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We study the evolution of embedded clusters. The equations of motion of the stars in the cluster are solved by direct N-body integration while taking the effects of stellar evolution and the hydrodynamics of the natal gas content into…
We investigate the early evolution of two distinct populations of low-mass stars in globular clusters under the influence of primordial gas expulsion driven by supernovae to study if this process can increase the fraction of second…
We model how the mid-infrared colors of Young Stellar Objects (YSOs) vary with stellar temperature. The spectral energy distribution (SED) of each object has contributions from thermal emission of circumstellar dust, from direct stellar…
After a review of the many effects of metallicity on the evolution of rotating and non-rotating stars, we discuss the consequences of a high metallicity on massive star populations and on stellar nucleosynthesis. The most striking effect of…
Planet accretion onto solar type stars may significantly change the stellar atmospheric abundances of 6Li and 7Li if it takes place after the star has arrived at the main sequence. Ingestion of planets at an earlier phase will not affect…
As a tool to interpret nearby and high redshift galaxy data from optical to K-band we present our chemically consistent spectrophotometric evolutionary synthesis models. These models take into account the increasing initial metallicity of…
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.…
Context: To investigate how the content of massive OB stars affects the long-term evolution of young open clusters and their tidal streams, and how such an effect influences the constraint of initial conditions by looking at the present-day…
We present the first "combined stellar structure and atmosphere models" (CoStar) for massive stars, which consistently treat the entire mass loosing star from the center out to the asymptotic wind velocity. The models use up-to-date input…
We analyse pre-Main Sequence evolutionary tracks for low mass stars with masses $m \le 1.4 \msol$ based on the Baraffe et al. (1998) input physics. We also extend the recent Chabrier et al. (2000) evolutionary models based on dusty…
One possible scenario for the formation of carbon-enhanced metal-poor stars is the accretion of carbon-rich material from a binary companion which may no longer visible. It is generally assumed that the accreted material remains on the…
The prediction of standard chemical evolution models of higher abundances of He3 at the solar and present-day epochs than are observed indicates a possible problem with the yield of He3 for stars in the range of 1-3 solar masses. Because…
We analyze the optical continuum of star-forming galaxies in SDSS by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation and star formation…
A new set of stellar models in the mass range 1.2 to 9 $M_{\odot}$ is presented. The adopted chemical compositions cover the typical galactic values, namely $0.0001 \le Z \le 0.02$ and $0.23 \le Y \le 0.28$. A comparison among the most…
[abridged] Many topical astrophysical research areas, such as the properties of planet host stars, the nature of the progenitors of different types of supernovae and gamma ray bursts, and the evolution of galaxies, require complete and…
Precise studies on the Galactic bulge, halo, thick disk, and globular clusters require stellar models with alpha enhancement and various He contents. For this purpose we complement existing PARSEC (PAdova-TRieste Stellar Evolution Code)…
We present preliminary results of a detailed chemical abundance analysis for a sample of solar-type stars known to exhibit excess infrared emission associated with dusty debris disks. Our sample of 28 stars was selected based on results…
Mixing processes such as convection, overshooting and rotational mixing have long been known to affect the evolutionary properties of low-mass stars. While modeling a 1.2 Msun star, we encountered a semiconvective region outside the fully…
The relationship between stellar populations and the ionizing flux with which they irradiate their surroundings has profound implications for the evolution of the intergalactic medium. We quantify the ionizing flux arising from synthetic…
The evolution of star clusters is studied using N-body simulations in which the evolution of single stars and binaries are taken self-consistently into account. Initial conditions are chosen to represent relatively young Galactic open…