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apec, vapec, vvapec: APEC emission spectrum

An emission spectrum from collisionally-ionized diffuse gas calculated from the AtomDB atomic database. More information can be found at http://atomdb.org/ which should be consulted by anyone running this model. This default version number can be changed by modifying the ATOMDB_VERSION string in your Xspec.init file.

The behaviour of the apec model and all other models which use the apec code can be changed using a number of options with the xset command.

APECROOT
  By default this model reads atomic physics continuum and line data from the files apec_v[version]_coco.fits and apec_v[version]_line.fits in $HEADAS/../spectral/modelData. There are several options to specify different files. APECROOT can be set to a version number (eg 1.10, 1.2.0, 3.0.3). In this case the value of APECROOT 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_v1.2.0) can be given. This root will be used as a prefix for the _coco.fits and _line.fits files. Finally, if neither of these work then the model will assume that the APECROOT value gives the complete directory path (eg /foo/bar/apec_v1.2.0 will use the input files /foo/bar/apec_v1.2.0_coco.fits and /foo/bar/apec_v1.2.0_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.
APECUSENEI
  Setting this option to yes routes the calculation of CEI spectra through the NEI code. This avoids potential problems when interpolating the CEI files on temperature because ion fractions can change quickly with temperature making interpolation less accurate than explicitly calculating the ion fractions for the required temperature (as performed by the NEI code). This option runs about six times slower.

For the apec model the parameters are:

par1 plasma temperature, keV
par2 Metal abundances (He fixed at cosmic). The elements included are C, N, O, Ne, Mg, Al, Si, S, Ar, Ca, Fe, Ni. Relative abundances are set by the abund command. The trace element abundances are from xset APEC_TRACE_ABUND, the default is 1.0.
par3 Redshift, z
norm ${10^{-14}\over{4\pi[D_A(1+z)]^2}}\int n_en_HdV$, where $D_A$ is the angular diameter distance to the source (cm), $n_e$ and $n_H$ are the electron and H densities (cm$^{-3}$), respectively

For the vapec variant the parameters are as follows.

par1 plasma temperature, keV
par2-par14 Abundances for He, C, N, O, Ne, Mg,Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command). The trace element abundances are from xset APEC_TRACE_ABUND, the default is 1.0.
par15 redshift, z
norm ${10^{-14}\over{4\pi[D_A(1+z)]^2}}\int n_en_HdV$, where $D_A$ is the angular diameter distance to the source (cm), $n_e$ and $n_H$ are the electron and H densities (cm$^{-3}$), respectively

For the vvapec variant the parameters are as follows.

par1 plasma temperature, keV
par2-par31 Abundances for H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn wrt Solar (defined by the abund command)
Par32 redshift, z
norm ${10^{-14}\over{4\pi[D_A(1+z)]^2}}\int n_en_HdV$, where $D_A$ is the angular diameter distance to the source (cm), $n_e$ and $n_H$ are the electron and H densities (cm$^{-3}$), respectively


next up previous contents
Next: atable: tabulated additive model Up: Additive Model Components Previous: agnslim, AGN super-Eddington accretion