Last modified: December 2022

AHELP for CIAO 4.15 Sherpa


Context: models


The XSPEC vnpshock model: shocked plasma, plane parallel, separate ion, electron temperatures.



The xsvnpshock model is an additive model component.


The model is described at [1] . The set_xsxset and get_xsxset functions are used to set and query the XSPEC XSET parameters, in particular the keyword "NEIVERS".


>>> create_model_component("xsvnpshock", "mdl")
>>> print(mdl)

Create a component of the xsvnpshock model and display its default parameters. The output is:

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.kT_a     thawed            1       0.0808         79.9        keV
   mdl.kT_b     thawed          0.5         0.01         79.9        keV
   mdl.H        frozen            1            0            1           
   mdl.He       frozen            1            0        10000           
   mdl.C        frozen            1            0        10000           
   mdl.N        frozen            1            0        10000           
   mdl.O        frozen            1            0        10000           
   mdl.Ne       frozen            1            0        10000           
   mdl.Mg       frozen            1            0        10000           
   mdl.Si       frozen            1            0        10000           
   mdl.S        frozen            1            0        10000           
   mdl.Ar       frozen            1            0        10000           
   mdl.Ca       frozen            1            0        10000           
   mdl.Fe       frozen            1            0        10000           
   mdl.Ni       frozen            1            0        10000           
   mdl.Tau_l    frozen            0            0        5e+13     s/cm^3
   mdl.Tau_u    thawed        1e+11        1e+08        5e+13     s/cm^3
   mdl.redshift frozen            0       -0.999           10           
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
kT_a The mean shock temperature, in keV.
kT_b The electron temperature immediately behind the shock front, in keV. See [1] for a discussion of the behavior of kT_a and kT_b.
H The H abundance: it should be set to 0 to switch on and 1 to switch off the free-free continuum.
He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni The abundance of the element, with respect to Solar.
Tau_l The lower limit on the ionization timescale in s/cm^3.
Tau_u The upper limit on the ionization timescale in s/cm^3.
redshift The redshift of the source.
norm The normalization of the model: see [1] for an explanation of the units.


XSPEC version

CIAO 4.15 comes with support for version 12.12.1c of the XSPEC models. This can be checked with the following:

% python -c 'from sherpa.astro import xspec;


See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

See Also

xsnpshock, xsvvnpshock