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2020JCAP...02..003A

Magnetically charged black holes from non-linear electrodynamics and the Event Horizon Telescope

2020-01-01

['-', '-', '-']

[]

Non-linear electrodynamics (NLED) theories are well-motivated extensions of QED in the strong field regime, and have long been studied in the search for regular black hole (BH) solutions. We consider two well-studied and well-motivated NLED models coupled to General Relativity: the Euler-Heisenberg model and the Bronnikov model. After carefully accounting for the effective geometry induced by the NLED corrections, we determine the shadows of BHs within these two models. We then compare these to the shadow of the supermassive BH M87* recently imaged by the Event Horizon Telescope collaboration. In doing so, we are able to extract upper limits on the black hole magnetic charge, thus providing novel constraints on fundamental physics from this new extraordinary probe.

[]

https://arxiv.org/pdf/1912.08231.pdf

2017MNRAS.472L.109A

Black holes on FIRE: stellar feedback limits early feeding of galactic nuclei

2017-01-01

['black hole physics', 'galaxies active', 'galaxies evolution', 'galaxies formation', 'galaxies quasars', 'cosmology theory', '-', '-', '-']

[]

We introduce massive black holes (BHs) in the Feedback In Realistic Environments (FIRE) project and perform high-resolution cosmological hydrodynamic simulations of quasar-mass haloes [M<SUB>halo</SUB>(z = 2) ≈ 10<SUP>12.5</SUP> M<SUB>⊙</SUB>] down to z = 1. These simulations model stellar feedback by supernovae, stellar winds and radiation, and BH growth using a gravitational torque-based prescription tied to the resolved properties of galactic nuclei. We do not include BH feedback. We show that early BH growth occurs through short (≲1 Myr) accretion episodes that can reach or even exceed the Eddington rate. In this regime, BH growth is limited by bursty stellar feedback continuously evacuating gas from galactic nuclei, and BHs remain undermassive in low-mass galaxies relative to the local M<SUB>BH</SUB>-M<SUB>bulge</SUB>relation. BH growth is more efficient at later times, when the nuclear stellar potential retains a significant gas reservoir, star formation becomes less bursty and galaxies settle into a more ordered state. BHs rapidly converge on to the observed scaling relations when the host reaches M<SUB>bulge</SUB> ∼ 10<SUP>10</SUP> M<SUB>⊙</SUB>. We show that resolving the effects of stellar feedback on the gas supply in the inner ∼100 pc of galaxies is necessary to accurately capture the growth of central BHs. Our simulations imply that bursty stellar feedback has important implications for BH-galaxy relations, AGN demographics and time variability, the formation of early quasars and massive BH mergers.

[]

https://arxiv.org/pdf/1707.03832.pdf

2013PhRvD..87d4014W

Critical phenomena and thermodynamic geometry of charged Gauss-Bonnet AdS black holes

2013-01-01

['-', '-', '-', '-', '-', 'thermodynamics', '-']

[]

In this paper, we study the phase structure and equilibrium state space geometry of charged topological Gauss-Bonnet black holes in d-dimensional anti-de Sitter spacetime. Several critical points are obtained in the canonical ensemble, and the critical phenomena and critical exponents near them are examined. We find that the phase structures and critical phenomena drastically depend on the cosmological constant Λ and dimensionality d. The result also shows that there exists an analogy between the black hole and the van der Waals liquid gas system. Moreover, we explore the phase transition and possible property of the microstructure using the state space geometry. It is found that the Ruppeiner curvature diverges exactly at the points where the heat capacity at constant charge of the black hole diverges. This black hole is also found to be a multiple system, i.e., it is similar to the ideal gas of fermions in some range of the parameters, while to the ideal gas of bosons in another range.

[]

https://arxiv.org/pdf/1209.1707.pdf

2003ApJ...585L.101H

Black Hole Mass and Spin Coevolution by Mergers

2003-01-01

['black hole physics', 'galaxies active', 'galaxies nuclei', 'gravitation', 'galaxies quasars', 'astrophysics', '-']

[]

Massive black holes appear to be present in the nuclei of almost all galaxies, but their genesis and evolution are not well understood. As astrophysical black holes are completely characterized by their masses and spins, the observed joint distribution of these quantities contains important clues to their history. We examine the coevolution of mass and spin in binary merger growth scenarios. We find that holes are typically spun down by mergers. Rapid rotation results only if the binary's larger member already spins quickly and the merger with the smaller hole is consistently near prograde, or if the binary's mass ratio approaches unity. If, as some observations have suggested, observed black holes spin rapidly, then this limits the importance of merger scenarios for the growth of black holes.

[]

https://arxiv.org/pdf/astro-ph/0208484.pdf

2009PASJ...61L...7O

Global Radiation-Magnetohydrodynamic Simulations of Black-Hole Accretion Flow and Outflow: Unified Model of Three States

2009-01-01

['-']

[]

Black-hole accretion systems are known to possess several distinct modes (or spectral states), such as low/hard state, high/soft state, and so on. Since the dynamics of the corresponding flows is distinct, theoretical models were separately discussed for each state. We here propose a unified model based on our new, global, two-dimensional radiation-magnetohydrodynamic simulations. By controlling a density normalization we could for the first time reproduce three distinct modes of accretion flow and outflow with one numerical code. When the density is large (model A), a geometrically thick, very luminous disk forms, in which photon trapping takes place. When the density is moderate (model B), the accreting gas can effectively cool by emitting radiation, thus generating a thin disk, i.e., the soft-state disk. When the density is too low for radiative cooling to be important (model C), a disk becomes hot, thick, and faint; i.e., the hard-state disk. The magnetic energy is amplified within the disk up to about twice, 30%, and 20% of the gas energy in models A, B, and C, respectively. Notably, the disk outflows with helical magnetic fields, which are driven either by radiation pressure force or magnetic pressure force, are ubiquitous in any accretion modes. Finally, our simulations are consistent with the phenomenological alpha-viscosity prescription, that is, the disk viscosity is proportional to the pressure.

[]

https://arxiv.org/pdf/0903.5364.pdf

1996PhRvD..54.2612C

Entropy of nonextreme charged rotating black holes in string theory

1996-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

We give the explicit expression for four-dimensional rotating charged black hole solutions of N=4 (or N=8) superstring vacua, parametrized by the ADM mass, four charges [two electric and two magnetic charges, each arising from a different U(1) gauge factor], and the angular momentum (as well as the asymptotic values of four toroidal moduli of a two-torus and the dilaton-axion field). The explicit form of the thermodynamic entropy is parametrized in a suggestive way as a sum of the product of the ``left-moving'' and the ``right-moving'' terms, which may have an interpretation in terms of the microscopic degrees of freedom of the corresponding D-brane configuration. We also give an analogous parametrization of the thermodynamic entropy for the recently obtained five-dimensional rotating charged black holes parametrized by the ADM mass, three U(1) charges, and two rotational parameters (as well as the asymptotic values of one toroidal modulus and the dilaton).

[]

https://arxiv.org/pdf/hep-th/9603147.pdf

1998NuPhB.523..293M

Universality of quantum entropy for extreme black holes

1998-01-01

['-', '-', '-', '-', '-', '-']

[]

We consider the extremal limit of a black hole geometry of the Reissner-Nordstrom type and compute the quantum corrections to its entropy. Universally, the limiting geometry is the direct product of two 2-dimensional spaces and is characterized by just a few parameters. We argue that the quantum corrections to the entropy of such extremal black holes due to a massless scalar field have a universal behavior. We obtain explicitly the form of the quantum entropy in this extremal limit as a function of the parameters of the limiting geometry. We generalize these results to black holes with toroidal or higher genus horizon topologies. In general, the extreme quantum entropy is completely determined by the spectral geometry of the horizon and in the ultra-extreme case it is just a determinant of the 2-dimensional Laplacian. As a byproduct of our considerations we obtain expressions for the quantum entropy of black holes which are not of the Reissner-Nordstrom type: the extreme dilaton and extreme Kerr-Newman black holes. In both cases the classical Bekenstein-Hawking entropy is modified by logarithmic corrections.

[]

https://arxiv.org/pdf/hep-th/9709064.pdf

2003PhRvD..68h4004R

Electrically charged compact stars and formation of charged black holes

2003-01-01

['-', '-', '-', '-', '-', 'relativity', '-', 'neutron', 'astrophysics', '-', '-', 'nuclear reactions;nucleosynthesis;abundances']

[]

We study the effect of electric charge in compact stars assuming that the charge distribution is proportional to the mass density. The pressure and the density of the matter inside the stars are large, and the gravitational field is intense. This indicates that electric charge and a strong electric field can also be present. The relativistic hydrostatic equilibrium equation, i.e., the Tolman-Oppenheimer-Volkoff equation, is modified in order to include electric charge. We perform a detailed numerical study of the effect of electric charge using a polytropic equation of state. We conclude that in order to see any appreciable effect on the phenomenology of the compact stars, the electric fields have to be huge (∼10<SUP>21</SUP> V/m), which implies that the total charge is Q∼10<SUP>20</SUP> Coulomb. From the local effect of the forces experienced on a single charged particle, it is expected that each individual charged particle is quickly ejected from the star. This in turn produces a huge force imbalance, and the gravitational force overwhelms the repulsive Coulomb and fluid pressure forces. The star can then collapse to form a charged black hole before all the charge leaves the system.

[]

https://arxiv.org/pdf/astro-ph/0307262.pdf

1992PhRvD..45.2751L

Black holes in magnetic monopoles

1992-01-01

['-', '-', '-', '-', '-', '-', 'magnetism', 'black hole physics', '-']

[]

We study magnetically charged classical solutions of a spontaneously broken gauge theory interacting with gravity. We show that nonsingular monopole solutions exist only if the Higgs-field vacuum expectation value v is less than or equal to a critical value v<SUB>cr</SUB>, which is of the order of the Planck mass. In the limiting case, the monopole becomes a black hole, with the region outside the horizon described by the critical Reissner-Nordström solution. For v&lt;v<SUB>cr</SUB>, we find additional solutions which are singular at r=0, but which have this singularity hidden within a horizon. These have nontrivial matter fields outside the horizon, and may be interpreted as small black holes lying within a magnetic monopole. The nature of these solutions as a function of v and of the total mass M and their relation to the Reissner-Nordström solutions are discussed.

[]

https://arxiv.org/pdf/hep-th/9112008.pdf

2015Sci...347..860N

Black hole feedback in the luminous quasar PDS 456

2015-01-01

['-', '-']

[]

The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow’s kinetic power larger than 10<SUP>46</SUP> ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.

[]

https://arxiv.org/pdf/1502.06636.pdf

2008ApJ...679..639Z

Fallback and Black Hole Production in Massive Stars

2008-01-01

['black hole physics', 'hydrodynamics', '-', 'stars novae;cataclysmic variables', 'astrophysics']

[]

The compact remnants of core-collapse supernovae—neutron stars and black holes—have properties that reflect both the structure of their stellar progenitors and the physics of the explosion. In particular, the masses of these remnants are sensitive to the density structure of the presupernova star and to the explosion energy. To a considerable extent, the final mass is determined by the "fallback," during the explosion, of matter that initially moves outward, yet ultimately fails to escape. We consider here the simulated explosion of a large number of massive stars (9-100 M<SUB>⊙</SUB>) of Population I (solar metallicity) and III (zero metallicity) and find systematic differences in the remnant mass distributions. As pointed out by Chevalier, supernovae in more compact progenitor stars have stronger reverse shocks and experience more fallback. For Population III stars above about 25 M<SUB>⊙</SUB> and explosion energies less than 1.5 × 10<SUP>51</SUP> ergs, black holes are a common outcome, with masses that increase with increasing main-sequence mass up to a maximum hole mass, for very low explosion energy, of about 40 M<SUB>⊙</SUB>. If such stars produce primary nitrogen, however, their black holes are systematically smaller. For modern supernovae with nearly solar metallicity, black hole production is much less frequent and the typical masses, which depend sensitively on explosion energy, are smaller. The maximum black hole mass is about 15 M<SUB>⊙</SUB>. We explore the neutron star initial mass function for both populations and, for reasonable assumptions about the initial mass cut of the explosion, find good agreement with the average of observed masses of neutron stars in binaries. We also find evidence for a bimodal distribution of neutron star masses with a spike around 1.2 M<SUB>⊙</SUB> (gravitational mass) and a broader distribution peaked around 1.4 M<SUB>⊙</SUB>.

[]

https://arxiv.org/pdf/astro-ph/0701083.pdf

2004ApJ...607..765E

The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei. I. Black Hole Merging in a Spherical Gas Cloud

2004-01-01

['black hole physics', 'cosmology theory', 'galaxies evolution', 'galaxies nuclei', 'hydrodynamics', 'galaxies quasars', 'astrophysics']

[]

Using high-resolution smoothed particle hydrodynamics numerical simulations, we investigate the effects of gas on the in-spiral and merger of a massive black hole binary. This study is motivated by both observational and theoretical work that indicate the presence of large amounts of gas in the central regions of merging galaxies. N-body simulations have shown that the coalescence of a massive black hole binary eventually stalls in a stellar background. However, our simulations suggest that the massive black hole binary will finally merge if it is embedded in a gaseous background. Here we present results in which the gas is assumed to be initially spherical with a relatively smooth distribution. In the early evolution of the binary, the separation decreases as a result of the gravitational drag exerted by the background gas. In the later stages, when the binary dominates the gravitational potential in its vicinity, the medium responds by forming an ellipsoidal density enhancement whose axis lags behind the binary axis, and this offset produces a torque on the binary that causes continuing loss of angular momentum and is able to reduce the binary separation to distances where gravitational radiation is efficient. Assuming typical parameters from observations of ultraluminous infrared galaxies, we predict that a black hole binary will merge within 10<SUP>7</SUP> yr; therefore, these results imply that in a merger of gas-rich galaxies, any massive central black holes will coalesce soon after the galaxies merge. Our work thus supports scenarios of massive black hole evolution and growth in which hierarchical merging plays an important role. The final coalescence of the black holes leads to gravitational radiation emission that would be detectable out to high redshift by LISA. We show that similar physical effects, which we simulate with higher resolution than in previous work, can also be important for the formation of close binary stars.

