The evolution of massive stars and their spectra

Groh, J. H.; Meynet, Georges; Ekström, Sylvia; Georgy, Cyril

doi:10.1051/0004-6361/201322573

Cited by 162 publications

(203 citation statements)

References 103 publications

(162 reference statements)

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“…Hence, to a first approximation a population consisting of non-rotating single stars and interacting binaries would be consistent with the NW C /NW N we observe. However, we caution that all comparisons of this nature are subject to how the physics contained in stellar models is expected to translate into observable properties, which currently rests on estimations of surface abundances and temperatures that may not be appropriate (Groh et al 2014), particularly for the transition between eWNE and eWNL subtypes.…”

Section: Discussionmentioning

confidence: 99%

“…As recently highlighted by Groh et al (2014), there is not a straightforward correspondence between spectroscopic and evolutionary phases in massive stars, particularly postmain sequence. Spectroscopically, any WN showing surface Hydrogen (WN#h or (h)) or with ionisation type 7 is identified as late-type (WNL), while H-free WN of ionisation type 6 or those displaying broad emission lines (WN#b) are early-type (WNE).…”

Section: Subtype Distributions Across the Galactic Metallicity Gradientmentioning

confidence: 99%

“…The transition between eWNE and eWNL phases (where 'e' denotes the definition in evolutionary models) is regarded to occur when XH < 10 −5 , and the eWC phase begins when carbon dominates nitrogen by mass (Meynet & Maeder 2005). By computing model spectra from evolutionary models, Groh et al (2014) have shown that spectroscopic WNE and WNL lifetimes can differ radically from eWNE and eWNL lifetimes, as a star may have a WNE spectrum while retaining some surface hydrogen, hence this is a poor indicator. The problem is not so severe regarding the transition from WN to WC stars, as the change in surface carbon abundance is a rapid process, meaning the eWC phase corresponds well to the spectroscopic WC phase.…”

Section: Subtype Distributions Across the Galactic Metallicity Gradientmentioning

confidence: 99%

“…Furthermore, rotationally induced mixing allows stars to become WR earlier in their evolution and experience an extended eWNL phase. The extreme sensitivity of the eWNE/eWNL transition to the chosen hydrogen surface abundance criterion clearly has a major influence on predictions (Groh et al 2014). Therefore we interpret the disparity shown in figure 8 largely as a symptom of these definitions rather than a serious conflict with evolutionary theory.…”

Section: Comparison To Evolutionary Predictionsmentioning

confidence: 99%

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

Rosslowe

Crowther

2015

Monthly Notices of the Royal Astronomical Society

128

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: Discussionmentioning

confidence: 99%

Section: Subtype Distributions Across the Galactic Metallicity Gradientmentioning

confidence: 99%

Section: Subtype Distributions Across the Galactic Metallicity Gradientmentioning

confidence: 99%

Section: Comparison To Evolutionary Predictionsmentioning

confidence: 99%

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

Rosslowe

Crowther

2015

Monthly Notices of the Royal Astronomical Society

128

143

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“…Their characterization and location in the Hertzsprung-Russell (HR) diagram are important to calibrate stellar evolutionary models of massive stars and to understand their further evolution toward SNe (e.g., Dessart et al 2013;Groh et al 2013Groh et al , 2014. The majority of massive stars are members of binary systems with a preference for close pairs (Podsiadlowski 2010;Sana et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Multi-epoch VLTI-PIONIER imaging of the supergiant V766 Cen

