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.

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

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

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

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