[]

https://arxiv.org/pdf/astro-ph/0310851.pdf

2004MNRAS.352..547R

X-ray pre-ionization powered by accretion on the first black holes - I. A model for the WMAP polarization measurement

2004-01-01

['methods numerical', 'cosmology theory', 'astrophysics']

[]

In this paper we investigate the possibility that there is a first phase of partial ionization due to X-rays produced by black hole (BH) accretion in small-mass galaxies at redshifts 7 &lt; z &lt; 20. This is followed by complete reionization by stellar sources at z~= 7. This scenario is motivated by the large optical depth to Thomson scattering, τ<SUB>e</SUB>~= 0.17 +/- 0.04, recently measured by the Wilkinson Microwave Anisotropy Probe (WMAP). However, it is also consistent with the observed Gunn-Peterson trough in the spectra of quasars at z~ 5-6. We use a semi-analytic code to explore models with different BH accretion histories and cosmological parameters. We find that `pre-ionization' by X-rays can increase the intergalactic medium (IGM) optical depth from τ<SUB>e</SUB>~ 0.06 given by stellar sources only, to 0.1 &lt;~τ<SUB>e</SUB>&lt;~ 0.2, if a fraction of baryons 10<SUP>-5</SUP>&lt;~ω<SUB>ac</SUB>&lt;~ 10<SUP>-4</SUP> is accreted on to seed BHs produced in the collapse of low-metallicity, high-mass stars before z~= 15. To be effective, pre-ionization requires a non-negligible star formation in the first small-mass galaxies in which seed BHs are formed. By z~ 20-25 the IGM is reheated to 10000 K and the ionization fraction is about 20 per cent. The increase of the IGM Jeans mass is effective in reducing star formation in the smaller mass haloes. Large values of τ<SUB>e</SUB> are obtained in models with top-heavy stellar initial mass function only if pair-instability supernovae (SNe) are not important. Seed BHs are assumed to accrete at near the Eddington limit with a duty cycle that decreases slowly with increasing time. Alternatively, a moderate fraction of the black holes must be ejected from the host galaxy or exist without merging into the supermassive BHs in galactic centres. The model predicts that dwarf spheroidal galaxies, if they are preserved fossils of the first galaxies, may host a mass in BHs that is 5-40 per cent of their stellar mass. The redshifted X-ray background produced by this early epoch of BH accretion constitutes about 5-10 per cent of the hard X-ray background in the 2-50keV bands and roughly half of the currently estimated BH mass density was formed at early times. Moreover, in most models, the photons from the redshifted background are sufficient to fully reionize HeII at redshift z~ 3 without any additional contribution from quasars at lower redshifts and the temperature of the mean density IGM remains close to 10<SUP>4</SUP>K down to redshift z~ 1.

[]

https://arxiv.org/pdf/astro-ph/0311003.pdf

2010PhRvD..81d6001G

Peculiar properties of a charged dilatonic black hole in AdS<SUB>5</SUB>

2010-01-01

['-', '-', '-', '-', '-', '-', '-']

[]

We study a charged dilatonic black hole in AdS<SUB>5</SUB>, derived from a Lagrangian involving a gauge field whose kinetic term is modified by the exponential of a neutral scalar. This black hole has two properties which one might reasonably demand of the dual of a Fermi liquid: Its entropy is proportional to temperature at low temperature, and its extremal limit supports normal modes of massless, charged bulk fermions. The black hole we study has a simple analytic form because it can be embedded in type IIB string theory as the near-horizon limit of D3-branes with equal spins in two of the three independent transverse planes. Two further properties can be deduced from this embedding: There is a thermodynamic instability, reminiscent of ferromagnetism, at low temperatures; and there is an AdS<SUB>3</SUB> factor in the extremal near-horizon geometry which accounts for the linear dependence of entropy on temperature. Altogether, it is plausible that the dilatonic black hole we study, or a relative of it with similar behavior in the infrared, is the dual of a Fermi liquid; however, the particular embedding in string theory that we consider is unlikely to have such a dual description, unless through some unexpected boson-fermion equivalence at large N.

[]

https://arxiv.org/pdf/0911.2898.pdf

2015PhRvD..92j4020H

Quantum-gravity effects outside the horizon spark black to white hole tunneling

2015-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

We show that there is a classical metric satisfying the Einstein equations outside a finite spacetime region where matter collapses into a black hole and then emerges from a white hole. We compute this metric explicitly. We show how quantum theory determines the (long) time for the process to happen. A black hole can thus quantum tunnel into a white hole. For this to happen, quantum gravity should affect the metric also in a small region outside the horizon; we show that, contrary to what is commonly assumed, this is not forbidden by causality or by the semiclassical approximation, because quantum effects can pile up over a long time. This scenario alters radically the discussion on the black hole information puzzle.

[]

https://arxiv.org/pdf/1407.0989.pdf

2012Natur.490...71S

Two stellar-mass black holes in the globular cluster M22

2012-01-01

['-', '-', '-']

[]

Hundreds of stellar-mass black holes probably form in a typical globular star cluster, with all but one predicted to be ejected through dynamical interactions. Some observational support for this idea is provided by the lack of X-ray-emitting binary stars comprising one black hole and one other star (`black-hole/X-ray binaries') in Milky Way globular clusters, even though many neutron-star/X-ray binaries are known. Although a few black holes have been seen in globular clusters around other galaxies, the masses of these cannot be determined, and some may be intermediate-mass black holes that form through exotic mechanisms. Here we report the presence of two flat-spectrum radio sources in the Milky Way globular cluster M22, and we argue that these objects are black holes of stellar mass (each ~10-20 times more massive than the Sun) that are accreting matter. We find a high ratio of radio-to-X-ray flux for these black holes, consistent with the larger predicted masses of black holes in globular clusters compared to those outside. The identification of two black holes in one cluster shows that ejection of black holes is not as efficient as predicted by most models, and we argue that M22 may contain a total population of ~5-100 black holes. The large core radius of M22 could arise from heating produced by the black holes.

[]

https://arxiv.org/pdf/1210.0901.pdf

2011A&A...528A.149M

Stellar black holes at the dawn of the universe

2011-01-01

['astronomy x rays', 'black hole physics', '-', '-', '-', 'cosmology miscellaneous', 'galaxies intergalactic medium', '-']

[]

Context. It is well established that between 380 000 and 1 billion years after the Big Bang the Inter Galactic Medium (IGM) underwent a "phase transformation" from cold and fully neutral to warm (≈ 10<SUP>4</SUP> K) and ionized. Whether this phase transformation was fully driven and completed by photoionization by young hot stars is a question of topical interest in cosmology. <BR /> Aims: We propose here that besides the ultraviolet radiation from massive stars, feedback from accreting black holes in high-mass X-ray binaries (BH-HMXBs) was an additional, important source of heating and reionization of the IGM in regions of low gas density at large distances from star-forming galaxies. <BR /> Methods: We use current theoretical models on the formation and evolution of primitive massive stars of low metallicity, and the observations of compact stellar remnants in the near and distant universe, to infer that a significant fraction of the first generations of massive stars end up as BH-HMXBs. <BR /> Results: The total number of energetic ionizing photons from an accreting stellar black hole in an HMXB is comparable to the total number of ionizing photons of its progenitor star. However, the X-ray photons emitted by the accreting black hole are capable of producing several secondary ionizations and the ionizing power of the resulting black hole could be greater than that of its progenitor. Feedback by the large populations of BH-HMXBs heats the IGM to temperatures of ≈ 10<SUP>4</SUP> K and maintains it ionized on large distance scales. <BR /> Conclusions: BH-HMXBs determine the early thermal history of the universe and maintain it as ionized over large volumes of space in regions of low density. This has a direct impact on the properties of the faintest galaxies at high redshifts, the smallest dwarf galaxies in the local universe, and on the existing and future surveys at radio wavelengths of atomic hydrogen in the early universe.

[]

https://arxiv.org/pdf/1102.1891.pdf

2016MNRAS.460.3119S

Selection bias in dynamically measured supermassive black hole samples: its consequences and the quest for the most fundamental relation

2016-01-01

['black hole physics', 'galaxies fundamental parameters', 'galaxies nuclei', 'galaxies structure', '-', '-']

[]

We compare the set of local galaxies having dynamically measured black holes with a large, unbiased sample of galaxies extracted from the Sloan Digital Sky Survey. We confirm earlier work showing that the majority of black hole hosts have significantly higher velocity dispersions σ than local galaxies of similar stellar mass. We use Monte Carlo simulations to illustrate the effect on black hole scaling relations if this bias arises from the requirement that the black hole sphere of influence must be resolved to measure black hole masses with spatially resolved kinematics. We find that this selection effect artificially increases the normalization of the M<SUB>bh</SUB>-σ relation by a factor of at least ∼3; the bias for the M<SUB>bh</SUB>-M<SUB>star</SUB> relation is even larger. Our Monte Carlo simulations and analysis of the residuals from scaling relations both indicate that σ is more fundamental than M<SUB>star</SUB> or effective radius. In particular, the M<SUB>bh</SUB>-M<SUB>star</SUB> relation is mostly a consequence of the M<SUB>bh</SUB>-σ and σ-M<SUB>star</SUB> relations, and is heavily biased by up to a factor of 50 at small masses. This helps resolve the discrepancy between dynamically based black hole-galaxy scaling relations versus those of active galaxies. Our simulations also disfavour broad distributions of black hole masses at fixed σ. Correcting for this bias suggests that the calibration factor used to estimate black hole masses in active galaxies should be reduced to values of f<SUB>vir</SUB> ∼ 1. Black hole mass densities should also be proportionally smaller, perhaps implying significantly higher radiative efficiencies/black hole spins. Reducing black hole masses also reduces the gravitational wave signal expected from black hole mergers.

[]

https://arxiv.org/pdf/1603.01276.pdf

2004PhRvD..70h4011C

Small Kerr anti-de Sitter black holes are unstable

2004-01-01

['-', '-', 'astrophysics', '-', '-']

[]

Superradiance in black hole spacetimes can trigger instabilities. Here we show that, due to superradiance, small Kerr anti-deSitter black holes are unstable. Our demonstration uses a matching procedure, in a long wavelength approximation.

[]

https://arxiv.org/pdf/hep-th/0405006.pdf

2005PhRvD..71b4033E

Supersymmetric black rings and three-charge supertubes

2005-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

We present supergravity solutions for 1/8-supersymmetric black supertubes with three charges and three dipoles. Their reduction to five dimensions yields supersymmetric black rings with regular horizons and two independent angular momenta. The general solution contains seven independent parameters and provides the first example of nonuniqueness of supersymmetric black holes. In ten dimensions, the solutions can be realized as D1-D5-P black supertubes. We also present a worldvolume construction of a supertube that exhibits three dipoles explicitly. This description allows an arbitrary cross section but captures only one of the angular momenta.

[]

https://arxiv.org/pdf/hep-th/0408120.pdf

2019JHEP...12..156M

Observables and amplitudes for spinning particles and black holes

2019-01-01

['scattering', 'black hole physics', '-', '-']

[]

We develop a general formalism for computing classical observables for relativistic scattering of spinning particles, directly from on-shell amplitudes. We then apply this formalism to minimally coupled Einstein-gravity amplitudes for the scattering of massive spin 1/2 and spin 1 particles with a massive scalar, constructed using the double copy. In doing so we reproduce recent results at first post-Minkowskian order for the scattering of spinning black holes, through quadrupolar order in the spin-multipole expansion.

[]

https://arxiv.org/pdf/1906.09260.pdf

2019MNRAS.485..889S

Merging black hole binaries with the SEVN code

2019-01-01

['black hole physics', 'gravitational waves', 'methods numerical', 'stars binaries general', 'stars luminosity function;mass function', '-', '-', '-']

[]

Studying the formation and evolution of black hole binaries (BHBs) is essential for the interpretation of current and forthcoming gravitational wave (GW) detections. We investigate the statistics of BHBs that form from isolated binaries, by means of a new version of the SEVN population-synthesis code. SEVN integrates stellar evolution by interpolation over a grid of stellar evolution tracks. We upgraded SEVN to include binary stellar evolution processes and we used it to evolve a sample of 1.5 × 10<SUP>8</SUP> binary systems, with metallicity in the range [10<SUP>-4</SUP>; 4 × 10<SUP>-2</SUP>]. From our simulations, we find that the mass distribution of black holes (BHs) in double compact-object binaries is remarkably similar to the one obtained considering only single stellar evolution. The maximum BH mass we obtain is ∼30, 45, and 55 M_{⊙} at metallicity Z = 2 × 10<SUP>-2</SUP>, 6 × 10<SUP>-3</SUP>, and 10<SUP>-4</SUP>, respectively. A few massive single BHs may also form (≲ 0.1 per cent of the total number of BHs), with mass up to ∼65, 90, and 145 M_{⊙} at Z = 2 × 10<SUP>-2</SUP>, 6 × 10<SUP>-3</SUP>, and 10<SUP>-4</SUP>, respectively. These BHs fall in the mass gap predicted from pair-instability supernovae. We also show that the most massive BHBs are unlikely to merge within a Hubble time. In our simulations, merging BHs like GW151226 and GW170608, form at all metallicities, the high-mass systems (like GW150914, GW170814, and GW170104) originate from metal-poor (Z ≲ 6 × 10<SUP>-3</SUP>) progenitors, whereas GW170729-like systems are hard to form, even at Z = 10<SUP>-4</SUP>. The BHB merger rate in the local Universe obtained from our simulations is ∼90Gpc<SUP>-3</SUP>yr<SUP>-1</SUP>, consistent with the rate inferred from LIGO-Virgo data.

