Skip to main content

Due to the lapse in federal government funding, NASA is not updating this website. We sincerely regret this inconvenience.

Xspec Home Page

next up previous contents
Next: Multiplicative Model Components Up: Additive Model Components Previous: voigt, zvoigt: Voigt line   Contents


vvoigt, zvvoigt: Voigt line profile with widths in km/s

A Voigt line profile with both $\sigma$ and $\gamma$ in km/s. The Voigt profile is the convolution of a Gaussian and a Lorentzian. It can be written as:

$\displaystyle A(E) = K Re[w(z)] / (\sigma(E_l/c)\sqrt{(2\pi)}) $

where $w(z) = exp(-z^2) erfc(-iz)$ is the Faddeeva function, and $z = (E-E_l + i\gamma(E_l/c)/2)/(\sqrt{2}\sigma(E_l/c))$

The parameters are:

par1 $E_l$, line energy in keV
par2 $\sigma$, gaussian line width in km/s
par3 $\gamma$, lorentzian FWHM line width in kms/
Norm $K$, total photons/cm$^{-2}$/s in the line

For zvoigt the parameters are:

par1 $E_l$, line energy in keV
par2 $\sigma$, gaussian line width in km/s
par3 $\gamma$, lorentzian FWHM line width in km/s
par4 $z$, redshift
Norm $K$, total photons/cm$^{-2}$/s in the line

The line is calculated out to fifty times the maximum of sigma and gamma. Note also that the normalization is defined as the integral over energies greater than zero since negative energies are unphysical.

next up previous contents
Next: Multiplicative Model Components Up: Additive Model Components Previous: voigt, zvoigt: Voigt line   Contents