Last modified: December 2023

AHELP for CIAO 4.16 Sherpa


Context: models


The XSPEC kyrline model: relativistic line from axisymmetric accretion disk



The xskyrline model is an additive model component.


The model is described at [1] .


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

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

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.a        thawed       0.9982            0            1       GM/c
   mdl.theta_o  thawed           30            0           89        deg
   mdl.rin      frozen            1            1         1000     GM/c^2       frozen            1            0            1           
   mdl.rout     frozen          400            1         1000     GM/c^2
   mdl.Erest    frozen          6.4            1           99        keV
   mdl.alpha    frozen            3          -20           20           
   mdl.beta     frozen            3          -20           20           
   mdl.rb       frozen          400            1         1000     GM/c^2
   mdl.zshift   frozen            0       -0.999           10           
   mdl.limb     frozen            1            0            2           
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
a Black Hole angular momentum, in units of GM/c.
theta_o The observer inclination, where 0 is pole on. The units are degrees.
rin The inner radius (units of GM/c^2).
ms A flag that determines whether to integrate from rin (0) or to integrate emission from above the marginally-stable orbit only (1)
rout The outer radius (units of GM/c^2).
Erest The line energy in keV.
alpha The accretion disk emissivity scales as r^(-alpha) for r < rb.
beta The accretion disk emissivity scales as r^(-beta) for r > rb.
rb The boundary radius between the inner and outer emissivity laws (units of GM/c^2).
zshift The overall Doppler shift.
limb 0 means isotropic emission, 1 means Laor's limb darkening (1 + 0.26 mu), 2 means Haardt's limb brightening (ln(1 + 1/mu))
norm The normalization.


Early releases of XSPEC 12.10.1 refer to the first parameter as a/M. As this is not a valid Python name, the parameter has been renamed "a" to better match other XSPEC models (after consultation with Keith Arnaud).


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.