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nei, vnei, vvnei: 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. 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. Versions 3.x and later can have their behaviour changed using a number of options with the xset command.

NEIAPECROOT
  By default this model reads atomic physics continuum and line data from the files apec_v[version]_nei_comp.fits and apec_v[version]_nei_line.fits in $HEADAS/../spectral/modelData. There are several options to specify different files. NEIAPECROOT can be set to a version number (eg 3.0.3, 3.0.7). In this case the value of NEIAPECROOT will be used to replace the default version number in the name of the standard files and the resulting files will be assumed to be in the modelData directory. Alternatively, a filename root (eg apec_v3.0.3) can be given. This root will be used as a prefix for the _nei_comp.fits and _nei_line.fits files. Finally, if neither of these work then the model will assume that the NEIAPECROOT value gives the complete directory path (eg /foo/bar/apec_v3.0.3 will use the input files /foo/bar/apec_v3.0.3_nei_comp.fits and /foo/bar/apec_v3.0.3_nei_line.fits).
APECTHERMAL
  Setting this option to yes thermally broadens lines. This runs significantly slower than the option without thermal broadening so should only be used when necessary.
APECVELOCITY
  Setting this option to a number velocity broadens lines using the given number as the line sigma in km/s. This is added in Gaussian quadrature with any thermal broadening in use.
APECMINFLUX
  Setting this option to some flux will ensure that all lines below this flux are not broadened.
APECBROADPSEUDO
  Setting this option to yes changes the default behaviour not to broaden the pseudo-continuum (low-flux lines which are not individually stored in the AtomDB output files) even if the stronger lines are being broadened.
APECNOLINES
  Setting this option to yes producesa continuum-only spectrum. This will turn off lines for all models using the apec files. Note that a line-free version of a single apec model is available as nlapec.
APEC_TRACE_ABUND
  This option can be used to set the abundances of the trace elements (ie Li, Be, B, F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu, Zn) when vv variants of models are not being used. These trace element abundances can be set either to the abundance of one of the main elements (give a string argument such as Fe) or to a numerical value (relative to Solar).
APECLOGINTERP
  Setting this option to yes uses logarithmic interpolation between tabulated temperatures.

For the nei 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/cm$^3$.
par4 redshift
norm $(10^{-14}/(4\pi[D_A(1+z)]^2))\int n_en_H dV$, where $D_A$ is the angular diameter distance to the source (cm), $n_e$ is the electron density (cm$^{-3}$), and $n_H$ is the hydrogen density (cm$^{-3}$).

For the vnei model, the parameters are:

par1 plasma temperature (keV)
par2 H abundance (set to 0 for no free-free continuum, otherwise 1)
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 $(10^{-14}/(4\pi[D_A(1+z)]^2))\int n_en_H dV$, where $D_A$ is the angular diameter distance to the source (cm), $n_e$ is the electron density (cm$^{-3}$), and $n_H$ is the hydrogen density (cm$^{-3}$).

Finally, for the vvnei model, the parameters are:

par1 plasma temperature (keV)
par2 H abundance (set to 0 for no free-free continuum, otherwise 1)
par3-par31 Abundances for all elements with 2 $\leq$ Z $\leq$ 30 wrt Solar (defined by the abund command)
par32 Ionization timescale in units of s/cm$^3$.
par33 Redshift, z
norm $(10^{-14}/(4\pi[D_A(1+z)]^2))\int n_en_H dV$, where $D_A$ is the angular diameter distance to the source (cm), $n_e$ is the electron density (cm$^{-3}$), and $n_H$ is the hydrogen density (cm$^{-3}$).


next up previous contents
Next: nlapec: continuum-only APEC emission Up: Additive Model Components Previous: mkcflow, vmcflow: cooling flow,