The Orbits of the Quadruple Star System 88 Tauri A from PHASES Differential Astrometry and Radial Velocity

Lane, Benjamin F.; Muterspaugh, Matthew W.; Fekel, Francis C.; Williamson, Michael H.; Browne, S. E.; Konacki, Maciej; Burke, B. F.; Colavita, M. M.; Kulkarni, S. R.; Shao, Michael

doi:10.1086/520877

Cited by 18 publications

(15 citation statements)

References 39 publications

(67 reference statements)

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“…The projected distance between the outer components A and B is 3500 au, with A being quadruple and B binary. Recently, interferometric astrometry has permitted to effectively resolve the inner subsystems Aa1,Aa2 and Ab1,Ab2 and to determine their orientation with respect to the 18‐yr orbit Aab (Lane et al 2007). Interestingly, the inclination of the more massive inner binary Aa1,Aa2 relative to the outer orbit was found to be 143°± 25, that is, it is counter‐rotating .…”

Section: Typical Quadruple Systemsmentioning

confidence: 99%

“…There are two simple quadruple stars, 88 Tau and μ Ori, with complete elements of both inner and outer orbits known. In 88 Tau, the inner orbits are not coplanar to the outer orbit, with Φ > 90° (counter‐rotation) for at least one subsystem (Lane et al 2007). Similarly, the Aab subsystem in μ Ori is counter‐rotating, Φ= 137°± 8°, while the orbit of the Bab subsystem is nearly perpendicular to the orbit of AB (Muterspaugh et al 2008).…”

Section: Comparison Between Triples and Quadruplesmentioning

confidence: 99%

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Comparative statistics and origin of triple and quadruple stars

Tokovinin

2008

Monthly Notices of the Royal Astronomical Society

199

174

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The statistics of catalogued quadruple stars consisting of two binaries (hierarchy 2+2) is studied in comparison with triple stars, with respective sample sizes of 81 and 724. Seven representative quadruple systems are discussed in greater detail. The properties of multiple stars do not correspond to the products of dynamical decay of small clusters, hence the N-body dynamics is not the dominant process of their formation. On the other hand, rotationally-driven (cascade) fragmentation possibly followed by migration of inner and/or outer orbits to shorter periods is a promising scenario to explain the origin of triple and quadruple stars. Our main results are: (i) Quadruple systems of Epsilon Lyr type with similar masses and inner periods are common. (ii) The distributions of the inner periods in triple and quadruple stars are similar and bimodal. The inner mass ratios do not correlate with the inner periods. (iii) The statistics of outer periods and mass ratios in triples and quadruples are different. The median outer mass ratio in triples is 0.39 independently of the outer period, which has a smooth distribution. In contrast, the outer periods of 25% quadruples concentrate in the narrow range from 10yr to 100yr, the outer mass ratios of these tight quadruples are above 0.6 and their two inner periods are similar to each other. (iv) The outer and inner mass ratios in triple and quadruple stars are not mutually correlated. (v) The inner and outer orbital angular momenta and periods in triple and quadruple systems with inner periods above 30d show some correlation, the ratio of outer-to-inner periods is mostly comprised between 5 and 10^4. In the systems with small period ratios the directions of the orbital spins are correlated, while in the systems with large ratios they are not.Comment: Accepted by MNRAS, 14 pages, 12 figures. Two electronic tables at http://www.ctio.noao.edu/ftp/pub/tokovinin/quadruples

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Section: Typical Quadruple Systemsmentioning

confidence: 99%

Section: Comparison Between Triples and Quadruplesmentioning

confidence: 99%

Comparative statistics and origin of triple and quadruple stars

Tokovinin

2008

Monthly Notices of the Royal Astronomical Society

199

174

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“…Combining astrometric with spectroscopic, radial-velocity observations of planetary systems can yield the complete orbital solution, hence solve for the planets' mass (Benedict et al 2002;Bean et al 2007;Pravdo & Shaklan 2009). Similarly, astrometric observations can yield the components' masses of binary systems (Muterspaugh et al 2005(Muterspaugh et al , 2008Lane et al 2007) and can be used to explore the dynamics of the stellar cluster close to the galactic centre's black hole (Bartko et al 2008). …”

