A multi-temperature blackbody model for a thin, steady-state, Newtonian accretion disk, assuming zero torque at the inner boundary for the disk at radius R_in. The temperature of the disk as a function of radius is assumed to be T(r) = T_* r^(-3/4) (1-r^(-1/2))^(1/4), where r = R/R_in and T_* = f(3 G M Mdot / 8 pi R_in^3 sigma)^(1/4). The maximum temperature in the disk is given by T_max = 0.488 T_*.
This model is an alternative to diskbb, which assumes a non-zero torque at the inner edge and a temperature profile T(r) = T_* r^(-3/4), and it should be used to fit spectra of disks when the zero-torque inner boundary condition is appropriate. For details see Zimmerman et al. (2004) astro-ph/0408209.
par1 = maximum temperature in the disk (keV)
par2 = (1/f^4) (R_in/D)^2 cos i, where R_in is the inner radius of the disk in km, D is the distance to the source in units of 10 kpc, i is the inclination, and f is the color to effective temperature ratio.