V471 Tauri - A three-body orbit

Beavers, W. I.; Herczeg, T.; Lui, A. T. Y.

doi:10.1086/163855

Cited by 19 publications

(11 citation statements)

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“…It was predicted by Beavers et al (1986) that a third body with a period of ∼ 25 years could exist in this system. Recently, Hardy et al (2015) used direct imaging to test the hypothesis, resulting in a nondetection of the proposed brown dwarf.…”

Section: V471 Taumentioning

confidence: 99%

Applegate mechanism in post-common-envelope binaries: Investigating the role of rotation

Navarrete

Schleicher

Zamponi

et al. 2018

A&A

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Context. Eclipsing time variations are observed in many close binary systems. In particular, for several post-common-envelope binaries (PCEBs) that consist of a white dwarf and a main sequence star, the Observed minus Calculated (O-C) diagram suggests that real or apparent orbital period variations are driven by Jupiter-mass planets or as a result of magnetic activity, the so-called Applegate mechanism. The latter explains orbital period variations as a result of changes in the stellar quadrupole moment due to magnetic activity. Aims. In this work we explore the feasibility of driving eclipsing time variations via the Applegate mechanism for a sample of PCEB systems, including a range of different rotation rates. Methods. We used the MESA code to evolve 12 stars with different masses and rotation rates. We applied simple dynamo models to their radial profiles to investigate the scale at which the predicted activity cycle matches the observed modulation period, and quantifiy the uncertainty. We further calculated the required energies to drive the Applegate mechanism. Results. We show that the Applegate mechanism is energetically feasible in 5 PCEB systems. In RX J2130.6+4710, it may be feasible as well considering the uncertainties. We note that these are the systems with the highest rotation rate compared to the critical rotation rate of the main-sequence star.Conclusions. The results suggest that the ratio of physical to critical rotation rate in the main sequence star is an important indicator for the feasibility of Applegate's mechanism, but exploring larger samples will be necessary to probe this hypothesis.

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Section: V471 Taumentioning

confidence: 99%

Applegate mechanism in post-common-envelope binaries: Investigating the role of rotation

Navarrete

Schleicher

Zamponi

et al. 2018

A&A

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“…Therefore, the O−C variation should have a cyclic character. However, Beavers, Herczeg & Lui (1986), İbanoǧlu et al (1994) and Guinan & Ribas (2001) re‐examined the variation in the apparent period under the third‐body hypothesis. They have estimated a period of about 24.6, 22 and 27.4 yr, respectively, for the hypothetical third‐body orbit.…”

Section: Analysis Of the O−c Curvementioning

confidence: 99%

New findings based on long-term photometric observations of the eclipsing binary V471 Tauri

İbanoǧlu

Evren

Taș

et al. 2005

Monthly Notices of the Royal Astronomical Society

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The post‐common envelope and pre‐cataclysmic binary V471 Tau has been observed by the authors since 1973. At least a complete light curve in B and V bands and more than two eclipse timings were obtained in each year. All the available data published so far (including the authors') have been collected and analysed for the brightness and orbital period changes. The system brightened about 0.22 mag in both B and V bands more or less regularly up to 1997 and started to decrease afterwards. A search for periodicity of this variation yields a period longer than 85 yr. In addition to this long‐period variation, a small amplitude of about 0.08 mag and short time‐interval fluctuations on the mean brightness have been detected. The variations of the mean brightness have been discussed and plausible causes suggested. The changes of the apparent period have been attributed to a third body. Analysis of all the ‘observed−calculated’ (O−C) data yields a period of 32.4 yr, with a semi‐amplitude of 151 s and an eccentricity of 0.30 for the third‐body orbit. For orbital inclinations greater than 34° the mass of the third body would possibly match to a brown dwarf. One of the most interesting features in the light curve of V471 Tau is the decrement of the eclipse depth with time. The depth of the eclipse in the B band has been decreased from 0.082 to 0.057 mag over 34 yr. Subtracting the variation of the depth due to the brightening of the red dwarf star, the actual variation in depth, originated from from the white dwarf, was found to be about 0.012 mag. This change in the brightness of the compact object has been attributed to the mass accretion from its primary component via thermally driven wind and/or flare‐like events.

