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.

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Next: plabs: power law absorption Up: Multiplicative Model Components Previous: pcfabs, zpcfabs: partial covering


phabs, vphabs, zphabs, zvphabs: photoelectric absorption

A photoelectric absorption using cross-sections set by the xsect command. The relative abundances are set by the abund command.

$\displaystyle M(E)=\exp[-\eta_H\sigma(E)] $

where $\sigma(E)$ is the photo-electric cross-section (NOT including Thomson scattering). Note that the default He cross-section changed in v11. The old version can be recovered using the command 

XSPEC12>xsect obcm

par1=$\eta_H$ equivalent hydrogen column (in units of $10^{22}$ atoms cm$^{-2}$)

The redshifted variant, zphabs, uses the formula

$\displaystyle M(E)=\exp[-\eta_H\sigma(E[1+z])] $

and has parameters

par1=$\eta_H$ equivalent hydrogen column (in units of $10^{22}$ atoms cm$^{-2}$)
par2=z redshift

The variants vphabs, zvphabs allow the user to set fixed abundance parameters with respect to the solar composition, as defined by the abund command. For vphabs (rest-frame) the parameters are

par1=$\eta_H$ equivalent hydrogen column (in units of $10^{22}$ atoms cm$^{-2}$)
par2-par18 abundances for He, C, N, O, Ne, Na, Mg, Al, Si, S, Cl, Ar, Ca, Cr, Fe, Co, Ni wrt to Solar

While the corresponding redshifted variant zvphabs has parameters

par1=$\eta_H$ equivalent hydrogen column (in units of $10^{22}$ atoms cm$^{-2}$)
par2-par18 abundances for He, C, N, O, Ne, Na, Mg, Al, Si, S, Cl, Ar, Ca, Cr, Fe, Co, Ni wrt to Solar (defined by the abund command)
par19=z redshift
next up previous contents Xspec Home Page
Next: plabs: power law absorption Up: Multiplicative Model Components Previous: pcfabs, zpcfabs: partial covering
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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.