# 4.1.3. Bb: blackbody model¶

The surface *energy* flux of a blackbody emitter is given by

(Chapter 1 of Rybicki & Lightman 1986).
We transform this into a spectrum with energy units (conversion from Hz to keV) and
obtain for the total *photon* flux:

where now is the photon energy in keV, the temperature in keV and is the elementary charge in Coulomb. Inserting numerical values and multiplying by the emitting area , we get

where N(E) is the photon spectrum in units of photons/s/keV and the emitting area in .

The parameters of the model are:

`norm`

: Normalisation (the emitting area, in units of
. Default value: 1.`t`

: The temperature in keV. Default value: 1 keV.*Recommended citation:* Kirchhoff (1860).