disk: accretion disk, black body

The spectrum from an accretion disk, where the opacities are dominated by free-free absorption, i.e., the so-called blackbody disk model. Not correct for a disk around a neutron star.

par1 accretion rate in Eddington Luminosities
par2 central mass in solar mass units
par3 inner disk radius in gravitational (= 3 Schwarzschild radii)
norm $2 \cos(i)/d^2$ where $i$ is the inclination of the disk and $d$ is the distance in units of 10 kpc