Position of PG 1159 stars (squares) and DO white dwarfs (circles) in the log g–T_eff diagram. Our two program stars and a particular DO are indicated with big symbols and name tags. Blue lines are evolutionary tracks by Althaus et al. (2009) with stellar masses of 0.514, 0.530, 0.542, 0.565, 0.584, 0.609, 0.664, and 0.741 M_⊙ (from top to bottom). The black line is the PG 1159 wind limit (see text).