equil, vequil: collisional plasma, ionization equilibrium

Ionization equilibrium collisional plasma model. This is the equilibrium version of Kazik Borkowski's NEI models. Several versions are available. To switch between them use the xset neivers command. The versions available are:

1.0	the version from xspec v11.1
1.1	as 1.0 but with updated ionization fractions using dielectronic recombination rates from Mazzotta et al (1998)
2.0	same ionization fractions as 1.1 but uses AtomDB v2 to calculate the resulting spectrum
3.x	ionization fractions and spectrum calculation uses AtomDB v3.x

Note that versions 1.x have no emission from Ar. For versions 3.x and later additional xset options are available and are listed under the documentation for nei.

For the equil model the parameters are:

par1	plasma temperature (keV)
par2	Metal abundances (He fixed at that defined by the abund command). The elements included are C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni. Abundances are defined by the abund command
par3	redshift
norm	${10^{-14}\over{4\pi[D_A(1+z)]^2}}\int n_en_HdV$, where $D_A$ is the angular diameter distance to the source (cm), $dV$ is the volume element (cm$^3$), and $n_e$ and $n_H$ are the electron and H densities (cm$^{-3}$), respectively

For the vequil model, the parameters are:

par1	plasma temperature (keV)
par2-par13	Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par14	Redshift, z
norm	${10^{-14}\over{4\pi[D_A(1+z)]^2}}\int n_en_HdV$, where $D_A$ is the angular diameter distance to the source (cm), $dV$ is the volume element (cm$^3$), and $n_e$ and $n_H$ are the electron and H densities (cm$^{-3}$), respectively

The references for this model are as follows:
Borkowski, Lyerly & Reynolds (2001)
Hamilton, Sarazin & Chevalier (1983)
Borkowski, Sarazin & Blondin (1994)
Liedahl, Osterheld & Goldstein (1995)