Barium stars and related systems, such as carbon-rich metal-poor stars, are the products of mass transfer from a binary companion during its thermally pulsing AGB phase. These systems are traditionally considered to result mostly from wind mass transfer, because Roche-lobe overflow (RLOF) from an AGB star is thought to be unstable and lead to a common envelope. Several recent theoretical...
Stars that evolve through the asymptotic giant branch (AGB) are vital to the chemical evolution of the universe as they produce a significant portion of the carbon, nitrogen, and elements heavier than iron. Most models studying the evolution and nucleosynthesis of AGB stars focus on single stars. However, at least half of these stars exist with a binary companion. In this study, we use the...
We will present recent SPH simulations of common envelope evolution including the formation of dust. Our calculations indicate that radiative acceleration on dust grains has a weak impact on the dynamics of the gas. However, dust formation can significantly alter the observational properties of the object.
I will review some findings about binary stars recently achieved using Gaia DR3 data, and bearing some relationships with nucleosynthesis. More details may be given in the corresponding focused contributions (if accepted):
1/ The red giant 56 UMa, formerly classified as a barium star, probably hosts a (dormant) neutron-star companion of mass 1.3 Msun. Its abundances have been reviewed and not...
The presence of close-by companions is believed to be an essential ingredient to shape the outflow of the progenitor of bipolar planetary nebulae. However, only an handful of AGB binaries have been detected so far and their orbital characteristics are not well constrained. Here, we target the well-known carbon-rich star V Hydrae (V Hya), known to exhibit a complex environment believed to be...
56 Ursae Majoris is a long-period binary that was thought to contain a chemically peculiar red giant and a faint companion. The red giant was classified as a barium (Ba) star in the 70s. This classification would imply that the companion is a white dwarf, since Ba stars form when s-process rich Asymptotic Giant Branch (AGB) companions transfer mass to them. However, combining more than 50...
Binary stars can display a diverse range of chemical signatures arising from strong yet poorly understood interactions with their companions. In observational studies focusing on low to intermediate-mass ($\rm 0.8-8~M_{\odot}$) binary stars, such as Barium stars, Carbon Enhanced Metal-Poor (CEMP-s) stars, and extrinsic s-stars, the observed enrichments in carbon and slow neutron capture...
Binary interaction is known to affect the chemical composition of low- and intermediate-mass (LIM) stars. In particular, post-AGB/post-RGB binary stars with circumbinary discs display photospheric chemical depletion with a notable underabundance of refractory elements in the stellar photospheres (e.g., Al, Fe, Ti, $s$-process elements) relative to volatile elements (e.g., S, Zn, Na, K). The...
Circumstellar disks surrounding both single and binary stars have been extensively investigated in the context of young stellar objects. However, in this talk, we shift the focus to the late stages of stellar evolution where stable compact disks were discovered around low-mass dying binary stars, such as post-Asymptotic Giant Branch (post-AGB) binaries. Observational studies have shown that...