Wittkowski

Abellán

Arroyo-Torres

et al. 2017

A&A

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Context. The star V766 Cen (=HR 5171A) was originally classified as a yellow hypergiant but lately found to more likely be a 27−36 M red supergiant (RSG). Recent observations indicated a close eclipsing companion in the contact or common-envelope phase. Aims. Here, we aim at imaging observations of V766 Cen to confirm the presence of the close companion. Methods. We used near-infrared H-band aperture synthesis imaging at three epochs in 2014, 2016, and 2017, employing the PIONIER instrument at the Very Large Telescope Interferometer (VLTI). Results. The visibility data indicate a mean Rosseland angular diameter of 4.1 ± 0.8 mas, corresponding to a radius of 1575 ± 400 R . The data show an extended shell (MOLsphere) of about 2.5 times the Rosseland diameter, which contributes about 30% of the H-band flux. The reconstructed images at the 2014 epoch show a complex elongated structure within the photospheric disk with a contrast of about 10%. The second and third epochs show qualitatively and quantitatively different structures with a single very bright and narrow feature and high contrasts of 20−30%. This feature is located toward the south-western limb of the photospheric stellar disk. We estimate an angular size of the feature of 1.7 ± 0.3 mas, corresponding to a radius of 650 ± 150 R , and giving a radius ratio of 0.42 +0.35 −0.10 compared to the primary stellar disk. Conclusions. We interpret the images at the 2016 and 2017 epochs as showing the close companion, or a common envelope toward the companion, in front of the primary. At the 2014 epoch, the close companion is behind the primary and not visible. Instead, the structure and contrast at the 2014 epoch are typical of a single RSG harboring giant photospheric convection cells. The companion is most likely a cool giant or supergiant star with a mass of 5 +15 −3 M .

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Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

et al. 2017

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Massive stars, at least ∼ 10 times more massive than the Sun, have two key properties that make them the main drivers of evolution of star clusters, galaxies, and the Universe as a whole. On the one hand, the outer layers of massive stars are so hot that they produce most of the ionizing ultraviolet radiation of galaxies; in fact, the first massive stars helped to re-ionize the Universe after its Dark Ages. Another important property of massive stars are the strong stellar winds and outflows they produce. This mass loss, and finally the explosion of a massive star as a supernova or a gamma-ray burst, provide a significant input of mechanical and radiative energy into the interstellar space. These two properties together make massive stars one of the most important cosmic engines: they trigger the star formation and enrich the interstellar medium with heavy elements, that ultimately leads to formation of Earth-like rocky planets and the development of complex life. The study of massive star winds is thus a truly multidisciplinary field and has a wide impact on different areas of astronomy.In recent years observational and theoretical evidences have been growing that these winds are not smooth and homogeneous as previously assumed, but rather populated by dense "clumps". The presence of these structures dramatically affects the mass loss rates derived from the study of stellar winds. Clump properties in isolated stars are nowadays inferred mostly through indirect methods (i.e., spectroscopic observations of line profiles in various wavelength regimes, and their analysis based on tailored, inhomogeneous wind models). The limited characterization of the clump physical properties (mass, size) obtained so far have led to large uncertainties in the mass loss rates from massive stars. Such uncertainties limit our understanding of the role of massive star winds in galactic and cosmic evolution.Supergiant high mass X-ray binaries (SgXBs) are among the brightest X-ray sources in the sky. A large number of them consist of a neutron star accreting from the wind of a massive companion and producing a powerful X-ray source. The characteristics of the stellar wind together with the complex interactions between the compact object and the donor star determine the observed X-ray output from all these systems. Consequently, the use of SgXBs for studies of massive stars is only possible when the physics of the stellar winds, the compact objects, and accretion mechanisms are combined together and confronted with observations. This detailed review summarises the current knowledge on the theory and observations of winds from massive stars, as well as on observations and accretion processes in wind-fed high mass X-ray binaries. The aim is to combine in the near future all available theoretical Unified view of of inhomogeneous stellar winds in supergiant stars and HXMB 3 diagnostics and observational measurements to achieve a unified picture of massive star winds in isolated objects and in binary systems.

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The evolution of massive stars and their spectra

Cited by 162 publications

References 103 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

Multi-epoch VLTI-PIONIER imaging of the supergiant V766 Cen

Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

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