Last modified: December 2018

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

logabsorption

Context: models

Synopsis

Gaussian function for modeling absorption (log of fwhm).

Syntax

logabsorption

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 Angstroms.


Example

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

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

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.fwhm     thawed          100  1.17549e-38  3.40282e+38       km/s
   mdl.pos      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:

fwhm

The full-width half-maximum of the feature in km/s.

pos

The center of the feature, in Angstroms.

tau

The optical depth of the feature.

Notes

The functional form of the model for points is:

f(x) = exp(-tau * (x / pos)^(term * alpha))

term = -1     if x >= pos

     = 1      otherwise

alpha = log(2) / log(1 + 0.5 * fwhm / c)

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
logemission