[]

https://arxiv.org/pdf/1809.04605.pdf

2015NatCo...6.7315C

High-quality sandwiched black phosphorus heterostructure and its quantum oscillations

2015-01-01

['-']

[]

Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices. The family of two-dimensional materials was recently joined by atomically thin black phosphorus which possesses high theoretical mobility and tunable bandgap structure. However, degradation of properties under atmospheric conditions and high-density charge traps in black phosphorus have largely limited its actual mobility thus hindering its future applications. Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ~1,350 cm<SUP>2</SUP>V<SUP>-1</SUP> s<SUP>-1</SUP> at room temperature and on-off ratios exceeding 10<SUP>5</SUP>. At low temperatures, the mobility even reaches ~2,700 cm<SUP>2</SUP>V<SUP>-1</SUP> s<SUP>-1</SUP> and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields. Importantly, the sandwiched heterostructures ensure that the quality of black phosphorus remains high under ambient conditions.

[]

https://arxiv.org/pdf/1412.1357.pdf

2014ApJ...784L..38M

Super-critical Growth of Massive Black Holes from Stellar-mass Seeds

2014-01-01

['accretion', 'accretion disks', 'black hole physics', 'cosmology miscellaneous', 'galaxies photometry', '-', '-']

[]

We consider super-critical accretion with angular momentum onto stellar-mass black holes as a possible mechanism for growing billion-solar-mass black holes from light seeds at early times. We use the radiatively inefficient "slim disk" solution—advective, optically thick flows that generalize the standard geometrically thin disk model—to show how mildly super-Eddington intermittent accretion may significantly ease the problem of assembling the first massive black holes when the universe was less than 0.8 Gyr old. Because of the low radiative efficiencies of slim disks around non-rotating as well as rapidly rotating black holes, the mass e-folding timescale in this regime is nearly independent of the spin parameter. The conditions that may lead to super-critical growth in the early universe are briefly discussed.

[]

https://arxiv.org/pdf/1402.6995.pdf

2013JHEP...04..156S

Logarithmic corrections to Schwarzschild and other non-extremal black hole entropy in different dimensions

2013-01-01

['black hole physics', 'black hole physics', '-', '-']

[]

Euclidean gravity method has been successful in computing logarithmic corrections to extremal black hole entropy in terms of low energy data, and gives results in perfect agreement with the microscopic results in string theory. Motivated by this success we apply Euclidean gravity to compute logarithmic corrections to the entropy of various non-extremal black holes in different dimensions, taking special care of integration over the zero modes and keeping track of the ensemble in which the computation is done. These results provide strong constraint on any ultraviolet completion of the theory if the latter is able to give an independent computation of the entropy of non-extremal black holes from microscopic description. For Schwarzschild black holes in four space-time dimensions the macroscopic result seems to disagree with the existing result in loop quantum gravity.

[]

https://arxiv.org/pdf/1205.0971.pdf

2005MNRAS.363L..91C

Supermassive black holes in elliptical galaxies: switching from very bright to very dim

2005-01-01

['galaxies active', 'galaxies jets', 'galaxies nuclei', 'astrophysics']

[]

Relativistic outflows (mainly observed in the radio) are a characteristic feature of both Galactic stellar-mass black holes and supermassive black holes (SMBHs). Simultaneous radio and X-ray observations of Galactic sources have shown that the outflow is strong at low accretion rates, but it weakens dramatically or disappears completely at high accretion rates, manifesting structural changes in the accretion flow. It is reasonable to assume that SMBHs follow the same trend. For low-luminosity SMBHs in nearby elliptical galaxies and clusters, recent observations strongly suggest that the outflows play the central role in keeping the gas hot (mechanical feedback). If the outflow is quenched in SMBHs at high accretion rates similarly to the behaviour of Galactic sources, then the straightforward consequence is a relatively weak feedback of rapidly accreting SMBHs. We argue that elliptical galaxies and their central engines should then evolve through two stages. Early on, the central SMBH rapidly grows by accreting cooling gas at a near-Eddington rate with high radiative efficiency but with weak feedback on the infalling gas. This stage terminates when the black hole has grown to a sufficiently large mass that its feedback (radiative and/or mechanical), despite the low gas heating efficiency, is able to suppress gas cooling. After that the system switches to a stable state corresponding to passively evolving ellipticals, when the accretion rate and radiative efficiency are very low, but the gas heating efficiency is high and energy input from the relativistic outflow keeps the gas hot.

[]

https://arxiv.org/pdf/astro-ph/0507073.pdf

2001ApJ...555..489O

A Black Hole in the Superluminal Source SAX J1819.3-2525 (V4641 Sgr)

2001-01-01

['stars binaries spectroscopic', 'black hole physics', '-', 'astronomy x rays', 'astrophysics']

[]

Spectroscopic observations of the fast X-ray transient and superluminal jet source SAX J1819.3-2525 (V4641 Sgr) reveal a best-fitting period of P<SUB>spect</SUB>=2.81678+/-0.00056 days and a semiamplitude of K<SUB>2</SUB>=211.0+/-3.1 km s<SUP>-1</SUP>. The optical mass function is f(M)=2.74+/-0.12 M<SUB>solar</SUB>. We find a photometric period of P<SUB>photo</SUB>=2.81730+/-0.00001 days using a light curve measured from photographic plates. The folded light curve resembles an ellipsoidal light curve with two maxima of roughly equal height and two minima of unequal depth per orbital cycle. The secondary star is a late B-type star that has evolved off the main sequence. Using a moderate resolution spectrum (R=7000) we measure T<SUB>eff</SUB>=10500+/-200 K, logg=3.5+/-0.1, and V<SUB>rot</SUB>sini=123+/-4 km s<SUP>-1</SUP> (1 σ errors). Assuming synchronous rotation, our measured value of the projected rotational velocity implies a mass ratio of Q≡M<SUB>1</SUB>/M<SUB>2</SUB>=1.50+/-0.08 (1 σ). The lack of X-ray eclipses implies an upper limit to the inclination of i&lt;=70.7d. On the other hand, the large amplitude of the folded light curve (~0.5 mag) implies a large inclination (i&gt;~60<SUP>deg</SUP>). Using the above mass function, mass ratio, and inclination range, the mass of the compact object is in the range 8.73&lt;=M<SUB>1</SUB>&lt;=11.70 M<SUB>solar</SUB> and the mass of the secondary star is in the range 5.49&lt;=M<SUB>2</SUB>&lt;=8.14 M<SUB>solar</SUB> (90% confidence). The mass of the compact object is well above the maximum mass of a stable neutron star, and we conclude that V4641 Sgr contains a black hole. The B-star secondary is by far the most massive, the hottest, and the most luminous secondary of the dynamically confirmed black hole X-ray transients. We find that the α-process elements nitrogen, oxygen, calcium, magnesium, and titanium may be overabundant in the secondary star by factors of 2-10 times with respect to the Sun. Finally, assuming E(B-V)=0.32+/-0.10, we find a distance 7.40&lt;=d&lt;=12.31 kpc (90% confidence). This large distance and the high proper motions observed for the radio counterpart make V4641 Sgr possibly the most superluminal galactic source known, with an apparent expansion velocity of &gt;~9.5c and a bulk Lorentz factor of Γ&gt;~9.5, assuming that the jets were ejected during one of the bright X-ray flares observed with the Rossi X-ray Timing Explorer. Based on observations collected at the European Southern Observatory, Chile (program 65.H-0360) and the William Herschel Telescope, operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

[]

https://arxiv.org/pdf/astro-ph/0103045.pdf

1999ApJ...520..276M

Black Hole and Neutron Star Transients in Quiescence

1999-01-01

['accretion', 'accretion disks', 'stars binaries close', 'black hole physics', 'stars magnetic fields', '-', 'astronomy x rays', 'accretion', 'accretion disks', 'stars binaries close', 'black hole physics', 'stars magnetic fields', '-', 'astronomy x rays', 'astrophysics', '-']

[]

We consider the X-ray luminosity difference between neutron star and black hole soft X-ray transients (NS and BH SXTs) in quiescence. The current observational data suggest that BH SXTs are significantly fainter than NS SXTs. The luminosities of quiescent BH SXTs are consistent with the predictions of binary-evolution models for the mass transfer rate if (1) accretion occurs via an advection-dominated accretion flow (ADAF) in these systems and (2) the accreting compact objects have event horizons. The luminosities of quiescent NS SXTs are not consistent with the predictions of ADAF models when combined with binary-evolution models, unless most of the mass accreted in the ADAF is prevented from reaching the neutron star surface. We consider the possibility that mass accretion is reduced in quiescent NS SXTs because of an efficient propeller and develop a model of the propeller effect that accounts for the observed luminosities. We argue that modest winds from ADAFs are consistent with the observations, while strong winds are probably not.

[]

https://arxiv.org/pdf/astro-ph/9810323.pdf

2006CQGra..23R.169E

TOPICAL REVIEW: Black rings

2006-01-01

['-', '-']

[]

A black ring is a five-dimensional black hole with an event horizon of topology S<SUP>1</SUP> × S<SUP>2</SUP>. We provide an introduction to the description of black rings in general relativity and string theory. Novel aspects of the presentation include a new approach to constructing black ring coordinates and a critical review of black ring microscopics.

[]

https://arxiv.org/pdf/hep-th/0608012.pdf

2005JHEP...09..034K

Microscopic black hole entropy in theories with higher derivatives

2005-01-01

['-', '-']

[]

We discuss higher derivative corrections to black hole entropy in theories that allow a near horizon AdS<SUB>3</SUB> × X geometry. In arbitrary theories with diffeomorphism invariance we show how to obtain the spacetime central charge in a simple way. Black hole entropy then follows from the euclidean partition function, and we show that this gives agreement with Wald's formula. In string theory there are certain diffeomorphism anomalies that we exploit. We thereby reproduce some recent computations of corrected entropy formulas, and extend them to the nonextremal, nonsupersymmetric context. Examples include black holes in M-theory on K3 × T<SUP>2</SUP>, whose entropy reproduces that of the perturbative heterotic string with both right and left movers excited and angular momentum included. Our anomaly based approach also sheds light on why exact results have been obtained in four dimensions while ignoring R<SUP>4</SUP> type corrections.

[]

https://arxiv.org/pdf/hep-th/0506176.pdf

2008ApJ...682...81S

The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei

2008-01-01

['galaxies active', 'galaxies nuclei', 'galaxies quasars', 'astronomy x rays', 'astrophysics']

[]

We study the hard X-ray spectral properties of 10 highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z = 1.3-3.2, including new XMM-Newton observations of four of these sources. We find a significant correlation between the normalized accretion rate (L/L<SUB>Edd</SUB>) and the hard X-ray photon index (Γ) for 35 moderate- to high-luminosity RQ AGNs, including our 10 highly luminous sources. Within the limits of our sample, we show that a measurement of Γ and L<SUB>X</SUB> can provide an estimate of L/L<SUB>Edd</SUB> and black hole mass (M<SUB>BH</SUB>) with a mean uncertainty of a factor of lesssim3 on the predicted values of these properties. This may provide a useful probe for tracing the history of BH growth in the universe, utilizing samples of X-ray-selected AGNs for which L/L<SUB>Edd</SUB> and M<SUB>BH</SUB> have not yet been determined systematically. It may prove to be a useful way to probe BH growth in distant Compton-thin type 2 AGNs. We also find that the optical-X-ray spectral slope (α<SUB>ox</SUB>) depends primarily on optical-UV luminosity rather than on L/L<SUB>Edd</SUB> in a sample of RQ AGNs spanning 5 orders of magnitude in luminosity and over 2 orders of magnitude in L/L<SUB>Edd</SUB>. We detect a significant Compton-reflection continuum in two of our highly luminous sources, and in the stacked X-ray spectrum of seven other sources with similar luminosities, we obtain a mean relative Compton reflection of R = 0.9<SUP>+ 0.6</SUP><SUB>-0.5</SUB> and an upper limit on the rest-frame equivalent width of a neutral Fe Kα line of 105 eV. We do not detect a significant steepening of the X-ray power-law spectrum below rest-frame 2 keV in any of our highly luminous sources, suggesting that a soft-excess feature, commonly observed in local AGNs, either does not depend strongly on L/L<SUB>Edd</SUB>, or is not accessible at high redshifts using current X-ray detectors.

