ΔRV vs. σ_det. Filled circles represent binaries, open circles represent candidate binaries, and crosses represent systems that do not meet the dual criteria described in Sect. 3.3. Wolf-Rayet stars are marked in black, O-type stars in blue, B0−B1.5 I stars in red, and later types are in green. X-ray detections from Paper II are marked with a black circle. Dashed lines and shaded areas mark the cutoffs described in the text. W13, W36, W53a, and W1021 have RV ranges that lie outside the bounds of this figure.