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

2019 ◽  
Vol 488 (2) ◽  
pp. 2825-2835 ◽  
Author(s):  
Giacomo Fragione ◽  
Nathan W C Leigh ◽  
Rosalba Perna
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Massive Stars ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Compact Objects ◽  
Large Numbers ◽  
Binary Case

ABSTRACT 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 an 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 time-scales. 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–$20\rm{\,per\,cent}$ of the binary fraction, they could contribute to the merger events observed by LIGO/VIRGO in comparable numbers.

scholarly journals Monte Carlo Simulations of the 2+1 Dimensional Fokker-Planck Equation: Spherical Star Clusters Containing Massive, Central Black Holes

1985 ◽  
Vol 113 ◽  
pp. 373-413 ◽  
Author(s):  
Stuart L. Shapiro
Keyword(s):  
Black Holes ◽  
Monte Carlo ◽  
Black Hole ◽  
Phase Space ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Planck Equation ◽  
Time Dependent ◽  
Central Black Hole ◽  
Fokker Planck Equation

The dynamical behavior of a relaxed star cluster containing a massive, central black hole poses a challenging problem for the theorist and intriguing possibilities for the observer. The historical development of the subject is sketched and the salient features of the physical solution and its observational consequences are summarized.The full dynamical problem of a relaxed, self-gravitating, large N-body system containing a massive central black hole has all the necessary ingredients to excite the most dispassionate many-body, computational physicist: it is a time-dependent, multidimensional, nonlinear problem which must be solved over widely disparate length and time scales simultaneously. The problem has been tackled at various levels of approximation over the years. A new 2+1 dimensional Monte Carlo simulation code has been developed in appreciable generality to solve the time-dependent Fokker-Planck equation in E-J space for this problem. The code incorporates such features as (1) a particle “cloning and renormalization” scheme to provide a statistically reliable population of test particles in low density regions of phase space and (2) a time-step “adjustment” algorithm to ensure integration on local relaxation timescales without having to follow typical particles on orbital trajectories. However, critical regions in phase space (e.g. disruption “loss-cone” trajectories) can still be followed on orbital timescales. Numerical results obtained with this Monte Carlo scheme for the dynamical structure and evolution of globular star clusters and dense galactic nuclei containing massive black holes are reviewed.Recent dynamical integrations of the Einstein field equations for spherical, collisionless (Vlasov) systems in General Relativity suggest a possible origin for the supermassive black holes believed to power quasars and active galactic nuclei. This scenario is discussed briefly.

scholarly journals Black hole and neutron star mergers in galactic nuclei

2019 ◽  
Vol 488 (1) ◽  
pp. 47-63 ◽  
Author(s):  
Giacomo Fragione ◽  
Evgeni Grishin ◽  
Nathan W C Leigh ◽  
Hagai B Perets ◽  
Rosalba Perna
Keyword(s):  
Black Holes ◽  
Semimajor Axis ◽  
Galactic Nuclei ◽  
Mass Function ◽  
Compact Objects ◽  
Star Formation History ◽  
Large Numbers ◽  
Formation History ◽  
Binary Mergers ◽  
First Time

Abstract Nuclear star clusters surrounding supermassive black holes (SMBHs) in galactic nuclei contain large numbers of stars, black holes (BHs), and neutron stars (NSs), a fraction of which are likely to form binaries. These binaries were suggested to form a triple system with the SMBH, which acts as a perturber and may enhance BH and NS mergers via the Lidov–Kozai mechanism. We follow-up previous studies, but for the first time perform an extensive statistical study of BH–BH, NS–NS, and BH–NS binary mergers by means of direct high-precision regularized N-body simulations, including post-Newtonian (PN) terms up to order PN2.5. We consider different SMBH masses, slopes for the BH mass function, binary semimajor axis and eccentricity distributions, and different spatial distributions for the binaries. We find that the merger rates are a decreasing function of the SMBH mass and are in the ranges ∼0.17–0.52, ∼0.06–0.10, and ∼0.04–0.16 Gpc−3 yr−1 for BH–BH, BH–NS, and NS–NS binaries, respectively. However, the rate estimate from this channel remains highly uncertain and depends on the specific assumptions regarding the star formation history in galactic nuclei and the supply rate of compact objects (COs). We find that ${\sim } 10\!-\!20{{\ \rm per\ cent}}$ of the mergers enter the LIGO band with eccentricities ≳0.1. We also compare our results to the secular approximation, and show that N-body simulations generally predict a larger number of mergers. Finally, these events can also be observable via their electromagnetic counterparts, thus making these CO mergers especially valuable for cosmological and astrophysical purposes.

