npshock, vnpshock, vvnpshock: shocked plasma, plane parallel, separate ion, electron temperatures

Plane-parallel shock plasma model with separate ion and electron
temperatures. This model is slow. `par1` provides a measure of
the average energy per particle (ions+electrons) and is constant
throughout the postshock flow in plane shock models (Borkowski et al.,
2001, ApJ, 548, 820). `par2` should always be less than
`par1`. If `par2` exceeds `par1` then their
interpretations are switched (ie the larger of `par1` and
`par2` is always the mean temperature). Additional references
can be found under the help for 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 |

3.0 | ionization fractions and spectrum calculation uses AtomDB v3 |

Note that versions 1.x have no emission from Ar. The default is
version 3.0. The vnpshock variant allows the user to set the
abundances for the more common elements. For versions 3 and above the
abundances of the trace elements (ie Li, Be, B, F, Na, P, Cl, K, Sc,
Ti, V, Cr, Mn, Co, Cu, Zn) can be set using xset **APEC_TRACE_ABUND**. These trace element abundances can be set
either to the abundance of one of the main elements or to a numerical
value (relative to Solar). For instance,

XSPEC12> xset APEC_TRACE_ABUND Fesets trace element abundances to that of iron while

XSPEC12> xset APEC_TRACE_ABUND 1.0sets them to Solar. The default value for APEC_TRACE_ABUND is 1.0. Full control over all the elemental abundances is available in the vvnpshock model.

For the npshock model the parameters are:

par1 | Mean shock temperature (keV) |

par2 | Electron temperature immediately behind the shock front (keV) |

par3 | 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 |

par4 | Lower limit on ionization timescale in units of s/cm. |

par5 | Upper limit on ionization timescale in units of s/cm. |

par6 | redshift |

norm | , where is the angular diameter distance to the source (cm), is the electron density (cm), and is the hydrogen density (cm). |

For the vnpshock model, the parameters are:

par1 | Mean shock temperature (keV) |

par2 | Electron temperature immediately behind the shock front (keV) |

par3 | H abundance (should take values of 0 or 1 to switch on and off free-free continuum) |

par4-par15 | Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command) |

par16 | Lower limit on ionization timescale in units of s/cm. |

par17 | Upper limit on ionization timescale in units of s/cm. |

par18 | Redshift, z |

norm | , where is the angular diameter distance to the source (cm), is the electron density (cm), and is the hydrogen density (cm). |

Finally, for the vvnpshock model, the parameters are:

par1 | Mean shock temperature (keV) |

par2 | Electron temperature immediately behind the shock front (keV) |

par3 | H abundance (should take values of 0 or 1 to switch on and off free-free continuum) |

par4-par32 | Abundances for all elements with 2 Z 30 wrt Solar (defined by the abund command) |

par33 | Lower limit on ionization timescale in units of s/cm. |

par34 | Upper limit on ionization timescale in units of s/cm. |

par35 | Redshift, z |

norm | , where is the angular diameter distance to the source (cm), is the electron density (cm), and is the hydrogen density (cm). |