1306.2134 (D. A. Garcia-Hernandez et al.)

Hot Bottom Burning and s-process nucleosynthesis in massive AGB stars at the beginning of the thermally-pulsing phase    [PDF]

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

We report the first spectroscopic identification of massive Galactic Asymptotic Giant Branch (AGB) stars at the beginning of the thermally-pulsing (TP) phase. These stars are the most Li-rich ('super Li-rich' with logE(Li)~3-4) massive AGBs found to date. 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 much more TPs 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 in agreement with the theoretical predictions when the 22Ne neutron source dominates the s-process nucleosynthesis.

View original: http://arxiv.org/abs/1306.2134