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 (\(10^{44}\) photons/s/keV):
where \(E\) is the photon energy in keV, \(T\) the temperature in keV and \(A\) the normalisation in units of \(10^{26}\) \(\mathrm{m}^{0.5}\), defined by
with \(n_{\mathrm e}\) the electron density (units: \(10^{20}\) \(\mathrm{m}^{-3}\)) and \(O\) the emitting source area (units: \(10^{16}\) m).
The parameters of the model are:
norm : Normalisation \(A\) (in units of
\(10^{26}\) \(\mathrm{m}^{0.5}\)). Default value: 1.t : The temperature \(T\) in keV. Default value: 1 keV.Recommended citation: Kaastra & Barr (1989) and Rybicki & Lightman (1986).