The Galactic WC and WO stars

  title={The Galactic WC and WO stars},
  author={Andreas A. C. Sander and W. R. Hamann and Helge Todt and Rainer Hainich and Tomer Shenar and Varsha Ramachandran and Lidia M Oskinova},
  journal={Astronomy \& Astrophysics},
Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. Thus, the determination of the WC star… 

The Wolf-Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud

Context. Massive Wolf–Rayet (WR) stars dominate the radiative and mechanical energy budget of galaxies and probe a critical phase in the evolution of massive stars prior to core collapse. It is not

The Galactic WN stars revisited

Comprehensive spectral analyses of the Galactic Wolf-Rayet stars of the nitrogen sequence (i.e. the WN subclass) have been performed in a previous paper. However, the distances of these objects were

The Physical Parameters of Four WC-type Wolf–Rayet Stars in the Large Magellanic Cloud: Evidence of Evolution

We present a spectral analysis of four Large Magellanic Cloud (LMC) WC-type Wolf–Rayet (WR) stars (BAT99-8, BAT99-9, BAT99-11, and BAT99-52) to shed light on two evolutionary questions surrounding

A spectroscopic multiplicity survey of Galactic Wolf-Rayet stars

Context. It is now well established that the majority of massive stars reside in multiple systems. However, the effect of multiplicity is not sufficiently understood, resulting in a plethora of

WO-type Wolf–Rayet Stars: The Last Hurrah of Massive Star Evolution

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 λλ3811,34

On the nature of massive helium star winds and Wolf–Rayet-type mass-loss

The mass-loss rates of massive helium stars are one of the major uncertainties in modern astrophysics. Regardless of whether they were stripped by a binary companion or managed to peel off their

Evolution of Wolf–Rayet stars as black hole progenitors

Evolved Wolf–Rayet stars form a key aspect of massive star evolution, and their strong outflows determine their final fates. In this study, we calculate grids of stellar models for a wide range of

The stellar and wind parameters of six prototypical HMXBs and their evolutionary status

Context. High-mass X-ray binaries (HMXBs) are exceptional astrophysical laboratories that offer a rare glimpse into the physical processes that govern accretion on compact objects, massive-star

A Study of the Stochastic Photometric Variability in the Winds of Galactic Wolf–Rayet Stars

In order to explore how the ubiquitous short-term stochastic variability in the photometric observations of Wolf–Rayet (WR) stars is related to various stellar characteristics, we examined a sample

Two Wolf–Rayet stars at the heart of colliding-wind binary Apep

Infrared imaging of the colliding-wind binary Apep has revealed a spectacular dust plume with complicated internal dynamics that challenges standard colliding-wind binary physics. Such challenges



Helium Stars: Towards an Understanding of Wolf-Rayet Evolution

Wolf-Rayet (WR) stars are massive stars that have lost most or all of their hydrogen via powerful stellar winds. Recent observations have indicated that hydrogen-free WR stars have cooler

The Galactic WC stars Stellar parameters from spectral analyses indicate a new evolutionary sequence

[Abridged] [...] AIMS: We aim to establish the stellar parameters and mass-loss rates of the Galactic WC stars. These data provide the empirical basis of studies of (i) the role of WC stars in the

Wolf-Rayet stars in the Small Magellanic Cloud: I. Analysis of the single WN stars

Wolf-Rayet (WR) stars have a severe impact on their environments owing to their strong ionizing radiation fields and powerful stellar winds. Since these winds are considered to be driven by radiation

Massive stars on the verge of exploding: the properties of oxygen sequence Wolf-Rayet stars

Context. Oxygen sequence Wolf-Rayet (WO) stars represent a very rare stage in the evolution of massive stars. Their spectra show strong emission lines of helium-burning products, in particular highly

Towards a better understanding of the evolution of Wolf–Rayet stars and Type Ib/Ic supernova progenitors

Hydrogen-deficient Wolf-Rayet (WR) stars are potential candidates of Type Ib/Ic supernova (SN Ib/Ic) progenitors and their evolution is governed by mass loss. Stellar evolution models with the most

The Wolf-Rayet stars in the Large Magellanic Cloud - A comprehensive analysis of the WN class

Context. Massive stars, although being important building blocks of galaxies, are still not fully understood. This especially holds true for Wolf-Rayet (WR) stars with their strong mass loss, whose

Stellar mass-loss near the Eddington limit Tracing the sub-photospheric layers of classical Wolf-Rayet stars

Context. Towards the end of their evolution, hot massive stars develop strong stellar winds and appear as emission line stars, such as Wolf-Rayet (WR) stars or luminous blue variables (LBVs). The

On the optically-thick winds of Wolf-Rayet stars

(abridged) The strong winds of Wolf-Rayet (WR) stars are important for the mechanical and chemical feedback of the most massive stars and determine whether they end their lives as neutron stars or

Wolf-Rayet stars in the Small Magellanic Cloud: II. Analysis of the binaries

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

Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit

The mass loss from Wolf-Rayet (WR) stars is of fundamental importance for the final fate of massive stars and their chemical yields. Its Z-dependence is discussed in relation to the formation of