absorptionlorentz

Context: models

Synopsis

Lorentz function for modeling absorption (equivalent width).

Syntax

absorptionlorentz

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("absorptionlorentz", "mdl")
>>> print(mdl)

Create a component of the absorptionlorentz 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.ewidth   thawed            1 -3.40282e+38  3.40282e+38

ATTRIBUTES

The attributes for this object are:

Attribute	Definition
fwhm	The full-width half-maximum of the model in km/s.
pos	The center of the lorentzian, in Angstroms.
ewidth	The equivalent width of the model, in Angstroms.

Notes

The functional form of the model for points is:

f(x) = 1 - ewidth * c / (1.571 * fwhm * pos * l(x))

l(x) = 1 + 4 * ((1 / x - 1 / pos) * pos * c / fwhm)^2

c = speed of light in km/s

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

The speed of light can be found by inspecting the module variable sherpa.astro.optical.c_km .

Bugs

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