The end of super AGB and massive AGB stars: I. The instabilities that determine the final mass of AGB stars

• Published in: Astronomy and astrophysics (Berlin) Vol. 542; p. 1
• Main Authors: LAU, H. H. B, GIL-PONS, P, DOHERTY, C, LATTANZIO, J
• Format: Journal Article
• Language: English
• Published: Les Ulis EDP Sciences 01.06.2012
• Subjects: Astronomy; Asymptotic giant branch stars; Divergence; Earth, ocean, space; Envelopes; Exact sciences and technology; Indexing in process; Instability; Mathematical models; Metallicity; Stability; Stellar winds; Convective shell; Supernovae; stars: interiors; stars: evolution; stars: AGB and post-AGB; Stellar evolution; M stars; stars: winds, outflows; Thermal equilibrium; Massive stars; Electron capture; Divergences; Electron shell; Stellar mass; Metallicity; Instability; Models; Opacity; Asymptotic giant branch; M shell
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201218826

The literature is rich in analysis and results related to thermally pulsing-asymptotic giant branch (TP-AGB) stars, but the problem of the instabilities that arise and cause the divergence of models during the late stages of their evolution is rarely addressed. The authors investigate the physical conditions, causes and consequences of the interruption in the calculations of massive AGB stars in the late thermally-pulsing AGB phase. They have thoroughly analysed the physical structure of a solar metallicity 8.5 M... star and described the physical conditions at the base of the convective envelope just prior to divergence. They find that the local opacity maximum caused by M-shell electrons of Fe-group elements lead to the accumulation of an energy excess, to the departure of thermal equilibrium conditions at the base of the convective envelope and, eventually, to the divergence of the computed models. For the 8.5 M... case they present in this work the divergence occurs when the envelope mass is about 2 M... . (ProQuest: ... denotes formulae/symbols omitted.)