photemis

The photoionized emitter can be invoked by typing 'mo photemis'. This model is the `thermal' (i.e. recombination and collisional excitation) emission which comes from the same plasma used in warmabs. Note that this does NOT include the resonant scattered emission associated with the warmabs line emission; the windabs model can be used, with a trick, to model this emission if desired (see below).

The model supplies to xspec the emissivity of the gas, in units of erg cm$^{-3}$ s$^{-1}$, times a factor 10$^{10}$. So the physical meaning of the normalization, $\kappa$, is

$$\kappa=\frac{{\rm EM}}{4\pi D^2} \times 10^{-10}$$ (8.1)

where EM is the emission measure of the gas in the source (at the ionization parameter used in the fit) and D is the distance to the source. This same relation applies to the results from the hotabs model.