Position of our programme stars in the T_eff–logg diagram among other O(He) stars (full circles) as well as RCB stars (crosses), EHe stars (open circles), and He-sdOs (squares), see Reindl et al. (2014b) and references therein. Red and purple lines are evolutionary tracks for a composite-merger scenario of two He-WDs (marked with the merger mass in M_⊙) from Zhang & Jeffery (2012b). The dashed black line is the zero-age helium main sequence.