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Paper: Light s-Process Element Production in Solar Metallicity AGB Stars
Volume: 378, Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes
Page: 37
Authors: Karakas, A.I.; Lugaro, M.; Gallino, R.
Abstract: Spectral lines of highly ionized neutron-capture elements have recently been detected in planetary nebulae (PNe), with derived abundances ranging from solar to factors of 3 to ~ 30 above solar. These observations indicate that the slow neutron-capture process (s process) operated in the parent star during the thermally-pulsing asymptotic giant branch (TP-AGB) phase. We compute a number of solar metallicity AGB models to compare with these observations. Within the uncertainties allowed by the observations, the models produce a reasonable match to the composition of most PNe. Model uncertainties (e.g. convection, mass loss) affect the results and could account for the composition of the most s-process-enriched objects. The occurrence of third dredge-up episodes at the tip of the AGB, when the envelope mass is small, or a late thermal pulse on the post-AGB track, could provide further enrichment. Further study is required to better assess how the model uncertainties affect the predictions and, consequently, whether a late TP should be invoked.
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