vashift: velocity shift an additive model

This convolution model velocity shifts an additive model. It takes the calculated model and shifts energies $-Ev/c$.

The energies command must be to used to extend the energy range over which the model.

The parameter is:

par1=$v$

velocity (km/s)

An example model use is:

XSPEC>model phabs*vashift*(pow+ga)

which velocity shifts the power-law and gaussian then multiplies by local absorption.