ABUNDANCES IN MAGELLANIC CLOUD PLANETARY-NEBULAE.
291 - 298.
The enhanced nitrogen abundances in planetary nebulae (PN) show the effects of CN-cycle processing at the tine of the first dredge-up, while their very enhanced carbon abundances show the effects of the third dredge-up. The efficiency of both the first and third dredge-ups increases with decreasing initial metallicity. ON-cycle depletion of oxygen via the second dredge-up does not appear to have been significant in LMC Type I planetary nebulae (those with N/O > 0.5) - these nebulae have experienced the third dredge-up and envelope-burning, giving enhanced C+N abundances. The LMC Type I PN show enhanced Ne/O ratios. Enrichment rates in nitrogen and carbon by PN are estimated for the ISM s of the Magellanic Clouds.
|Title:||ABUNDANCES IN MAGELLANIC CLOUD PLANETARY-NEBULAE|
|Keywords:||ASYMPTOTIC GIANT BRANCH, INTERMEDIATE-MASS STARS, CHEMICAL-COMPOSITIONS, EVOLUTION, SAMPLE|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Physics and Astronomy|
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