Skip to main content

The NASA/GSFC network is currently experiencing intermittent issues that affect our services. We are working on it and apologize for the inconvenience.
The offline tool hark (also on github) can be used to find and download data from the cloud.

Xspec Home Page

next up previous contents
Next: vlorentz, zvlorentz: lorentz line Up: Additive Model Components Previous: vagauss, zvagauss: gaussian line   Contents


vgauss, zvgauss: gaussian line profile with sigma in velocity

A simple gaussian line profile with the sigma parameter as velocity-width in km/s. If the width is $\leq 0$ then it is treated as a delta function. The zvgauss variant computes a redshifted gaussian.

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

where:

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

For zvgauss the corresponding formula is:

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

and parameter settings are:

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

The line is calculated out to six sigma.

next up previous contents
Next: vlorentz, zvlorentz: lorentz line Up: Additive Model Components Previous: vagauss, zvagauss: gaussian line   Contents