A Very Hot, Hydrogen-rich, White Dwarf Planetary Nucleus
Abstract
We report new spectrophotometry and a detailed analysis of the DA white dwarf nucleus of the planetary nebula WDHS 1 (PK 197-6.1 deg). Based on model atmosphere fits to the Balmer line profiles, the possible Teff for this star ranges from 165,000 K if the helium abundance is zero to approximately 100,000 K if a marginally detectable abundance of N(He)/N(H) = 10-2 is present in the atmosphere; log approx. = 7.6 in either case. The nucleus of WDHS 1 is thus the hottest known high gravity star with a hydrogen-rich atmosphere. We present CCD imaging of the nebulae showing this to have an angular extent of 22 min. At the distance (d) of 1.0 +/- 0.25 kpc estimated from the white dwarf analysis, WDHS 1 is one of the largest known planetary nebulae with a diameter of 6.4 (d/1 kpc) pc. The implied kinematic age of the nebulae is a few times 105 yr, which might be consistent with the post-Asymptotic Giant Branch (AGB) lifetime of the nucleus. We discuss the apparent paucity of objects such as the nucleus of WDHS 1 in comparison with their hydrogen-poor counterparts among planetary nuclei and field dwarfs.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1994
- DOI:
- 10.1086/173933
- Bibcode:
- 1994ApJ...424..817L
- Keywords:
-
- Abundance;
- Balmer Series;
- Helium;
- Hydrogen;
- Planetary Nebulae;
- Stellar Atmospheres;
- White Dwarf Stars;
- Charge Coupled Devices;
- Chronology;
- Distance;
- Imagery;
- Schmidt Telescopes;
- Size (Dimensions);
- Stellar Models;
- Stellar Spectrophotometry;
- Stellar Temperature;
- Astrophysics