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We present post process neutron capture computations for Asymptotic Giant Branch stars of 1.5 to 3 Mo and metallicities -1.3 to 0.1. The reference stellar models are computed with the FRANEC code, using the Schwarzschilds criterion for convection. Motivations for this choice are outlined. We assume that MHD processes induce the penetration of protons below the convective boundary, when the third dredge up occurs. There, the 13C(alpha,n)16O neutron source can subsequently operate, merging its effects with those of the 22Ne(alpha,n)25Mg reaction, activated at the temperature peaks characterizing AGB stages. This work has three main scopes. i) We provide a grid of abundance yields, as produced through our MHD mixing scheme, uniformly sampled in mass and metallicity. From it, we deduce that the solar s process distribution, as well as the abundances in recent stellar populations, can be accounted for, without the need of the extra primary like contributions suggested in the past. ii) We formulate analytical expressions for the mass of the 13C pockets generated, in order to allow easy verification of our findings. iii) We compare our results with observations of evolved stars and with isotopic ratios in presolar SiC grains, also noticing how some flux tubes should survive turbulent disruption, carrying C rich materials into the winds even when the envelope is O rich. This wind phase is approximated through the G component of AGB s processing. We conclude that MHD induced mixing is adequate to drive slow neutron capture phenomena accounting for observations. Our prescriptions should permit its inclusion into current stellar evolutionary codes.
The s-process in massive stars, producing nuclei up to $Aapprox 90$, has a different behaviour at low metallicity if stellar rotation is significant. This enhanced s-process is distinct from the s-process in massive stars around solar metallicity, an
Origin of enhanced abundance of heavy elements observed in the surface chemical composition of carbon-enhanced metal-poor (CEMP) stars still remain poorly understood. Here, we present detailed abundance analysis of seven CEMP stars based on high reso
By using updated stellar low mass stars models, we can systematically investigate the nucleosynthesis processes occurring in AGB stars, when these objects experience recurrent thermal pulses and third dredge-up episodes. In this paper we present the
We present a new set of models for intermediate mass AGB stars (4.0, 5.0 and, 6.0 Msun) at different metallicities (-2.15<=Fe/H]<=+0.15). This integrates the existing set of models for low mass AGB stars (1.3<=M/M<=3.0) already included in the FRUITY
It is important to properly describe the mass-loss rate of AGB stars, in order to understand their evolution from the AGB to PN phase. The primary goal of this study is to investigate the influence of metallicity on the mass-loss rate, under well det