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bknpower: broken power law

A broken power law.


\begin{displaymath}
A(E) = \left\{ \begin{array}{ll}
K E^{-\Gamma_1} & \mbox{if...
...Gamma_2} &
\mbox{if $E > E_{break}$} \\
\end{array} \right.
\end{displaymath}

where:

par1 = $\Gamma_1$ power law photon index for $E < E_{break}$
par2 = $E_{break}$ break point for the energy in keV
par3 = $\Gamma_2$ power law photon index for $E > E_{break}$
norm = K photons/keV/cm$^2$/s 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 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.