Definition of power law with exponential cut off about gamma-cat HOT 2 CLOSED

@GernotMaier - The difference in the equations you give is just whether they contain e_cut or lambda=1/e_cut, right?

In gamma-cat we currently use e_cut.

You can see this in the schema:

Indeed when we map to a spectral model in Gammapy
https://github.com/gammapy/gammapy/blob/f48b22d7f7ab9430bb2ab78521736a6e381b5318/gammapy/catalog/gammacat.py#L271
we use
http://docs.gammapy.org/dev/api/gammapy.spectrum.models.ExponentialCutoffPowerLaw.html which has lambda, but that is filled as lambda=1/e_cut.

Note that if needed, we can add more spectral models to gamma-cat and Gammapy.
E.g. in Gammapy we already have this second ECPL parametrisation because it was used in the Fermi-LAT 3FGL catalog: http://docs.gammapy.org/dev/api/gammapy.spectrum.models.ExponentialCutoffPowerLaw3FGL.html

@GernotMaier - So is there an issue with the data entry for VERITAS?

The HESS catalog will come out soon and I want to add the data to gamma-cat. There we use lambda and lambda_err. So I guess we should add an ECPL variant to gamma-cat that supports direct data entry of lambda and lambda_err, no? Any suggestion for what to call it? I think in HESS this is "ecpl3". :-)

from gamma-cat.

OK - everything clear. I missed the 1/E_cut and was simply confused - so nothing additional is needed and there is no issue with this.

(good to be closed).

from gamma-cat.