  The $2p$-$3s$ lines of Fe XVII in the X-ray spectrum of the O-type star
$\zeta$ Puppis exhibit an anomalous (3G + M2)/(3F) line ratio of $\sim$1.4, in
comparison with $\sim$2.4 for almost all other collisionally excited
astrophysical spectra. Based on the work of Mauche et al. (2001), we
conjectured that the strong UV field of $\zeta$ Puppis produces the observed
ratio by depopulation of metastable $3s$ excited states, and that the ratio can
potentially be used as an independent diagnostic of plasma formation radius. We
used the Flexible Atomic Code (FAC) collisional-radiative model to model the
effect of UV photoexcitation from O stars on the Fe XVII lines. We compared our
model calculations to archival spectra of coronal and hot stars from the
Chandra HETGS and XMM-Newton RGS to benchmark our calculations for various
electron densities and UV field intensities. Our calculations show that UV
photoexcitation does not produce a sufficiently large dynamic range in the
3F/(3F + 3G + M2) fraction to explain the difference in the observed ratio
between coronal stars and $\zeta$ Pup. Thus, this effect likely cannot explain
the observed line ratio of $\zeta$ Pup, and its origin is still unexplained.
