Stellar and wind properties of LMC WC4 stars

Crowther, P. A.; Dessart, Luc; Hillier, D. J.; Abbott, Jay B.; Fullerton, A. W.

doi:10.1051/0004-6361:20020941

Cited by 202 publications

(320 citation statements)

References 47 publications

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“…6. Although WC stars of the Crowther sample (Crowther et al 2002) have fairly high luminosities (log L/L ⊙ > 5.4), the two WO stars are very faint (log L/L ⊙ ≃ 5.20 − 5.25) compared to other WR stars in the LMC. Like in the case of Galactic WR stars, the standard NL prescription cannot explain these faint WO stars because He star models of this luminosity does not become He-poor at LMC metallicity.…”

Section: Evolutionary Models Vs Observed Wr Starsmentioning

confidence: 90%

“…Our He star models can crudely predict the properties of SN Ib/Ic progenitors for both single and binary stars as long as M He,i 4.0 M ⊙ This is because once such a hydrogen-poor star is made either by stellar wind mass loss from a single star or by mass transfer in a biary system, the subsequent (Hainich et al 2014), and the coral squares are the LMC WC stars of Crowther et al (2002). The two orange triangles are the LMC WO stars in the TSK sample.…”

Section: Implications For Sn Ib/ic Progenitorsmentioning

confidence: 99%

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

Yoon

2017

Monthly Notices of the Royal Astronomical Society

110

160

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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 popular prescription for WR mass-loss rates given by Nugis & Lamers have difficulties in explaining the luminosity distribution of WR stars of WC and WO types and the SN Ic progenitor properties. Here we suggest some improvements in the WR mass-loss rate prescription and discuss its implications for the evolution of WR stars and SN Ib/Ic progenitors. Recent studies on Galactic WR stars clearly indicate that the mass-loss rates of WC stars are systematically higher than those of WNE stars for a given luminosity. The luminosity and initial metallicity dependencies of WNE mass-loss rates are also significantly different from those of WC stars. These factors have not been adequately considered together in previous stellar evolution models. We also find that an overall increase of WR mass loss rates by about 60 per cent compared to the empirical values obtained with a clumping factor of 10 is needed to explain the most faint WC/WO stars. This moderate increase with our new WR mas-loss rate prescription results in SN Ib/Ic progenitor models more consistent with observations than those given by the Nugis & Lamers prescription. In particular, our new models predict that the properties of SN Ib and SN Ic progenitors are distinctively different, rather than they form a continuous sequence.

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Section: Evolutionary Models Vs Observed Wr Starsmentioning

confidence: 90%

Section: Implications For Sn Ib/ic Progenitorsmentioning

confidence: 99%

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

Yoon

2017

Monthly Notices of the Royal Astronomical Society

110

160

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“…The winds of Wolf-Rayet stars, which are typically the cause of the loss of this envelope, are known to increase in strength with stellar metallicity (particularly iron) [44]. Importantly, in this wind-induced loss process, angular momentum (which is particularly important for forming jets [45]) is lost along with mass [46].…”

Section: Metals and The Predicted Grb Ratementioning

confidence: 99%

Enhanced cosmological GRB rates and implications for cosmogenic neutrinos

Yüksel

Kistler

2007

Phys. Rev. D

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Gamma-ray bursts, which are among the most violent events in the Universe, are one of the few viable candidates to produce ultra high-energy cosmic rays. Recently, observations have revealed that GRBs generally originate from metal-poor, low-luminosity galaxies and do not directly trace cosmic star formation, as might have been assumed from their association with core-collapse supernovae. Several implications follow from these findings. The redshift distribution of observed GRBs is expected to peak at higher redshift (compared to cosmic star formation), which is supported by the mean redshift of the Swift GRB sample, hzi 3. If GRBs are, in fact, the source of the observed UHECR, then cosmic-ray production would evolve with redshift in a stronger fashion than has been previously suggested. This necessarily leads, through the GZK process, to an enhancement in the flux of cosmogenic neutrinos, providing a near-term approach for testing the gamma-ray burst-cosmic-ray connection with ongoing and proposed UHE neutrino experiments.

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“…Observational evidence for a Z-dependence of WR mass-loss has been found by comparisons of the sample of WC stars with known distances in the Galaxy and LMC by Gräfener et al (1998) and Crowther et al (2002). In the following, we invoke the results of theoretical studies to understand how the properties of WR stars are expected to change over a broad range of Z.…”

Section: Wr Mass Loss At Low Metallicities Zmentioning

confidence: 82%

Narrow He II emission in star-forming galaxies at low metallicity

Gräfener

2015

A&A

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Context. In a recent study, star-forming galaxies with He ii λ1640 emission at moderate redshifts between 2 and 4.6 have been found to occur in two modes that are distinguished by the width of their He ii emission lines. Broad He ii emission has been attributed to stellar emission from a population of evolved Wolf-Rayet (WR) stars. The origin of narrow He ii emission is less clear but has been attributed to nebular emission excited by a population of very hot Pop III stars formed in pockets of pristine gas at moderate redshifts.Aims. We propose an alternative scenario for the origin of the narrow He ii emission, namely very massive stars (VMS) at low metallicity (Z), which form strong but slow WR-type stellar winds due to their proximity to the Eddington limit.Methods. We estimated the expected He ii line fluxes and equivalent widths based on wind models for VMS and Starburst99 population synthesis models and compared the results with recent observations of star-forming galaxies at moderate redshifts. Results. The observed He ii line strengths and equivalent widths are in line with what is expected for a population of VMS in one ormore young super-clusters located within these galaxies.Conclusions. In our scenario the two observed modes of He ii emission originate from massive stellar populations in distinct evolutionary stages at low Z (∼0.01 Z ). If this interpretation is correct, there is no need to postulate the existence of Pop III stars at moderate redshifts to explain the observed narrow He ii emission. An interesting possibility is the existence of self-enriched VMS with similar WR-type spectra at extremely low Z. Stellar He ii emission from such very early generations of VMS may be detectable in future studies of star-forming galaxies at high redshifts with the James Webb Space Telescope (JWST). The fact that the He ii emission of VMS is largely neglected in current population synthesis models will generally affect the interpretation of the integrated spectra of young stellar populations.

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Stellar and wind properties of LMC WC4 stars

Cited by 202 publications

References 47 publications

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

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

Enhanced cosmological GRB rates and implications for cosmogenic neutrinos

Narrow He II emission in star-forming galaxies at low metallicity

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