Empirical bounds for the ionizing fluxes of Wolf-Rayet stars

Hα photometry and spectroscopic data have been obtained for 10 Wolf-Rayet nebulae, representing a wide variety of WN spectral types. We use these data to constrain the ionizing flux of the exciting Wolf-Rayet star, calculating lower bounds for the Lyman continuum flux (Q₀) and for the He⁰- and He⁺ionizing fluxes (Q₁ and Q₂). We find that Q₀ appears independent of WN spectral type, and lower bound estimates tend to cluster around 48 dex. Finally, we discuss the effects of potential shock excitation and density bounding on these nebulae and compare our results to recent models. Our results are consistent with the predictions of line-blanketed ISA-wind models and nonblanketed CMFGEN models but are consistent with only some of the line-blanketed CMFGEN models.