Synthetic PoWR spectra (black line) adopting parameters for AAΩ 30 Dor 254 from Evans et al. (2010). The spectra plotted in red, moving from the top to bottom, are models which vary the mass-loss rate (M_dot), terminal velocity (v_∞) clumping factor (f_cl), microturbulence (ξ), iron abundance (X_Fe, to investigate possible blanketing effects), and carbon abundance (X_C), as detailed in Sect. 3.1. The lines identified in the lower panel are He II λλ4542, 4686; N V λλ4604-20, and C IV λ4658.