Last modified: December 2025

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

xscplinear

Context: models

Synopsis

The XSPEC cplinear model: a non-physical piecewise-linear model for low count background spectra.

Syntax

xscplinear

The xscplinear model is an additive model component.

Description

The model is described at [1] .


Example

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

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

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.energy00 frozen          0.5            0           10        keV
   mdl.energy01 frozen            1            0           10        keV
   mdl.energy02 frozen          1.5            0           10        keV
   mdl.energy03 frozen            2            0           10        keV
   mdl.energy04 frozen            3            0           10        keV
   mdl.energy05 frozen            4            0           10        keV
   mdl.energy06 frozen            5            0           10        keV
   mdl.energy07 frozen            6            0           10        keV
   mdl.energy08 frozen            7            0           10        keV
   mdl.energy09 frozen            8            0           10        keV
   mdl.log_rate00 frozen            0          -20           20           
   mdl.log_rate01 frozen            1          -20           20           
   mdl.log_rate02 frozen            0          -20           20           
   mdl.log_rate03 frozen            1          -20           20           
   mdl.log_rate04 frozen            0          -20           20           
   mdl.log_rate05 frozen            1          -20           20           
   mdl.log_rate06 frozen            0          -20           20           
   mdl.log_rate07 frozen            1          -20           20           
   mdl.log_rate08 frozen            0          -20           20           
   mdl.log_rate09 frozen            1          -20           20           
   mdl.norm     thawed            1            0        1e+24           

ATTRIBUTES

The attributes for this object are:

Attribute Definition
energy00, energy01, energy02, energy03, energy04, energy05, energy06, energy07, energy08, energy09 Energy in keV.
log_rate01, log_rate02, log_rate03, log_rate04, log_rate05, log_rate06, log_rate07, log_rate08, log_rate09 Log of the rate.
norm The normalization of the model.

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.