[]

https://arxiv.org/pdf/0804.0803.pdf

2009ApJ...698.1367G

Luminous Thermal Flares from Quiescent Supermassive Black Holes

2009-01-01

['black hole physics', 'galaxies nuclei', 'astronomy uv', 'astronomy x rays', '-']

[]

A dormant supermassive black hole lurking in the center of a galaxy will be revealed when a star passes close enough to be torn apart by tidal forces, and a flare of electromagnetic radiation is emitted when the bound fraction of the stellar debris falls back onto the black hole and is accreted. Although the tidal disruption of a star is a rare event in a galaxy, ≈10<SUP>-4</SUP> yr<SUP>-1</SUP>, observational candidates have emerged in all-sky X-ray and deep ultraviolet (UV) surveys in the form of luminous UV/X-ray flares from otherwise quiescent galaxies. Here we present the third candidate tidal disruption event discovered in the Galaxy Evolution Explorer (GALEX) Deep Imaging Survey: a 1.6 × 10<SUP>43</SUP> erg s<SUP>-1</SUP> UV/optical flare from a star-forming galaxy at z = 0.1855. The UV/optical spectral energy distribution (SED) during the peak of the flare measured by GALEX and Palomar Large Field Camera imaging can be modeled as a single temperature blackbody with T <SUB>bb</SUB> = 1.7 × 10<SUP>5</SUP> K and a bolometric luminosity of 3 × 10<SUP>45</SUP> erg s<SUP>-1</SUP>, assuming an internal extinction with E(B - V)<SUB>gas</SUB> = 0.3. The Chandra upper limit on the X-ray luminosity during the peak of the flare, L<SUB>X</SUB> (2 - 10 keV)&lt;10<SUP>41</SUP> erg s<SUP>-1</SUP>, is 2 orders of magnitude fainter than expected from the ratios of UV to X-ray flux density observed in active galaxies. We compare the light curves and broadband properties of all three tidal disruption candidates discovered by GALEX, and find that (1) the light curves are well fitted by the power-law decline expected for the fallback of debris from a tidally disrupted solar-type star and (2) the UV/optical SEDs can be attributed to thermal emission from an envelope of debris located at roughly 10 times the tidal disruption radius of a ≈10<SUP>7</SUP> M <SUB>sun</SUB> central black hole. We use the observed peak absolute optical magnitudes of the flares (-17.5&gt;M<SUB>g</SUB> &gt; - 18.9) to predict the detection capabilities of upcoming optical synoptic surveys.

[]

https://arxiv.org/pdf/0904.1596.pdf

2012MNRAS.423.2533B

The evolution of massive black holes and their spins in their galactic hosts

2012-01-01

['black hole physics', 'gravitational waves', 'galaxies evolution', 'galaxies formation', '-', '-']

[]

Future space-based gravitational-wave detectors, such as the Laser Interferometer Space Antenna (LISA/SGO) or a similar European mission (eLISA/NGO), will measure the masses and spins of massive black holes up to very high redshift, and in principle discriminate among different models for their evolution. Because the masses and spins change as a result of both accretion from the interstellar medium and the black hole mergers that are expected to naturally occur in the hierarchical formation of galaxies, their evolution is inextricably entangled with that of their galactic hosts. On the one hand, the amount of gas present in galactic nuclei regulates the changes in the black hole masses and spins through accretion, and affects the mutual orientation of the spins before mergers by exerting gravitomagnetic torques on them. On the other hand, massive black holes play a central role in galaxy formation because of the feedback exerted by active galactic nuclei on the growth of structures. In this paper, we study the mass and spin evolution of massive black holes within a semi-analytical galaxy-formation model that follows the evolution of dark-matter haloes along merger trees, as well as that of the baryonic components (hot gas, stellar and gaseous bulges, and stellar and gaseous galactic discs). This allows us to study the mass and spin evolution in a self-consistent way, by taking into account the effect of the gas present in galactic nuclei both during the accretion phases and during mergers. Also, we present predictions, as a function of redshift, for the fraction of gas-rich black hole mergers - in which the spins prior to the merger are aligned due to the gravitomagnetic torques exerted by the circumbinary disc - as opposed to gas-poor mergers, in which the orientation of the spins before the merger is roughly isotropic. These predictions may be tested by LISA or similar spaced-based gravitational-wave detectors such as eLISA/NGO or SGO.

[]

https://arxiv.org/pdf/1201.5888.pdf

2010ApJ...710.1032A

New Limits on an Intermediate-Mass Black Hole in Omega Centauri. I. Hubble Space Telescope Photometry and Proper Motions

2010-01-01

['catalogs', 'clusters globular', 'clusters globular', 'stars kinematics and dynamics', 'techniques image processing', 'techniques photometric', '-', '-']

[]

We analyze data from the Hubble Space Telescope's (HST) Advanced Camera for Surveys of the globular cluster (GC) Omega Cen. We construct a photometric catalog of 1.2 × 10<SUP>6</SUP> stars over a 10' × 10' central field down to below B <SUB>F435W</SUB> = 25 (M ~ 0.35 M <SUB>sun</SUB>). The 2.5 to 4 year baseline between observations yields a catalog of some 10<SUP>5</SUP> proper motions over a smaller area, with 53,382 "high-quality" measurements in a central R &lt;~ 2' field. Artificial-star tests characterize the photometric incompleteness. We determine the cluster center to ~1'' accuracy from star counts using two different methods, one based on isodensity contours and the other on "pie slices." We independently confirm the result by determining also the kinematical center of the HST proper motions, as well as the center of unresolved light seen in Two Micron All Sky Survey data. All results agree to within their 1''-2'' levels of uncertainty. The proper-motion dispersion of the cluster increases gradually inward, but there is no variation in kinematics with position within the central ~15'': there is no dispersion cusp and no stars with unusually high velocities. We measure for the first time in any GC the variation in internal kinematics along the main sequence. The variation of proper-motion dispersion with mass shows that the cluster is not yet in equipartition. There are no differences in proper-motion kinematics between the different stellar populations of Omega Cen. Our results do not confirm the arguments put forward by Noyola, Gebhardt, and Bergmann to suspect an intermediate-mass black hole (IMBH) in Omega Cen. They determined line-of-sight velocity dispersions in two 5'' × 5'' fields, and reported higher motions in their central field. We find the proper-motion kinematics to be the same in both fields. Also, we find that they (as well as other previous studies) did not accurately identify the cluster center, so that both of their fields are in fact 12'' from the true center. We also do not confirm the central density cusp they reported (in part due to the different center, and in part due to biases induced by their use of unresolved light). The surface number-density distribution near the center does not differ strongly from a single-mass King model, although a shallow cusp may not be ruled out. In the companion paper, which is Paper II in this series, we present new dynamical models for the high-quality data presented here, with the aim of putting quantitative constraints on the mass of any possible IMBH. <P />Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

[]

https://arxiv.org/pdf/0905.0627.pdf

2019PhRvL.122n1302G

Abundance of Primordial Black Holes Depends on the Shape of the Inflationary Power Spectrum

2019-01-01

['-', '-', '-']

[]

In this Letter, combining peak theory and the numerical analysis of gravitational collapse in the radiation dominated era, we show that the abundance of primordial blacks holes, generated by an enhancement in the inflationary power spectrum, is extremely dependent on the shape of the peak. Given the amplitude of the power spectrum, we show that the density of primordial black holes generated from a narrow peak is exponentially smaller than in the case of a broad peak. Specifically, for a top-hat profile of the power spectrum in Fourier space, we find that to have primordial black holes comprising all of the dark matter, one would only need a power spectrum amplitude an order of magnitude smaller than suggested previously, whereas in the case of a narrow peak, one would instead need a much larger power spectrum amplitude, which in many cases would invalidate the perturbative analysis of cosmological perturbations. Finally, we show that, although critical collapse gives a broad mass spectrum, the density of primordial black holes formed is dominated by masses roughly equal to the cosmological horizon mass measured at horizon crossing.

[]

https://arxiv.org/pdf/1805.04087.pdf

1997ApJ...489..573L

Optical Appearance of the Debris of a Star Disrupted by a Massive Black Hole

1997-01-01

['black hole physics', 'galaxies nuclei', 'galaxies quasars', '-', 'astrophysics']

[]

We show that the disruption of a star by a ~10<SUP>6</SUP> M<SUB>⊙</SUB> black hole in a galactic nucleus could under favorable circumstances produce an optically thick envelope that radiates with a thermal spectrum at the Eddington limit, ~10<SUP>44</SUP> ergs s<SUP>-1</SUP>, for tens of years. The low apparent temperature of this envelope, ~10<SUP>4</SUP> K, would be easily detectable in optical surveys. If most galaxies harbor a massive black hole at their center, then the Sloan Digital Sky Survey might find hundreds of galaxies with nuclear activity of this type. Because the envelope is driven to shine near the Eddington limit, a measurement of the source redshift and total luminosity could yield the black hole mass.

[]

https://arxiv.org/pdf/astro-ph/9703079.pdf

1997PhRvD..55.7615B

Regular black holes and topology change

1997-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

The conditions are clarified under which regular (i.e., singularity-free) black holes can exist. It is shown that in a large class of spacetimes that satisfy the weak energy condition the existence of a regular black hole requires topology change.

[]

https://arxiv.org/pdf/gr-qc/9612057.pdf

2002PhRvD..65j4007H

Black holes and asymptotics of 2+1 gravity coupled to a scalar field

2002-01-01

['-', '-', '-', '-', 'methods analytical', '-', '-', '-']

[]

We consider 2+1 gravity minimally coupled to a self-interacting scalar field. The case in which the fall-off of the fields at infinity is slower than that of a localized distribution of matter is analyzed. It is found that the asymptotic symmetry group remains the same as in pure gravity (i.e., the conformal group). The generators of the asymptotic symmetries, however, acquire a contribution from the scalar field, but the algebra of the canonical generators possesses the standard central extension. In this context, new massive black hole solutions with a regular scalar field are found for a one-parameter family of potentials. These black holes are continuously connected to the standard zero mass black hole.

[]

https://arxiv.org/pdf/hep-th/0201170.pdf

2014SSRv..183..223C

Mass Measurements of Stellar and Intermediate-Mass Black Holes

2014-01-01

['black hole physics', 'astronomy x rays', 'accretion disks', '-', '-']

[]

We discuss the method, and potential systematic effects therein, used for measuring the mass of stellar-mass black holes in X-ray binaries. We restrict our discussion to the method that relies on the validity of Kepler's laws; we refer to this method as the dynamical method. We briefly discuss the implications of the mass distribution of stellar-mass black holes and provide an outlook for future measurements. Further, we investigate the evidence for the existence of intermediate-mass black holes i.e. black holes with masses above 100 M<SUB>⊙</SUB>, the limit to the black hole mass that can be produced by stellar evolution in the current Universe.

[]

https://arxiv.org/pdf/1311.5118.pdf

2006MNRAS.367..905B

Imaging optically-thin hotspots near the black hole horizon of Sgr A* at radio and near-infrared wavelengths

2006-01-01

['black hole physics', 'polarization', 'techniques interferometric', 'galaxy center', 'astronomy infrared', 'astronomy submillimeter', 'astrophysics']

[]

Submilliarcsecond astrometry and imaging of the black hole Sgr A* at the Galactic Centre may become possible in the near future at infrared and submillimetre wavelengths. Motivated by the observations of short-term infrared and X-ray variability of Sgr A*, in a previous paper, we computed the expected images and light curves, including polarization, associated with a compact emission region orbiting the central black hole. We extend this work, using a more realistic hotspot model and including the effects of opacity in the underlying accretion flow. We find that at infrared wavelengths, the qualitative features identified by our earlier work are present, namely it is possible to extract the black hole mass and spin from spot images and light curves of the observed flux and polarization. At radio wavelengths, disc opacity produces significant departures from the infrared behaviour, but there are still generic signatures of the black hole properties. Detailed comparison of these results with future data can be used to test general relativity and to improve existing models for the accretion flow in the immediate vicinity of the black hole.

[]

https://arxiv.org/pdf/astro-ph/0509237.pdf

2015CaJPh..93..999K

Black hole chemistry1

2015-01-01

['-', '-']

[]

The mass of a black hole has traditionally been identified with its energy. We describe a new perspective on black hole thermodynamics, one that identifies the mass of a black hole with chemical enthalpy, and the cosmological constant as thermodynamic pressure. This leads to an understanding of black holes from the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids, reentrant phase transitions, and triple points. Both charged and rotating black holes exhibit novel chemical-type phase behaviour, hitherto unseen.

[]

https://arxiv.org/pdf/1404.2126.pdf

2021PhRvD.104f5014B

Spinning black hole binary dynamics, scattering amplitudes, and effective field theory

2021-01-01

['-', '-', '-']

[]

We describe a systematic framework for finding the conservative potential of compact binary systems with spin based on scattering amplitudes of particles of arbitrary spin and effective field theory. An arbitrary-spin formalism is generally required in the classical limit. By matching the tree and one-loop amplitudes of four spinning particles with those of a suitably chosen effective field theory, we obtain the spin<SUB>1</SUB> -spin<SUB>2</SUB> terms of a two-body effective Hamiltonian through O (G<SUP>2</SUP>) and valid to all orders in velocity. Solving Hamilton's equations yields the impulse and spin changes of the individual bodies. We write them in a surprisingly compact form as appropriate derivatives of the eikonal phase obtained from the amplitude. It seems likely this structure persists to higher orders. We also point out various double-copy relations for general spin.

[]

https://arxiv.org/pdf/2005.03071.pdf

1993PhRvD..47.5370K

Cosmological multi-black-hole solutions

1993-01-01

['-', '-', '-', 'black hole physics', '-', '-']

[]

We present simple, analytic solutions to the Einstein-Maxwell equation, which describe an arbitrary number of charged black holes in a spacetime with a positive cosmological constant Λ. In the limit Λ=0, these solutions reduce to the well-known Majumdar-Papapetrou (MP) solutions. Like the MP solutions, each black hole in a Λ&gt;0 solution has charge Q equal to its mass M, up to a possible overall sign. Unlike the Λ=0 limit, however, solutions with Λ&gt;0 are highly dynamical. The black holes move with respect to one another, following natural trajectories in the background de Sitter spacetime. Black holes moving apart eventually go out of causal contact. Black holes on approaching trajectories ultimately merge. To our knowledge, these solutions give the first analytic description of coalescing black holes. Likewise, the thermodynamics of the Λ&gt;0 solutions is quite interesting. Taken individually, a ||Q||=M black hole is in thermal equilibrium with the background de Sitter Hawking radiation. With more than one black hole, because the solutions are not static, no global equilibrium temperature can be defined. In appropriate limits, however, when the black holes are either close together or far apart, approximate equilibrium states are established.

