Dynamical formation and scattering of hierarchical triples: cross-sections, Kozai–Lidov oscillations, and collisions

Antognini, Joseph M.; Thompson, Todd A.

doi:10.1093/mnras/stv2938

Cited by 73 publications

(67 citation statements)

References 140 publications

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“…Dynamical interactions in unstable multiples should leave residual misaligned triples, often with highly eccentric orbits (Antognini & Thompson 2016). It seems that chaotic stellar dynamics played a larger role in the formation of massive stars.…”

Section: Discussionmentioning

confidence: 99%

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Orbit Alignment in Triple Stars

Tokovinin

2017

ApJ

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Statistics of the angle Φ between orbital angular momenta in hierarchical triple systems with known inner visual or astrometric orbits are studied. Correlation between apparent revolution directions proves partial orbit alignment known from earlier works. The alignment is strong in triples with outer projected separation less than ∼50 AU, where the average Φ is about 20• . In contrast, outer orbits wider than 1000 AU are not aligned with the inner orbits. It is established that the orbit alignment decreases with increasing mass of the primary component. Average eccentricity of inner orbits in well-aligned triples is smaller than in randomly aligned ones. These findings highlight the role of dissipative interactions with gas in defining the orbital architecture of low-mass triple systems. On the other hand, chaotic dynamics apparently played a role in shaping more massive hierarchies. Analysis of projected configurations and triples with known inner and outer orbits indicates that the distribution of Φ is likely bimodal, where 80% of triples have Φ < 70• and the remaining ones are randomly aligned.

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Section: Discussionmentioning

confidence: 99%

“…• and their relative inclination and inner eccentricity change periodically in the Kozai-Lidov cycles (see the references in Antognini & Thompson 2016). In these cycles, the inner eccentricity can reach high values.…”

Section: Introductionmentioning

confidence: 99%

Orbit Alignment in Triple Stars

Tokovinin

2017

ApJ

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“…Antognini & Thompson (2016) demonstrate that even in the case of the most optimistic interaction cross sections, t ion ∼ 2 Gyr, implying that ∼ 10% of systems with planets on wide orbits would have been ionized in a cluster with an age of 200 Myr. In the field, these authors find t ion ∼ 4 × 10 12 yr and therefore 1% of wide-separation planetary systems would have been ionized in the lifetime of the Galaxy.…”

Section: Introductionmentioning

confidence: 94%

“…Similarly, ionization by interloping stars requires initially wide planetary orbits and a dense stellar environment since the ionization time scales as t ion ∝ ν −1 a −2 , where ν is the local stellar number density and a is the semimajor axis (see Antognini & Thompson 2016, and references therein). Antognini & Thompson (2016) demonstrate that even in the case of the most optimistic interaction cross sections, t ion ∼ 2 Gyr, implying that ∼ 10% of systems with planets on wide orbits would have been ionized in a cluster with an age of 200 Myr.…”

Section: Introductionmentioning

confidence: 99%

Constraining the Frequency of Free-Floating Planets From a Synthesis of Microlensing, Radial Velocity, and Direct Imaging Survey Results

Clanton

Gaudi

2016

ApJ

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A microlensing survey by Sumi et al. (2011) exhibits an overabundance of short-timescale events (t E 2 days) relative to that expected from known stellar populations and a smooth power-law extrapolation down to the brown dwarf regime. This excess has been interpreted as a population of approximately Jupiter-mass objects that outnumber main-sequence stars by nearly twofold; however the microlensing data alone cannot distinguish between events due to wide-separation (a 10 AU) and free-floating planets. Assuming these short-timescale events are indeed due to planetary-mass objects, we aim to constrain the fraction of these events that can be explained by bound but wideseparation planets. We fit the observed timescale distribution with a lens mass function comprised of brown dwarfs, main-sequence stars, white dwarfs, neutron stars, and black holes, finding and thus corroborating the initial identification of an excess of short-timescale events. Including a population of bound planets with distributions of masses and separations that are consistent with the results from representative microlensing, radial velocity, and direct imaging surveys, we then determine what fraction of these bound planets are expected not to show signatures of the primary lens (host) star in their microlensing light curves, and thus what fraction of the short-timescale event excess can be explained by bound planets alone. We find that, given our model for the distribution of planet parameters, bound planets alone cannot explain the entire excess without violating the constraints from the surveys we consider, and thus some fraction of these events must be due to free-floating planets, if our model for bound planets holds. We estimate a median fraction of short-timescale events due to free-floating planets to be f = 0.67 (0.23-0.85 at 95% confidence) when assuming "hot-start" planet evolutionary models and f = 0.58 (0.14-0.83 at 95% confidence) for "cold-start" models. Assuming a delta-function distribution of free-floating planets of mass m p = 2 M Jup yields a number of free-floating planets per main sequence star of N = 1.4 (0.48-1.8 at 95% confidence) in the "hot-start" case and N = 1.2 (0.29-1.8 at 95% confidence) in the "cold-start" case.

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“…Hut & Bahcall 1983;Samsing et al 2014;Antognini & Thompson 2016;Samsing et al 2016), to full GC simulations (e.g. Wang et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Dissipative Evolution of Unequal-mass Binary–single Interactions and Its Relevance to Gravitational-wave Detections

Samsing

MacLeod

Ramírez-Ruiz

2018

ApJ

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We present a study on binary-single interactions with energy loss terms such as tidal dissipation and gravitational wave emission added to the equation-of-motion. The inclusion of such terms leads to the formation of compact binaries that form during the three-body interaction through two-body captures. These binaries predominantly merge relative promptly at high eccentricity, with several observable and dynamical consequences to follow. Despite their possibility for being observed in both present and upcoming transient surveys, their outcomes are not firmly constrained. In this paper we present an analytical framework that allows to estimate the cross section of such two-body captures, which permits us to study how the corresponding rates depends on the initial orbital parameters, the mass hierarchy, the type of interacting objects, and the energy dissipation mechanism. This formalism is applied here to study the formation of two-body gravitational wave captures, for which we estimate absolute and relative rates relevant to Advanced LIGO detections. It is shown that two-body gravitational wave captures should have compelling observational implications if a sizable fraction of detected compact binaries are formed via dynamical interactions.

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Dynamical formation and scattering of hierarchical triples: cross-sections, Kozai–Lidov oscillations, and collisions

Cited by 73 publications

References 140 publications

Orbit Alignment in Triple Stars

Orbit Alignment in Triple Stars

Constraining the Frequency of Free-Floating Planets From a Synthesis of Microlensing, Radial Velocity, and Direct Imaging Survey Results

Dissipative Evolution of Unequal-mass Binary–single Interactions and Its Relevance to Gravitational-wave Detections

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