Colour–magnitude diagrams depicting the positions of the systems listed in the SB9 catalogue using Gaia DR2 (left) and HIPPARCOS astrometry (right panel). Magenta dots indicate candidates of hosting primaries in advanced phases of stellar evolution. Blue dots mark the remaining systems. The grey line indicates the selection criterion for red-giant candidates. The background density plots represent the distribution of all stars measured by the respective mission, with a limiting magnitude in V of 10 mag.