SUPER-AGB-AGB EVOLUTION AND THE CHEMICAL INVENTORY IN NGC 2419
- INAF-Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio (Italy)
- INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy)
- INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)
- Department of Astronomy, Indiana University, Bloomington (United States)
We follow the scenario of formation of second-generation stars in globular clusters by matter processed by hot bottom burning (HBB) in massive asymptotic giant branch (AGB) stars and super-AGB stars (SAGB). In the cluster NGC 2419 we assume the presence of an extreme population directly formed from the AGB and SAGB ejecta, so we can directly compare the yields for a metallicity Z = 0.0003 with the chemical inventory of the cluster NGC 2419. At such a low metallicity, the HBB temperatures (well above 10{sup 8} K) allow a very advanced nucleosynthesis. Masses {approx}6 M{sub Sun} deplete Mg and synthesize Si, going beyond Al, so this latter element is only moderately enhanced; sodium cannot be enhanced. The models are consistent with the observations, although the predicted Mg depletion is not as strong as in the observed stars. We predict that the oxygen abundance must be depleted by a huge factor (>50) in the Mg-poor stars. The HBB temperatures are close to the region where other p-capture reactions on heavier nuclei become possible. We show that high potassium abundance found in Mg-poor stars can be achieved during HBB by p-captures on the argon nuclei, if the relevant cross section(s) are larger than listed in the literature or if the HBB temperature is higher. Finally, we speculate that some calcium production is occurring owing to proton capture on potassium. We emphasize the importance of a strong effort to measure a larger sample of abundances in this cluster.
- OSTI ID:
- 22078365
- Journal Information:
- Astrophysical Journal Letters, Vol. 761, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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