Spectroscopic survey of faint planetary-nebula nuclei

VII. Thirty new hydrogen-deficient central stars

¹ Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Eberhard Karls Universität, Sand 1, 72076 Tübingen, Germany
² Department of Astronomy and Astrophysics, Penn State University, University Park, PA 16802, USA
³ Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
⁴ Hobby-Eberly Telescope, University of Texas at Austin, Austin, TX 78712, USA

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 17 March 2026
Accepted: 1 April 2026

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_eff = 110 000180 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_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_eff = 70 000-100 000 K). They are the first objects of this spectral class found to be associated with a planetary nebula.