Related papers: Abundance Patterns in S-type AGB stars : Setting C…
The primary objective of this study is to accurately determine the abundances of Cu, Sr, Y, Zr, Ba, La, and Ce in selected solar-type stars. This will allow us to establish observational abundance-metallicity and abundance-age relations and…
The origin of carbon-enhanced metal-poor (CEMP) stars plays a key role in characterising the formation and evolution of the first stars and the Galaxy since the extremely-poor (EMP) stars with [Fe/H] \leq -2.5 share the common features of…
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 Schwarzschild's criterion for…
It is well appreciated that the description of overadiabatic convection affects the structure of the envelopes of luminous asymptotic giant branch (AGB) stars in the phase of ``hot bottom burning '' (HBB). We stress that this important…
W Aql is an asymptotic giant branch (AGB) star with an atmospheric elemental abundance ratio C/O$\approx$0.98 and reported circumstellar molecular abundances intermediate between those of M-type (C/O$<$1) and C-type (C/O$>$1) AGB stars.…
We present new synthetic models of the TP-AGB evolution. They are computed for 7 values of initial metal content (Z from 0.0001 to 0.03) and for initial masses between 0.5 and 5.0 Msun, thus extending the low- and intermediate-mass tracks…
A systematic investigation on the third dredge up in a 3M$_{\odot}$, solar metallicity AGB star will be presented. The model evolves from the main sequence up to the Asymptotic Giant Branch (AGB). Intermediate mass stars are important…
The integrated luminosity of the TP-AGB phase is a major uncertainty in stellar population synthesis models. We use the white dwarf initial final mass relation and stellar interiors models to demonstrate that a significant fraction of the…
Most heavy elements beyond the iron peak are synthesized via neutron capture processes. The nature of the astrophysical sites of neutron capture processes is still very unclear. In this work we explore the observational constraints of the…
Abridged: Getting a better understanding of the evolution and nucleosynthetic yields of the most metal-poor stars (appr. Z<=10^-5) is critical because they are part of the big picture of the history of the primitive Universe. Yet many of…
We discuss the occurrence of the s-process during the radiative interpulse phase of rotating AGB stars. Due to differential rotation, protons are mixed into C12-rich layers after thermal pulses, in the course of the so called third dredge…
We discuss the self-enrichment scenario by AGB stars for the formation of multiple populations in globular clusters (GCs) by analyzing data set of giant stars observed in 9 Galactic GCs, covering a wide range of metallicities and for which…
Many disc-type post-asymptotic giant branch (post-AGB) stars are chemically peculiar, showing underabundances of refractory elements in their photospheres that correlate with condensation temperature. The aim of this paper is to investigate…
Lead (Pb) is predominantly produced by the slow neutron-capture process (s process) in asymptotic giant branch (AGB) stars. In contrast to significantly enhanced Pb abundances predicted by low-mass, low-metallicity AGB-models, observations…
The results of a study of the AGB phase of stellar evolution are presented. Abundances have been determined for Fe, C, O, the light s-process elements, Y and Zr, the heavy s-process elements, La and Nd, and the r-process element, Eu. The…
Classical barium stars are red giants that received from their evolved binary companions material exposed to the \textit{slow} neutron-capture nucleosynthesis, i.e., the $s$-process. Such a mechanism is expected to have taken place in the…
Recent models for evolved Low Mass Stars (with $M \lesssim 3M_\odot$), undergoing the AGB phase assume that magnetic flux-tube buoyancy drives the formation of $^{13}$C reservoirs in He-rich layers. We illustrate their crucial properties,…
An analysis of the fluorine abundance in Galactic AGB carbon stars (24 N-type, 5 SC-type and 5 J-type) is presented. This study uses the state- of-the-art carbon rich atmosphere models and improved atomic and molecular line lists in the 2.3…
We review the observed properties of extremely hot hydrogen-deficient post-AGB stars of spectral type [WC] and PG1159. Their H-deficiency is probably caused by a (very) late helium-shell flash or a AGB final thermal pulse, laying bare…
To better characterize the abundance patterns produced by the r-process, we have derived new abundances or upper limits for the heavy elements zinc (Zn), yttrium (Y), lanthanum (La), europium (Eu), and lead (Pb). Our sample of 161…