[]

https://arxiv.org/pdf/hep-th/9212035.pdf

2011PhRvD..83j4002Y

Nonspinning black holes in alternative theories of gravity

2011-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

We study two large classes of alternative theories, modifying the action through algebraic, quadratic curvature invariants coupled to scalar fields. We find one class that admits solutions that solve the vacuum Einstein equations and another that does not. In the latter, we find a deformation to the Schwarzschild metric that solves the modified field equations in the small-coupling approximation. We calculate the event horizon shift, the innermost stable circular orbit shift, and corrections to gravitational waves, mapping them to the parametrized post-Einsteinian framework.

[]

https://arxiv.org/pdf/1101.2921.pdf

2011PhRvD..83l4043B

Black holes in Einstein-aether and Hořava-Lifshitz gravity

2011-01-01

['-', '-', '-', '-', '-', '-', '-']

[]

We study spherical black hole solutions in Einstein-aether theory, a Lorentz-violating gravitational theory consisting of general relativity with a dynamical unit timelike vector (the “aether”) that defines a preferred timelike direction. These are also solutions to the infrared limit of Hořava-Lifshitz gravity. We explore parameter values of the two theories where all presently known experimental constraints are satisfied, and find that spherical black hole solutions of the type expected to form by gravitational collapse exist for all those parameters. Outside the metric horizon, the deviations away from the Schwarzschild metric are typically no more than a few percent for most of the explored parameter regions, which makes them difficult to observe with electromagnetic probes, but in principle within reach of future gravitational-wave detectors. Remarkably, we find that the solutions possess a universal horizon, not far inside the metric horizon, that traps waves of any speed relative to the aether. A notion of a black hole thus persists in these theories, even in the presence of arbitrarily high propagation speeds.

[]

https://arxiv.org/pdf/1104.2889.pdf

2000JHEP...01..021E

Exact description of black holes on branes II: comparison with BTZ black holes and black strings

2000-01-01

['-', '-']

[]

We extend our recent discussion of four-dimensional black holes bound to a two-brane to include a negative cosmological constant on the brane. We find that for large masses, the solutions are precisely BTZ black holes on the brane, and BTZ `black strings' in the bulk. For smaller masses, there are localized black holes which look like BTZ with corrections that fall off exponentially. We compute when the maximum entropy configuration changes from the black string to the black hole. We also present exact solutions describing rotating black holes on two-branes which are either asymptotically flat or asymptotically AdS<SUB>3</SUB>. The mass and angular momentum on the brane agree with that in the bulk.

[]

https://arxiv.org/pdf/hep-th/9912135.pdf

2012MNRAS.427.3103B

Accreting supermassive black holes in the COSMOS field and the connection to their host galaxies

2012-01-01

['-']

[]

Using the wide multi-band photometry available in the COSMOS field we explore the host galaxy properties of a large sample of Active Galactic Nuclei (AGN) obtained by combining X-ray and optical spectroscopic selections. Based on a careful study of their Spectral Energy Distribution (SED), which has been parametrized using a 2-component (AGN+galaxy) model fit, we derived dust-corrected rest-frame magnitudes, colors, stellar masses and star formation rates (SFRs). We find that AGN hosts span a large range of stellar masses and SFRs. No color-bimodality is seen at any redshift in the AGN hosts, which are found to be mainly massive, red galaxies. Once accounting for the color-mass degeneracy in well defined mass-matched samples, we find a residual marginal enhancement of AGN incidence in redder galaxies with lower specific star formation rates, and we argue that this result might emerge because of our ability to properly account for AGN light contamination and dust extinction. Interestingly, we find that the probability for a galaxy to host a black hole growing at any given "specific accretion rate" (i.e. the ratio of X-ray luminosity to the host stellar mass) is almost independent of the host galaxy mass, while it decreases as a power-law with Lx/M. By analyzing the normalization of such probability distribution, we show how the incidence of AGN increases with redshift as rapidly as (1+z)^4, in close resemblance with the overall evolution of the specific star formation rate of the entire galaxy population. Although AGN activity and star formation in galaxies do appear to have a common triggering mechanism, at least in a statistical sense, within the COSMOS sample we do not find strong evidence of any 'smoking gun' signaling powerful AGN influence on the star-forming properties of their hosts galaxies.

[]

https://arxiv.org/pdf/1209.1640.pdf

1997NewA....2..533Q

The dynamical evolution of massive black hole binaries — II. Self-consistent N-body integrations

1997-01-01

['astrophysics']

[]

We use a hybrid N-body program to study the evolution of massive black hole binaries in the centers of galaxies, mainly to understand the factors affecting the binary eccentricity, the response of the galaxy to the binary merger, and the effect of loss-cone depletion on the merger time. The scattering experiments from paper I (Quinlan, 1996)[NewA, 1, 35] showed that the merger time is not sensitive to the eccentricity growth unless a binary forms with at least a moderate eccentricity. We find here that the eccentricity can become large under some conditions if a binary forms in a galaxy with a flat core or with a radial bias in its velocity distribution, especially if the dynamical friction is enhanced by resonances as suggested by Rauch &amp; Tremaine (1996)[NewA, 1, 149]. But the necessary conditions seem unlikely, and our prediction from paper I remains unchanged: in most cases the eccentricity will start and remain small. The ejection of stars caused by the hardening of a binary may explain why large elliptical galaxies have weaker density cusps than smaller galaxies. If so, the central velocity distributions in those galaxies should have strong tangential anisotropies. The wandering of a binary from the center of a galaxy counteracts the effects of loss-cone depletion and helps the binary merge.

[]

https://arxiv.org/pdf/astro-ph/9706298.pdf

2011ApJ...742...85G

The Extreme Spin of the Black Hole in Cygnus X-1

2011-01-01

['accretion', 'accretion disks', 'black hole physics', '-', 'astronomy x rays', '-', '-', '-']

[]

The compact primary in the X-ray binary Cygnus X-1 was the first black hole to be established via dynamical observations. We have recently determined accurate values for its mass and distance, and for the orbital inclination angle of the binary. Building on these results, which are based on our favored (asynchronous) dynamical model, we have measured the radius of the inner edge of the black hole's accretion disk by fitting its thermal continuum spectrum to a fully relativistic model of a thin accretion disk. Assuming that the spin axis of the black hole is aligned with the orbital angular momentum vector, we have determined that Cygnus X-1 contains a near-extreme Kerr black hole with a spin parameter a <SUB>*</SUB> &gt; 0.95 (3σ). For a less probable (synchronous) dynamical model, we find a <SUB>*</SUB> &gt; 0.92 (3σ). In our analysis, we include the uncertainties in black hole mass, orbital inclination angle, and distance, and we also include the uncertainty in the calibration of the absolute flux via the Crab. These four sources of uncertainty totally dominate the error budget. The uncertainties introduced by the thin-disk model we employ are particularly small in this case given the extreme spin of the black hole and the disk's low luminosity.

[]

https://arxiv.org/pdf/1106.3690.pdf

2019PhRvD..99f4045V

Surrogate model of hybridized numerical relativity binary black hole waveforms

2019-01-01

['-']

[]

Numerical relativity (NR) simulations provide the most accurate binary black hole gravitational waveforms, but are prohibitively expensive for applications such as parameter estimation. Surrogate models of NR waveforms have been shown to be both fast and accurate. However, NR-based surrogate models are limited by the training waveforms' length, which is typically about 20 orbits before merger. We remedy this by hybridizing the NR waveforms using both post-Newtonian and effective one-body waveforms for the early inspiral. We present NRHybSur3dq8, a surrogate model for hybridized nonprecessing numerical relativity waveforms, that is valid for the entire LIGO band (starting at 20 Hz) for stellar mass binaries with total masses as low as 2.25 M<SUB>⊙</SUB>. We include the ℓ≤4 and (5, 5) spin-weighted spherical harmonic modes but not the (4, 1) or (4, 0) modes. This model has been trained against hybridized waveforms based on 104 NR waveforms with mass ratios q ≤8 , and |χ<SUB>1 z</SUB>|,|χ<SUB>2 z</SUB>|≤0.8 , where χ<SUB>1 z</SUB> (χ<SUB>2 z</SUB>) is the spin of the heavier (lighter) black hole in the direction of orbital angular momentum. The surrogate reproduces the hybrid waveforms accurately, with mismatches ≲3 ×10<SUP>-4</SUP> over the mass range 2.25 M<SUB>⊙</SUB>≤M ≤300 M<SUB>⊙</SUB>. At high masses (M ≳40 M<SUB>⊙</SUB>), where the merger and ringdown are more prominent, we show roughly 2 orders of magnitude improvement over existing waveform models. We also show that the surrogate works well even when extrapolated outside its training parameter space range, including at spins as large as 0.998. Finally, we show that this model accurately reproduces the spheroidal-spherical mode mixing present in the NR ringdown signal.

[]

https://arxiv.org/pdf/1812.07865.pdf

2016JCAP...12..031G

Gravitational waves at interferometer scales and primordial black holes in axion inflation

2016-01-01

['-', '-', '-', '-']

[]

We study the prospects of detection at terrestrial and space interferometers, as well as at pulsar timing array experiments, of a stochastic gravitational wave background which can be produced in models of axion inflation. This potential signal, and the development of these experiments, open a new window on inflation on scales much smaller than those currently probed with Cosmic Microwave Background and Large Scale Structure measurements. The sourced signal generated in axion inflation is an ideal candidate for such searches, since it naturally grows at small scales, and it has specific properties (chirality and non-gaussianity) that can distinguish it from an astrophysical background. We study under which conditions such a signal can be produced at an observable level, without the simultaneous overproduction of scalar perturbations in excess of what is allowed by the primordial black hole limits. We also explore the possibility that scalar perturbations generated in a modified version of this model may provide a distribution of primordial black holes compatible with the current bounds, that can act as a seeds of the present black holes in the universe.

[]

https://arxiv.org/pdf/1610.03763.pdf

2009ApJ...697..900M

Stellar-Mass Black Hole Spin Constraints from Disk Reflection and Continuum Modeling

2009-01-01

['black hole physics', 'stars novae;cataclysmic variables', 'astronomy x rays', '-', '-']

[]

Accretion disk reflection spectra, including broad iron emission lines, bear the imprints of the strong Doppler shifts and gravitational redshifts close to black holes. The extremity of these shifts depends on the proximity of the innermost stable circular orbit to the black hole, and that orbit is determined by the black hole spin parameter. Modeling relativistic spectral features, then, gives a means of estimating black hole spin. We report on the results of fits made to archival X-ray spectra of stellar-mass black holes and black hole candidates, selected for strong disk reflection features. Following recent work, these spectra were fit with reflection models and disk continuum emission models (where required) in which black hole spin is a free parameter. Although our results must be regarded as preliminary, we find evidence for a broad range of black hole spin parameters in our sample. The black holes with the most relativistic radio jets are found to have high spin parameters, though jets are observed in a black hole with a low spin parameter. For those sources with constrained binary system parameters, we examine the distribution of spin parameters versus black hole mass, binary mass ratio, and orbital period. We discuss the results within the context of black hole creation events, relativistic jet production, and efforts to probe the innermost relativistic regime around black holes.

[]

https://arxiv.org/pdf/0902.2840.pdf

2019PhRvD..99d4001B

Probing ultralight bosons with binary black holes

2019-01-01

['-', '-', '-', '-', '-']

[]

We study the gravitational-wave (GW) signatures of clouds of ultralight bosons around black holes (BHs) in binary inspirals. These clouds, which are formed via superradiance instabilities for rapidly rotating BHs, produce distinct effects in the population of BH masses and spins, and a continuous monochromatic GW signal. We show that the presence of a binary companion greatly enriches the dynamical evolution of the system, most remarkably through the existence of resonant transitions between the growing and decaying modes of the cloud (analogous to Rabi oscillations in atomic physics). These resonances have rich phenomenological implications for current and future GW detectors. Notably, the amplitude of the GW signal from the clouds may be reduced, and in many cases terminated, much before the binary merger. The presence of a boson cloud can also be revealed in the GW signal from the binary through the imprint of finite-size effects, such as spin-induced multipole moments and tidal Love numbers. The time dependence of the cloud's energy density during the resonance leads to a sharp feature, or at least attenuation, in the contribution from the finite-size terms to the waveforms. The observation of these effects would constrain the properties of putative ultralight bosons through precision GW data, offering new probes of physics beyond the Standard Model.

[]

https://arxiv.org/pdf/1804.03208.pdf

2019JHEP...04..156C

The simplest massive S-matrix: from minimal coupling to black holes

2019-01-01

['black hole physics', '-', 'scattering', '-', '-']

[]

In this paper, we explore the physics of electromagnetically and gravitationally coupled massive higher spin states from the on-shell point of view. Starting with the three-point amplitude, we focus on the simplest amplitude characterized by matching to minimal coupling in the UV. In the IR, for charged states this leads to g = 2 for arbitrary spin, and the leading deformation corresponds to the anomalous magnetic dipole moment. We proceed to construct the (gravitational) Compton amplitude for generic spins via consistent factorization. We find that in gravitation couplings, the leading deformation leads to inconsistent factorization. This implies that for systems with Gauge<SUP>2</SUP> = Gravity relations, such as perturbative string theory, all charged states must have g = 2. It is then natural to ask for generic spin, what is the theory that yields such minimal coupling. By matching to the one body effective action, we verify that for large spins the answer is Kerr black holes. This identification is then an on-shell avatar of the no- hair theorem. Finally using this identification as well as the newly constructed Compton amplitudes, we proceed to compute the spin-dependent pieces for the classical potential at 2PM order up to degree four in spin operator of either black holes.

