Physical Properties of Wolf-Rayet Stars

Crowther, P. A.

doi:10.1146/annurev.astro.45.051806.110615

Cited by 916 publications

(1,010 citation statements)

References 187 publications

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“…Wolf-Rayet (WR) stars represent the ultimate, short-lived (< 1Myr) evolutionary phase of only the most massive (Mi > 25 M⊙) O-stars (see Crowther 2007). They possess dense and fast stellar winds, giving them characteristic strong and broad emission line spectra.…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population

Rosslowe

Crowther

2015

Monthly Notices of the Royal Astronomical Society

125

143

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We construct revised near-infrared absolute magnitude calibrations for 126 Galactic Wolf-Rayet (WR) stars at known distances, based in part upon recent large scale spectroscopic surveys. Application to 246 WR stars located in the field, permits us to map their Galactic distribution. As anticipated, WR stars generally lie in the thin disk (∼40 pc half width at half maximum) between Galactocentric radii 3.5-10 kpc, in accordance with other star formation tracers. We highlight 12 WR stars located at vertical distances of 300 pc from the midplane. Analysis of the radial variation in WR subtypes exposes a ubiquitously higher N W C /N W N ratio than predicted by stellar evolutionary models accounting for stellar rotation. Models for non-rotating stars or accounting for close binary evolution are more consistent with observations. We consolidate information acquired about the known WR content of the Milky Way to build a simple model of the complete population. We derive observable quantities over a range of wavelengths, allowing us to estimate a total number of 1200 +300 −100 Galactic WR stars, implying an average duration of ∼ 0.25 Myr for the WR phase at the current Milky Way star formation rate. Of relevance to future spectroscopic surveys, we use this model WR population to predict follow-up spectroscopy to K S ≃ 13 mag will be necessary to identify 95% of Galactic WR stars. We anticipate that ESA's Gaia mission will make few additional WR star discoveries via low-resolution spectroscopy, though will significantly refine existing distance determinations. Appendix A provides a complete inventory of 322 Galactic WR stars discovered since the VIIth catalogue (313 including Annex), including a revised nomenclature scheme.

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Section: Introductionmentioning

confidence: 99%

Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population

Rosslowe

Crowther

2015

Monthly Notices of the Royal Astronomical Society

125

143

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“…Higher mass (25-30 M ) RSGs can also become WR stars. The characteristic emission lines arise from fast stellar winds and heavy mass loss from the star (Crowther 2007).…”

Section: Wolf-rayet Features In Clustersmentioning

confidence: 99%

Studying the YMC population of M83: how long clusters remain embedded, their interaction with the ISM and implications for GC formation theories

Hollyhead

Bastian

Adamo

et al. 2015

Monthly Notices of the Royal Astronomical Society

145

129

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The study of young massive clusters can provide key information for the formation of globular clusters, as they are often considered analogues. A currently unanswered question in this field is how long these massive clusters remain embedded in their natal gas, with important implications for the formation of multiple populations that have been used to explain phenomena observed in globular clusters. We present an analysis of ages and masses of the young massive cluster population of M83. Through visual inspection of the clusters, and comparison of their spectral energy distributions (SEDs) and position in colour-colour space, the clusters are all exposed (no longer embedded) by <4 Myr, most likely less, indicating that current proposed age spreads within older clusters are unlikely. We also present several methods of constraining the ages of very young massive clusters. This can often be difficult using SED fitting due to a lack of information to disentangle age-extinction degeneracies and possible inaccurate assumptions in the models used for the fitting. The individual morphology of the Hα around each cluster has a significant effect on the measured fluxes, which contributes to inaccuracies in the age estimates for clusters younger than 10 Myr using SED fitting. This is due to model uncertainties and aperture effects. Our methods to help constrain ages of young clusters include using the near-infrared and spectral features, such as Wolf-Rayet stars.

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“…We have calculated two cases: a uniform external medium ρ = const and a wind-like medium ρ = Ar −2 , where A is a constant which depends on the mass-loss rate of the GRB progenitor. Its typical range for galactic Wolf-Rayet stars is 10 11 − 10 12 g cm −1 (Crowther 2007 is shown by the dashed curve, and the final distribution (after internal shocks) is shown by the solid curve. Right: bolometric light-curves (assuming a radiative efficiency ǫ e = 0.1) calculated for different ambient media (dotted lines).…”

Section: Flares: a Simplified Modelmentioning

confidence: 99%

X-ray flares from dense shells formed in gamma-ray burst explosions

Hascoët

Beloborodov

Daigne

et al. 2017

Monthly Notices of the Royal Astronomical Society: Letters

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Bright X-ray flares are routinely detected by the Swift satellite during the early afterglow of gamma-ray bursts, when the explosion ejecta drives a blast wave into the external medium. We suggest that the flares are produced as the reverse shock propagates into the tail of the ejecta. The ejecta is expected to contain a few dense shells formed at an earlier stage of the explosion. We show an example of how such dense shells form and describe how the reverse shock interacts with them. A new reflected shock is generated in this interaction, which produces a short-lived X-ray flare. The model provides a natural explanation for the main observed features of the X-ray flares -the fast rise, the steep power-law decline, and the characteristic peak duration ∆t/t = (0.1 − 0.3).

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Physical Properties of Wolf-Rayet Stars

Cited by 916 publications

References 187 publications

Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population

Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population

Studying the YMC population of M83: how long clusters remain embedded, their interaction with the ISM and implications for GC formation theories

X-ray flares from dense shells formed in gamma-ray burst explosions

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