4.1.42. Vcom: Compton shoulder broadening model

This multiplicative model broadens an arbitrary additive component with a Compton shoulder.

The profile shape is given by

Here is a dimensionless parameter between -2 and 0. A value of -1 corresponds to an energy offset of E/mc^2 with E the energy of the original photon.

The parameter is introduced to allow some empirical skewness of the line profile.

The profile can be scaled in the energy direction by . For truly Compton scattering, this parameter should be kept to 1, otherwise it is not physical. However, if the user wants to mimic a double-horned profile (without the physics of Compton scattering), they may use this parameter for scaling.

. Therefore if a delta-line at energy is convolved with this component, its full energy width will be , and line photons get a rectangular distribution between and . Of course, any line or continuum emission component can be convolved with the this broadening model.

The parameters of the model are:

s : Scaling of the profile in energy space , dimensionless. Default value: 1.

a : Skewness parameter , dimensionless. Default value: 0.