Location of HD 49798 (red error ellipse) in the log T_eff−log g plane compared with three MESA models for the evolution of He cores with different masses (orange tracks, evolution towards lower log g, taken from Brooks et al. 2017). The blue error ellipse shows the error limits of Krtička et al. (2019). Positions of sdB (Geier et al. 2017, blue, open squares), sdO stars (Geier 2020, green, open rhombs), and Hrich WDs (Gianninas et al. 2010, green, dashed lines) are indicated. Four post-EHB evolutionary tracks, labeled with the stellar mass in M_☉, (Dorman et al. 1993, blue, dashed lines for Y = 0.459 ≈ 1.6 × Y_☉) are shown to indicate their evolution. The dashed green lines indicate the He main sequence and the zero- and terminal-age EHB.