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: gnei, vgnei, vvgnei, bgnei, Up: Additive Model Components Previous: gadem, vgadem, vvgadem, bgadem,   Contents


gauss, zgauss: gaussian line profile

A simple gaussian line profile. If the width is $\leq 0$ then it is treated as a delta function. The zgauss variant computes a redshifted gaussian.

$\displaystyle A(E) = K{2\over{\sigma\sqrt{2\pi}(1-\mathit{erf}(-E_l/(\sqrt{2}\sigma)))}} \exp\left({-(E-E_l)^2\over{2\sigma^2}}\right) $

where:

par1 $E_l$, line energy in keV
par2 $\sigma$, line width in keV
Norm $K$, total photons/cm$^2$/s in the line

For zgauss the corresponding formula is:

$\displaystyle A(E) = K{1\over{(1+z)\sigma\sqrt{2\pi}(1-\mathit{erf}(-E_l/(\sqrt{2}\sigma)))}} \exp\left({-(E(1+z)-E_l)^2\over{2\sigma^2}}\right) $

and parameter settings are:

par1 $E_l$, source frame line energy in keV
par2 $\sigma$, source frame line width in keV
par3 $z$, redshift
Norm $K$, source frame total photons/cm$^2$/s in the line

The line is calculated out to six sigma. 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: gnei, vgnei, vvgnei, bgnei, Up: Additive Model Components Previous: gadem, vgadem, vvgadem, bgadem,   Contents