Galactic extinction: the Cardelli, Clayton, and Mathis model.
The interstellar extinction is calculated using the formula from  . 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 Angstrom.
>>> create_model_component("ccm", "mdl") >>> print(mdl)
Create a component of the ccm model and display its default parameters. The output is:
mdl Param Type Value Min Max Units ----- ---- ----- --- --- ----- mdl.ebv thawed 0.5 -3.40282e+38 3.40282e+38 mdl.r thawed 3.2 -3.40282e+38 3.40282e+38
The attributes for this object are:
When evaluated on a binned grid, the lower-edges of the bins are used for the calculation.
-  Cardelli, Clayton, & Mathis, 1989, ApJ, 345, 245-256. http://adsabs.harvard.edu/abs/1989ApJ...345..245C
See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.