Abstract
High-angular resolution imaging, speckle, optical or near-infrared interferometric techniques have been used to determine the visual orbits of many nearby bright massive stars. Moreover, the combination of visual orbits and radial-velocity (RV) curves provides a method to derive the true orbit of the system, and hence, masses for each stellar component. The possibility to combine visual/spectroscopic orbits leads to the exploration of wider systems with longer periods (months to years time-scale). We are conducting a spectroscopic monitoring survey of about 240 southern galactic O and WN stars (OWN Survey). More than one hundred stars show RV variations larger than 10 km s^{-1}, allowing us to discover 26 new spectroscopic binaries. One of our goals is to derive RVs with errors lower than 1 km s^{-1}. One of the more remarkable discoveries of the survey is the multiple nature of the O-type system Herschel 36.
