Radio Continuum Measurements of Southern Early‐Type Stars. II. A Distance‐limited Sample of Wolf‐Rayet Stars

Leitherer, Claus; Chapman, Jessica M.; Koribalski, B. S.

doi:10.1086/304096

Cited by 100 publications

(115 citation statements)

References 49 publications

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“…1) Chlebowski et al (1989); 2) Pollock et al (1995) A28, page 14 of 20 References. 1) Bieging et al (1989); 2) Drake (1990); 3) Leitherer et al (1997) O + B system but rather from the interaction between the close system and the third and distant star orbiting with a very long period.…”

Section: Discussionmentioning

confidence: 99%

Catalogue of particle-accelerating colliding-wind binaries

Becker

Raucq

2013

A&A

118

138

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Massive systems made of two or more stars are known to be the site for interesting physical processes -including at least in some cases -particle acceleration. Over the past decade, this topic motivated a particular effort to unveil the properties of these systems and characterize the circumstances responsible for the acceleration of particles and the potential role of pre-supernova massive stars in the production of high energy particles in our Galaxy. Although previous studies on this topic were mostly devoted to processes in general, or to a few individual objects in particular, a unified target-oriented census of particle-accelerating colliding-wind binaries (hereafter PACWBs) does not exist yet. This paper aims at making a general and unified census of these systems, emphasizing their main properties. A general discussion includes energetic considerations along with wind properties in relation with non-thermal emission processes that are likely at work in colliding-wind binaries. Finally, some guidelines for future observational and theoretical studies are drawn.

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Section: Discussionmentioning

confidence: 99%

Catalogue of particle-accelerating colliding-wind binaries

Becker

Raucq

2013

A&A

118

138

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“…For the WNVLh star WR L we adopt μ = 2.0, Z = 1.0 and γ = 1.0 (e.g. Leitherer et al 1997), resulting iṅ M = 2 × 10 −5 (v ∞ /1000 km s −1 ) f 1/2 M yr −1 respectively. For the WC9 star WR F adopting μ = 4.7, Z = 1.1 and γ = 1.1 yieldsṀ = 3.3 × 10 −5 (v ∞ /1000km s −1 ) f 1/2 M yr −1 .…”

Section: Wolf-rayet Starsmentioning

confidence: 99%

Radio emission from the massive stars in the galactic super star cluster Westerlund 1

Dougherty

Clark

Negueruela

et al. 2010

A&A

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Aims. Current mass-loss rate estimates imply that main sequence line-driven winds are not sufficient to strip away the H-rich envelope to yield Wolf-Rayet (WR) stars. The rich transitional population of the young massive cluster Westerlund 1 (Wd 1) provides an ideal laboratory to observe and constrain mass-loss processes throughout the transitional phase of stellar evolution. Methods. We present an analysis of deep radio continuum observations of Wd 1 obtained with the Australia Telescope Compact Array at four frequency bands that permit investigation of the intrinsic characteristics of the radio emission. Results. We detect 18 cluster members, a sample dominated by the cool hypergiants, with additional detections amongst the hotter OB supergiants and WR stars. The radio properties of the sample are diverse, with thermal, non-thermal and composite thermal/nonthermal sources present. Mass-loss rates determined for stars with partially optically thick stellar winds are ∼10 −5 M yr −1 across all spectral types, insufficient to enable the formation of WRs during a massive star lifetime, and the stars must undergo a period of greatly enhanced mass loss. The sgB[e] star W9, the brightest radio source in Wd 1, may provide an example, with a current mass-loss rate an order of magnitude higher than the other cluster members, and an extended nebula interpreted as a wind from an earlier epoch with a density ∼3× the current wind. Such an envelope structure in W9 is reminiscent of luminous blue variables, and one that shows evidence of two eras of high, possibly eruptive mass loss. Surprisingly, three of the OB supergiants are detected, implying unusually dense winds, though they are embedded in more extended emission regions that may influence the derived parameters. They also may have composite spectra, suggesting binarity, which can lead to a higher flux than expected from a stellar wind. Spatially resolved nebulae are associated with three of the four RSGs and three of the six YHGs in the cluster, which are due to quiescent mass loss rather than outbursts. The extended nebulae of W20 and W26 have a cometary morphology, implying significant interaction with either the intracluster medium or cluster wind. For some of the cool star winds, the ionizing source may be a companion star though the cluster radiation density is sufficiently high to provide the necessary ionizing radiation. Five WR stars are detected with composite spectra, interpreted as arising in colliding-wind binaries.

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“…The other parameters of this equation are not very well known, but we can take either the usual or average values of the WN winds, assuming that the Gaunt factor is g = 1 and that the terminal velocity is υ ∞ = 1000 km s −1 (Crowther 2003a), and using a wind composition typical of late WN stars µ = 2, γ e = 1, and Z = 1 (Leitherer et al 1997). Note that the adopted velocity is also compatible with the observations of the H α stationary lines in the optical spectrum; van den Heuvel (1981) reported Doppler widths of ∼1−2 × 10 3 km s −1 , and recently Gies et al (2002b) measured FWHM of ∼15 Å (∼ 680 km s −1 ).…”

Section: Mass Loss Evaluationmentioning

confidence: 99%

SS 433: a phenomenon imitating a Wolf-Rayet star

Fuchs

Miramond

Ábrahám

2006

A&A

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We present mid-infrared (2-12 µm) spectra of the microquasar SS 433 obtained with the Infrared Space Observatory (spectroscopic mode of ISOPHOT and ISOCAM). We compare them to the spectra of four Wolf-Rayet stars: WR 78, WR 134, WR 136, and WR 147 in the same wavelength range. The mid-infrared spectrum of SS 433 mainly shows H i and He i emission lines and is very similar to the spectrum of WR 147, a WN8(h)+B0.5V binary. The 2-12 µm continuum emission of SS 433 corresponds to optically thin and partially optically thick free-free emission, from which we calculate a mass loss rate of 2−3 × 10 −4 M yr −1 if the wind is homogeneous and a third of these values if it is clumped. This is consistent with a strong stellar wind from a WN star. However, following recent studies concluding that the mass donor star of SS 433 is not a Wolf-Rayet star, we propose that this strong wind out flows from a geometrically thick envelope of material that surrounds the compact object like a stellar atmosphere, imitating the Wolf-Rayet phenomenon. This wind could also wrap the mass donor star, and at larger distances (∼40 AU), it might form a dust envelope from which the thermal emission, detected with ISOPHOT at 25 µm and 60 µm, would originate. This wind also probably feeds the material that is ejected in the orbital plane of the binary system and that forms the equatorial outflow detected in radio at distances > 100 AU.

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Radio Continuum Measurements of Southern Early‐Type Stars. II. A Distance‐limited Sample of Wolf‐Rayet Stars

Cited by 100 publications

References 49 publications

Catalogue of particle-accelerating colliding-wind binaries

Catalogue of particle-accelerating colliding-wind binaries

Radio emission from the massive stars in the galactic super star cluster Westerlund 1

SS 433: a phenomenon imitating a Wolf-Rayet star

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