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 photemis using the supplied population emissivity and opacity files does NOT include emission due to continuum photoexcitation associated with the warmabs line emission; continuum photoexcitation can be included by using xstar to make a new set of population and emissivity and opacity files with continuum photoexcitation turned on by running the input for this procedure given elsewhere in this chapter, but with the value of the cfrac parameter set to zero.

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.