Third-dredge-up oxygen in planetary nebulae
P\'equignot D., Walsh J.R., Zijlstra A.A., Dudziak G., 2000,
A&A, 361, L1
Abstract
The planetary nebulae H2 2-436 and Wray16-423 in the
Sagittarius dwarf galaxy appear to result from nearly twin stars,
except that third dredge-up carbon is more abundant in He 2-436. A
photo-ionization model analysis implies that the ratios Ne/O, S/O and Ar/O
are significantly smaller in He 2-436, indicative of third-dredge-up
oxygen enrichment. The relative incremental enrichment of oxygen with
respect to carbon is 7 per cent within a factor of 2. Excess nitrogen
in Wray 16-423 suggests third dredge-up of late-CN-cycle products even in these
low-mass, intermediate metallicity stars.
paper (postscript, 650k)
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