compbb: Comptonization, black body

Comptonized blackbody model by Nishimura, Mitsuda and Itoh (1986, PASJ 38, 819). The electron temperature should normally be kept fixed since the Compton $y$ parameter is the product of the electron temperature and optical depth.

par1 blackbody temperature (keV)
par2 electron temperature of the hot plasma (keV)
par3 optical depth of the plasma
norm $(L_{39}/D_{10})^2$, where $L_{39}$ is the source luminosity in units of $10^{39}$ erg/s and $D_{10}$ is the distance to the source in units of 10 kpc (the same definition used for the bbodyrad model)