HEASARC Staff Scientist Position - Applications are now being accepted for a Staff Scientist with significant experience and interest in the technical aspects of astrophysics research, to work in the High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA Goddard Space Flight Center (GSFC) in Greenbelt, MD. Refer to the AAS Job register for full details.

Search:

[Advanced Search]



next up previous contents Xspec Home Page
Next: pshock, vpshock, vvpshock, bpshock, Up: Additive Model Components Previous: posm: positronium continuum


powerlaw, zpowerlw: power law photon spectrum

powerlaw is a simple photon power law. The zpowerlw variant computes a redshifted spectrum.

$\displaystyle A(E) = K E^{-\alpha} $

where:

par1 $\alpha$, photon index of power law (dimensionless)
norm $K$, photons/keV/cm$^2$/s at 1 keV

For zpowerlw the formula and corresponding parameters are:

$\displaystyle A(E) = K [E(1+z)]^{-\alpha} $

where:

par1 $\alpha$, photon index of power law (dimensionless)
par2 $z$, 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.

HEASARC Home | Observatories | Archive | Calibration | Software | Tools | Students/Teachers/Public
Last modified: Friday, 23-Aug-2024 13:20:40 EDT

HEASARC Staff Scientist Position - Applications are now being accepted for a Staff Scientist with significant experience and interest in the technical aspects of astrophysics research, to work in the High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA Goddard Space Flight Center (GSFC) in Greenbelt, MD. Refer to the AAS Job register for full details.