A 2.3 Day Periodic Variability in the Apparently Single Wolf‐Rayet Star WR 134: Collapsed Companion or Rotational Modulation?

Morel, Thierry; Марченко, С. В.; Moffat, A. F. J.; Koenigsberger, Gloria; Antokhin, I. I.; Eversberg, Thomas; Tovmassian, G.; Hill, G. M.; Cardona, O.; St-Louis, N.

doi:10.1086/307250

Cited by 41 publications

(47 citation statements)

References 82 publications

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“…3.1.2, magnetic fields are unlikely to be the reason for the line effect in WR stars because the required field strengths would be extremely high. CIRs, on the other hand, are commonly observed via line-profile variations (LPVs) in WR spectra (Morel et al 1997(Morel et al , 1999Flores et al 2007;Chené & St.-Louis 2010), in agreement with theoretical models by Dessart & Owocki (2002). Whether CIRs are able to cause a global wind asymmetry that is sufficient to cause a line effect, has not yet been investigated.…”

Section: The Line Effect As An Indicator Of Enhanced Rotationmentioning

confidence: 81%

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Rotating Wolf-Rayet stars in a post RSG/LBV phase

Gräfener

Harries

Langer

2012

A&A

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Context. Wolf-Rayet (WR) stars with fast rotating cores are thought to be the direct progenitors of long-duration gamma-ray bursts (LGRBs). A well accepted evolutionary channel towards LGRBs is chemically-homogeneous evolution at low metallicities, which completely avoids a red supergiant (RSG), or luminous blue variable (LBV) phase. On the other hand, strong absorption features with velocities of several hundred km s −1 have been found in some LGRB afterglow spectra (GRB 020813 and GRB 021004), which have been attributed to dense circumstellar (CS) material that has been ejected in a previous RSG or LBV phase, and is interacting with a fast WR-type stellar wind. Aims. Here we investigate the properties of Galactic WR stars and their environment to identify similar evolutionary channels that may lead to the formation of LGRBs. Methods. We compile available information on the spectropolarimetric properties of 29 WR stars, the presence of CS ejecta for 172 WR stars, and the CS velocities in the environment of 34 WR stars in the Galaxy. We use linear line-depolarization as an indicator of rotation, nebular morphology as an indicator of stellar ejecta, and velocity patterns in UV absorption features as an indicator of increased velocities in the CS environment. Results. Based on previous nebular classifications, we determine an incidence rate of ∼23% of WR stars with "possible ejecta nebulae" in the Galaxy. We find that this group of objects dominates the population of WR stars with spectropolarimetric signatures of rotation, while WR stars without such nebulae only rarely show indications of rotation. This confirms the correlation between rotation and CS ejecta from our previous work. The corresponding objects are most likely in an early stage after a preceding RSG or LBV phase, and have not yet lost their angular momenta due to the strong mass-loss in the WR phase. From their photometric periods we estimate rotation parameters in the range ω = rot / crit = 0.04...0.25, corresponding to moderate rotation speeds of 36...120 km s −1 . These values are very uncertain, but comply with the specific surface angular momentum requirement for LGRB progenitors. From UV absorption profiles we only find weak evidence for a correlation between rotation and increased CS velocities. In particular, the CS velocities of Galactic WR stars are much lower than what is observed for GRB 020813 and GRB 021004. Conclusions. Our results indicate that, in the Galaxy, "young" WR stars shortly after a RSG/LBV phase, show spectropolarimetric signatures of rotation. Their rotation rates are likely to be enhanced with respect to the majority of Galactic WR stars. According to their estimated specific surface angular momenta, a subgroup of stars exploding in this phase may represent an evolutionary channel towards LGRBs at high metallicities, comparable to the Galaxy. Although the UV absorption features in our sample turn out to be different from those observed in GRB 020813 and GRB 021004, it is interesting that for three WR stars with s...

