We have used an updated version of the empirically and semi-empirically calibrated BaSeL library of synthetic stellar spectra of Lejeune et al. (1997, 1998) and Westera et al. (1999) to calculate synthetic photometry in the (UBV)J (RI)C JHKLL M, HST-WFPC2, Geneva, and Washington systems for the entire set of non-rotating Geneva stellar evolution models covering masses from 0.4– 0.8 to 120–150 M...

Open and globular star clusters have served as benchmarks for the study of stellar evolution owing to their supposed nature as simple stellar populations of the same age and metallicity. After a brief review of some of the pioneering work that established the importance of imaging stars in these systems, we focus on several recent studies that have challenged our fundamental picture of star clu...

Planetary Nebulae (PNs) in the Magellanic Clouds offer the unique opportunity to study both the population and evolution of lowand intermediate-mass stars, in an environment that is free of the distance scale bias and the differential reddening that hinder the observations of the Galactic sample. The study of LMC and SMC PNs also offers the direct comparison of stellar populations with differen...

We demonstrate the necessity of using realistic stellar models taken from stellar evolution codes, as opposed to polytropes, for starting models in smoothed particle hydrodynamics calculations of collisions between main sequence stars. Evolved stars have mean molecular weight gradients, which affect their entropy profiles and therefore affect how they react during a collision. The structure of ...

We investigate the evolution of collisionally merged stars with mass of ∼ 100M⊙ which might be formed in dense star clusters. We assumed that massive stars with several tens M⊙ collide typically after ∼ 1Myr of the formation of the cluster and performed hydrodynamical simulations of several collision events. Our simulations show that after the collisions, merged stars have extended envelopes an...

We present new results from a systematic study of absorption line strengths of galaxies in clusters approaching redshifts of unity. In this paper, we specifically compare the strengths of the high-order Balmer absorption features of Hγ and Hδ in E/S0s in the four clusters Abell 2256 (z=0.06), CL1358+62 (z = 0.33), MS2053–04 (z = 0.58), and MS1054–03 (z = 0.83). By comparing the correlation of B...

The small and elusive Carina dSph still presents many open questions concerning its stellar populations and dynamical evolution. It presents a unique star formation history, with well separated episodes over a time of ∼10 Gyr. However, the complex star formation history does not seem to have caused a strong chemical evolution of its stellar content. Moreover, the occurrence of extra-tidal stars...

A model for rotation evolution of an intermediate mass star with the primordial magnetic field in the pre-main sequence (PMS) phase was developed. It takes into account the accretion of matter along the magnetic field lines, the stellar field-disk interaction and a magnetized wind. Variations of stellar moment of inertia were included based on evolutionary models of PMS evolution of such stars....

The buildup of stellar mass and the 3.6 µm luminosity function in clusters from z = 1.25 to z = 0.2. Abstract. We have measured the 3.6 µm luminosity evolution of about 1000 galaxies in 32 clusters at 0.2 < z < 1.25, without any a priori assumption about luminosity evolution, i.e. in a logically rigorous way. We find that the luminosity of our galaxies evolves as an old and passively evolving p...

We study the short-term evolution of starspots on the ultrafast-rotating star HD197890 (“Speedy Mic” = BO Mic, K 0-2V, Prot = 0.380 d) based on two Doppler images taken about 13 stellar rotations apart. Each image is based on spectra densely sampling a single stellar rotation. The images were reconstructed by our Doppler imaging code CLDI (Clean-like Doppler imaging) from line profiles extracte...