Mathematics – Logic
Scientific paper
Dec 1984
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984apj...287..341d&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 287, Dec. 1, 1984, p. 341-352.
Mathematics
Logic
43
Abundance, Planetary Nebulae, Star Clusters, Chemical Composition, Electrophotometry, Emission Spectra, Iue, Nuclear Fusion, Radio Emission, Ultraviolet Spectra
Scientific paper
The planetary nebula NGC 2818, or PK 261 + 8 deg 1, is of special interest due to its apparent association with a Population I open cluster (of the same designation). The results of new observations of the nebula are presented, including interference-filter imagery, photoelectric photometry, and ground-based and IUE spectroscopy. Analysis of its composition based on new IUE and ground-based spectroscopy and model calculations of the very similar planetary nebula NGC 2440 suggests that NGC 2818 is a prototype of the He-rich and N-rich Type I group. Compared to the composition of H II regions in the solar neighborhood, He is 60 percent overabundant, C is 0.3 dex lower, N is 1.0 dex higher, and O, Ne, Si, Cl, and Ar are essentially at comparable values. Analysis of kinematical and morphological data suggests that the nebula is probably associated with the star cluster (revised distance = 3.5 kpc). If so, then it is of exceptional size (radius approximately 1.1 pc), mass (greater than or equal to 0.6 solar mass), expansion velocity (52 + or - 3 km/s), and age (possibly as old as 22,000 yr). Some implications of the results regarding the masses of planetary-nebula progenitors, the nucleosynthesis processes in stars of intermediate mass, and the formation of planetary nebulae are also discussed.
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