Greatly Enhanced Merger Rates of Compact-object Binaries in Non-spherical Nuclear Star Clusters

Petrovich, Cristóbal; Antonini, Fabio

doi:10.3847/1538-4357/aa8628

Cited by 197 publications

(190 citation statements)

References 103 publications

(163 reference statements)

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“…Moreover, the number of systems that merge in the equal mass case is comparable to the other models (see Table 1). These results indicate therefore that the effect of the octupole order terms is not great in our simulations (in agreement with Petrovich & Antonini 2017). For other choices of initial conditions the octupole order terms could become more important (Stephan et al 2016).…”

Section: Inclination Distributionsupporting

confidence: 89%

Massive binary star mergers in galactic nuclei: implications for blue stragglers, binary S-stars, and gravitational waves

Fragione

Antonini

2019

Monthly Notices of the Royal Astronomical Society

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Galactic nuclei are often found to contain young stellar populations and, in most cases, a central supermassive black hole (SMBH). Most known massive stars are found in binaries or higher-multiplicity systems, and in a galactic nucleus the gravitational interaction with the SMBH can affect their long-term evolution. In this paper, we study the orbital evolution of stellar binaries near SMBHs using high precision Nbody simulations, and including tidal forces and Post-Newtonian corrections to the motion. We focus on the Lidov-Kozai (LK) effect induced by the SMBH on massive star binaries. We investigate how the properties of the merging binaries change with varying the SMBH mass, the slope of the initial mass function, the distributions of the binary orbital parameters and the efficiency in energy dissipation in dissipative tides. We find that the fraction of merging massive binary stars is in the range ∼ 4%-15% regardless of the details of the initial distributions of masses and orbital elements. For a Milky Way-like nucleus, we find a typical rate of binary mergers Γ ≈ 1.4×10 −7 yr −1 . The merger products of massive binaries can be rejuvenated blue-straggler stars, more massive than each of their original progenitors, and G2-like objects. Binary systems that survive the LK cycles can be source of X-rays and gravitational waves, observable with present and upcoming instruments.

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Section: Inclination Distributionsupporting

confidence: 89%

Massive binary star mergers in galactic nuclei: implications for blue stragglers, binary S-stars, and gravitational waves

Fragione

Antonini

2019

Monthly Notices of the Royal Astronomical Society

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“…We also did not consider dynamical formation of merging binaries in galactic nuclei, which may contribute significantly. Indeed, Petrovich & Antonini (2017) estimated the NS-NS and NS-BH merger rates in galactic nuclei, and found them comparable to our predicted merger rates from GCs.…”

Section: Discussion and Summarysupporting

confidence: 77%

On the Rate of Neutron Star Binary Mergers from Globular Clusters

Fong

Kremer

et al. 2019

ApJL

178

134

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The first detection of gravitational waves from a neutron star -neutron star (NS-NS) merger, GW170817, and the increasing number of observations of short gamma-ray bursts (SGRBs) have greatly motivated studies of the origins of NS-NS and neutron star -black hole (NS-BH) binaries. We calculate the merger rates of NS-NS and NS-BH binaries from globular clusters (GCs) using realistic GC simulations with the CMC cluster catalog. We use a large sample of models with a range of initial numbers of stars, metallicities, virial radii and galactocentric distances, representative of the present-day Milky Way GCs, to quantify the inspiral times and volumetric merger rates as a function of redshift, both inside and ejected from clusters. We find that over the complete lifetime of most GCs, stellar BHs dominate the cluster cores and prevent the mass segregation of NSs, thereby reducing the dynamical interaction rates of NSs so that at most a few NS binary mergers are ever produced. We estimate the merger rate in the local universe to be ∼ 0.02 Gpc −3 yr −1 for both NS-NS and NS-BH binaries, or a total of ∼ 0.04 Gpc −3 yr −1 for both populations. These rates are about 5 orders of magnitude below the current empirical merger rate from LIGO/Virgo. We conclude that dynamical interactions in GCs do not play a significant role in enhancing the NS-NS and NS-BH merger rates.

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“…This also affects the relative LK dynamics and renders the 4-body approximation insufficient. The in-plane precession induced by the nuclear cluster potential and departures from spherical symmetry in the galactic nucleus would make the CO center of mass orbit precess even faster than is quantified by vector resonant relaxation alone in a MW-like nucleus (Petrovich & Antonini 2017). However, a relevant constraint for the triples lifetime in galactic nuclei comes from their evaporation as a result of the encounters with other stars, which takes place on timescales Myr for a Milky Way-like galaxy.…”

Section: Initial Conditionsmentioning

confidence: 99%

Black hole and neutron star mergers in galactic nuclei: the role of triples

Fragione

Leigh

Perna

2019

Monthly Notices of the Royal Astronomical Society

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Nuclear star clusters that surround supermassive black holes (SMBHs) in galactic nuclei are thought to contain large numbers of black holes (BHs) and neutron stars (NSs), a fraction of which form binaries and could merge by Kozai-Lidov oscillations (KL). Triple compact objects are likely to be present, given what is known about the multiplicity of massive stars, whose life ends either as a NS or a BH. In this paper, we present a new possible scenario for merging BHs and NSs in galactic nuclei. We study the evolution of a triple black hole (BH) or neutron star (NS) system orbiting an SMBH in a galactic nucleus by means of direct high-precision N -body simulations, including Post-Newtonian terms. We find that the four-body dynamical interactions can increase the KL angle window for mergers compared to the binary case and make BH and NS binaries merge on shorter timescales. We show that the merger fraction can be up to ∼ 5-8 times higher for triples than for binaries. Therefore, even if the triple fraction is only ∼ 10%-20% of the binary fraction, they could contribute to the merger events observed by LIGO/VIRGO in comparable numbers.

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Greatly Enhanced Merger Rates of Compact-object Binaries in Non-spherical Nuclear Star Clusters

Cited by 197 publications

References 103 publications

Massive binary star mergers in galactic nuclei: implications for blue stragglers, binary S-stars, and gravitational waves

Massive binary star mergers in galactic nuclei: implications for blue stragglers, binary S-stars, and gravitational waves

On the Rate of Neutron Star Binary Mergers from Globular Clusters

Black hole and neutron star mergers in galactic nuclei: the role of triples

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