sentences:  A number of lines of evidence point to a high binary fraction amongst the high-mass stars in Wd1.Some massive binaries are detected directly 
  through photometry and radial velocity observations, while many others are inferred through secondary characteristics (such as high X-ray luminosity, non-thermal radio spectra and excess infra-red emission) that are typical of colliding-wind binaries or dust-forming Wolf–Rayet stars.Overall binary fractions of 70% for the Wolf–Rayet population and in excess of 40% for the OB supergiants are currently estimated, although both may be incomplete.