Nucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison to Observations of Type I Planetary Nebulae

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dc.creatorKarakas, Amanda I.
dc.creatorvan Raai, Mark A.
dc.creatorLugaro, Maria
dc.creatorSterling, N. C.
dc.creatorDinerstein, Harriet L.
dc.date2008-09-08
dc.date.accessioned2026-07-07T12:15:35Z
dc.date.available2026-07-07T12:15:35Z
dc.descriptionType I planetary nebulae (PNe) have high He/H and N/O ratios and are thought to be descendants of stars with initial masses of ~3-8Msun. These characteristics indicate that the progenitor stars experienced proton-capture nucleosynthesis at the base of the convective envelope, in addition to the slow neutron capture process operating in the He-shell (the s-process). We compare the predicted abundances of elements up to Sr from models of intermediate-mass asymptotic giant branch (AGB) stars to measured abundances in Type I PNe. In particular, we compare predictions and observations for the light trans-iron elements Se and Kr, in order to constrain convective mixing and the s-process in these stars. A partial mixing zone is included in selected models to explore the effect of a 13C pocket on the s-process yields. The solar-metallicity models produce enrichments of [(Se, Kr)/Fe] < 0.6, consistent with Galactic Type I PNe where the observed enhancements are typically < 0.3 dex, while lower metallicity models predict larger enrichments of C, N, Se, and Kr. O destruction occurs in the most massive models but it is not efficient enough to account for the > 0.3 dex O depletions observed in some Type I PNe. It is not possible to reach firm conclusions regarding the neutron source operating in massive AGB stars from Se and Kr abundances in Type I PNe; abundances for more s-process elements may help to distinguish between the two neutron sources. We predict that only the most massive models would evolve into Type I PNe, indicating that extra-mixing processes are active in lower-mass stars (3-4Msun), if these stars are to evolve into Type I PNe.
dc.description39 pages, accepted for publication in ApJ
dc.identifierhttps://arxiv.org/abs/0809.1456
dc.identifierhttp://arxiv.org/abs/0809.1456
dc.identifierAstrophys.J.690:1130-1144,2009
dc.identifierdoi:10.1088/0004-637X/690/2/1130
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/211534
dc.subjectAstrophysics
dc.titleNucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison to Observations of Type I Planetary Nebulae
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