The ionization of the most abundant elements in planetary nebulae has
been determined for a number of models of nebulae at different epochs in
their expansion. The values used for the temperatures and radii of the central
stars and the sizes and densities of the shells have come from Seaton's
evolutionary sequence. The ionizing radiation field has been taken from
model atmosphere calculations of the central stars by Gebbie and Seaton,
and Biihm and Deinzer. Emission -line fluxes have been calculated for the
models and compared with observations of planetary nebulae by O'Dell,
Osterbrock's group, and Aller and his collaborators. Results indicate that
the central stars have strong He+ Lyman continuum excesses, similar to those
predicted by Gebbie and Seaton. The mean abundance determinations for the
nebulae made by Aller are confirmed, with the exception of nitrogen, which
appears to be 3 or 4 times more abundant than his value. It is also seen
that the electron temperatures of the nebulae are higher than previous
theoretical determinations, providing better agreement with empirically
derived values.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/623821 |
| Date | 08 1900 |
| Creators | Williams, R. E. |
| Contributors | Univ Arizona, Steward Observ |
| Publisher | Steward Observatory, The University of Arizona (Tucson, Arizona) |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Article |
| Source | Steward Observatory Parker Library SO QB 4 .S752 ARCH |
| Rights | Copyright © All Rights Reserved. |
| Relation | Preprints of the Steward Observatory #10, http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1968IAUS...34..190W&db_key=AST&data_type=HTML&format=&high=3ed65e9cd024029 |
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