Photometry, polarimetry, spectroscopy, and spectropolarimetry of the enigmatic Wolf-Rayet star EZ Canis Majoris

Robert, Christian P.; Moffat, A. F. J.; Drissen, Laurent; Lamontagne, R.; Seggewiß, W.; Niemelä, Virpi Sinikka; Cerruti, M. A.; Barrett, P.; Bailey, Jeremy; Garcia, Jorge; Tapia, S.

doi:10.1086/171786

Cited by 60 publications

(49 citation statements)

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“…The data show strong epoch-dependent variations, with a clear single-wave variation in U (less clear in Q) in 1985 and a fairly clear double-wave modulation in Q (less clear in U) in 1986. This behavior is qualitatively very similar to what is observed in EZ CMa (e.g., Robert et al 1992), although the polarimetric variations are not as clearly phase-locked in WR 134. Such a drastic change from a single-wave to a double-wave modulation in data taken 1 yr apart is not easily accommo- FIG.…”

Section: W Ind-related V Ariability ?supporting

confidence: 85%

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

Morel

Марченко

Moffat

et al. 1999

ApJ

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The apparently single WN 6 type star WR 134 (HD 191765) is distinguished among the Wolf-Rayet star population by its strong, presumably cyclical (P B 2.3 day) spectral variations. A true periodicityÈ which is still very much debatedÈwould render WR 134 a prime candidate for harboring either a collapsed companion or a rotating, large-scale, inhomogeneous outÑow. We have carried out an intensive campaign of spectroscopic and photometric monitoring of WR 134 from 1989 to 1997 in an attempt to reveal the true nature of this object. This unprecedentedly large data set allows us to conÐrm unambiguously the existence of a coherent 2.25^0.05 day periodicity in the line-proÐle changes of He II j4686, although the global pattern of variability is di †erent from one epoch to another. This period is only marginally detected in the photometric data set. Assuming the 2.25 day periodic variability to be induced by orbital motion of a collapsed companion, we develop a simple model that aims to investigate (1) the e †ect of this strongly ionizing, accreting companion on the Wolf-Rayet wind structure, and (2) the expected emergent X-ray luminosity. We argue that the predicted and observed X-ray Ñuxes can only be matched if the accretion on the collapsed star is signiÐcantly inhibited. Additionally, we performed simulations of line-proÐle variations caused by the orbital revolution of a localized, strongly ionized wind cavity surrounding the X-ray source. A reasonable Ðt is achieved between the observed and modeled phase-dependent line proÐles of He II j4686. However, the derived size of the photoionized zone substantially exceeds our expectations, given the observed low-level X-ray Ñux. Alternatively, we explore rotational modulation of a persistent, largely anisotropic outÑow as the origin of the observed cyclical variability. Although qualitative, this hypothesis leads to greater consistency with the observations.

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Section: W Ind-related V Ariability ?supporting

confidence: 85%

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

Morel

Марченко

Moffat

et al. 1999

ApJ

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“…Similar bumps have been observed in optical Hel Unes (Robert et al 1992). For this reason we have proposed that there are only one or two jets or streams consisting of both rarefied gas and clumps.…”

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confidence: 75%

The hard life of clumps in atmospheres of early-type stars

Холтыгин¹

1994

Symp. - Int. Astron. Union

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Abstract. As has been recently established, the atmospheres of early-type stars are strongly disheveled. These atmospheres consist of dense clumps and a more rarefied interclump medium. We consider the forces that determine the motion of the clumps. We show that the main force is gravitational attraction of the clumps to the star. For stars with a high effective temperature (T e fr > 6 · 10 4 K) it appears that the clump/interclump gas number density ratio is > 30. In this case we can conclude that the clumps are formed by shock waves. Some evidence as to the existence of gas jets in the atmospheres of WolfRayet stars have recently been presented. We propose that such jets may be a common feature of all early-type stars. Profiles of Hel lines in spectra of clumped atmospheres with jets have been calculated. We have considered the forces that determine the motion of clumps in an atmosphere and concluded that the main force is gravitational attraction to the core and that the clumps should therefore be decelerated in the atmosphere. However, the cluster of clumps seems to be accelerated (e. There is now much evidence (both theoretical and observational) that inhomogeneities exist in the atmospheres

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“…A similar method was applied to WR 6 by Robert et al (1992). We check the stability of the wavelength calibration by measuring also the interstellar and atmospheric lines.…”

Section: Bi-sectorial Radial Velocity K-amplitudesmentioning

confidence: 99%

The enigmatic WR46: A binary or a pulsator in disguise

Veen

Genderen

Crowther

et al. 2002

A&A

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Abstract. We present spectroscopic monitoring of the Wolf-Rayet (WR) star WR 46 between 1989 and 1998, which has been obtained simultaneously with multicolour photometry (Veen et al. 2002a, Paper I). The spectroscopic monitoring data show that the radiative fluxes of the optical emission lines (O vi 3811/34, O vi 5290, N v 4944, N v 4604/20, He ii 4686, He ii 4859, He ii 5411, He ii 6560) vary in concert with the photometric single-wave (sw) frequency fsw (Paper I), and also the difference of that period between 1989 and 1991. The line-flux variability does not provide obvious support for a short second period (Paper I). The radial-velocity variations show a remarkable behaviour: usually, they display a coherent single-wave on the time scale of the double-wave period, while during some nights the radial velocity appears surprisingly to stay constant (see also Marchenko et al. 2000). These so-called stand-stills may be related to the observed time-delay effects. A time-delay effect manifests itself in several phenomena. Firstly, the line flux shows small, but persistent, time-delays for lines originating from lower optical depths, the outer-wind lines (N v 4604/20 and He ii). Secondly, the radial-velocity variations display much larger time-delays than the line fluxes and their behaviour appears less consistent. Assuming that the double-wave period controls the radial velocity, the stand-still is observed to start when the radial motion is in anti-phase with the presumed orbital motion. Thirdly, the outer-wind lines are observed to enter a stand-still much later than the inner-wind lines. Fourthly, the radial-velocity variations of the peaks of the emission lines precede the radial-velocity variations of the wings of those lines. In addition to line-flux-and radial-velocity variability, the He ii 4686 emission line shows pronounced line-profile changes on a time scale of hours. Our monitoring is not sufficient to study this in detail. Furthermore, we discern a flaring behaviour, i.e., an emission bump appeared on the blue wing of two He ii-lines (around −1700 km s −1 ) lasting less than 5 min. Finally, the line fluxes follow the observed brightenings, also on a time scale of years. We conclude that the short-term cyclic variability confirms the WR nature as established from the WR standard model analysis by Crowther et al. (1995; hereafter referred to as CSH). The various time-delay effects are consistent with the formation of the spectrum in a stratified stellar wind. The outer layers trail the inner ones. The variability is inconsistent with the formation of the spectrum in a stellar disc as proposed by Niemela et al. (1995) and Steiner & Diaz (1998). The long-term cyclic variability of the brightness and line fluxes is related to an increase of the mass-loss-rate, and, possibly, to the period changes. The interpretation of the nature of the variability is deferred to Veen et al. (2002b, Paper III).

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Photometry, polarimetry, spectroscopy, and spectropolarimetry of the enigmatic Wolf-Rayet star EZ Canis Majoris

Cited by 60 publications

References 0 publications

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

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

The hard life of clumps in atmospheres of early-type stars

The enigmatic WR46: A binary or a pulsator in disguise

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