Related papers: Low-luminosity Wolf-Rayet stars: a model-data comp…
The recent discovery of a gravitational wave from the merging of two black holes of about 30 solar masses each challenges our incomplete understanding of massive stars and their evolution. Critical ingredients comprise mass-loss, rotation,…
We summarise recent developments on synthesis models for massive star populations with a particular emphasis on Wolf-Rayet (WR) stars. Quantitative analysis of the stellar content of WR galaxies are reviewed. Comparing observations of WR…
We study the stellar and wind properties of a sample of Galactic O dwarfs to track the conditions under which weak winds (i.e mass loss rates lower than ~ 1e-8 Msol/yr) appear. The sample is composed of low and high luminosity dwarfs…
We present new atmosphere models for Wolf-Rayet stars that include a self-consistent solution of the wind hydrodynamics. We demonstrate that the formation of optically thick WR winds can be explained by radiative driving on Fe line…
Envelope stripping, whether through single-star wind mass loss or binary mass transfer, is a key evolutionary pathway for the formation of classical Wolf-Rayet stars and lower-mass stripped helium (He) stars. However, to study the evolution…
We summarize past and current surveys for Wolf-Rayet stars among the Local Group galaxies, emphasizing both the how and the why. Such studies are invaluable for helping us learn about massive star evolution, and for providing sensitive…
Today, we have a sufficiently complete picture of what the Wolf--Rayet (WR) stars are. Predictions of stellar evolution theory are in a good agreement with their parameters, estimated from observational data using stellar atmospheres codes;…
The total population of Wolf-Rayet (WR) stars in the Galaxy is predicted by models to be as many as $\sim$6000 stars, and yet the number of catalogued WR stars as a result of optical surveys was far lower than this ($\sim$200) at the turn…
We present spectroscopic observations of the central star clusters in NGC 5253 the aim of which is to search for WC stars. Our observations show the presence of Wolf-Rayet (WR) stars not only of WN but also of WC subtype in two star forming…
(abridged) We propose the new designation ``WNH'' for luminous Wolf-Rayet (WR) stars of the nitrogen sequence with H in their spectra. These are commonly called WNL stars (e.g., WN7h), but this new shorthand avoids confusion because there…
We present here tests of a five-filter photometric system aimed at WR classification. In addition to the well-known easy separation between the WN and WC spectral types, these tests indicate interesting potentialities in the discrimination…
Wolf-Rayet (WR) stars of the WNh category contain a significant fraction of hydrogen at their surface. They can be hydrogen-burning, very massive stars or stars in a post-main sequence phase of evolution. Also, WNh stars are sometimes not…
Are WO-type Wolf Rayet (WR) stars in the final stage of massive star evolution before core-collapse? Although WC- and WO-type WRs have very similar spectra, WOs show a much stronger O VI $\lambda \lambda$3811,34 emission-line feature. This…
New spectroscopic observations of the metal poor galaxy IZw 18 are discussed. Wolf-Rayet stars of WC type have been detected in the NW-HII region contrary to evolutionary synthesis model predictions. Implications on the mass loss rate and…
We report the discovery of fifteen previously unknown Wolf-Rayet (WR) stars found as part of an infrared broad-band study of candidate WR stars in the Galaxy. We have derived an empirically-based selection algorithm which has selected ~5000…
Context. Oxygen sequence Wolf-Rayet (WO) stars are thought to represent the final evolutionary stage of the most massive stars. The characteristic strong O vi emission possibly originates from an enhanced oxygen abundance in the stellar…
The central region of the Milky Way provides a unique laboratory for a systematic, spatially-resolved population study of evolved massive stars of various types in a relatively high metallicity environment. We have conducted a…
ABRIGED: Quantifying the number, type and distribution of W-R stars is a key component in the context of galaxy evolution, since they put constraints on the age of the star formation bursts. Nearby galaxies (d<5 Mpc) are particularly…
Wolf-Rayet stars (WRs) represent the end of a massive star's life as it is about to turn into a supernova. Obtaining complete samples of such stars across a large range of metallicities poses observational challenges, but presents us with…
In order to predict the black hole mass distributions at high redshift, we need to understand whether very massive single stars ($M>40$ M$_\odot$) at low metallicity $Z$ lose their hydrogen-rich envelopes, like their metal-rich…