Last modified: December 2023

AHELP for CIAO 4.16 Sherpa


Context: models


The XSPEC plcabs model: powerlaw observed through dense, cold matter.



The xsplcabs model is an additive model component.


The model is described at [1] .


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

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

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.nH       thawed            1            0        1e+06 10^22 atoms / cm^2
   mdl.nmax     frozen            1 -3.40282e+38  3.40282e+38           
   mdl.FeAbun   frozen            1            0           10           
   mdl.FeKedge  frozen         7.11            7           10        KeV
   mdl.PhoIndex thawed            2           -3           10           
   mdl.HighECut frozen           95         0.01          200        keV
   mdl.foldE    frozen          100            1        1e+06           
   mdl.acrit    frozen            1            0            1           
   mdl.FAST     frozen            0 -3.40282e+38  3.40282e+38           
   mdl.redshift frozen            0       -0.999           10           
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
nH The column density, in units of 10^22 cm^-2.
nmax The maximum number of scatterings. This parameter can not be thawed.
FeAbun The iron abundance.
FeKedge The energy of the Fe K edge, in keV.
PhoIndex The power law photon index.
HighECut The high-energy cut-off threshold energy, in keV.
foldE The high-energy cut-off e-folding energy, in keV.
acrit The critical albedo for switching to elastic scattering. See [1] for more details.
FAST If set to a value above 1, use a mean energy shift instead of integration. This parameter can not be thawed.
redshift The redshift of the source.
norm The normalization of the model.


XSPEC version

CIAO 4.16 comes with support for version 12.13.1e 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.