Hertzsprung–Russell diagram for our sample. Overlaid in solid black lines are non-rotating SMC isochrones for different ages (≈0−10 Myr). Dashed black lines are the SMC rotating evolutionary tracks for stellar masses in the range of ≈10–60 M_⊙ with a rotational velocity of 110 km s⁻¹. Both the isochrones and evolutionary tracks are adopted from Brott et al. (2011). The shaded area is defined by the HD limit (Humphreys & Davidson 1979; Smith et al. 2004; Davies et al. 2018).