Single vs binary hot subdwarfs: Towards a 200-pc volume-limited complete sample

From current statistics, based on magnitude-limited samples, ~35% of sdO/B hot subdwarfs are in close binaries with M-dwarf/WD companions, ~30% are in wide binaries with FGK MS stars, and ~35% are apparently single. However, without a companion it is hard to explain the huge mass loss near the RGB tip needed to form an sdB star. The presence of a substellar companion, difficult to detect, is a possibility. The goal of this project is to shed light on the formation mechanisms of single sdO/B stars by searching for binary signatures on a small but complete 200-pc volume-limited sample using different data/methods: TESS light curves, Gaia spectra, SEDs, and precise RVs from HARPS/HARPS-N spectra.