BLACK HOLE MERGERS AND BLUE STRAGGLERS FROM HIERARCHICAL TRIPLES FORMED IN GLOBULAR CLUSTERS

By F. Antonini, S. Chatterjee, C. Rodriguez, M. Morscher, Bharath Pattabiraman, Vicky Kalogera, F. Rasio. 2015

153 citations recorded by the source corpus.

Hierarchical triple-star systems are expected to form frequently via close binary–binary encounters in the dense cores of globular clusters (GCs). In a sufficiently inclined triple, gravitational interactions between the inner and outer binary can cause large-amplitude oscillations in the eccentricity of the inner orbit (“Lidov–Kozai (LK) cycles”), which can lead to a collision and merger of the two inner components. In this paper we use Monte Carlo models of dense star clusters to identify all triple systems formed dynamically and we compute their evolution using a highly accurate three-body integrator which incorporates relativistic and tidal effects. We find that a large fraction of these triples evolve through a non-secular dynamical phase which can drive the inner binary to higher eccentricities than predicted by the standard secular perturbation theory (even including octupole-order terms). We place constraints on the importance of LK-induced mergers for producing: (i) gravitational wave sources detectable by Advanced LIGO (aLIGO), for triples with an inner pair of stellar black holes (BHs); and (ii) blue straggler stars, for triples with main-sequence-star components. We find a realistic aLIGO detection rate of BH mergers due to the LK mechanism of ∼1 yr−1, with about 20% of these having a finite eccentricity when they first chirp into the aLIGO frequency band. While rare, these events are likely to dominate among eccentric compact object inspirals that are potentially detectable by aLIGO. For blue stragglers, we find that the LK mechanism can contribute up to ∼10% of their total numbers in GCs.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c0bf537240eae82b922df82231e0d042e3a330ed

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In Astronomy and Astrophysics

1. F. Antonini
2. Ilya Mandel
3. F. Rasio
4. D. Holz
5. B. Kocsis
6. Michela Mapelli
7. J. Samsing
8. C. Rodriguez

Citations in the corpus

• ASTROPHYSICAL IMPLICATIONS OF THE BINARY BLACK HOLE MERGER GW150914 (2016, background): “A small fraction of BBHs may form through triple stars in globular clusters and potentially maintain significant eccentricities until the merger (Samsing et al. 2014; Antonini et al. 2015).”
• Eccentric Black Hole Gravitational-wave Capture Sources in Galactic Nuclei: Distribution of Binary Parameters (2017, methodology): “A merger rate density of order 1–5 Gpc−3 yr−1 is expected for BH binaries forming via the Kozai–Lidov mechanism in GCs (Antonini et al. 2014, 2016; Rodriguez et al. 2016a, 2016b) and GNs (Antonini & Perets 2012; Hoang et al. 2018), and non-spherical nuclear star clusters may produce BH–BH binary…”
• MERGING BLACK HOLE BINARIES IN GALACTIC NUCLEI: IMPLICATIONS FOR ADVANCED-LIGO DETECTIONS (2016, background): “Finally, we note that Antonini et al. (2016) argued that even the rate of eccentric mergers from BH-BH scattering in NSCs is likely to be much smaller to that of eccentric mergers from BH triples formed in GCs.”
• Lidov–Kozai Cycles with Gravitational Radiation: Merging Black Holes in Isolated Triple Systems (2016, background): “Antonini et al. (2016) study black holes that merge due to evolution in triple systems that dynamically form in globular clusters.”
• Binary Black Hole Mergers from Field Triples: Properties, Rates, and the Impact of Stellar Evolution (2017, background): “One finds that the inner binary can enter the non-secular regime if (Antonini et al. 2016): a2(1− e2) a1 .”
• Deep Learning for Real-time Gravitational Wave Detection and Parameter Estimation with Advanced LIGO Data (2017, methodology): “However, matched-filtering, the most sensitive search algorithm used by LIGO, targets only a 3D parameter space (spin-aligned binaries on quasi-circular orbits) [8, 9, 10]—a subset of the over 8D parameter space of GW signals [11, 12, 13, 14, 15].”
• The chemically homogeneous evolutionary channel for binary black hole mergers: rates and properties of gravitational-wave events detectable by advanced LIGO (2016, background): “These include: (i) dynamical formation, which requires a dense star cluster (e.g., Sigurdsson & Hernquist 1993; Portegies Zwart & McMillan 2000; Miller & Lauburg 2009; Rodriguez et al. 2015; Antonini et al. 2016).”
• Rates of compact object coalescences (2021, background): “…channel may operate in a number of regimes, from isolated stellar triples (Silsbee and Tremaine, 2017) to dynamically formed triples in clusters (Antonini et al., 2016) to triples in which the outer companion is a massive black hole in a galactic center (Antonini and Perets, 2012; Hoang et al.,…”
• The origin of spin in binary black holes (2019, background): “…stars not born in the same binary (e.g., Sigurdsson & Hernquist 1993; Portegies Zwart & McMillan 2000; Miller & Lauburg 2009; Rodriguez et al. 2015; Antonini et al. 2016); or (vi) Lidov–Kozai resonance bringing the inner binary to merge in hierarchical triple systems (e.g., Silsbee & Tremaine…”
• Eccentric Black Hole Mergers in Dense Star Clusters: The Role of Binary–Binary Encounters (2018, background): “…the high GW frequencies accessible to ground-based detectors, such as the merger of binaries in hierarchical triples from the LidovKozai mechanism (Antonini et al. 2016; Silsbee & Tremaine 2017; Randall & Xianyu 2018a), single-single captures in NSCs (O’leary et al. 2009; Lee et al. 2010; Kocsis…”
• DYNAMICAL FORMATION OF THE GW150914 BINARY BLACK HOLE (2016, background): “Note that we do not consider relativistic effects, such as post-Newtonian corrections to close dynamical encounters (Samsing et al. 2014) or long-term secular effects, such as Lidov–Kozai and gravitational-wave emission in BH triple systems (Antonini et al. 2014, 2016).”