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Model to aid estimating photon fluxes and errors

NOTE: This model is now in the Xspec release and this page is superceded by the Xspec manual

This convolution model can be used with any other combination of models in order to estimate the photon flux and errors. The first two parameters are the minimum and maximum energy (in keV) over which the flux is calculated. These parameters must be frozen. The third parameter is the photon flux in photons/cm^2/s. It is important to ensure that the energy range over which the model is calculated (which is determined by the response matrix in use) covers the energy range for which the photon flux is calculated. To use this model place the cpflux component immediately in front of the component(s) for which you want to estimate the photon flux and fix the normalization parameter of one of the additive components. Now fit and use the error command as usual on the flux parameter. For instance, suppose the model is :
phabs*(pow + gauss)

then
cpflux*phabs*(pow + gauss)

with the normalizaton of the power-law model fixed gives the photon flux and error on the entire model.

phabs*cpflux*(pow + gauss)

again with the normalization of the power-law fixed gives the unabsorbed photon flux and error. Finally,

phabs*(pow + cpflux*gauss)

with the normalizaton of the gaussian fixed gives the photon flux and error on the gaussian component.

The source code file required is cpflux.cxx with the parameter information in cpflux_lmodel.dat.

Keith Arnaud, Lab. for High Energy Astrophysics, NASA/Goddard Space Flight Center

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Last modified: Tuesday, 14-Feb-2023 16:41:55 EST