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lorabs, zlorabs: lorentzian absorption line

A lorentzian absorption line as a multiplicative model. The zlorabs variant includes redshift as a parameter.

$\displaystyle M(E) = exp(-d*l(E)) $
$\displaystyle l(E) = {\sigma\over{(\pi-2\arctan(-2E_L/\sigma))}}{1\over{(E-E_L)^2 + (\sigma/2)^2}} $
where:

par1 $E_l$, line energy in keV.
par2 $\sigma$, line width (FWHM) in keV.
par3 $d$, line depth in keV.

For zlorabs the corresponding formula is:

$\displaystyle M(E) = exp(-d*g(E)) $
$\displaystyle l(E) = {1\over{(1+z)}}{\sigma\over{(\pi-2\arctan(-2E_L/\sigma))}}{1\over{(E(1+z)-E_L)^2 + (\sigma/2)^2}} $
where:

par1 $E_l$, line energy in keV.
par2 $\sigma$, line width (FWHM) in keV.
par3 $d$, line depth in keV.
par4 $z$, redshift