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“…One is that the system should have received a recoil velocity on the order of the orbital speed (scaled appropriately by the masses) when one star was ejected, yet the binaryÏs space motion is measured to be within a few kilometers per second of the cluster velocity. The other is that several authors (Beavers, Herczeg, & Liu 1986 ;Guinan & Ribas 2001) have I0 banog' lu proposed that V471 Tau has a distant third companion with an orbital period of D30 yr and eccentricity D0.3. This suggestion is based on eclipse timings that show a periodic variation in the orbital period ; if attributed to the light-travel time e †ect, the third companionÏs mass is only according to Guinan & Ribas.…”

Section: Blue Straggler Scenariosmentioning

confidence: 99%

Hubble Space TelescopeSpectroscopy of V471 Tauri: Oversized K Star, Paradoxical White Dwarf

O'Brien

Bond

Sion

2001

ApJ

109

106

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We have used the Goddard High Resolution Spectrograph on board the Hubble Space T elescope to obtain Lya spectra of the hot white dwarf (WD) component of the short-period eclipsing DA]dK2 precataclysmic binary V471 Tauri, a member of the Hyades star cluster. Radial velocities of the WD were determined from eight post-COSTAR spectra obtained near the two quadratures of the orbit. When combined with ground-based measurements of the dK velocities, eclipse timings, and a determination of the dK starÏs rotational velocity, the data constrain the orbital inclination to be i \ 77¡ and yield dynamical masses for the components of and Model atmosphere M WD \ 0.84 M dK \ 0.93 M _ . Ðtting of the Lya proÐle provides the e †ective temperature (34,500 K) and surface gravity (log g \ 8.3) of the WD. The radius of the dK component is about 18% larger than that of a normal Hyades dwarf of the same mass. This expansion is attributed to the large degree of coverage of the stellar surface by starspots, which is indicated by both radiometric measurements and ground-based Doppler imaging ; in response, the star has expanded in order to maintain the luminosity of a 0.93 dwarf. The radius of M _ the WD, determined from a radiometric analysis and from eclipse ingress timings, is 0.0107 The R _ . position of the star in the mass-radius plane is in full accord with theoretical predictions for a degenerate carbon-oxygen WD with a surface temperature equal to that observed. The position of the WD in the H-R diagram is also fully consistent with that expected for a WD with our dynamically measured mass. Both comparisons with theory are probably the most stringent yet made for any WD. The theoretical cooling age of the WD is 107 yr. The high e †ective temperature and high mass of the WD present an evolutionary paradox. The WD is the most massive one known in the Hyades but also the hottest and youngest, in direct conÑict with expectation. We examine possible resolutions of the paradox, including the possibility of a nova outburst in the recent past, but conclude that the most likely explanation is that the WD is indeed very young and is descended from a blue straggler. A plausible scenario is that the progenitor system was a triple, with a close inner pair of main-sequence stars whose masses were both similar to that of the present cluster turno †. These stars became an Algol-type binary, which merged after several hundred million years to produce a single blue straggler of about twice the turno † mass. When this star evolved to the asymptotic giant branch phase, it underwent a common envelope interaction with a distant dK companion, which spiraled down to its present separation, and ejected the envelope. We estimate that the common envelope efficiency parameter was on the order of 0.3È1.0, in a CE good agreement with recent hydrodynamical simulations.

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V471 Tauri - A three-body orbit

Cited by 19 publications

References 0 publications

Applegate mechanism in post-common-envelope binaries: Investigating the role of rotation

Applegate mechanism in post-common-envelope binaries: Investigating the role of rotation

New findings based on long-term photometric observations of the eclipsing binary V471 Tauri

Hubble Space TelescopeSpectroscopy of V471 Tauri: Oversized K Star, Paradoxical White Dwarf

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