nei, vnei

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 characterization 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, and xset neivers 3.0 uses the beta release from AtomDB 3.0. Note that versions 1.x have no emission from Ar. The default is version 3.0.

The vnei variant allows the user to set the abundances of the most common elements and vvnei allows the user to set the abundances of all elements with Z<=30.

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. Relative abundances are defined by the abund command.
par3	Ionization timescale in units of s cm^–3.
par4	Redshift z
norm	where D_A is the angular diameter distance to the source (cm), and n_{e ,} n_H (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 (defined by the abund command)
par15	Ionization timescale in units of s cm^–3.
par16	Redshift z
norm	where D_A is the angular diameter distance to the source (cm) , and n_{e ,} n_H (cm^-3) are the electron and hydrogen densities respectively.

For the vvnei variant the parameters are:

par1	Plasma temperature (keV)
par2	H density in cm^-3
par3-par32	Abundances for all elements with Z <= 30 wrt Solar (defined by the abund command)
par33	Ionization timescale in units of s cm^–3.
par34	Redshift z
norm	where D_A is the angular diameter distance to the source (cm) , and n_{e ,} n_H (cm^-3) are the electron and hydrogen densities respectively.