Spectroscopic survey of faint planetary-nebula nuclei. VII. Thirty new hydrogen-deficient central stars

TL;DR

This spectroscopic survey discovered 30 new hydrogen-deficient planetary-nebula nuclei, significantly expanding known PG1159, O(He), and helium-rich white dwarf classes, with implications for stellar evolution and pulsation studies.

Contribution

The paper reports the discovery of 30 new hydrogen-deficient central stars, including new subclasses, and provides spectral analysis that enhances understanding of their temperatures and evolutionary status.

Findings

Increased the known PG1159 stars from 25 to 46.

Identified six new O(He) type stars, tripling their known numbers.

Discovered three hot helium-rich white dwarfs associated with planetary nebulae.

Abstract

Our ongoing spectroscopic survey of faint planetary-nebula nuclei (PNNi) has revealed 30 new hydrogen-deficient central stars. The majority of them (21) belong to the PG1159 spectral class (having He-C-O-dominated atmospheres). They increase the number of known PN central stars of this type from 25 to 46. Our spectral analysis finds that their effective temperatures are high (T$_{\rm eff}$ = 110,000 - 180,000 K), locating them in the GW Vir pulsational instability strip. Future photometric observations should therefore substantially increase the number of known PNN pulsators (currently, it is nine). We found six new members of the O(He) spectral type (with He-dominated atmospheres; T$_{\rm eff}$ = 120,000 - 150,000 K), tripling the number of known PNNi of this class. Finally, we identified three hot helium-rich white dwarfs with traces of carbon and/or nitrogen (spectral type DOZ; T$_{\rm eff}$ = 70,000 - 100,000 K). They are the first objects of this spectral class found to be associated with a planetary nebula.