Physics
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992hst..prop.4226h&link_type=abstract
HST Proposal ID #4226
Physics
Hst Proposal Id #4226
Scientific paper
Planetary nebulae (PNe) form in the final stages of evolution of intermediate- and low-mass stars, and show abundances consistent with contamination by modest amounts of processed material. There is however an exceptional group of PNe with nebular gas that consists of nearly undiluted products of nuclear burning. These hydrogen-poor PNe are thought to result when a final helium shell flash occurs after the complete removal of the hydrogen envelope. We propose to study 5 of the 6 currently known H-poor PNe with HST. The best studied object, Abell 30, shows that the majority of the emission line radiation is in the UV, and thus UV spectrophotometry is indispensable for quantitative analysis. Our proposed HST observations (in conjunction with our ground based work) will provide fundamental information (1) on helium-burning nucleosynthesis, by determining the ionic concentrations of H and He burning products; (2) on the physics of very dusty gas, by determining the energy balance; this is crucial since it now appears that due to the high dust-to-gas ratio, the energy input may be partially, and in some cases, primarily, due to photoelectric ejection by grains rather than by photoionization; and (3) on the interaction of the several thousand km/sec stellar winds with the nearby clumps of nebular material, by analysis of the velocity structure of the C IV 1550 line.
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