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        powerlaw, zpowerlw:  power law photon spectrum

powerlaw is a simple photon power law. The zpowerlw variant computes a redshifted spectrum.

A(E) = K Eα

where:

par1 = α

photon index of power law (dimensionless)

norm= K

photons keV–1cm–2s–1 at 1 keV

 

For zpowerlw the formula and corresponding parameters are:

 

A(E) = K [E(1+z)]α

where :

par1= α

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.

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Next: Pshock Up: Additive Model Components Previous: Posm