![]() In this paper we present the first observational evidence of a star that has failed the third dredge-up (TDU). The discovery of J005252.87-722842.9 reveals a new stellar evolutionary channel whereby a star evolves without any TDU episodes.Ībstract = "Post-asymptotic giant branch (post-AGB) stars are known to be chemically diverse. If they have low luminosities, then they are likely to be dusty post-RGB stars. We identify two possible Galactic analogs that are likely to be post-AGB stars, but the lack of accurate distances (hence luminosities) to these objects does not allow us to confirm their post-AGB status. However, our observations are in contrast with these predictions. Based on its derived stellar parameters and inferred evolutionary state, single-star nucleosynthesis models predict that this star should have undergone TDU episodes while on the AGB, and it should be carbon enriched. The chemical pattern displayed by this object has not been observed in single or binary post-AGBs. We could not derive an upper limit for the nitrogen abundance as there are no useful nitrogen lines within our spectral coverage. For Fe and O, we took the effects of nonlocal thermodynamic equilibrium into account. We derived an oxygen abundance of = 0.29 ± 0.1. ![]() ![]() ![]() Through a systematic abundance study, using high-resolution optical spectra from UVES, we found that this likely post-AGB object shows an intriguing photospheric composition with no confirmed carbon-enhancement (upper limit of < 0.50) nor enrichment of s-process elements. Post-asymptotic giant branch (post-AGB) stars are known to be chemically diverse. ![]()
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