Heavy-element yields and abundances of asymptotic giant branch models with a Small Magellanic Cloud metallicity

• Published in: Monthly notices of the Royal Astronomical Society Vol. 477; no. 1; pp. 421 - 437
• Main Authors: Karakas, Amanda I, Lugaro, Maria, Carlos, Marília, Cseh, Borbála, Kamath, Devika, García-Hernández, D A
• Format: Journal Article
• Language: English
• Published: Oxford University Press 11.06.2018
• Subjects: stars: AGB and post-AGB; Magellanic Clouds; nuclear reactions, nucleosynthesis, abundances; galaxies: abundances; ISM: abundances
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/sty625

Abstract We present new theoretical stellar yields and surface abundances for asymptotic giant branch (AGB) models with a metallicity appropriate for stars in the Small Magellanic Cloud (SMC, Z = 0.0028, [Fe/H] ≈ −0.7). New evolutionary sequences and post-processing nucleosynthesis results are presented for initial masses between 1 and 7  M⊙, where the 7  M⊙ is a super-AGB star with an O–Ne core. Models above 1.15  M⊙ become carbon rich during the AGB, and hot bottom burning begins in models M ≥ 3.75 M⊙. We present stellar surface abundances as a function of thermal pulse number for elements between C to Bi and for a selection of isotopic ratios for elements up to Fe and Ni (e.g. 12C/13C), which can be compared to observations. The integrated stellar yields are presented for each model in the grid for hydrogen, helium, and all stable elements from C to Bi. We present evolutionary sequences of intermediate-mass models between 4 and 7  M⊙ and nucleosynthesis results for three masses (M = 3.75, 5, and 7 M⊙) including s-process elements for two widely used AGB mass-loss prescriptions. We discuss our new models in the context of evolved AGB and post-AGB stars in the SMCs, barium stars in our Galaxy, the composition of Galactic globular clusters including Mg isotopes with a similar metallicity to our models, and to pre-solar grains which may have an origin in metal-poor AGB stars.