Last modified: December 2025

URL: https://cxc.cfa.harvard.edu/sherpa/ahelp/xskyrline.html
AHELP for CIAO 4.18 Sherpa

xskyrline

Context: models

Synopsis

The XSPEC kyrline model: relativistic line from axisymmetric accretion disk

Syntax

xskyrline

The xskyrline model is an additive model component.

Description

The model is described at [1] .


Example

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

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

mdl
   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
   mdl.ms       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           

ATTRIBUTES

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.

Notes

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).

References

[1]

XSPEC version

CIAO 4.18 comes with support for version 12.14.0k of the XSPEC models. This can be checked with the following:

% python -c 'from sherpa.astro import xspec;
print(xspec.get_xsversion())'
12.14.0k

Bugs

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