A search for hot pulsators similar to PG 1159-035 and the central star of K 1-16
The four known pulsators lie at 80, 000 K < Teff < 160, 000 K and 6 < log g < 8, or about 1.5 < log L/L < 3, in the HR diagram. Our non-pulsating DO white dwarfs may be outside the temperature range of the instability strip, being slightly cooler than the GW Vir pulsators (or slightly hotter in the case of H 1504+65).The non-pulsating planetary nuclei have high temperatures and show helium and carbon features in their spectra, but are more luminous than the pulsators, since they have decidedly lower surface gravities.
More puzzling are our null results for the three PG objects 1151-029, 1424+535, and 1520+525, which have spectra closely resembling those of the G W Vir pulsators (Wesemael et al. 1985). Possibly the pulsational instability may be critically sensitive to the CNO abundances (which have not yet been determined in these objects) or to temperature or surface-gravity differences too small to be apparent in the spectra.
A more detailed version of this paper has been submitted for publication in The Astrophysical Journal.
KeywordsCentral Star Planetary Nebula Detailed Version Astrophysical Journal Instability Strip
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