[]

https://arxiv.org/pdf/1812.08752.pdf

1997gr.qc.....7012T

Black Holes

1997-01-01

['-']

[]

Lecture notes for a 'Part III' course 'Black Holes' given in DAMTP, Cambridge. The course covers some of the developments in Black Hole physics of the 1960s and 1970s.

[]

https://arxiv.org/pdf/gr-qc/9707012.pdf

2014ApJ...796....2R

A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass

2014-01-01

['astrometry', 'black hole physics', '-', '-', 'astronomy x rays', '-', '-']

[]

Using the Very Long Baseline Array, we have measured a trigonometric parallax for the microquasar GRS 1915+105, which contains a black hole and a K-giant companion. This yields a direct distance estimate of 8.6<SUP>+2.0</SUP><SUB>{-</SUB>1.6} kpc and a revised estimate for the mass of the black hole of 12.4<SUP>+2.0</SUP><SUB>-1.8</SUB> M <SUB>⊙</SUB>. GRS 1915+105 is at about the same distance as some H II regions and water masers associated with high-mass star formation in the Sagittarius spiral arm of the Galaxy. The absolute proper motion of GRS 1915+105 is -3.19 ± 0.03 mas yr<SUP>-1</SUP> and -6.24 ± 0.05 mas yr<SUP>-1</SUP> toward the east and north, respectively, which corresponds to a modest peculiar speed of 22 ± 24 km s<SUP>-1</SUP> at the parallax distance, suggesting that the binary did not receive a large velocity kick when the black hole formed. On one observational epoch, GRS 1915+105 displayed superluminal motion along the direction of its approaching jet. Considering previous observations of jet motions, the jet in GRS 1915+105 can be modeled with a jet inclination to the line of sight of 60° ± 5° and a variable flow speed between 0.65c and 0.81c, which possibly indicates deceleration of the jet at distances from the black hole &gt;~ 2000 AU. Finally, using our measurements of distance and estimates of black hole mass and inclination, we provisionally confirm our earlier result that the black hole is spinning very rapidly.

[]

https://arxiv.org/pdf/1409.2453.pdf

2006PhRvD..74j4005B

Transition from inspiral to plunge in precessing binaries of spinning black holes

2006-01-01

['-', '-', '-', '-', 'waves', '-', 'perturbation theory', '-', '-', '-', '-']

[]

We investigate the nonadiabatic dynamics of spinning black-hole binaries by using an analytical Hamiltonian completed with a radiation-reaction force, containing spin couplings, which matches the known rates of energy and angular-momentum losses on quasicircular orbits. We consider both a straightforward post-Newtonian-expanded Hamiltonian (including spin-dependent terms), and a version of the resummed post-Newtonian Hamiltonian defined by the effective one-body approach. We focus on the influence spin terms have on the dynamics and waveforms. We evaluate the energy and angular momentum released during the final stage of inspiral and plunge. For an equal-mass binary the energy released between 40 Hz and the frequency beyond which our analytical treatment becomes unreliable is found to be, when using the effective one-body dynamics, 0.6%M for antialigned maximally spinning black holes, 5%M for aligned maximally spinning black holes, and 1.8%M for nonspinning configurations. In confirmation of previous results, we find that, for all binaries considered, the dimensionless rotation parameter J/E<SUP>2</SUP> is always smaller than unity at the end of the inspiral, so that a Kerr black hole can form right after the inspiral phase. By matching a quasinormal mode ring down to the last reliable stages of the plunge, we construct complete waveforms approximately describing the gravitational-wave signal emitted by the entire process of coalescence of precessing binaries of spinning black holes.

[]

https://arxiv.org/pdf/gr-qc/0508067.pdf

2014PhRvD..89h4050A

Asymptotically locally AdS and flat black holes in Horndeski theory

2014-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

In this paper we construct asymptotically locally AdS and flat black holes in the presence of a scalar field whose kinetic term is constructed out from a linear combination of the metric and the Einstein tensor. The field equations as well as the energy-momentum tensor are second order in the metric and the field, therefore the theory belongs to the ones defined by Horndeski. We show that in the presence of a cosmological term in the action, it is possible to have a real scalar field in the region outside the event horizon. The solutions are characterized by a single integration constant, the scalar field vanishes at the horizon and it contributes to the effective cosmological constant at infinity. We extend these results to the topological case. The solution is disconnected from the maximally symmetric AdS background, however, within this family there exists a gravitational soliton which is everywhere regular. This soliton is therefore used as a background to define a finite Euclidean action and to obtain the thermodynamics of the black holes. For a certain region in the space of parameters, the thermodynamic analysis reveals a critical temperature at which a Hawking-Page phase transition between the black hole and the soliton occurs. We extend the solution to arbitrary dimensions greater than 4 and show that the presence of a cosmological term in the action allows one to consider the case in which the standard kinetic term for the scalar it is not present. In such a scenario, the solution reduces to an asymptotically flat black hole.

[]

https://arxiv.org/pdf/1312.3597.pdf

2011ApJ...741L..33B

Black Hole Growth and Active Galactic Nuclei Obscuration by Instability-driven Inflows in High-redshift Disk Galaxies Fed by Cold Streams

2011-01-01

['galaxies active', 'galaxies formation', 'galaxies photometry', 'galaxies nuclei', 'astronomy x rays', '-']

[]

Disk galaxies at high redshift have been predicted to maintain high gas surface densities due to continuous feeding by intense cold streams leading to violent gravitational instability, transient features, and giant clumps. Gravitational torques between the perturbations drive angular momentum out and mass in, and the inflow provides the energy for keeping strong turbulence. We use analytic estimates of the inflow for a self-regulated unstable disk at a Toomre stability parameter Q ~ 1, and isolated galaxy simulations capable of resolving the nuclear inflow down to the central parsec. We predict an average inflow rate ~10 M <SUB>sun</SUB> yr<SUP>-1</SUP> through the disk of a 10<SUP>11</SUP> M <SUB>sun</SUB> galaxy, with conditions representative of z ~ 2 stream-fed disks. The inflow rate scales with disk mass and (1 + z)<SUP>3/2</SUP>. It includes clump migration and inflow of the smoother component, valid even if clumps disrupt. This inflow grows the bulge, while only a fraction of &gt;~ 10<SUP>-3</SUP> of it needs to accrete onto a central black hole (BH), in order to obey the observed BH-bulge relation. A galaxy of 10<SUP>11</SUP> M <SUB>sun</SUB> at z ~ 2 is expected to host a BH of ~10<SUP>8</SUP> M <SUB>sun</SUB>, accreting on average with moderate sub-Eddington luminosity L <SUB>X</SUB> ~ 10<SUP>42</SUP>-10<SUP>43</SUP> erg s<SUP>-1</SUP>, accompanied by brighter episodes when dense clumps coalesce. We note that in rare massive galaxies at z ~ 6, the same process may feed ~10<SUP>9</SUP> M <SUB>sun</SUB> BH at the Eddington rate. High central gas column densities can severely obscure active galactic nuclei in high-redshift disks, possibly hindering their detection in deep X-ray surveys.

[]

https://arxiv.org/pdf/1107.1483.pdf

2018ApJ...863L..41F

Does the Black Hole Merger Rate Evolve with Redshift?

2018-01-01

['stars binaries general', 'gravitational waves', 'methods data analysis', 'stars black holes', '-', '-', '-']

[]

We explore the ability of gravitational-wave detectors to extract the redshift distribution of binary black hole (BBH) mergers. The evolution of the merger rate across redshifts 0 &lt; z ≲ 1 is directly tied to the formation and evolutionary processes, providing insight regarding the progenitor formation rate together with the distribution of time delays between formation and merger. Because the limiting distance to which BBHs are detected depends on the masses of the binary, the redshift distribution of detected binaries depends on their underlying mass distribution. We therefore consider the mass and redshift distributions simultaneously, and fit the merger rate density, dN/dm <SUB>1</SUB> dm <SUB>2</SUB> dz. Our constraints on the mass distribution agree with previously published results, including evidence for an upper mass cutoff at ∼40 M <SUB>⊙</SUB>. Additionally, we show that the current set of six BBH detections are consistent with a merger rate density that is uniform in comoving volume. Although our constraints on the redshift distribution are not yet tight enough to distinguish between BBH formation channels, we show that it will be possible to distinguish between different astrophysically motivated models of the merger rate evolution with ∼100-300 Laser Interferometer Gravitational-Wave Observatory/Virgo detections (to be expected within 2-5 years). Specifically, we will be able to infer whether the formation rate peaks at higher or lower redshifts than the star formation rate, or the typical time delay between formation and merger. Meanwhile, with ∼100 detections, the inferred redshift distribution will place constraints on more exotic scenarios such as modified gravity.

[]

https://arxiv.org/pdf/1805.10270.pdf

1994PhRvL..72.3297P

Colliding black holes: The close limit

1994-01-01

['-', '-', '-', 'waves', 'methods numerical', '-', '-', 'astrophysics']

[]

The problem of the mutual attraction and joining of two black holes is of importance as both a source of gravitational waves and as a testbed of numerical relativity. If the holes start out close enough that they are initially surrounded by a common horizon, the problem can be viewed as a perturbation of a single black hole. We take initial data due to Misner for close black holes, apply perturbation theory, and evolve the data with the Zerilli equation. The computed gravitational radiation agrees with and extends the results of full numerical computations.

[]

https://arxiv.org/pdf/gr-qc/9402039.pdf

1995ApJ...446..543R

Ultra--Low-Frequency Gravitational Radiation from Massive Black Hole Binaries

1995-01-01

['black hole physics', 'galaxies interactions', 'galaxies nuclei', 'radiation', 'astrophysics']

[]

For massive black hole binaries produced in galactic mergers, we examine the possibility of inspiral induced by interaction with field stars. We model the evolution of such binaries for a range of galaxy core and binary parameters, using numerical results from the literature to compute the binary's energy and angular momentum loss rates due to stellar encounters and including the effect of back-action on the field stars. We find that only a small fraction of binary systems can merge within a Hubble time via unassisted stellar dynamics. External perturbations may, however, cause efficient inspiral. Averaging over a population of central black holes and galaxy mergers, we computed the expected background of gravitational radiation with periods P<SUB>w</SUB> ∼ 1-10 yr. Comparison with sensitivities from millisecond pulsar timing suggests that the strongest sources may be detectable with modest improvements to present experiments.

[]

https://arxiv.org/pdf/astro-ph/9412038.pdf

1995ApJ...443L..61C

Unified Description of Accretion Flows around Black Holes

1995-01-01

['accretion disks', 'hydrodynamics', 'black hole physics', 'astronomy visual', 'radiative transfer', '-', 'thermodynamics', 'radiative transfer', 'steady state', 'methods analytical', 'variability', '-', 'accretion', 'accretion disks', 'instabilities', 'astrophysics']

[]

We provide a unified description of thermal equilibria of black hole accretion disks, including the newly-discovered advection-dominated solutions. We classify the solutions on the basis of optical depth and importance of advection cooling. We demonstrate that only four physically distinct topological types of equilibria exist. Two of the types correspond to optically thin and optically thick equilibria, while the other two types are distinguished by whether advection is negligible or dominant. A stable Shakura-Sunyaev disk exists only for accretion rates $\dot M$ below a certain maximum. However, there is a critical viscosity parameter $\alpha_{\rm crit}$, which is a function of radius, such that for $\alpha&gt;\alpha_{\rm crit}$ advection-dominated solutions exist for all $\dot M$. Even when $\alpha&lt; \alpha_{\rm crit}$, the advection-dominated solutions are available for a wide range of $\dot M$ except for a gap around the Eddington rate. We therefore suggest that advection-dominated flows may be more common than standard thin disks in black hole systems. For certain ranges of radii and $\dot M$, no stable steady state solution is possible. In these cases, we suggest that limit cycle behavior may occur, leading to variability.

[]

https://arxiv.org/pdf/astro-ph/9502015.pdf

1994PhRvD..50.3987F

Black hole thermodynamics and information loss in two dimensions

1994-01-01

['-', '-', '-', '-', '-', '-', '-']

[]

Black hole evaporation is investigated in a (1+1)-dimensional model of quantum gravity. Quantum corrections to the black hole entropy are computed, and the fine-grained entropy of the Hawking radiation is studied. A generalized second law of thermodynamics is formulated, and shown to be valid under suitable conditions. It is also shown that, in this model, a black hole can consume an arbitrarily large amount of information.

[]

https://arxiv.org/pdf/hep-th/9403137.pdf

2008CQGra..25s5023H

Higher-dimensional charged black hole solutions with a nonlinear electrodynamics source

2008-01-01

['-']

[]

We obtain electrically charged black hole solutions of the Einstein equations in arbitrary dimensions with a nonlinear electrodynamics source. The matter source is derived from a Lagrangian given by an arbitrary power of the Maxwell invariant. The form of the general solution suggests a natural partition for the different ranges of this power. For a particular range, we exhibit a class of solutions whose behavior resembles the standard Reissner Nordström black holes. There also exists a range for which the black hole solutions approach asymptotically the Minkowski spacetime slower than the Schwarzschild spacetime. We have also found a family of non-asymptotical flat black hole solutions with an asymptotic behavior growing slower than the Schwarzschild (anti)-de Sitter spacetime. In odd dimensions, there exists a critical value of the exponent for which the metric involves a logarithmic dependence. This critical value corresponds to the transition between the standard behavior and the solution decaying to Minkowski slower than the Schwarzschild spacetime.

