The role of carbon stars in the build-up of chemical elements in galaxies is discussed on the basis of stellar evolution calculations and estimated stellar yields, abundance analyses of AGB stars, galactic-evolution models and abundance trends among solar-type disk stars. We conclude that the AGB stars in general, and carbon stars in particular, probably are main contributors of s-elements, tha...

Johann Wolfgang Goethe " Faust " Der Tragödie erster Teil 447ff vi Contents Zusammenfassung xv 1 Introduction 1 1.

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 chemical evolution model incorporating custom-made stellar evolution yields calculated using a detailed stellar evolution code. By tracing the chemical evolution o...

Assuming that Dark Matter is dominated by WIMPs, it accretes by gravitational attraction and scattering over baryonic material and annihilates inside celestial objects, giving rise to a “Dark Luminosity” which may potentially affect the evolution of stars. We estimate the Dark Luminosity achieved by different kinds of stars in a halo with DM properties characteristic of the ones where the first...

Assuming that Dark Matter is dominated by WIMPs, it accretes by gravitational attraction and scattering over baryonic material and annihilates inside celestial objects, giving rise to a “Dark Luminosity” which may potentially affect the evolution of stars. In this short letter we estimate the Dark Luminosity achieved by different kinds of stars in a halo with DM properties characteristic of the...

Massive stars played a key role in the early evolution of the Universe. They formed with the first halos and started the re-ionisation. It is therefore very important to understand their evolution. In this paper, we describe the strong impact of rotation induced mixing and mass loss at very low Z. The strong mixing leads to a significant production of primary N, C and Ne. Mass loss during the r...

Compared to earlier studies on the subject, we use results of intermediate mass case B close binary evolution computed with updated data, to predict the population of B-type accretion stars for different regions of star formation, in the Galaxy and in the Magellanic Clouds. We will make a distinction between accretion stars with a (helium burning) subdwarf, respectively white dwarf and neutron ...

The presence of a substantial number of hot stars in the extremely metal-rich open cluster NGC 6791 has been a mystery. If these hot stars are in their core helium burning phase, they are significantly bluer (hotter) than predicted by canonical stellar evolution theory. No obvious explanation is available yet. We consider the effects of mass loss during the evolution of horizontal branch (HB) s...

The first generation of stars was formed from primordial gas. Numerical simulations suggest that the first stars were predominantly very massive, with typical masses M ≥ 100M⊙. These stars were responsible for the reionization of the universe, the initial enrichment of the intergalactic medium with heavy elements, and other cosmological consequences. In this work, we study the structure of Zero...

The thermal, spin and magnetic evolution of neutron stars in the old low mass binaries is first explored. Recycled to very short periods via accretion torques, the neutron stars lose their magnetism progressively. If accretion proceeds undisturbed for 100 Myrs these stars can rotate close to break up with periods far below the minimum observed of 1.558 ms. We investigate their histories using p...