Last modified: December 2018

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

absorptionedge

Context: models

Synopsis

Optical model of an absorption edge.

Syntax

absorptionedge

Description

This model is intended to be used to modify another model (e.g. by multiplying the two together). It is for use when the independent axis is in wavelength units (e.g. Angstrom).


Example

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

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

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.edgew    frozen         5000  1.17549e-38  3.40282e+38  angstroms
   mdl.tau      thawed          0.5 -3.40282e+38  3.40282e+38           

ATTRIBUTES

The attributes for this object are:

egdew

The location of the edge. Above this value the model is set to 1.

tau

The optical depth of the edge.

index

The exponent used for the relative distance from the edge. It is a hidden parameter, with a value fixed at 3.

Notes

The functional form of the model for points is:

f(x) = exp(-tau * (x / edgew)^index)   for x <= edgew

     = 1                               otherwise

and for integrated data sets the low-edge of the grid is used.


Bugs

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

See Also

models
absorptiongaussian, absorptionlorentz, absorptionvoigt, opticalgaussian