RADIATION SPECTRA OF THE INNER REGION TOWARDS THE OUTER REGION IN ACCRETION DISCS
Zhu Ci-sheng(Department of Astronomy, Nanjing University)
In this paper we refer to the optically thick (geometrically thin) inner parts of a steady accretion discs as the inner region and the optically thin (geometrically thick) outer parts as the outer region. We intend to find the spectra S_v of integrated radiation that is emitted from the inner region towards the outer region. It is necessary to introduce, in integral (4), a weighting function Ω relevant to the solid angle subtended by the outer region at some point of the inner region with radius rand to the effective emitting area of disc annulus viewed from the outer region. Calculations are carried out for some values of parameters. The flux distributions S_v are showed on logarithmic scale in Figs. 1—3, where S_v and v are in arbitrary units. For intermediate frequencies such that kT_1/hvkT_0/h, the form of S_v is apparently different from a power law with spectral index equal to 1/3. We divide each curve of S_v in such intermediate range of spectra into two sections, and then fit them with a power law S_v∝v~α. The spectral index α evaluated for the different sections is listed in Table 1. The results in this paper present input spectra for the irradiated outer region of an accretion disc. We expect that they might be meaningful in the research of continuum spectra and emission lines of accretion discs and in the construction of self-irradiated accretion disc models.