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The goal of the present study is twofold. First, we employ new HST/STISspectra and photoionization modeling techniques to determine the progenitormasses of eight planetary nebulae (IC 2165, IC 3568, NGC 2440, NGC 3242, NGC5315, NGC 5882, NGC 7662 and PB6). Second, for the first time we are able tocompare each object's observed nebular abundances of helium, carbon andnitrogen with abundance predictions of these same elements by a stellar modelthat is consistent with each object's progenitor mass. Important resultsinclude the following: 1) the mass range of our objects' central stars matcheswell with the mass distribution of other PN central stars and white dwarfs; 2)He/H is above solar in all of our objects, in most cases likely due to thepredicted effects of first dredge up; 3) most of our objects show negligible Cenrichment, probably because their low masses preclude 3rd dredge-up; 4) C/Oversus O/H for our objects appears to be inversely correlated, perhapsconsistent with the conclusion of theorists that the extent of atmosphericcarbon enrichment from first dredge-up is sensitive to a parameter whose valueincreases as metallicity declines; 5) stellar model predictions of nebular Cand N enrichment are consistent with observed abundances for progenitor starmasses <=1.5 Msun. Finally, we present the first published photoionizationmodels of NGC 5315 and NGC 5882.

astrophysical journal/the astrophysical journal

Co-spatial Long-slit UV/Optical Spectra of Ten Galactic Planetary  Nebulae with HST/STIS II. Nebular Models, Central Star Properties and He+CNO  Synthesis