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. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

 

The vequil variant allows the user to set the abundances for the model.

 

 

For the equil model the parameters are:

par1	plasma temperature (keV)
par2	Metal abundances (He fixed at cosmic). The elements included are C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni. Abundances are given by the Anders & Grevesse mixture
par3	redshift
norm	where DA is the angular size distance to the source (cm), ne is the electron density (cm-3), and nH is the hydrogen density (cm-3)

 

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 (given by the Anders & Grevesse mixture)
par14	Redshift, z
norm	where DA is the angular size distance to the source (cm), ne is the electron density (cm-3), and nH is the hydrogen density (cm-3)

 

The references for this model are as follows:

Borkowski, Lyerly  & Reynolds, 2001, ApJ, 548, 820

Hamilton, A.J.S., Sarazin, C. L. & Chevalier, R. A. , 1983,ApJS, 51,115

Borkowski, K.J., Sarazin, C.L. & Blondin, J.M. 1994, ApJ, 429, 710

Liedahl, D.A., Osterheld, A.L. Goldstein, W.H. 1995, ApJ, 438, L11