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We present the results of new time series photometric observations of 29pre-white dwarf stars of PG 1159 spectral type, carried out in the years2014-2022. For the majority of stars, a median noise level in Fourier amplitudespectra of 0.5-1.0 mmag was achieved. This allowed the detection of pulsationsin the central star of planetary nebula Abell 72, consistent with g-modesexcited in GW Vir stars, and variability in RX J0122.9-7521 that could be dueto pulsations, binarity or rotation. For the remaining stars from the samplethat were not observed to vary, we placed upper limits for variability. Aftercombination with literature data, our results place the fraction of pulsatingPG 1159 stars within the GW Vir instability strip at 36%. An updated list ofall known PG 1159 stars is provided, containing astrometric measurements fromthe recent Gaia DR3 data, as well as information on physical parameters,variability, and nitrogen content. Those data are used to calculateluminosities for all PG 1159 stars to place the whole sample on the theoreticalHertzsprung-Russell diagram for the first time in that way. The pulsating starsare discussed as a group, and arguments are given that the traditionalseparation of GW Vir pulsators in "DOV" and "PNNV" stars is misleading andshould not be used.

The GW Vir instability strip in the light of new observations of PG 1159  stars. Discovery of pulsations in the central star of Abell 72 and  variability of RX J0122.9-7521