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A controversy has developed regarding the stellar wind mass loss rates inO-stars. The current consensus is that these winds may be clumped which impliesthat all previously derived mass loss rates using density-squared diagnosticsare overestimated by a factor of ~ 2. However, arguments based on FUSEobservations of the P V resonance line doublet suggest that these rates shouldbe smaller by another order of magnitude, provided that P V is the dominantphosphorous ion among these stars. Although a large mass loss rate reductionwould have a range of undesirable consequences, it does provide astraightforward explanation of the unexpected symmetric and un-shifted X-rayemission line profiles observed in high energy resolution spectra. Butacceptance of such a large reduction then leads to a contradiction with animportant observed X-ray property: the correlation between He-like ion sourceradii and their equivalent X-ray continuum optical depth unity radii. Here weexamine the phosphorous ionization balance since the P V fractional abundance,q(P V), is fundamental to understanding the magnitude of this mass lossreduction. We find that strong "XUV" emission lines in the He II Lymancontinuum can significantly reduce q(P V). Furthermore, owing to the uniqueenergy distribution of these XUV lines, there is a negligible impact on the S Vfractional abundance (a key component in the FUSE mass loss argument). Weconclude that large reductions in O-star mass loss rates are not required, andthe X-ray optical depth unity relation remains valid.

The Importance of XUV Radiation as a Solution to the P V Mass Loss Rate Discrepancy in O-Stars