The asymptotic giant branch (AGB) evolution of stars is interesting from many points of view. It is the nal evolutionary phase for the large majority of all stars in the Universe that have left the main sequence. During this stage they contribute to the chemical evolution of galaxies, contribute to the integrated starlight of many galaxies, may provide the only interstellar matter there is in s...

We present near infrared J, H, and K images and K−band spectroscopy in the giant H II region W42. A massive star cluster is revealed; the color–color plot and K−band spectroscopic morphology of two of the brighter objects suggest the presence of young stellar objects. The spectrum of the bright central star is similar to unobscured stars with MK spectral types of O5–O6.5. If this star is on the...

Star formation and chemical enrichment histories of the dwarf spheroidal galaxies (dSphs) Draco, Sextans, and Ursa Minor are investigated by means of chemical evolution models and a simulation code for colour-magnitude diagrams (CMDs). The CMD simulation code is designed to fully consider effects of the chemical evolution on stellar evolution and photometric properties. For this aim, star forma...

The lightcurve of the Large Magellanic Cloud (LMC) variable star MACHO 81.8997.87 shows evidence for photometric variations due to both stellar pulsation, with a 2.035 day period, and eclipsing behavior, with an 800.4 day period. The primary star of the system has been identified as a first-overtone Cepheid but the nature of the secondary star has not been determined. Here we present multicolor...

We present results on the analysis of background Ðeld stars found in Hubble Space T elescope Wide Field Planetary Camera 2 observations of six of the old globular clusters of the Large Magellanic Cloud. Treated as contaminants by the globular cluster analysts, we produce (V [I, V) color-magnitude diagrams (CMDs) of the Ðeld stars and use them to explore the LMCÏs star formation history. The pho...

It is inferred from the symmetrical and luminous X-ray emission of fossil groups that they are mature, relaxed galaxy systems. Cosmological simulations and observations focusing on their dark halo and inter-galactic medium properties confirm their early formation. Recent photometric observations suggest that, unlike the majority of non-fossil brightest group galaxies (BGGs), the central early-t...