Whole Earth Telescope observations of V471 Tauri - The nature of the white dwarf variations

Clemens, J. C.; Nather, R. E.; Winget, D. E.; Robinson, E. L.; Wood, M. A.; Claver, C. F.; Provençal, J. L.; Kleinman, S. J.; Bradley, P. A.; Frueh, M.; Grauer, A. D.; Hine, Butler; Fontaine, G.; Achilleos, N.; Wickramasinghe, D. T.; Marar, T. M. K.; Seetha, S.; Ashoka, B. N.; O’Donoghue, D.; Warner, Brian D.; Kurtz, D. W.; Martinez, Peter; Vauclair, G.; Chevreton, M.; Barstow, M. A.; Kanaan, A.; Kepler, S. O.; Augusteijn, T.; Paradijs, J. van; Hansen, Carl J.

doi:10.1086/171387

Cited by 26 publications

(27 citation statements)

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“…The detection of pulsations in the soft X-ray Ñux (Jensen et al 1986) suggests that the binary contains a signiÐcantly magnetized white dwarf accreting at a low rate onto its magnetic poles. The detection of optical pulses of the same period (Robinson, Clemens, & Hine 1988), and the 180¡ o †set between the X-ray and optical pulsations (Barstow et al 1992 ;Clemens et al 1992) strongly support this interpretation. Mullan et al (1991) proposed that the accretion rate of the white dwarf must be very small if the mass-loss rate of the K dwarf is as high as they infer.…”

Section: Modelmentioning

confidence: 71%

Nonthermal Radio Emission from the Precataclysmic Binary System V471 Tauri

Nicholls

Storey

1999

ApJ

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Recent observations have presented strong evidence for the existence of eclipses in the nonthermal radio emission from the precataclysmic binary system V471 Tau. In this paper we calculate the gyrosynchrotron emission from models assuming a dipole-shaped magnetosphere and a magnetized wind around the K dwarf. The model assumes that electrons are accelerated to mildly relativistic energies in the region where the magnetic Ðelds of the two stars interact and become trapped in the K dwarfÏs magnetosphere. Comparison with the data indicates that azimuthal drift and energy loss lead to a region of enhanced density of mildly relativistic electrons, extending for over 100¡ in azimuth and preceding the white dwarf in phase. The data is best Ðtted by models assuming a power-law drop with azimuthal angle of this enhancement in mildly relativistic electron density.

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Section: Modelmentioning

confidence: 71%

Nonthermal Radio Emission from the Precataclysmic Binary System V471 Tauri

Nicholls

Storey

1999

ApJ

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“…Jensen et al (1986) and Sion et al (1998) found a periodic 9.25 minute modulation in the soft X-ray and EUV bands of V471 Tau, which was subsequently found in the optical band by Robinson et al (1988). It is now believed that the variability is caused by rotational modulation of the magnetic white dwarf (Clemens et al 1992;Barstow et al 1993). Wheatley (1998) found that the rotation rate and X-ray luminosity of the K star in V471 Tau are typical of K stars found in the Pleiades.…”

Section: V471 Taumentioning

confidence: 92%

The Coronae of AB Doradus and V471 Tauri: Primordial Angular Momentum versus Tidal Spin‐up

García-Álvarez

Drake

Lin

et al. 2005

ApJ

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The zero-age main-sequence star AB Dor and the K dwarf component of the V471 Tau close binary have essentially identical rotation rates and spectral types. An analysis of their high-resolution Chandra X-ray spectra reveals remarkably similar coronal characteristics in terms of both temperature structure and element abundances. Both stars show depletions of low first ionization potential (FIP) elements by factors of $3, with higher FIP elements showing more mild depletions. No evidence for enhancements of very low FIP (<7 eV) elements, such as Na, Al, and Ca, as compared to other low-FIP elements, was found. The abundance anomaly pattern for AB Dor and V471 Tau is similar to, although less extreme than, the abundance anomalies exhibited by active RS CVn-type binaries. While we find statistically significant structure in the underlying differential emission measure distributions of these stars over narrow temperature intervals, this structure is strongly dependent on the lines used in the analysis and is probably spurious. On the basis of their X-ray similarities, we conclude that the exact evolutionary state of a star has little effect on coronal characteristics and that the parameters that dominate coronal structure and composition are simply the rotation rate and spectral type.

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“…It is composed of a DA white dwarf and a coronally active K2V star. Hosting the hottest and youngest Hyades white dwarf, V471 Tau has been studied extensively (e.g., Nelson & Young 1970Guinan & Sion 1984;Clemens et al 1992;Shipman et al 1995;Marsh et al 1997). The system is a pre-cataclysmic variable: the K star does not fill its Roche lobe yet.…”

Section: White Dwarfsmentioning

confidence: 99%

A Hipparcos study of the Hyades open cluster

Bruijne¹,

Hoogerwerf²,

Zeeuw³

2001

A&A

166

175

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Abstract. Hipparcos parallaxes fix distances to individual stars in the Hyades cluster with an accuracy of ∼6 percent. We use the Hipparcos proper motions, which have a larger relative precision than the trigonometric parallaxes, to derive ∼3 times more precise distance estimates, by assuming that all members share the same space motion. An investigation of the available kinematic data confirms that the Hyades velocity field does not contain significant structure in the form of rotation and/or shear, but is fully consistent with a common space motion plus a (one-dimensional) internal velocity dispersion of ∼0.30 km s −1 . The improved parallaxes as a set are statistically consistent with the Hipparcos parallaxes. The maximum expected systematic error in the proper motion-based parallaxes for stars in the outer regions of the cluster (i.e., beyond ∼2 tidal radii ∼20 pc) is < ∼ 0.30 mas. The new parallaxes confirm that the Hipparcos measurements are correlated on small angular scales, consistent with the limits specified in the Hipparcos Catalogue, though with significantly smaller "amplitudes" than claimed by Narayanan & Gould. We use the Tycho-2 long time-baseline astrometric catalogue to derive a set of independent proper motion-based parallaxes for the Hipparcos members. The new parallaxes provide a uniquely sharp view of the three-dimensional structure of the Hyades. The colour-absolute magnitude diagram of the cluster based on the new parallaxes shows a well-defined main sequence with two "gaps"/"turn-offs". These features provide the first direct observational support of Böhm-Vitense's prediction that (the onset of) surface convection in stars significantly affects their (B − V ) colours. We present and discuss the theoretical Hertzsprung-Russell diagram (log L versus log T eff ) for an objectively defined set of 88 high-fidelity members of the cluster as well as the δ Scuti star θ 2 Tau, the giants δ 1 , θ 1 , , and γ Tau, and the white dwarfs V471 Tau and HD 27483 (all of which are also members). The precision with which the new parallaxes place individual Hyades in the Hertzsprung-Russell diagram is limited by (systematic) uncertainties related to the transformations from observed colours and absolute magnitudes to effective temperatures and luminosities. The new parallaxes provide stringent constraints on the calibration of such transformations when combined with detailed theoretical stellar evolutionary modelling, tailored to the chemical composition and age of the Hyades, over the large stellar mass range of the cluster probed by Hipparcos.

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Whole Earth Telescope observations of V471 Tauri - The nature of the white dwarf variations

Cited by 26 publications

References 0 publications

Nonthermal Radio Emission from the Precataclysmic Binary System V471 Tauri

Nonthermal Radio Emission from the Precataclysmic Binary System V471 Tauri

The Coronae of AB Doradus and V471 Tauri: Primordial Angular Momentum versus Tidal Spin‐up

A Hipparcos study of the Hyades open cluster

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