Last modified: December 2018

URL: http://cxc.harvard.edu/sherpa/ahelp/bpl1d.html
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AHELP for CIAO 4.11 Sherpa v1

bpl1d

Context: models

Synopsis

One-dimensional broken power-law function.

Syntax

bpl1d

Example

>>> create_model_component("bpl1d", "mdl")
>>> print(mdl)

Create a component of the bpl1d model and display its default parameters. The output is:

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.gamma1   thawed            0          -10           10           
   mdl.gamma2   thawed            0          -10           10           
   mdl.eb       thawed          100            0         1000           
   mdl.ref      frozen            1 -3.40282e+38  3.40282e+38           
   mdl.ampl     thawed            1        1e-20  3.40282e+38           

ATTRIBUTES

The attributes for this object are:

gamma1

The slope of the power law below the break point.

gamma2

The slope of the power law above the break point.

eb

The position of the break point.

ref

The reference position for the amplitude.

ampl

The amplitude, defined with respect to the reference position.

Notes

The functional form of the model for points is:

 f(x) = ampl * (x / ref)^(-gamma1)   x <= eb

      = ampl' * (x / ref)^(-gamma2)  otherwise

ampl' = ampl (eb / ref)^(gamma2 - gamma1)

and for an integrated grid it is the integral of this over the bin.


Bugs

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