Other
Scientific paper
Apr 1980
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980mnras.191..301f&link_type=abstract
Monthly Notices of the Royal Astronomical Society, vol. 191, Apr. 1980, p. 301-308.
Other
4
Absorption Spectra, Astronomical Models, Helium Isotopes, Lyman Alpha Radiation, Planetary Nebulae, Electron Energy, Temperature Distribution
Scientific paper
Detailed models of planetary nebulae have failed to correctly predict the line intensities of atoms in low stages of ionization unless certain ad hoc assumptions are made. Of the various processes which may be able to explain this discrepancy, we investigate the role of He II Lyα photons produced in recombinations of He2+ ions and electrons. These photons may escape from the inner and be absorbed in the outer regions of a high excitation nebula, thereby raising the electron temperature and increasing the emission in the forbidden lines of singly ionized atoms. In this paper, we assess the importance of this process in a nebula which is optically thick in the H I Ly continuum. It is concluded that the intensities of lines emitted by singly ionized atoms are not sufficiently enhanced, and that appeal must be made to other physical processes, in particular, to charge transfer between atomic hydrogen and doubly ionized atoms.
Flower David R.
Perinotto Mario
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