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phabs ⚬ˣˢᵖᵉᶜ｜Documentation｜1st｜20251021141957-00-⌔

phabs, vphabs, zphabs, zvphabs: photoelectric absorption

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

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The redshifted variant, zphabs, uses the formula

$M(E)=\exp [-{\eta }_H\sigma (E[1+z])]$

and has parameters

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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

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While the corresponding redshifted variant zvphabs has parameters

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Printed 2026-06-28.

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