Related papers: Are Wolf-Rayet winds driven by radiation?
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),…
Context. Very massive clusters and regions of intense star formation such as the center of our Milky Way contain young, hydrogen-burning stars very close to the Eddington Limit. Formally classified as hydrogen-rich Wolf-Rayet stars, the…
Dusty Wolf-Rayet stars are few but remarkable in terms of dust production rates (up to one millionth of solar mass per year). Infrared excesses associated to mass-loss are found in the sub-types WC8 and WC9. Few WC9d stars are hosting a…
We measure transverse proper motion velocities of LMC Wolf-Rayet (WR) stars using Gaia DR3 astrometry. The combined velocity distribution of WNh, O If*/WN, and WNL very massive stars ($>100\ M_\odot$; VMS) shows both slow, unejected objects…
We construct helium (He) star models with optically thick winds and compare them with the properties of Galactic Wolf-Rayet (WR) stars. Hydrostatic He-core solutions are connected smoothly to trans-sonic wind solutions that satisfy the…
We report precision ground-based broadband optical intensity and linear-polarisation light-curves for the sky's brightest WN8 star, WR40. WN8 stars are notorious for their high level of variability, stemming from stochastic clumps in their…
We present refined color-color selection criteria for identifying Wolf-Rayet (WR) stars using available mid infrared (MIR) photometry from WISE in combination with near infrared (NIR) photometry from 2MASS. Using a sample of spectrally…
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;…
Wolf-Rayet stars have strong, hot winds, with mass-loss rates at least a factor of ten greater than their O-star progenitors, although their terminal wind speeds are similar. In this paper we use the technique of multiband linear…
The Small Magellanic Cloud (SMC) hosts 12 known Wolf-Rayet (WR) stars, seven of which are apparently single. Their formation is a challenge for current stellar evolution models because line-driven winds are generally assumed to be quenched…
The physical basis for interpreting observations of nebular morphology around massive stars in terms of the evolution of the central stars is reviewed, and examples are discussed, including NGC 6888, OMC-1, and eta Carinae.
Massive stars that become stripped of their hydrogen envelope through binary interaction or winds can be observed either as Wolf-Rayet stars, if they have optically thick winds, or as transparent-wind stripped-envelope stars. We approximate…
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…
Context. Radiation-driven mass loss is key to our understanding of massive-star evolution. However, for low-luminosity O-type stars there are big discrepancies between theoretically predicted and empirically derived mass-loss rates (called…
Photospheric radiation momentum is efficiently transferred by absorption through metal lines to the gaseous matter in the atmospheres of massive stars, sustaining strong winds and mass loss rates. Not only is this critical for the evolution…
This review briefly summarizes our knowledge of the X-ray emission from single WN, WC, and WO stars. These stars have relatively modest X-ray luminosities, typically not exceeding L_sun. The analysis of X-ray spectra usually reveals thermal…
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,…
The spin of Wolf-Rayet (WR) stars at low metallicity (Z) is most relevant for our understanding of gravitational wave sources such as GW 150914, as well as the incidence of long-duration gamma-ray bursts (GRBs). Two scenarios have been…
We present a simple analytical method to describe the structure of a spherically expanding envelope with strong mass outflow. The structure is consistently connected to the hydrostatic stellar interior and provides an adequate description…
The massive evolved Wolf-Rayet stars sometimes occur in colliding-wind binary systems in which dust plumes are formed as a result of the collision of stellar winds. These structures are known to encode the parameters of the binary orbit and…