Related papers: Element Abundance Determination in Hot Evolved Sta…
A self-consistent model of the chemical evolution of the globular cluster NGC 6752 is presented to test a popular theory that observed abundance anomalies are due to ``internal pollution'' from intermediate mass asymptotic giant branch…
An abundance analysis has been conducted for a sample of nine post-AGB candidate stars; eight of them have not been explored before. We find four very promising objects like HD 105262, HD 53300 and CpD$-62^o5428$ among them. We find strong…
We are in the process of testing a popular theory that the observed abundance anomalies in the Globular Cluster NGC 6752 are due to `internal pollution' from intermediate mass asymptotic giant branch stars. To this end we are using a…
Structural and chemical changes during the AGB and post-AGB evolution are discussed with respect to two recent observational and theoretical findings. On the one hand, high-resolution infrared observations revealed details of the dynamical…
Context. Many protoplanetary nebulae show strong asymmetries in their surrounding shell, pointing to asymmetries during the mass loss phase. Questions concerning the origin and the onset of deviations from spherical symmetry are important…
Recent improvements in globular cluster colour-magnitude diagrams, coupled with an increase in large-sample spectroscopic abundance studies of cluster giants, finally allow some attempts at a statistically meaningful comparison of the…
It is now about 30 years ago that photometric and spectroscopic surveys of asymptotic giant branch (AGB) stars in the Magellanic Clouds (MCs) uncovered the first examples of truly massive (> 3-4 M_s) O-rich AGB stars experiencing hot bottom…
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…
The mechanisms responsible for chemical depletion across diverse astrophysical environments are not yet fully understood. In this paper, we investigate chemical depletion in post-AGB/post-RGB binary stars hosting second-generation…
Nucleosynthesis in evolved (RGB and AGB) low-mass stars is reviewed under the light of the reaction rates recommended in the NACRE compilation (Angulo et al. 1999). We use a parametric model of stellar nucleosynthesis to investigate the…
We calculated models of massive AGB stars with a self-consistent coupling of time-dependent mixing and nuclear burning for 30 isotopes and 74 reactions. Overshoot with an exponentially declining velocity field was considered and applied…
We present stellar evolutionary sequences for asymptotic giant branch (AGB) stars in the Magellanic Cloud clusters NGC 1978, NGC 1846 and NGC 419. The new stellar models for the three clusters match the observed effective temperatures on…
The evolution on the AGB and beyond is reviewed with respect to the origin of Wolf-Rayet central stars. We focus on thermal pulses due to their particular importance for the evolution of hydrogen deficient stars. It is shown that overshoot…
The metal abundances in the atmospheres of hot white dwarfs (WDs) entering the cooling sequence are determined by the preceding Asymptotic Giant Branch (AGB) evolutionary phase and, subsequently, by the onset of gravitational settling and…
The results from a Hubble Space Telescope (HST) snapshot survey of post-AGB objects are shown. The aim of the survey is to complement existing HST images of PPN and to connect various types of nebulosities with physical and chemical…
Differences in chemical composition among main sequence stars within a given cluster are probably due to differences in their masses and other effects such as radiative diffusion, magnetic field, rotation, mixing mechanisms, mass loss,…
The recent parameterisation by the GSP-spec module of Gaia/RVS spectra has produced an homogeneous catalogue of about 174,000 AGB stars. Among the 13 chemical elements presented in this catalogue, the abundance of 2 of them (Ce and Nd) have…
AGB stars are responsible for producing a variety of elements, including carbon, nitrogen, and the heavy elements produced in the slow neutron-capture process ($s$-elements). There are many uncertainties involved in modelling the evolution…
In early type stars the ultraviolet spectral region is important for several reasons. Firstly, since the majority of the total flux is emitted here, it provides a rather sensitive indicator of a photospheric temperature and luminosity.…
We present a high resolution detailed abundance analysis for a sample of six post-AGB candidate stars, five of them had not been studied spectroscopically in the optical region. All the analyzed objects are IRAS sources identified as…