[]

https://arxiv.org/pdf/0803.2946.pdf

2005Natur.434..738A

Rapid growth of black holes in massive star-forming galaxies

2005-01-01

['astrophysics']

[]

The tight relationship between the masses of black holes and galaxy spheroids in nearby galaxies implies a causal connection between the growth of these two components. Optically luminous quasars host the most prodigious accreting black holes in the Universe, and can account for ≳30 per cent of the total cosmological black-hole growth. As typical quasars are not, however, undergoing intense star formation and already host massive black holes (&gt; 10<SUP>8</SUP>M<SUB>solar</SUB>, where M<SUB>solar</SUB> is the solar mass), there must have been an earlier pre-quasar phase when these black holes grew (mass range ~(10<SUP>6</SUP>-10<SUP>8</SUP>)M<SUB>solar</SUB>). The likely signature of this earlier stage is simultaneous black-hole growth and star formation in distant (redshift z &gt; 1; &gt;8 billion light years away) luminous galaxies. Here we report ultra-deep X-ray observations of distant star-forming galaxies that are bright at submillimetre wavelengths. We find that the black holes in these galaxies are growing almost continuously throughout periods of intense star formation. This activity appears to be more tightly associated with these galaxies than any other coeval galaxy populations. We show that the black-hole growth from these galaxies is consistent with that expected for the pre-quasar phase.

[]

https://arxiv.org/pdf/astro-ph/0503453.pdf

2015ApJ...801...90P

The Landscape of the Neutrino Mechanism of Core-collapse Supernovae: Neutron Star and Black Hole Mass Functions, Explosion Energies, and Nickel Yields

2015-01-01

['shock waves', 'stars black holes', '-', 'stars novae;cataclysmic variables', '-']

[]

If the neutrino luminosity from the proto-neutron star formed during a massive star core collapse exceeds a critical threshold, a supernova (SN) results. Using spherical quasi-static evolutionary sequences for hundreds of progenitors over a range of metallicities, we study how the explosion threshold maps onto observables, including the fraction of successful explosions, the neutron star (NS) and black hole (BH) mass functions, the explosion energies (E <SUB>SN</SUB>) and nickel yields (M <SUB>Ni</SUB>), and their mutual correlations. Successful explosions are intertwined with failures in a complex pattern that is not simply related to initial progenitor mass or compactness. We predict that progenitors with initial masses of 15 ± 1, 19 ± 1, and ~21-26 M <SUB>⊙</SUB> are most likely to form BHs, that the BH formation probability is non-zero at solar-metallicity and increases significantly at low metallicity, and that low luminosity, low Ni-yield SNe come from progenitors close to success/failure interfaces. We qualitatively reproduce the observed E <SUB>SN</SUB>-M <SUB>Ni</SUB> correlation, we predict a correlation between the mean and width of the NS mass and E <SUB>SN</SUB> distributions, and that the means of the NS and BH mass distributions are correlated. We show that the observed mean NS mass of ~= 1.33 M <SUB>⊙</SUB> implies that the successful explosion fraction is higher than 0.35. Overall, we show that the neutrino mechanism can in principle explain the observed properties of SNe and their compact objects. We argue that the rugged landscape of progenitors and outcomes mandates that SN theory should focus on reproducing the wide ranging distributions of observed SN properties.

[]

https://arxiv.org/pdf/1409.0540.pdf

1998ApJ...500..899G

Gamma-Ray Spectral States of Galactic Black Hole Candidates

1998-01-01

['stars binaries close', 'black hole physics', 'gamma rays', 'radiation', 'astronomy x rays', 'stars binaries close', 'black hole physics', 'gamma rays', 'radiation', 'astronomy x rays', 'astrophysics']

[]

OSSE has observed seven transient black hole candidates: GRO J0422+32, GX 339-4, GRS 1716-249, GRS 1009-45, 4U 1543-47, GRO J1655-40, and GRS 1915+105. Two gamma-ray spectral states are evident, and based on a limited number of contemporaneous X-ray and gamma-ray observations, these states appear to be correlated with X-ray states. The former three objects show hard spectra below 100 keV (photon number indices Γ &lt; 2) that are exponentially cut off with folding energy ~100 keV, a spectral form that is consistent with thermal Comptonization. This ``breaking gamma-ray state'' is the high-energy extension of the X-ray low, hard state. In this state, the majority of the luminosity is above the X-ray band, carried by photons of energy ~100 keV. The latter four objects exhibit a ``power-law gamma-ray state,'' with a relatively soft spectral index (Γ ~ 2.5-3) and no evidence for a spectral break. For GRO J1655-40, the lower limit on the break energy is 690 keV. GRS 1716-249 exhibits both spectral states, with the power-law state having significantly lower gamma-ray luminosity. The power-law gamma-ray state is associated with the presence of a strong ultrasoft X-ray excess (kT ~ 1 keV), the signature of the X-ray high, soft (or perhaps very high) state. The physical process responsible for the unbroken power law is not well understood, although the spectra are consistent with bulk-motion Comptonization in the convergent accretion flow.

[]

https://arxiv.org/pdf/astro-ph/9802242.pdf

2014JHEP...11..081D

Thermoelectric DC conductivities from black hole horizons

2014-01-01

['-', 'black hole physics', '-', '-', '-', '-']

[]

An analytic expression for the DC electrical conductivity in terms of black hole horizon data was recently obtained for a class of holographic black holes exhibiting momentum dissipation. We generalise this result to obtain analogous expressions for the DC thermoelectric and thermal conductivities. We illustrate our results using some holographic Q-lattice black holes as well as for some black holes with linear massless axions, in both D = 4 and D = 5 bulk spacetime dimensions, which include both spatially isotropic and anisotropic examples. We show that some recently constructed ground states of holographic Q-lattices, which can be either electrically insulating or metallic, are all thermal insulators.

[]

https://arxiv.org/pdf/1406.4742.pdf

2013PhRvD..88d4002J

Regular black hole metric with three constants of motion

2013-01-01

['-', '-', '-', '-', '-', '-']

[]

According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric spacetimes that deviate from the Kerr metric have been proposed in order to test this theorem with observations of black holes in both the electromagnetic and gravitational-wave spectra. Such metrics often contain naked singularities or closed timelike curves in the vicinity of the compact objects, which can limit the applicability of the metrics to compact objects that do not spin rapidly, and generally admit only two constants of motion. The existence of a third constant, however, can facilitate the calculation of observables, because the equations of motion can be written in first-order form. In this paper, I design a Kerr-like black hole metric which is regular everywhere outside of the event horizon, possesses three independent constants of motion, and depends nonlinearly on four free functions that parametrize potential deviations from the Kerr metric. This metric is generally not a solution to the field equations of any particular gravity theory, but can be mapped to known four-dimensional black hole solutions of modified theories of gravity for suitable choices of the deviation functions. I derive expressions for the energy, angular momentum, and epicyclic frequencies of a particle on a circular equatorial orbit around the black hole and compute the location of the innermost stable circular orbit. In addition, I write the metric in a Kerr-Schild-like form, which allows for a straightforward implementation of fully relativistic magnetohydrodynamic simulations of accretion flows in this metric. The properties of this metric make it a well-suited spacetime for strong-field tests of the no-hair theorem in the electromagnetic spectrum with black holes of arbitrary spin.

[]

https://arxiv.org/pdf/1501.02809.pdf

2018ApJ...856..173T

Measuring the Binary Black Hole Mass Spectrum with an Astrophysically Motivated Parameterization

2018-01-01

['stars binaries general', 'gravitational waves', 'stars black holes', '-', '-']

[]

Gravitational-wave detections have revealed a previously unknown population of stellar mass black holes with masses above 20 M <SUB>⊙</SUB>. These observations provide a new way to test models of stellar evolution for massive stars. By considering the astrophysical processes likely to determine the shape of the binary black hole mass spectrum, we construct a parameterized model to capture key spectral features that relate gravitational-wave data to theoretical stellar astrophysics. In particular, we model the signature of pulsational pair-instability supernovae, which are expected to cause all stars with initial mass 100 M <SUB>⊙</SUB> ≲ M ≲ 150 M <SUB>⊙</SUB> to form ∼40 M <SUB>⊙</SUB> black holes. This would cause a cutoff in the black hole mass spectrum along with an excess of black holes near 40 M <SUB>⊙</SUB>. We carry out a simulated data study to illustrate some of the stellar physics that can be inferred using gravitational-wave measurements of binary black holes and demonstrate several such inferences that might be made in the near future. First, we measure the minimum and maximum stellar black hole mass. Second, we infer the presence of a peak due to pair-instability supernovae. Third, we measure the distribution of black hole mass ratios. Finally, we show how inadequate models of the black hole mass spectrum lead to biased estimates of the merger rate and the amplitude of the stochastic gravitational-wave background.

[]

https://arxiv.org/pdf/1801.02699.pdf

2020A&A...635A..97B

The origin of spin in binary black holes. Predicting the distributions of the main observables of Advanced LIGO

2020-01-01

['stars black holes', 'gravitational waves', 'stars binaries close', 'black hole physics', '-']

[]

Context. After years of scientific progress, the origin of stellar binary black holes is still a great mystery. Several formation channels for merging black holes have been proposed in the literature. As more merger detections are expected with future gravitational-wave observations, population synthesis studies can help to distinguish between them. <BR /> Aims: We study the formation of coalescing binary black holes via the evolution of isolated field binaries that go through the common envelope phase in order to obtain the combined distributions of observables such as black-hole spins, masses and cosmological redshifts of mergers. <BR /> Methods: To achieve this aim, we used a hybrid technique that combines the parametric binary population synthesis code COMPAS with detailed binary evolution simulations performed with the MESA code. We then convolved our binary evolution calculations with the redshift- and metallicity-dependent star-formation rate and the selection effects of gravitational-wave detectors to obtain predictions of observable properties. <BR /> Results: By assuming efficient angular momentum transport, we are able to present a model that is capable of simultaneously predicting the following three main gravitational-wave observables: the effective inspiral spin parameter χ<SUB>eff</SUB>, the chirp mass M<SUB>chirp</SUB> and the cosmological redshift of merger z<SUB>merger</SUB>. We find an excellent agreement between our model and the ten events from the first two advanced detector observing runs. We make predictions for the third observing run O3 and for Advanced LIGO design sensitivity. We expect approximately 80% of events with χ<SUB>eff</SUB> &lt; 0.1, while the remaining 20% of events with χ<SUB>eff</SUB> ≥ 0.1 are split into ∼10% with M<SUB>chirp</SUB> &lt; 15 M<SUB>⊙</SUB> and ∼10% with M<SUB>chirp</SUB> ≥ 15 M<SUB>⊙</SUB>. Moreover, we find that M<SUB>chirp</SUB> and χ<SUB>eff</SUB> distributions are very weakly dependent on the detector sensitivity. <BR /> Conclusions: The favorable comparison of the existing LIGO/Virgo observations with our model predictions gives support to the idea that the majority, if not all of the observed mergers, originate from the evolution of isolated binaries. The first-born black hole has negligible spin because it lost its envelope after it expanded to become a giant star, while the spin of the second-born black hole is determined by the tidal spin up of its naked helium star progenitor by the first-born black hole companion after the binary finished the common-envelope phase.

[]

https://arxiv.org/pdf/1906.12257.pdf

2007CMaPh.271..699H

A Higher Dimensional Stationary Rotating Black Hole Must be Axisymmetric

2007-01-01

['-', '-', 'black hole physics', '-', '-', '-', '-']

[]

A key result in the proof of black hole uniqueness in 4-dimensions is that a stationary black hole that is "rotating"—i.e., is such that the stationary Killing field is not everywhere normal to the horizon—must be axisymmetric. The proof of this result in 4-dimensions relies on the fact that the orbits of the stationary Killing field on the horizon have the property that they must return to the same null geodesic generator of the horizon after a certain period, P. This latter property follows, in turn, from the fact that the cross-sections of the horizon are two-dimensional spheres. However, in spacetimes of dimension greater than 4, it is no longer true that the orbits of the stationary Killing field on the horizon must return to the same null geodesic generator. In this paper, we prove that, nevertheless, a higher dimensional stationary black hole that is rotating must be axisymmetric. No assumptions are made concerning the topology of the horizon cross-sections other than that they are compact. However, we assume that the horizon is non-degenerate and, as in the 4-dimensional proof, that the spacetime is analytic.

