Abstract
Asymptotic Giant Branch (AGB) stars play a key role in the chemical evolution of galaxies. These stars are the fundamental stellar site for the production of light elements such as C, N and F, and half of the elements heavier than Fe via the slow neutron capture process (s-process). Hence, detailed computational models of AGB stars’ evolution and nucleosynthesis are essential for galactic chemical evolution. In this work, we discuss the progress in updating the NuGrid data set of AGB stellar models and abundance yields. All stellar models have been computed using the MESA stellar evolution code, coupled with the post-processing mppnp code to calculate the full nucleosynthesis. The final data set will include the initial masses Mini/M⊙ = 1, 1.65, 2, 3, 4, 5, 6 and 7 for initial metallicities Z = 0.0001, 0.001, 0.006, 0.01, 0.02 and 0.03. Observed s-process abundances on the surfaces of evolved stars as well as the typical light elements in the composition of H-deficient post-AGB stars are reproduced. A key short-term goal is to complete and expand the AGB stars data set for the full metallicity range. Chemical yield tables are provided for the available models.
Highlights
The abundance distribution in the solar system is the result of the nucleosynthesis in several generations of stars [1–5]
Metallicity-dependent stellar yields from theoretical stellar models are a fundamental ingredient of galactic chemical evolution, and are used to study how the abundances have formed in the Sun and in other stars in the Galaxy
Contribute to the chemical evolution of the interstellar medium over longer timescales. These types of stars finish their evolution as a compact white dwarf, and predominantly eject nucleosynthesis products via stellar winds during the asymptotic giant branch (AGB)
Summary
The abundance distribution in the solar system is the result of the nucleosynthesis in several generations of stars [1–5]. Battino et al [33] calculated new AGB models where CBM at the bottom envelope during the third dredge-up is instead induced by internal gravity waves (IGWs), as described by [50] This results in a 3–4 times larger radiative 13 C-pocket, increasing the total s-process production by about the same factor. An additional extension of the set of the new AGB models was presented in [51], focused on low-metallicity (Z = 0.001, 0.002), low-mass AGB models From these models, it is shown that stellar models with a 13 C-pocket size of at least ∼3 × 10−4 M (see e.g., [21,42,52]), and with very low mixing below the He intershell region during helium flashes [53], are favored when compared to more s-process-rich observations.
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