= Multitemperature blackbody disk
A \b[multitemperature blackbody disk] adds the radiation from annuli with different effective <temperatures>. For a steady, radiatively efficient <accretion disk>, the inner annuli are hotter and dominate higher photon frequencies, while cooler outer annuli contribute at lower frequencies. With $T(r)\propto r^{-3/4}$, integrating the <Planck law> produces the intermediate-frequency slope $F_\nu\propto\nu^{1/3}$. This slope applies between the outer thermal turnover and inner high-frequency cutoff, rather than across the entire spectrum.<Dynamics of Astrophysical Discs, Lecture 5: Boundary Conditions and Steady Accretion by Gordon I. Ogilvie>[Section5.2: radial effective temperature and annular emission]{ref}
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