Abstract
The issue of the multiplicity of massive stars can be addressed through the investigation of radial velocity variations in spectral lines, or by the detection of blended asymmetric line profiles. However, the absence of such signatures should by no mean be interpreted as an evidence that the star is single. The non-detection of the spectral line of the secondary can indeed be due to a high luminosity ratio of the two components of the binary. The lack of significant radial velocity variation can also be due to a very low inclination angle of the orbit, a poor sampling of an eccentric orbit, or even a very long orbital period.