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Section: The Line Effect As An Indicator Of Enhanced Rotationmentioning

confidence: 81%

“…Table 2). References for the photometric periods are (1) Morel et al (1997); (2) Lamontagne & Moffat (1987); (3) Morel et al (1999); (4) St.-Louis et al (1989); (5) Lefèvre et al (2005).…”

Section: Rotational Velocitiesmentioning

confidence: 99%

Rotating Wolf-Rayet stars in a post RSG/LBV phase

Gräfener

Harries

Langer

2012

A&A

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“…This clearly pertains to WR 4, where the blueward displacement of the He ii 4686 peak maẙ A point to a high optical density of clumps. However, the disparity of the He ii 4859 and 5412 distributions prompts an alternative A explanation; the spectral variability could be, in part, related to the presence of corotating interacting regions (CIRs; Massa et al 1995;Morel et al 1999 and references therein), as seen in several Galactic W-R stars. One may notice the synchronized redward migration of weak emission features in the first half of night 1…”

Section: Discussionmentioning

confidence: 99%

Spectroscopy of SMC Wolf-Rayet Stars Suggests that Wind Clumping Does Not Depend on Ambient Metallicity

Марченко¹,

Foellmi²,

Moffat³

et al. 2007

ApJ

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The mass-loss rates of hot, massive, luminous stars are considered a decisive parameter in shaping the evolutionary tracks of such stars and influencing the interstellar medium on galactic scales. The small-scale structures (clumps) that are omnipresent in such winds may reduce empirical estimates of mass-loss rates by an evolutionarily significant factor of ≥3. So far, there has been no direct observational evidence that wind clumping may persist at the same level in environments with a low ambient metallicity, where the wind-driving opacity is reduced. Here we report the results of time-resolved spectroscopy of three presumably single Population I Wolf-Rayet stars in the Small Magellanic Cloud, where the ambient metallicity is ∼ Z , . We detect numerous small-scale 1 5 emission peaks moving outward in the accelerating parts of the stellar winds. The general properties of the moving features, such as their velocity dispersions, emissivities, and average accelerations, closely match the corresponding characteristics of small-scale inhomogeneities in the winds of Galactic Wolf-Rayet stars.

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“…candidates are reported: e.g., HD 197406/WR 148 (Marchenko et al 1996), HD 191765/WR 134 (Morel et al 1999), HD 104994/WR 46 (Marchenko et al 2000). However, it is still unclear whether the companions to these WR stars really have a relativistic nature, as the systems lack the X-ray luminosity expected in such a case.…”

Section: Discussionmentioning

confidence: 99%

Cygnus X-3 and the problem of the missing Wolf-Rayet X-ray binaries

Lommen¹,

Yungelson

Heuvel³

et al. 2005

A&A

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Cygnus X-3 is a strong X-ray source (L X ≈ 10 38 erg s −1 ) which is thought to consist of a compact object accreting matter from a helium star. We analytically find that the estimated ranges of mass-loss rate and orbital-period derivative for Cyg X-3 are consistent with two models: i) the system is detached and the mass loss from the system comes from the stellar wind of a massive helium star, of which only a fraction that allows for the observed X-ray luminosity is accreted, or ii) the system is semidetached and a Roche-lobe-overflowing low-or moderate-mass helium donor transfers mass to the compact object, followed by ejection of its excess over the Eddington rate from the system. These analytical results appear to be consistent with evolutionary calculations. By means of population synthesis we find that currently in the Galaxy there may exist ∼1 X-ray binary with a black hole that accretes from a > ∼ 7 M Wolf-Rayet star and ∼1 X-ray binary in which a neutron star accretes matter from a Roche-lobe-overflowing helium star with mass < ∼ 1.5 M . Cyg X-3 is probably one of these systems.

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A 2.3 Day Periodic Variability in the Apparently Single Wolf‐Rayet Star WR 134: Collapsed Companion or Rotational Modulation?

Cited by 41 publications

References 82 publications

Rotating Wolf-Rayet stars in a post RSG/LBV phase

Rotating Wolf-Rayet stars in a post RSG/LBV phase

Spectroscopy of SMC Wolf-Rayet Stars Suggests that Wind Clumping Does Not Depend on Ambient Metallicity

Cygnus X-3 and the problem of the missing Wolf-Rayet X-ray binaries

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