Spectrophotometric Studies of Gaseous Nebulae. XX. The Inhomogeneous, Low Excitation, Planetary NGC 40.
Abstract
NGC 40 is characterized by extremely low excitation, an extremely irregular and inhomogeneous structure, and a bright Woff-Rayet-type central star. Photoelectric and photographic measurements of line intensities, secured at Mount Wilson, Lick, and Kitt Peak Observatories, are interpreted in terms of ionic concentrations, with the aid of two suggested excitational modds for the nebula. Large pockets of cool, neutral gas must exist in NGC 40.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1972
- DOI:
- 10.1086/151354
- Bibcode:
- 1972ApJ...172..361A