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

Abstract

We present new theoretical stellar yields and surface abundances for\nasymptotic giant branch (AGB) models with a metallicity appropriate for stars\nin the Small Magellanic Cloud (SMC, $Z= 0.0028$, [Fe/H] $\\approx -0.7$). New\nevolutionary sequences and post-processing nucleosynthesis results are\npresented for initial masses between 1$M_{\\odot}$ and 7$M_{\\odot}$, where the\n7$M_{\\odot}$ is a super-AGB star with an O-Ne core. Models above\n1.15$M_{\\odot}$ become carbon rich during the AGB, and hot bottom burning\nbegins in models $M \\ge 3.75 M_{\\odot}$. We present stellar surface abundances\nas a function of thermal pulse number for elements between C to Bi and for a\nselection of isotopic ratios for elements up to Fe and Ni (e.g.,\n$^{12}$C/$^{13}$C), which can be compared to observations. The integrated\nstellar yields are presented for each model in the grid for hydrogen, helium\nand all stable elements from C to Bi. We present evolutionary sequences of\nintermediate-mass models between 4--7$M_{\\odot}$ and nucleosynthesis results\nfor three masses ($M=3.75, 5, 7M_{\\odot}$) including $s$-process elements for\ntwo widely used AGB mass-loss prescriptions. We discuss our new models in the\ncontext of evolved AGB stars and post-AGB stars in the Small Magellanic Clouds,\nbarium stars in our Galaxy, the composition of Galactic globular clusters\nincluding Mg isotopes with a similar metallicity to our models, and to\npre-solar grains which may have an origin in metal-poor AGB stars.\n