Section: Scientific Rationalementioning

confidence: 99%

The PRIMA fringe sensor unit

Ménardi¹,

Abuter²,

Accardo³

et al. 2009

A&A

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Context. The fringe sensor unit (FSU) is the central element of the phase referenced imaging and micro-arcsecond astrometry (PRIMA) dual-feed facility and provides fringe sensing for all observation modes, comprising off-axis fringe tracking, phase referenced imaging, and high-accuracy narrow-angle astrometry. It is installed at the Very Large Telescope Interferometer (VLTI) and successfully served the fringe-tracking loop during the initial commissioning phase. Aims. To maximise sensitivity, speed, and robustness, the FSU is designed to operate in the infrared K-band and to include spatial filtering after beam combination and a very-low-resolution spectrometer without photometric channels. It consists of two identical fringe sensors for dual-star operation in PRIMA astrometric mode. Methods. Unique among interferometric beam combiners, the FSU uses spatial phase modulation in bulk optics to retrieve real-time estimates of fringe phase after spatial filtering. The beam combination design accommodates a laser metrology for pathlength monitoring. An R = 20 spectrometer across the K-band makes the retrieval of the group delay signal possible. The calibration procedure uses the artificial light source of the VLTI laboratory and is based on Fourier transform spectroscopy to remove instrumental effects. Results. The FSU was integrated and aligned at the VLTI in July and August 2008. It yields phase and group delay measurements at sampling rates up to 2 kHz, which are used to drive the fringe-tracking control loop. During the first commissioning runs, the FSU was used to track the fringes of stars with K-band magnitudes as faint as m K = 9.0, using two VLTI auxiliary telescopes (AT) and baselines of up to 96 m. Fringe tracking using two Very Large Telescope (VLT) unit telescopes was demonstrated. Conclusions. The concept of spatial phase-modulation for fringe sensing and tracking in stellar interferometry is demonstrated for the first time with the FSU. During initial commissioning and combining stellar light with two ATs, the FSU showed its ability to improve the VLTI sensitivity in K-band by more than one magnitude towards fainter objects, which is fundamental for achieving the scientific objectives of PRIMA.

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“…Ground-based optical interferometers achieve the necessary precision to detect orbital motions of binary and multiple systems and to determine the orbital parameters in combination with radial-velocity measurements (Hummel et al 1993;Muterspaugh et al 2006;Lane et al 2007). The astrometric detection of planetary orbits using IR-interferometry is the aim of the extrasolar-planet search with PRIMA project (ESPRI, Launhardt et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Search for brown-dwarf companions of stars

Sahlmann

Ségransan

Queloz

et al. 2010

A&A

209

314

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Context. The frequency of brown-dwarf companions in close orbit around Sun-like stars is low compared to the frequency of planetary and stellar companions. There is presently no comprehensive explanation of this lack of brown-dwarf companions. Aims. By combining the orbital solutions obtained from stellar radial-velocity curves and Hipparcos astrometric measurements, we attempt to determine the orbit inclinations and therefore the masses of the orbiting companions. By determining the masses of potential brown-dwarf companions, we improve our knowledge of the companion mass-function. Methods. The radial-velocity solutions revealing potential brown-dwarf companions are obtained for stars from the CORALIE and HARPS planet-search surveys or from the literature. The best Keplerian fit to our radial-velocity measurements is found using the Levenberg-Marquardt method. The spectroscopic elements of the radial-velocity solution constrain the fit to the intermediate astrometric data of the new Hipparcos reduction. The astrometric solution and the orbit inclination are found using non-linear χ 2 -minimisation on a two-parameter search grid. The statistical confidence of the adopted orbital solution is evaluated based on the distribution-free permutation test. Results. The discovery of nine new brown-dwarf candidates orbiting stars in the CORALIE and HARPS radial-velocity surveys is reported. New CORALIE radial velocities yielding accurate orbits of six previously-known hosts of potential brown-dwarf companions are presented. Including the literature targets, 33 hosts of potential brown-dwarf companions are examined. Employing innovative methods, we use the new reduction of the Hipparcos data to fully characterise the astrometric orbits of six objects, revealing M-dwarf companions of masses between 90 M J and 0.52 M . In addition, the masses of two companions can be restricted to the stellar domain. The companion to HD 137510 is found to be a brown dwarf. At 95% confidence, the companion of HD 190228 is also a brown dwarf. Twenty-three companions remain brown-dwarf candidates. On the basis of the CORALIE planet-search sample, we obtain an upper limit of 0.6% for the frequency of brown-dwarf companions around Sun-like stars. We find that the companion-mass distribution function increases toward the lower end of the brown-dwarf mass range, suggesting that we detect the high-mass tail of the planetary distribution. Conclusions. Our findings agree with the results of previous similar studies and confirm the pronounced paucity of brown-dwarf companions around Sun-like stars. They are affected by the Hipparcos astrometric precision and mission duration, which limits the minimum detectable companion mass, and some of the remaining candidates are probably brown-dwarf companions.

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The Orbits of the Quadruple Star System 88 Tauri A from PHASES Differential Astrometry and Radial Velocity

Cited by 18 publications

References 39 publications

Comparative statistics and origin of triple and quadruple stars

Comparative statistics and origin of triple and quadruple stars

The PRIMA fringe sensor unit

Search for brown-dwarf companions of stars

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