powerlaw is a simple photon power law. The zpowerlw variant computes a redshifted spectrum.
|
par1 = a |
photon index of power law (dimensionless) |
|
norm= K |
photons keV–1cm–2s–1 at 1 keV |
For zpowerlw the formula and corresponding parameters are:
where :
|
par1= a |
photon index of power law (dimensionless) |
|
par2= z |
Redshift |
|
norm= K |
photons keV–1cm–2s–1 at 1 keV |
If POW_EMIN and POW_EMAX have been defined by the xset command then the norm becomes the flux in units of 10-12 ergs cm-2 s-1 over the energy range (POW_EMIN, POW_EMAX) keV unless POW_EMIN = POW_EMAX in which case the norm becomes the flux density in micro-Jansky at POW_EMIN keV. In these cases it is important that POW_EMIN and POW_EMAX lie within the energy range on which the model is being evaluated.