The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei. II. Black Hole Merging in a Nuclear Gas Disk

2005 ◽  
Vol 630 (1) ◽  
pp. 152-166 ◽  
Author(s):  
Andres Escala ◽  
Richard B. Larson ◽  
Paolo S. Coppi ◽  
Diego Mardones
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Galactic Nuclei ◽  
Massive Black Holes

scholarly journals Formation and Evolution of Black Holes in Galactic Nuclei and Star Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 346-350
Author(s):  
R. Spurzem ◽  
P. Berczik ◽  
I. Berentzen ◽  
D. Merritt ◽  
M. Preto ◽  
...  
Keyword(s):  
Black Holes ◽  
Gravitational Waves ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Stellar Dynamics ◽  
Compact Objects ◽  
Binary Black Holes ◽  
Black Hole Binaries ◽  
Orbital Parameters ◽  
Work Done

AbstractWe study the formation, growth, and co-evolution of single and multiple supermassive black holes (SMBHs) and compact objects like neutron stars, white dwarfs, and stellar mass black holes in galactic nuclei and star clusters, focusing on the role of stellar dynamics. In this paper we focus on one exemplary topic out of a wider range of work done, the study of orbital parameters of binary black holes in galactic nuclei (binding energy, eccentricity, relativistic coalescence) as a function of initial parameters. In some cases the classical evolution of black hole binaries in dense stellar systems drives them to surprisingly high eccentricities, which is very exciting for the emission of gravitational waves and relativistic orbit shrinkage. Such results are interesting to the emerging field of gravitational wave astronomy, in relation to a number of ground and space based instruments designed to measure gravitational waves from astrophysical sources (VIRGO, Geo600, LIGO, LISA). Our models self-consistently cover the entire range from Newtonian dynamics to the relativistic coalescence of SMBH binaries.

Black Hole, Neutron Star and Numerical Relativity

2021 ◽  
Vol 30 (6) ◽  
pp. 7-13
Author(s):  
Jinho KIM
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Neutron Star ◽  
Neutron Stars ◽  
Numerical Method ◽  
High Velocity ◽  
Compact Objects ◽  
Compact Stars ◽  
Speed Of Light

Compact stars, e.g., black holes and neutron stars, are the most energetic objects in astrophysics. These objects are accompanied by extremely strong gravity and a high velocity, which approaches the speed of light. Therefore, compact objects should be dealt with in Einstein’s relativity. This article will briefly introduce a numerical method that will allow us to obtain general solutions in general relativity. Several applications using numerical relativistic simulations will also be presented.

Stars and Black Holes

2020 ◽  
pp. 40-57
Author(s):  
John W. Moffat
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Gravitational Collapse ◽  
Massive Stars ◽  
Electron Gas ◽  
Life Cycles ◽  
Maximum Mass ◽  
Degenerate Electron ◽  
New Information

Physicists began to believe in black holes when research revealed new information about the constitution of stars and their life cycles, indicating that a black hole represents the death of certain massive stars. Chandrasekhar used quantum mechanics and the notion of a degenerate electron gas to obtain the maximum mass of a white dwarf. A degenerate neutron gas produced enough pressure to stop the gravitational collapse of a massive star, producing a neutron star or pulsar. For a massive-enough star, the degenerate neutron gas fails to prevent gravitational collapse into a black hole. Supernovae explosions and implosions produce a neutron star or black hole as remnants. Oppenheimer and Volkoff used general relativity to derive the maximum mass of a star that would produce a black hole. Wheeler conceived of a “hairless black hole” in which only the mass, charge, and angular momentum determined the properties of the black hole.

