Last modified: December 2020

AHELP for CIAO 4.13 Sherpa v1


Context: models


The XSPEC xion model: reflected spectrum of photo-ionized accretion disk/ring.



The xsxion model is a multiplicative model component.


The model is described at [1] .

Deprecated in Sherpa 4.10.0

The lxld parameter has been renamed lxovrld to match the XSPEC definition. The name lxld can still be used to access the parameter, but this name will be removed in a future release.


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

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

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.height   thawed            5            0          100        r_s
   mdl.lxovrld  thawed          0.3         0.02          100           
   mdl.rate     thawed         0.05        0.001            1           
   mdl.cosAng   thawed          0.9            0            1           
   mdl.inner    thawed            3            2         1000        r_s
   mdl.outer    thawed          100          2.1       100000        r_s
   mdl.index    thawed            2          1.6          2.2           
   mdl.redshift frozen            0       -0.999           10           
   mdl.Feabun   frozen            1            0            5           
   mdl.E_cut    thawed          150           20          300        keV
   mdl.Ref_type frozen            1            1            3           
   mdl.Rel_smear frozen            4            1            4           
   mdl.Geometry frozen            1            1            4           


The attributes for this object are:

Attribute Definition
height The height of the source above the disk (in Schwarzschild radii).
lxovrld The ratio of the X-ray source luminosity to that of the disk.
rate The accretion rate (in Eddington units).
cosAng The cosine of the inclination angle (1 is face on).
inner The inner radius of the disk (in Schwarzschild radii).
outer The outer radius of the disk (in Schwarzschild radii).
index The photon index of the source.
redshift The redshift of the absorber.
Feabun The Fe abundance relative to Solar: see [1] for more details.
E_cut The exponential high energy cut-off energy for the source.
Ref_type See [1] for details.
Ref_smear See [1] for details.
Geometry See [1] for details.


XSPEC version

CIAO 4.13 comes with support for version 12.10.1s 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.