Asymptotic giant branch (AGB) stars synthesize half of the elements heavier than iron through the slow neutron capture process.
Despite the significant progresses in theory over the last few decades, many uncertainties still affect AGB models. The most notable example
is the mechanism responsible for the formation of the main neutron source in AGB stars, the so called 13C pocket....
Our understanding of stellar evolution and nucleosynthesis is limited by the uncertainties coming from the complex multi-dimensional processes in stellar interiors, such as convection and nuclear burning. 3D stellar models can improve this knowledge by studying realistic multi-D processes for a short timerange (minutes or hours). Recent advances in computing resources have enabled 3D stellar...
According to a standard initial mass function, stars in the range 7-12 Msun constitute $\sim$ 50$\%$ (by number) of the stars more massive than 7 Msun. Despite this, their evolutionary properties, particularly their final fate, remain mostly understudied. In this talk I will present some of the results published in our recent paper, where we discussed in details the evolutionary properties of...
The initial-final mass relation (IFMR) plays a crucial role in understanding stellar structure and evolution by linking a star’s initial mass to the mass of the resulting white dwarf. This study explores the IFMR using full PARSEC evolutionary calculations supplemented with COLIBRI computations to complete the ejection of the envelope and obtain the final core mass. Recent works have shown...
Recently (Marigo et al. 2020-22), identified a kink in the initial-final mass relation around M$_i \simeq 1.65-2.10$ M$_\odot$, based on Gaia DR2 and EDR3 data for white dwarfs in open clusters aged 1.5-2.5 Gyr. Notably, wide dwarfs at this kink, all from NGC 7789, exhibit masses of $\simeq 0.70-0.74$ M$_\odot$, usually associated with stars of M$_i\simeq 3-4$ M$_\odot$. The above kink in the...
The origin of trans-iron elements is not yet fully understood. In addition to the slow (s) and rapid (r) neutron capture processes, an intermediate neutron capture process (i-process) is thought to exist at neutron densities intermediate between the s- and r-processes. The chemical composition of the so-called r/s-stars support the existence of this process but the astrophysical site(s)...
Barium (Ba) stars belong to binary systems where a former asymptotic giant branch (AGB, now a white dwarf) star polluted the less evolved companion, which became enriched with material produced through the slow neutron capture process (s process). The currently observed Ba star preserves the abundance pattern of the AGB, allowing us to test the imprints of the s process. Comparing different...
The nucleosynthetic slow neutron capture process (s-process) in AGB stars between ∼ 1 − 6 M⊙ is responsible for creating about half of the heavy elements in the universe. The s-process can be traced directly through AGBs, or indirectly through their binary companions (CEMP-s stars, Ba stars, CH stars), as thermally pulsing AGBs will dredge s-process material from the inter-shell to the...
The observed surface abundance distribution of Carbon-enhanced metal-poor (CEMP) r/s-stars suggests that these stars have been polluted by an intermediate neutron-capture process (the so-called i-process) occurring at intermediate neutron densities between the r- and s-processes. Triggered by the ingestion of protons inside a convective He-burning zone, the i-process could be hosted in several...
Recently, there have been hints that an increasing number of extrinsic stars (barium, CH and CEMP) could be enriched in chemical elements produced by the i-process (characterised by neutron densities $N_n \sim 10^{14-15}$ cm$^{-3}$) rather than by the s-process ($N_n \sim 10^{8}$ cm$^{-3}$) .
Different isotopic mixtures are predicted for the s-process on the one hand, and for the r- or...
Barium (Ba) stars are peculiarly enriched in s-process elements, even though they have not yet reached the AGB evolutionary phase. This enrichment can be explained by contamination from a companion star when that was an AGB star. Ba stars preserve this material for a long time and are easy to derive their high-resolution spectra, making them objects ideal for testing models of AGB star...
