Related papers: Stellar evolution with rotation XI: Wolf-Rayet sta…
Rotation is of key importance for the evolution of hot massive stars, however, the rotational velocities of these stars are difficult to determine. Based on our own data for 31 Galactic O stars and incorporating similar data for 86 OB…
We present a new set of synthesis models for stellar populations obtained with Starburst99, which are based on new stellar evolutionary tracks with rotation. We discuss models with zero rotation velocity and with velocities of 40% 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…
Massive Wolf-Rayet (WR) stars comprise a spectroscopic class characterized by high temperatures (Teff > ~30 kK) and powerful and rapid stellar winds. Hydrogen-rich WR stars represent the most massive stars in existence (M > ~100 Msun),…
We study the evolution, rotation, and surface abundances of O-type dwarfs in the Small Magellanic Cloud. We analyzed the UV and optical spectra of twenty-three objects and derived photospheric and wind properties. The observed binary…
We calculated pre-supernova evolution models of single rotating massive stars. These models reproduce observations during the early stages of the evolution very well, in particular Wolf--Rayet (WR) populations and ratio between type II and…
Massive WR stars are evolved massive stars characterized by strong mass-loss. Hypothetically, they can form either as single stars or as mass donors in close binaries. About 40% of the known WR stars are confirmed binaries, raising the…
Wolf-Rayet stars (WRs) are evolved massive stars, and the relative number of WC-type and WN-type WRs should vary with metallicity, providing a sensitive test of stellar evolutionary theory. The observed WC/WN ratio is much higher than that…
High precision photometry and spectroscopy of low-mass stars reveal a variety of properties standard stellar evolution cannot predict. Rotation, an essential ingredient of stellar evolution, is a step towards resolving the discrepancy…
Here we examine 12 Galactic clusters and OB associations containing Wolf-Rayet stars (W-Rs) and/or Luminous Blue Variables (LBVs), in order to assess the progentor masses of these evolved massive stars. We find that in the Milky Way,…
Stellar evolution models of massive stars are very sensitive to the adopted mass-loss scheme. The magnitude and evolution of mass-loss rates significantly affect the main sequence evolution, and the properties of post-main sequence objects,…
We investigate the evolution of the surface properties of models for rotating massive stars, i.e., their luminosities, effective temperatures, surface rotational velocities, and surface abundances of all isotopes, from the zero age main…
The stellar winds of massive stars show large changes in mass-loss rates and terminal velocities during their evolution from O-star through the Luminous Blue Variable phase to the Wolf-Rayet phase. The luminosity remains approximately…
Wolf-Rayet stars are evolved massive stars, and the relative number of WC-type and WN-type WRs should vary with the metallicity of the host galaxy, providing a sensitive test of stellar evolutionary theory. However, past studies of the WR…
Rotation has a number of important effects on the evolution of stars. Apart from structural changes because of the centrifugal force, turbulent mixing and meridional circulation caused by rotation can dramatically affect a star's chemical…
The favoured progenitors of long-duration gamma-ray bursts (GRBs) are rapidly rotating Wolf-Rayet (WR) stars. However, most Galactic WR stars are slow rotators, as stellar winds are thought to remove angular momentum. This poses a challenge…
We use a large sample of 174 Wolf-Rayet (WR) galaxies drawn from the Sloan Digital Sky Survey to study whether and how the slope of the stellar initial mass function depends on metallicity. We calculate for each object its oxygen abundance…
We calculated a grid of evolutionary tracks of rotating models with masses between 1.0 and 3.0 $M_{\odot}$ and a resolution $\delta M \leq 0.02$ $M_{\odot}$, which can be used to study the effects of rotation on stellar evolutions and on…
[Abridged] Context: Radiation-driven mass loss plays a key role in the life-cycles of massive stars. However, basic predictions of such mass loss still suffer from significant quantitative uncertainties. Aims: We develop new…
The effects of rotation on low-metallicity stellar models are twofold: first, the models reach break-up during main sequence and may lose mass by mechanical process; second, strong internal mixing brings freshly synthesized elements towards…