# 4.1.24. Mbb: modified blackbody model¶

This model describes the spectrum of a black body modified by coherent Compton scattering. This is in several instances a much better description than a simple black body (for example accretion disk spectra of AGN). The physical background is described for example by Rybicki & Lightman (1986), pages 218–219. The formulae that we use here with a derivation are given by Kaastra & Barr (1989). From that work we derive the spectrum ( photons/s/keV):

where is the photon energy in keV, the temperature in keV and the normalisation in units of , defined by

with the electron density (units: ) and the emitting source area (units: m).

The parameters of the model are:

norm : Normalisation (in units of ). Default value: 1.
t : The temperature in keV. Default value: 1 keV.

Recommended citation: Kaastra & Barr (1989) and Rybicki & Lightman (1986).