redge: emission, recombination edge

Recombination edge emission.

$$A(E) = \left\{ \begin{array}{ll} 0 & \mbox{if $E < E_c$} \\... ...c)\over{T_p}}] & \mbox{if $E >= E_c$} \\ \end{array} \right.$$

where:

par1	$E_c$, threshold energy
par2	$T_p$, plasma temperature (keV)
norm	$K$, photons/cm$^2$/s in the line