nei, vnei: collisional plasma, non-equilibrium, constant temperature

Non-equilibrium ionization collisional plasma model. This assumes a constant temperature and single ionization parameter. It provides a characterisation of the spectrum but is not a physical model. The references for this model can be found under the description of the equil model. The references for this model can be found under the description of the equil model. 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 vnei variant allows the user to set the abundance vector.

 

For the nei version 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	Ionization timescale in units of s cm–3.
par4	redshift z
norm	where DA is the angular size distance to the source (cm), and ne , nH (cm-3) are the electron and hydrogen densities respectively.

 

For the vnei variant the parameters are:

 

 

par1	plasma temperature (keV)
par2	H density in cm-3
par3-par14	Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (given by the Anders & Grevesse mixture)
par15	Ionization timescale in units of s cm–3.
par16	redshift z
norm	where DA is the angular size distance to the source (cm) , and ne , nH (cm-3) are the electron and hydrogen densities respectively.