Examples of stars rejected for further analysis in this work, based on spectral features. The metal lines in the spectrum of HD 46966 (top-left panel) show a systematic double-peak structure. The spectrum of HD 37061 (top-right panel) has three distinct components, which change position in wavelength with time. The helium lines in HD 66788 (bottom panels a and b) and HD 155889 (bottom panels c and d) show asymmetric line profiles, indicating a second line component in the blue wings. We note that He I λ4922 Å is asymmetric because of a forbidden component in the blue wing, but the observed extended blue wing in panel b is wider than expected if the star were to be single.