Hot bottom burning and s-process nucleosynthesis in massive AGB stars at the beginning of the thermally-pulsing phase

D. A. García-Hernández, O. Zamora, A. Yagüe, S. Uttenthaler, A. I. Karakas, M. Lugaro, P. Ventura, D. L. Lambert

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    67 Citations (Scopus)

    Abstract

    We report the first spectroscopic identification of massive Galactic asymptotic giant branch (AGB) stars at the beginning of the thermal pulse (TP) phase. These stars are the most Li-rich massive AGBs found to date, super Li-rich AGBs with log ε (Li) ~ 3-4. The high Li overabundances are accompanied by weak or no s-process element (i.e. Rb and Zr) enhancements. A comparison of our observations with the most recent hot bottom burning (HBB) and s-process nucleosynthesis models confirms that HBB is strongly activated during the first TPs but the 22Ne neutron source needs many more TP and third dredge-up episodes to produce enough Rb at the stellar surface. We also show that the short-lived element Tc, usually used as an indicator of AGB genuineness, is not detected in massive AGBs, which is in agreement with the theoretical predictions when the 22Ne neutron source dominates the s-process nucleosynthesis.

    Original languageEnglish
    Article numberL3
    JournalAstronomy and Astrophysics
    Volume555
    DOIs
    Publication statusPublished - 2013

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