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: bmc: Comptonization by relativistic Up: Additive Model Components Previous: bkn2pow: broken power law,   Contents


bknpower, zbknpower: broken power law

bknpower is a broken power law and zbknpower a redshifted variant.

$\displaystyle A(E) = \left\{ \begin{array}{ll} K E^{-\Gamma_1} & \mbox{if $E \... ...k} (E/1 keV)^{-\Gamma_2} & \mbox{if $E > E_{break}$} \\ \end{array} \right. $

where:

par1 = $\Gamma_1$ power law photon index for $E < E_{break}$
par2 = $E_{break}$ break point for the energy in keV
par3 = $\Gamma_2$ power law photon index for $E > E_{break}$
norm = K photons/keV/cm$^2$/s at 1 keV

The formula and parameters for the redshifted variant are:

$\displaystyle A(E) = \left\{ \begin{array}{ll} K [E(1+z)]^{-\Gamma_1} & \mbox{... ... keV)^{-\Gamma_2} & \mbox{if $[E(1+z)] > E_{break}$} \\ \end{array} \right. $

where:

par1 = $\Gamma_1$ power law photon index for $E < E_{break}$
par2 = $E_{break}$ break point for the energy in keV
par3 = $\Gamma_2$ power law photon index for $E > E_{break}$
par4 = $z$ redshift
norm = K photons/keV/cm$^2$/s at 1 keV

If POW_EMIN and POW_EMAX have been defined by the xset command then the norm becomes the flux in units of $10^{-12}$ ergs/cm$^2$/s over the energy range (POW_EMIN, POW_EMAX) keV unless POW_EMIN = POW_EMAX in which case the norm becomes the flux density in micro-Jansky at POW_EMIN keV. In these cases it is important that POW_EMIN and POW_EMAX lie within the energy range on which the model is being evaluated.

next up previous contents
Next: bmc: Comptonization by relativistic Up: Additive Model Components Previous: bkn2pow: broken power law,   Contents