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gnei, vgnei, vvgnei: collisional plasma, non-equilibrium, temperature evolution

Non-equilibrium ionization collisional plasma model. This is a generalization of the nei model where the temperature is allowed to have been different in the past i.e. the ionization timescale averaged temperature is not necessarily equal to the current temperature. For example, in a standard Sedov model with equal electron and ion temperatures, the ionization timescale averaged temperature is always higher than the current temperature for each fluid element. 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 (1998), 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 vgnei variant allows the user to set the abundances of the most common elements and vvgnei allows the user to set the abundances of all elements with Z<=30.

 

For the gnei 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 defined by the abund command

par3

Ionization timescale in units of s/cm3.

par4

Ionization timescale averaged plasma temperature (keV)

par5

Redshift

norm

 where DA is the angular diameter distance to the source (cm), ne and nH (cm-3) are the electron and hydrogen densities respectively.

 

For vgnei the parameters are:

 

par1

Plasma temperature (keV)

par2

H abundance (should take values of 0 or 1 to switch on and off free-free continuum).

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/cm3.

par16

Ionization timescale averaged plasma temperature (keV)

par17

Redshift

norm

 where DA is the angular diameter distance to the source (cm), and ne , nH (cm-3) are the electron and hydrogen densities respectively.

 

For vvgnei the parameters are:

 

par1

Plasma temperature (keV)

par2

H abundance (should take values of 0 or 1 to switch on and off free-free continuum).

par3-par31

Abundances for all elements with 2 <= Z <= 30 wrt Solar (defined by the abund command)

par32

Ionization timescale in units of s/cm3.

par33

Ionization timescale averaged plasma temperature (keV)

par34

Redshift

norm

 where DA is the angular diameter distance to the source (cm), and ne , nH (cm-3) are the electron and hydrogen densities respectively.

 

 

next up previous contents
Next: Grad Up: Additive Model Components Previous: Gaussian