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 include the line emission due to continuum photoexcitation unless this is included in the xo01_detail.fits file created by xstar, by setting the cfrac input parameter to a value less than unity.

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


\begin{displaymath}
\kappa=\frac{{\rm EM}}{4\pi D^2} \times 10^{-10}
\end{displaymath} (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.