks even for the model with the modified blackbody spectrum. The present model is suitable for a wide range of disk parameters.