Supermassive Black Holes

2013 ◽  
Author(s):  
Abraham Loeb ◽  
Steven R. Furlanetto
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Massive Stars ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Supermassive Black Holes ◽  
Material Object ◽  
Formation Mechanisms ◽  
Host Galaxies ◽  
Bright Source

This chapter analyzes formation mechanisms for supermassive black holes, their observable characteristics, and their interactions with their host galaxies and the wider Universe. A black hole is the end product of the complete gravitational collapse of a material object, such as a massive star. It is surrounded by a horizon from which even light cannot escape. Astrophysical black holes appear in two flavors: stellar-mass black holes that form when massive stars die, and the monstrous supermassive black holes that sit at the center of galaxies, reaching masses of up to ten billion Suns. The latter type is observed as active galactic nuclei (AGN), and the chapter introduces the quasar—a point-like (“quasi-stellar”) bright source at the center of a galaxy which serves as the most powerful type of AGN—in discussing the observable nature of supermassive black holes.

GRAVITATIONAL THERMODYNAMICS AND BLACK-HOLE MERGERS

2000 ◽  
Vol 15 (30) ◽  
pp. 4871-4875 ◽  
Author(s):  
SIMON F. PORTEGIES ZWART ◽  
STEPHEN L. W. MCMILLAN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Gravitational Waves ◽  
Star Clusters ◽  
Black Hole Binaries ◽  
Orbital Periods ◽  
Binary Evolution ◽  
Event Rates ◽  
Gravitational Thermodynamics

Black holes become the most massive objects early in the evolution of star clusters. Dynamical relaxation then causes them to sink to the cluster core, where they form binaries which become more tightly bound by superelastic encounters with other cluster members. Ultimately, these binaries are ejected from the cluster. The majority of escaping black-hole binaries have orbital periods short enough and eccentricities high enough that the emission of gravitational waves causes them to coalesce within a few billion years. The rate at which such collisions occur is on the order of 10-7 per year per cubic megaparsec. This implies event rates for gravitational-wave detectors substantially greater than current estimates of the corresponding rates from neutron-star mergers or black-hole mergers stemming from pure binary evolution.

Black Hole, Observed

2020 ◽  
Vol 29 (12) ◽  
pp. 23-28
Author(s):  
Bong Won SOHN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Observation Methods ◽  
History Of ◽  
Astronomy And Astrophysics ◽  
Future Plans

The author explains black holes in the context of astronomy and astrophysics. The history of black hole research and black hole discovery are covered briefly. The author explains why supermassive black holes in active galactic nuclei are the most promising candidates for imaging black holes. The principles of radio interferometers used as observation methods are covered. The Event Horizon Telescope Collaboration, its future plans, and the role of the Korean members are introduced.

scholarly journals Recent LIGO-Virgo discoveries

2021 ◽  
pp. 2130010
Author(s):  
Maximiliano Isi
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Neutron Star ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Compact Objects ◽  
Tests Of General Relativity ◽  
Mass Gap ◽  
Cosmic History

The LIGO and Virgo gravitational-wave detectors carried out the first half of their third observing run from April through October 2019. During this period, they detected 39 new signals from the coalescence of black holes or neutron stars, more than quadrupling the total number of detected events. These detections included some unprecedented sources, like a pair of black holes with unequal masses (GW190412), a massive pair of neutron stars (GW190425), a black hole potentially in the supernova pair-instability mass gap (GW190521), and either the lightest black hole or the heaviest neutron star known to date (GW190814). Collectively, the full set of signals provided astrophysically valuable information about the distributions of compact objects and their evolution throughout cosmic history. It also enabled more constraining and diverse tests of general relativity, including new probes of the fundamental nature of black holes. This review summarizes the highlights of these results and their implications.

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