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Early-type dwarfs (dEs) are by far the most abundant galaxy population in nearby clusters. Whether these objects are primordial, or the recent end-products of the different physical mechanisms that can transform galaxies once they enter…
Element diffusion is expected to occur in all kinds of stars : according to the relative effect of gravitation and radiative acceleration, they can fall or be pushed up in the atmospheres. Helium sinks in all cases, thereby creating a…
We analyse high-resolution archival UVES data of turnoff and subgiant stars in the nearby globular cluster NGC 6397 ([Fe/H] = -2). Balmer-profile analyses are performed to derive reddening-free effective temperatures. Due to the limited S/N…
For the well studied halo star HD 122563 and the four stars in the globular cluster NGC 6397, we determine NLTE abundances of iron using classical plane-parallel model atmospheres. Each star reveals a discrepancy in abundances between the…
The new generation of 3D hydrodynamical model atmospheres have been employed to study the impact of a realistic treatment of stellar convection on element abundance determinations of globular cluster stars for a range of atomic and…
A significant fraction of stars in globular clusters (about 70%-85%) exhibit peculiar chemical patterns with strong abundance variations in light elements along with constant abundances in heavy elements. These abundance anomalies can be…
The study of the chemistry of the stellar populations in Globular Clusters (GCs) is a fundamental task to unveil their formation in the high-redshift universe and to reconstruct the build up of our Galaxy. Using metallicity estimates from…
The determination of Li and proton-capture element abundances in globular cluster (GC) giants allows us to constrain several key questions on the multiple population scenarios in GCs, from formation and early evolution, to pollution and…
A number of planetary nebulae show binary central stars and significant abundance discrepancies between values estimated from colisionally excited lines when compared to the same abundances estimated from recombination lines. One approach…
To explain the observed anomalies in stellar populations within globular clusters, many globular cluster formation theories require two independent episodes of star formation. A fundamental prediction of these models is that the clusters…
Globular clusters contain many stars with surface abundance patterns indicating contributions from hydrogen burning products, as seen in the anti-correlated elemental abundances of e.g. sodium and oxygen, and magnesium and aluminium.…
It has been well established that Galactic Globular clusters (GCs) harbour more than one stellar population, distinguishable by the anti-correlations of light element abundances (C-N, Na-O, and Mg-Al). These studies have been extended…
We use Cycle 21 Hubble Space Telescope (HST) observations and HST archival ACS Treasury observations of 30 Galactic Globular Clusters to characterize two distinct stellar populations. A sophisticated Bayesian technique is employed to…
We report moderate resolution, high signal-to-noise spectroscopy of globular clusters around NGC 1399, the central cD galaxy in the Fornax cluster. We address issues as diverse as element abundances of globular clusters versus stellar…
Following work by W\"unsch and collaborators, we investigate a self-enrichment scenario for second generation star formation in globular clusters wherein wind material from first generation massive stars rapidly radiatively cools. Radiative…
Globular clusters (GCs), the oldest stellar systems observed in the Milky Way, have for long been considered single stellar populations. As such, they provided an ideal laboratory to understand stellar dynamics and primordial star formation…
Multiple populations, defined by correlations between light element abundances, are an almost ubiquitous property of globular clusters. On the other hand, dispersions among the heavy elements are limited to a few rare clusters. In this…
We present absorption-line strengths on the Lick/IDS line-strength system of 381 galaxies and 38 globular clusters in the 4000--6400 \AA region. All galaxies were observed at Lick Observatory between 1972 and 1984 with the Cassegrain Image…
Globular clusters (GCs) are known to host multiple stellar populations showing chemical anomalies in the content of light elements. The origin of such anomalies observed in Galactic GCs is still debated. Here we analyse data compiled from…
We find that the radiative diffusivity associated with the radiative viscosity generates a mixing that diminishes the efficiency of the gravitational settling in the external layers of stellar models corresponding to types earlier than G.…