Related papers: Abundances of massive stars: some recent developme…
We study the evolutionary and physical properties of evolved O stars in the Small Magellanic Cloud (SMC), with a special focus on their surface abundances to investigate the efficiency of rotational mixing as a function of age, rotation and…
One of the challenges for stellar astrophysics is to reach the point at which we can undertake reliable spectral synthesis of unresolved populations in young, star-forming galaxies at high redshift. Here I summarise recent studies of…
The chemical abundances of metal-poor stars provide a great deal of information regarding the individual nucleosynthetic processes that created the observed elements and the overall process of chemical enrichment of the galaxy since the…
We carefully analyze how the abundance of Nitrogen over Oxygen evolves when dependent on metallicity stellar yields with a primary component of N proceeding from AGBs stars are used. We show the results obtained with a chemical evolution…
Recent observations have revealed the existence of a population of slowly-rotating, nitrogen-rich B dwarfs that are not predicted by evolutionary models including rotational mixing. However, as theoretical arguments suggest that magnetic…
The most metal-poor stars found in the Galaxy and in nearby galaxies are witnesses of the early evolution of the Universe. In a general picture in which we expect the metallicity to increase monotonically with time, as a result of the metal…
The evolution of massive stars is still partly unconstrained. Mass, metallicity, mass loss and rotation are the main drivers of stellar evolution. Binarity and magnetic field may also significantly affect the fate of massive stars. Our goal…
Over the last half-century quantitative stellar spectroscopy has made great progress. However, most stellar abundance analyses today still employ rather simplified models, which can introduce severe systematic errors swamping the…
The abundance patterns of metal-poor stars provide us a wealth of chemical information about various stages of cosmic chemical evolution. In particular, these stars allow us to study the formation and evolution of the elements, and the…
The abundance patterns of metal-poor stars provide us a wealth of chemical information about various stages of the chemical evolution of the Galaxy. In particular, these stars allow us to study the formation and evolution of the elements…
Metal-poor stars provide information on the characteristics and chemical evolution of the halo population of the Galaxy, the first epoch of star formation and Galaxy formation (not just locally but with relevance to high-redshift objects),…
We argue that extreme metal-poor stars show a high dispersion in metallicity, because their abundances are the outcome of very few supernova events. Abundance anomalies should appear because of the discrete range of progenitor masses. There…
Although the theoretical study of very low metallicity (Z) and metal-free stars is not new, their importance has recently greatly increased since two related fields have been developing rapidly. The first is cosmological simulations of the…
Stellar rotation produces an internal mixing of the elements due to shear instability and meridional circulation. This leads to observable $N/C$ enhancements in massive stars above about 7--9 $M_{\odot}$. Rotation also favours mass loss by…
The past decade has witnessed impressive progress in our understanding of the physical properties of massive stars in the Magellanic Clouds, and how they compare to their cousins in the Galaxy. I summarise new results in this field,…
It is currently impossible to determine the abundances of stellar populations star-by-star in dense stellar systems more distant than a few megaparsecs. Therefore, methods to analyse the composite light of stellar systems are required. I…
Some useful developments in the model physics are briefly presented, followed by model results on chemical enrichments and WR stars. We discuss the expected rotation velocities of WR stars. We emphasize that the (C+O)/He ratio is a better…
Although globular clusters are generally chemically homogeneous, substantial abundance variations are sometimes seen even among unevolved main sequence stars, especially for the CNO group of elements. Multi-object intermediate-dispersion…
CNO abundances in galaxies bear on issues of galactic evolution as well as stellar evolution and nucleosynthesis. Knowledge about them in dwarf and spiral galaxies depends mainly on emission lines from H II regions, with information from…
Aims. A sample of early B-type stars in OB associations and the field within the solar neighbourhood is studied comprehensively. Present-day abundances for the astrophysically most interesting chemical elements are derived. Methods.…