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tokens: stars within 10 arcmin of 30 Dor. In this resulting spectroscopically selected pseudo-BBS sample, the early B-type stars outnumber the O-type stars roughly 3–1, although the implications of this are unclear since we don’t know the level of incompleteness for either. Fig. 2 shows an HR diagram with the spectroscopic OB stars plotted without (left) and with (right) an average reddening correction of E ( B − V ) = 0.13 mag applied (the average value for OB stars in the LMC adopted by A19). Also shown for comparison are LBV stars in the LMC and SMC, plotted using T eff and L Bol values from the literature (see Smith et al. 2019 ), and single-star evolutionary tracks (Brott et al. 2011 ). OB stars are placed on this HR diagram by taking their apparent or reddening corrected B − V colour as a proxy for temperature, and the luminosity comes from the V mag and a bolometric correction for the corresponding T eff value, with relations adopted from Torres ( 2010 ) and Flower ( 1996 ). These are by no means intended to be taken as accurate T eff and L Bol values; they are meant to illustrate the range of these values one might infer from apparent magnitudes and colours when only photometry is available. The red diagonal lines in Fig. 2 indicate where the V mag cut-off resides. Even though these are not the same stars as in the photometric BBS sample, there are several salient points that one can glean from Fig. 2 . Figure 2. HR diagrams comparing LBVs to inferred properties of OB stars derived from photometric colours. The T eff value used to plot each OB star is the temperature one would infer by converting the apparent B − V colour to a temperature, and the luminosity comes from the bolometric correction for that T eff value (relations adopted from Torres 2010 and Flower 1996 ) and its apparent V magnitude. The left-hand panel (a) shows the result when no reddening correction is adopted, whereas the right-hand panel (b) shows the values after applying a single average correction for E ( B − V ) = 0.13 mag to all OB stars. The black unfilled circles are spectroscopically confirmed O-type stars (similar to the sample in ST15), and the blue filled circles are spectroscopically confirmed early B-type stars, with spectral types between O9.5 and B2 (see text). Both samples are limited to spectroscopically confirmed O or early B stars brighter than V = 13.9 mag (to be consistent with the value adopted by A19), corresponding roughly to an absolute V magnitude of M V = −5. The diagonal red line in each panel shows the cut-off of V = 13.9 mag, and the four red hash marks show temperatures corresponding to different values of ( B − V ) = −0.32, −0.30, −0.20, and −0.10 mag. In both panels, the orange dashed lines are single-star evolutionary tracks from Brott et al. ( 2011 ), with initial masses in M ⊙ labelled in orange. Light yellow and blue shaded areas indicate expected effective temperature and luminosity ranges for O-type and early B-type stars