Last modified: December 2023

AHELP for CIAO 4.16 Sherpa


Context: models


The XSPEC kerrd model: optically thick accretion disk around a Kerr black hole.



The xskerrd model is an additive model component.


The model is described at [1] .

Deprecated in Sherpa 4.10.0

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


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

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

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.distance frozen            1         0.01         1000        kpc
   mdl.TcoloTeff frozen          1.5            1            2           
   mdl.M        thawed            1          0.1          100      solar
   mdl.Mdot     thawed            1         0.01          100       1e18
   mdl.Incl     frozen           30            0           90        deg
   mdl.Rin      frozen        1.235        1.235          100         Rg
   mdl.Rout     frozen       100000        10000        1e+08         Rg
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
distance The distance, in units of kpc.
TcoloTeff The spectral hardening factor, Tcol/Teff. See [1] for more details.
M The mass of the central object, in solar masses.
Mdot The mass accretion rate in units of 10^18 g/s.
Incl The disk inclination angle, in degrees. A face-on disk has Incl=0.
Rin The inner radius, in units of GM/c^2. The last stable orbit is 1.235.
Rout The outer radius, in units of GM/c^2.
norm The normalization of the model. It should be fixed to 1.


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.