An Analytical Portrait of Binary Mergers in Hierarchical Triple Systems

Randall, Lisa; Xianyu, Zhong-Zhi

doi:10.3847/1538-4357/aad7fe

Cited by 86 publications

(56 citation statements)

References 87 publications

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“…A similar result for T m , but neglecting singly-averaged effects 5 (i.e. with e max = e max ), has been previously used by several authors to calculate merger times of binaries driven to high eccentricity via the LK mechanism (Thompson 2011;Antonini & Perets 2012;Liu & Lai 2018;Grishin et al 2018;Randall & Xianyu 2018).…”

Section: Merger Time T Mmentioning

confidence: 73%

Compact Object Binary Mergers Driven By Cluster Tides: A New Channel for LIGO/Virgo Gravitational-wave Events

Hamilton¹,

Rafikov²

2019

ApJL

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The detections of gravitational waves produced in mergers of binary black holes (BH) and neutron stars (NS) by LIGO/Virgo have stimulated interest in the origin of the progenitor binaries. Dense stellar systems -globular and nuclear star clusters -are natural sites of compact object binary formation and evolution towards merger. Here we explore a new channel for the production of binary mergers in clusters, in which the tidal field of the cluster secularly drives the binary to high eccentricity (even in the absence of a central massive black hole) until gravitational wave emission becomes important. We employ the recently developed secular theory of cluster tide-driven binary evolution to compute present day merger rates for BH-BH, NS-BH and NS-NS binaries, varying cluster potential and central concentration of the binary population (but ignoring cluster evolution and stellar flybys for now). Unlike other mechanisms, this new dynamical channel can produce a significant number of mergers out to cluster-centric distances of several pc. For NS-NS binaries we find merger rates in the range 0.01 − 0.07 Gpc −3 yr −1 from globular clusters and 0.1 − 0.2 Gpc −3 yr −1 from cusped nuclear clusters. For NS-BH and BH-BH binaries we find small merger rates from globular clusters, but a rate of 0.1 − 0.2 Gpc −3 yr −1 from cusped nuclear clusters, contributing to the observed LIGO/Virgo rate at the level of several per cent. Therefore, cluster tide-driven mergers constitute a new channel that can be further explored with current and future gravitational wave detectors.

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Section: Merger Time T Mmentioning

confidence: 73%

Compact Object Binary Mergers Driven By Cluster Tides: A New Channel for LIGO/Virgo Gravitational-wave Events

Hamilton¹,

Rafikov²

2019

ApJL

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“…This type of evolution is analogous to the 'fast' type of mergers occurring in black hole triple systems (e.g., Randall & Xianyu 2018), or stellar/planetary systems in which tidal friction is important (e.g., Petrovich 2015).…”

Section: Nonzero Ejection/accretion Radiimentioning

confidence: 92%

An Analytic Model for Mass Transfer in Binaries with Arbitrary Eccentricity, with Applications to Triple-star Systems

Hamers

Dosopoulou

2019

ApJ

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Most studies of mass transfer in binary systems assume circular orbits at the onset of Roche lobe overflow. However, there are theoretical and observational indications that mass transfer could occur in eccentric orbits. In particular, eccentricity could be produced via sudden mass loss and velocity kicks during supernova explosions, or Lidov-Kozai (LK) oscillations in hierarchical triple systems, or, more generally, secular evolution in multiple-star systems. However, current analytic models of eccentric mass transfer are faced with the problem that they are only well defined in the limit of very high eccentricities, and break down for less eccentric and circular orbits. This provides a major obstacle to implementing such models in binary and higher-order population synthesis codes, which are useful tools for studying the long-term evolution of a large number of systems. Here, we present a new analytic model to describe the secular orbital evolution of binaries undergoing conservative mass transfer. The main improvement of our model is that the mass transfer rate is a smoothly varying function of orbital phase, rather than a delta function centered at periapsis. Consequently, our model is in principle valid for any eccentricity, thereby overcoming the main limitation of previous works. We implement our model in an easy-to-use and publicly available code that can be used as a basis for implementations of our model into population synthesis codes. We investigate the implications of our model in a number of applications with circular and eccentric binaries, and triples undergoing LK oscillations.

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“…It has been shown that aLIGO can distinguish eccentric stellar-mass compact binary mergers from circular ones for e  0.05-0.081 at 10 Hz (Lower et al 2018;Gondán & Kocsis 2019). Broadly speaking, mergers from dynamical channels are expected to be more eccentric in the LIGO band than mergers from isolated binary evolution in the field, which are expected to be predominantly circular (e.g., O' Leary et al 2009;Cholis et al 2016;Gondán et al 2018b;Lower et al 2018;Rodriguez et al 2018b;Randall & Xianyu 2018;Samsing 2018;Zevin et al 2019). Among dynamical merger channels, some channels are predicted to yield more eccentric mergers than others.…”

Section: Discussionmentioning

confidence: 99%

Neutron Star–Black Hole Mergers from Gravitational-wave Captures

Hoang

Naoz

Kremer

2020

ApJ

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LIGO's third observing run (O3) has reported several neutron star-black hole (NSBH) merger candidates. From a theoretical point of view, NSBH mergers have received less attention in the community than either binary black holes, or binary neutron stars. Here we examine single-single (sin-sin) gravitational wave (GW) captures in different types of star clusters-galactic nuclei, globular clusters, and young stellar clusters-and compare the merger rates from this channel to other proposed merger channels in the literature. There are currently large uncertainties associated with every merger channel, making a definitive conclusion about the origin of NSBH mergers impossible. However, keeping these uncertainties in mind, we find that sin-sin GW capture is unlikely to significantly contribute to the overall NSBH merger rate. In general, it appears that isolated binary evolution in the field or in clusters, and dynamically interacting binaries in triple configurations, may result in a higher merger rate.

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An Analytical Portrait of Binary Mergers in Hierarchical Triple Systems

Cited by 86 publications

References 87 publications

Compact Object Binary Mergers Driven By Cluster Tides: A New Channel for LIGO/Virgo Gravitational-wave Events

Compact Object Binary Mergers Driven By Cluster Tides: A New Channel for LIGO/Virgo Gravitational-wave Events

An Analytic Model for Mass Transfer in Binaries with Arbitrary Eccentricity, with Applications to Triple-star Systems

Neutron Star–Black Hole Mergers from Gravitational-wave Captures

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