Orbit Alignment in Triple Stars

Tokovinin, Andreï

doi:10.3847/1538-4357/aa7746

Cited by 75 publications

(57 citation statements)

References 22 publications

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“…Nevertheless, a trend of smaller inner eccentricities at projected outer separations s < 100 au is emerging. As noted by Tokovinin (2017), compact hierarchies also tend to have more aligned orbits. Further accumulation of data on orbits in hierarchical stellar systems, especially in compact ones, will help to clarify these trends.…”

Section: Discussionmentioning

confidence: 74%

“…Kepler-1647, Kostov et al 2016). Low-mass triple systems with outer separations of the order of ∼50 au or less also have a strong alignment trend, even though the typical relative angles between orbital planes are still substantial, ∼30 • (Tokovinin 2017). Formation of companions in a massive circumstellar disc, their subsequent growth and inward migration seem to match the prevalent architecture of compact "planetary-like" (i.e.…”

Section: Introductionmentioning

confidence: 96%

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Speckle Observations and Orbits of Multiple Stars

Tokovinin

Everett

Horch

et al. 2019

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We report results of speckle-interferometric monitoring of visual hierarchical systems using the newly commissioned instrument NESSI at the 3.5-m WIYN telescope. During one year, 390 measurements of 129 resolved subsystems were made, while some targets were unresolved. Using our astrometry and archival data, we computed 36 orbits (27 for the first time). Spectro-interferometric orbits of seven pairs are determined by combining positional measurements with radial velocities measured, mostly, with the Center for Astrophysics digital speedometers. For the hierarchical systems HIP 65026 (periods 49 and 1.23 years) and HIP 85209 (periods 34 and 1.23 years) we determined both the inner and the outer orbits using astrometry and radial velocities and measured the mutual orbit inclinations of 11. • 3±1. • 0 and 12. • 0±3. • 0, respectively. Four bright stars are resolved for the first time; two of those are triple systems. Several visual subsystems announced in the literature are shown to be spurious. We note that subsystems in compact hierarchies with outer separations less than 100 au tend to have less eccentric orbits compared to wider hierarchies.

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Section: Discussionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 96%

Speckle Observations and Orbits of Multiple Stars

Tokovinin

Everett

Horch

et al. 2019

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“…This choice of orbital angles corresponds to isotropic orbital distributions. However, observations suggest that the orbital alignment in triple stars is not isotropic (Tokovinin 1993;Sterzik & Tokovinin 2002), and, in particular, is correlated with the separation of the tertiary companion (Tokovinin 2017). Tokovinin (2017) found that tight triples with inner semimajor axes less than about 50 tend to be aligned in their orbits (with a mean mutual inclination of Φ ∼ 20 • ), whereas triples with wider inner orbits tend to have isotropic relative orbital orientations.…”

Section: Initial Conditionsmentioning

confidence: 99%

A census of main-sequence interactions in the Multiple Star Catalogue

Hamers

2020

Monthly Notices of the Royal Astronomical Society

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Statistics of hierarchical systems containing three or more stars are continuously improving. The Multiple Star Catalogue (MSC) is currently the most comprehensive catalogue of multiplestar systems and contains component masses, orbital periods, and additional information. The systems in the MSC are interesting for several reasons, including the long-term dynamical evolution of few-body systems. Although the secular evolution of triples and quadruples has been explored before, a systematic study of the systems in the MSC including also quintuples and sextuples has not been carried out. Here, we explore the main-sequence (MS) evolution of stars from the MSC based on approximately 2 × 10 5 secular dynamical integrations. We estimate statistical probabilities for strong interactions during the MS such as tidal evolution and mass transfer, and the onset of dynamical instability. Depending on the assumed model for the unknown orbital elements, we find that the fraction of noninteracting systems is largest for triples (∼ 0.9), and decreases to ∼ 0.6-0.8 for sextuples. The fraction of strong interactions increases from ∼ 0.1 to ∼ 0.2 from triples to sextuples, and the fraction of dynamically unstable systems increases from ∼ 0.001 to ∼ 0.1-0.2. The larger fractions of strong interactions and dynamical instability in systems with increasing multiplicity can be attributed to increasingly complex secular evolution in these systems. Our results indicate that a significant fraction of high-multiplicity systems interact or become dynamically unstable already during the MS, with an increasing importance as the number of stars increases.

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“…(below the opacity limit), actually have quasi-planar architectures (Borkovits et al 2016;Tokovinin 2017). Not only does this severely limit the fraction of triples that undergo Kozai-Lidov oscillations, but points to the dominant role of disk fragmentation and migration in the formation of close binaries and compact triples (see also Tobin et al 2016).…”

Section: Introductionmentioning

confidence: 98%

Formation of close binaries by disc fragmentation and migration, and its statistical modelling

Tokovinin

Moe

2019

Monthly Notices of the Royal Astronomical Society

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129

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Joint statistics of periods and mass ratios of close binaries and its dependence on primary mass can be explained by assuming that seed binary companions are formed by disc fragmentation at random intervals during assemblage of stellar mass and migrate inwards as they accrete from the circumbinary disk. A toy model based on simple prescriptions for the companion growth and migration reproduces such aspects of close solar-mass binaries as the distribution of binary periods P , the brown dwarf desert at short P , the nearly uniform distribution of mass ratios, and a population of equal-mass binaries (twins) that decreases linearly in frequency with log P . For massive stars, the model predicts a large fraction of early mergers, a distribution of log P with a negative slope, and a mass-ratio distribution that is also uniform but with a substantially reduced twin fraction. By treating disc fragmentation as a stochastic process, we also reproduce the observed properties of compact triples. Success of our toy model suggests that most close binaries and compact triples indeed formed by disc fragmentation followed by accretion-driven inward migration.

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Orbit Alignment in Triple Stars

Cited by 75 publications

References 22 publications

Speckle Observations and Orbits of Multiple Stars

Speckle Observations and Orbits of Multiple Stars

A census of main-sequence interactions in the Multiple Star Catalogue

Formation of close binaries by disc fragmentation and migration, and its statistical modelling

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