Optical spectra reproduced from Izotov et al. (1997, their Fig. 1). Spectrophotometric observations were obtained by the MMT Observatory using a 1$\stackrel{″}{.}$5 × 180″ slit (blue channel) and a spatial scale of 0″3 per pixel along the slit. Note the prominent broad He IIλ4686 Å and C IVλ5808 Å bumps, both explained by our WO stars (as well as the classical WC-star scenario). As for the O VIλ3818 Å, which would prove that the source is WO (and not WC), it is impossible to say if a broad component is there or not, as the flux calibration seems off at this position. For more discussion, see Sect. 4.1.