  We consider photon emission from a supercritical accretion disk in which
photons in the inner regions are trapped and advected in towards the center.
Such disks are believed to be present in failed supernovae and gamma-ray
bursts, and possibly also in ultra-luminous X-ray sources. We show that the
luminosity from a supercritical accretion disk is proportional to the logarithm
of the mass accretion rate when the vertical profile of the matter density is
exponential. We obtain analytical results also for other density profiles, but
the dependence of the luminosity on the accretion rate is no longer
logarithmic.