[]

https://arxiv.org/pdf/gr-qc/0605106.pdf

2010ApJ...710.1063V

New Limits on an Intermediate-Mass Black Hole in Omega Centauri. II. Dynamical Models

2010-01-01

['clusters globular', 'stars kinematics and dynamics', '-', '-']

[]

We present a detailed dynamical analysis of the projected density and kinematical data available for the globular cluster ω Centauri. We solve the spherical anisotropic Jeans equation for a given density profile to predict the projected profiles of the rms velocity {\bar{σ}}(R), in each of the three orthogonal coordinate directions (line of sight, proper motion radial, and proper motion tangential). The models allow for the presence of a central dark mass, such as a possible intermediate-mass black hole (IMBH). We fit the models to new Hubble Space Telescope star count and proper motion data near the cluster center presented in the companion paper, which is Paper I in this series, combined with existing ground-based measurements at larger radii. The projected density profile is consistent with being flat near the center, with an upper limit γ &lt;~ 0.07 on the central logarithmic slope. The rms proper motion profile is also consistent with being flat near the center. The velocity anisotropy profile, distance, and stellar mass-to-light ratio are all tightly constrained by the data and found to be in good agreement with previous determinations by van de Ven et al. To fit the kinematics, we consider anisotropic models with either a flat core (γ = 0) or a shallow cusp (γ = 0.05). Core models provide a good fit to the data with M <SUB>BH</SUB> = 0; cusp models require a dark mass. If the dark mass in cusp models is an IMBH, then M <SUB>BH</SUB> = (8.7 ± 2.9) × 10<SUP>3</SUP> M <SUB>sun</SUB>; if it is a dark cluster, then its extent must be lsim0.16 pc. Isotropic models do not fit the observed proper motion anisotropy and yield spuriously high values for any central dark mass. These models do provide a good fit to the Gauss-Hermite moments of the observed proper motion distributions (h <SUB>4</SUB> = -0.023 ± 0.004, h <SUB>6</SUB> = 0.001 ± 0.004). There are no unusually fast-moving stars observed in the wings of the proper motion distribution, but we show that this does not strongly constrain the mass of any possible IMBH. The overall end result of the modeling is an upper limit to the mass of any possible IMBH in ω Centauri: M <SUB>BH</SUB> &lt;~ 1.2 × 10<SUP>4</SUP> M <SUB>sun</SUB> at ~1σ confidence (or lsim1.8 × 10<SUP>4</SUP> M <SUB>sun</SUB> at ~3σ confidence). The 1σ limit corresponds to M <SUB>BH</SUB>/M <SUB>tot</SUB> &lt;~ 0.43%. We combine this with results for other clusters and discuss the implications for globular cluster IMBH demographics. Tighter limits will be needed to rule out or establish whether globular clusters follow the same black hole demographics correlations as galaxies. The arguments put forward by Noyola et al. to suspect an IMBH in ω Centauri are not confirmed by our study; the value of M <SUB>BH</SUB> they suggested is firmly ruled out. <P />Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

[]

https://arxiv.org/pdf/0905.0638.pdf

1992NuPhB.368..444H

Exact black string solutions in three dimensions

1992-01-01

['-']

[]

A family of exact conformal field theories is constructed which describe charged black strings in three dimensions. Unlike previous charged black hole or extended black hole solutions in string theory, the low-energy space-time metric has a regular inner horizon (in addition to the event horizon) and a timelike singularity. As the charge to mass ratio approaches unity, the event horizon remains but the singularity disappears.

[]

https://arxiv.org/pdf/hep-th/9108001.pdf

2010ApJ...718L.117S

The Constant Inner-disk Radius of LMC X-3: A Basis for Measuring Black Hole Spin

2010-01-01

['accretion', 'accretion disks', 'black hole physics', '-', 'astronomy x rays', '-']

[]

The black hole binary system LMC X-3 has been observed by virtually every X-ray mission since the inception of X-ray astronomy. Among the persistent sources, LMC X-3 is uniquely both habitually soft and highly variable. Using a fully relativistic accretion disk model, we analyze hundreds of spectra collected during eight X-ray missions that span 26 years. For a selected sample of 391 RXTE spectra, we find that to within ≈2% the inner radius of the accretion disk is constant over time and unaffected by source variability. Even considering an ensemble of eight X-ray missions, we find consistent values of the radius to within ≈4%-6%. Our results provide strong evidence for the existence of a fixed inner-disk radius. The only reasonable inference is that this radius is closely associated with the general relativistic innermost stable circular orbit. Our findings establish a firm foundation for the measurement of black hole spin.

[]

https://arxiv.org/pdf/1006.5729.pdf

2007CQGra..24S..33H

Unequal mass binary black hole plunges and gravitational recoil

2007-01-01

['-', 'astrophysics']

[]

We present results from fully nonlinear simulations of unequal mass binary black holes plunging from close separations well inside the innermost stable circular orbit with mass ratios q ≡ M<SUB>1</SUB>/M<SUB>2</SUB> = {1, 0.85, 0.78, 0.55, 0.32}, or equivalently, with reduced mass parameters η ≡ M<SUB>1</SUB>M<SUB>2</SUB>/(M<SUB>1</SUB> + M<SUB>2</SUB>)<SUP>2</SUP> = {0.25, 0.248, 0.246, 0.229, 0.183}. For each case, the initial binary orbital parameters are chosen from the Cook Baumgarte equal-mass ISCO configuration. We show waveforms of the dominant ell = 2, 3 modes and compute estimates of energy and angular momentum radiated. For the plunges from the close separations considered, we measure kick velocities from gravitational radiation recoil in the range 25 82 km s<SUP>-1</SUP>. Due to the initial close separations our kick velocity estimates should be understood as a lower bound. The close configurations considered are also likely to contain significant eccentricities influencing the recoil velocity.

[]

https://arxiv.org/pdf/gr-qc/0601026.pdf

2001ForPh..49....3M

Black Hole Entropy, Special Geometry and Strings

2001-01-01

['-']

[]

We review work done over the last years on the macroscopic and microscopic entropy of supersymmetric black holes in fourdimensional N=2 supergravity and in N=2 compactifications of string theory and M-theory. Particular emphasis is put on the crucial role of higher curvature terms and of modifications of the area law in obtaining agreement between the macroscopic entropy, which is a geometric property of black hole solutions and the microscopic entropy, which is computed by state counting in Calabi-Yau compactifications of string or M-theory. We also discuss invariance properties of the entropy under stringy T-duality and S-duality transformations in N=2,4 compactifications in presence of higher curvature terms. In order to make the paper self-contained we review the laws of black hole mechanics in higher derivative gravity, the definition of entropy as a surface charge, the superconformal off-shell description of N=2 supergravity, special geometry, and N=2 compactifications of heterotic and type II string theory and of M-theory.

[]

https://arxiv.org/pdf/hep-th/0007195.pdf

2016MNRAS.463.2145C

A population of short-period variable quasars from PTF as supermassive black hole binary candidates

2016-01-01

['galaxies quasars', '-', '-']

[]

Supermassive black hole binaries (SMBHBs) at sub-parsec separations should be common in galactic nuclei, as a result of frequent galaxy mergers. Hydrodynamical simulations of circum-binary discs predict strong periodic modulation of the mass accretion rate on time-scales comparable to the orbital period of the binary. As a result, SMBHBs may be recognized by the periodic modulation of their brightness. We conducted a statistical search for periodic variability in a sample of 35 383 spectroscopically confirmed quasars in the photometric data base of the Palomar Transient Factory (PTF). We analysed Lomb-Scargle periodograms and assessed the significance of our findings by modelling each individual quasar's variability as a damped random walk (DRW). We identified 50 quasars with significant periodicity beyond the DRW model, typically with short periods of a few hundred days. We find 33 of these to remain significant after a re-analysis of their periodograms including additional optical data from the intermediate-PTF and the Catalina Real-Time Transient Survey. Assuming that the observed periods correspond to the redshifted orbital periods of SMBHBs, we conclude that our findings are consistent with a population of unequal-mass SMBHBs, with a typical mass ratio as low as q ≡ M<SUB>2</SUB>/M<SUB>1</SUB> ≈ 0.01.

[]

https://arxiv.org/pdf/1604.01020.pdf

2018ApJ...868...63E

Modeling the Radio Background from the First Black Holes at Cosmic Dawn: Implications for the 21 cm Absorption Amplitude

2018-01-01

['-', '-', '-', '-', '-']

[]

We estimate the 21 cm radio background from accretion onto the first intermediate-mass black holes between z ≈ 30 and z ≈ 16. Combining potentially optimistic, but plausible, scenarios for black hole formation and growth with empirical correlations between luminosity and radio emission observed in low-redshift active galactic nuclei, we find that a model of black holes forming in molecular cooling halos is able to produce a 21 cm background that exceeds the cosmic microwave background (CMB) at z ≈ 17, though models involving larger halo masses are not entirely excluded. Such a background could explain the surprisingly large amplitude of the 21 cm absorption feature recently reported by the EDGES collaboration. Such black holes would also produce significant X-ray emission and contribute to the 0.5-2 keV soft X-ray background at the level of ≈10<SUP>-13</SUP>-10<SUP>-12</SUP> erg s<SUP>-1</SUP> cm<SUP>-2</SUP> deg<SUP>-2</SUP>, consistent with existing constraints. In order to avoid heating the intergalactic medium (IGM) over the EDGES trough, these black holes would need to be obscured by hydrogen column depths of N <SUB>H</SUB> ∼ 5 × 10<SUP>23</SUP> cm<SUP>-2</SUP>. Such black holes would avoid violating constraints on the CMB optical depth from Planck if their UV photon escape fractions were below f <SUB>esc</SUB> ≲ 0.1, which would be a natural result of N <SUB>H</SUB> ∼ 5 × 10<SUP>23</SUP> cm<SUP>-2</SUP> being imposed by an unheated IGM.

[]

https://arxiv.org/pdf/1803.01815.pdf

2014PhRvD..89j4017T

Rotating regular black hole solution

2014-01-01

['-', '-', '-', '-', '-', '-', '-']

[]

Based on the Newman-Janis algorithm, the Ayón-Beato-García spacetime metric [Phys. Rev. Lett. 80, 5056 (1998)] of the regular spherically symmetric, static, and charged black hole has been converted into rotational form. It is shown that the derived solution for rotating a regular black hole is regular and the critical value of the electric charge for which two horizons merge into one sufficiently decreases in the presence of the nonvanishing rotation parameter a of the black hole.

[]

https://arxiv.org/pdf/1404.6443.pdf

2020PhRvD.102f4002G

Multimode frequency-domain model for the gravitational wave signal from nonprecessing black-hole binaries

2020-01-01

['-']

[]

We present the IMRPHENOMXHM frequency domain phenomenological waveform model for the inspiral, merger, and ringdown of quasicircular nonprecessing black hole binaries. The model extends the IMRPHENOMXAS waveform model [G. Pratten, S. Husa, C. García-Quirós, M. Colleoni, A. Ramos-Buades, H. Estellés, and R. Jaume, preceding paper, Phys. Rev. D 102, 064001 (2020), 10.1103/PhysRevD.102.064001], which describes the dominant quadrupole modes ℓ=|m |=2 , to the harmonics (ℓ,|m |)=(2 ,1 ),(3 ,3 ),(3 ,2 ),(4 ,4 ), and includes mode mixing effects for the (3,2) spherical harmonic. IMRPHENOMXHM is calibrated against hybrid waveforms, which match an inspiral phase described by the effective-one-body model and post-Newtonian amplitudes for the subdominant harmonics to numerical relativity waveforms and numerical solutions to the perturbative Teukolsky equation for large mass ratios up to 1000.

[]

https://arxiv.org/pdf/2001.10914.pdf

2007ApJ...669...32K

Black Hole Masses and Enrichment of z ~ 6 SDSS Quasars

2007-01-01

['galaxies evolution', 'galaxies formation', 'galaxies fundamental parameters', 'galaxies photometry', 'galaxies quasars', 'galaxies quasars', 'galaxies quasars', 'galaxies quasars', 'galaxies quasars', 'astrophysics']

[]

We present sensitive near-infrared spectroscopic observations for a sample of five z~6 quasars. These quasars are among the most distant, currently known quasars in the universe. The spectra have been obtained using ISAAC at the VLT and include the C IV, Mg II, and Fe II lines. We measure the Fe II/Mg II line ratio, as an observational proxy for the Fe/α-element ratio. We derive a ratio of 2.7+/-0.8 for our sample, which is similar to that found for lower redshift quasars; i.e., we provide additional evidence for the lack of evolution in the Fe II/Mg II line ratio of quasars up to the highest redshifts. This result demonstrates that star formation must have commenced at z&gt;=8 in the quasar hosts. The line widths of the Mg II and C IV lines give two estimates for the black hole masses. A third estimate is given by assuming that the quasars emit at their Eddington luminosity. The derived masses using these three methods agree well, implying that the quasars are not likely to be strongly lensed. We derive central black hole masses of (0.3-5.2)×10<SUP>9</SUP> M<SUB>solar</SUB>. We use the difference between the redshift of Mg II (a proxy for the systemic redshift of the quasar) and the onset of the Gunn-Peterson trough to derive the extent of the ionized Strömgren spheres around our target quasars. The derived physical radii are about 5 Mpc. Using a simple ionization model, the emission of the central quasars would need of order 10<SUP>6</SUP>-10<SUP>8</SUP> yr to create these cavities. As the e-folding timescale for the central accreting black hole is on the order of a few times 10<SUP>7</SUP> yr, it can grow by one e-folding or less within this time span. <P />Based on observations carried out at the European Southern Observatory, Paranal, Chile under programs 267.A-5689, 069.B-0289, 071.B-0525, 074.A-0447, and 076.A-0304.

[]

https://arxiv.org/pdf/0707.1662.pdf

2009PhRvL.103n1101J

Overspinning a Black Hole with a Test Body

2009-01-01

['-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

It has long been known that a maximally spinning black hole cannot be overspun by tossing in a test body. Here we show that if instead the black hole starts out with below maximal spin, then indeed overspinning can be achieved. We find that requirements on the size and internal structure of the test body can be met if the body carries in orbital but not spin angular momentum. Our analysis neglects radiative and self-force effects, which may prevent the overspinning.

[]

https://arxiv.org/pdf/0907.4146.pdf

1993PhRvD..47.5259M

Charged black holes in effective string theory

1993-01-01

['-', '-', '-', 'black hole physics', '-']

[]

We investigate the qualitative new features of charged dilatonic black holes which emerge when both the Yang-Mills and Gauss-Bonnet curvature corrections are included in the effective action. We consider these perturbative effects by an expansion up to second order in the inverse string tension on the four-dimensional Schwarzschild background and determine the back reaction. We calculate the thermodynamical functions and show that they can behave like those of the Garfinkle-Horowitz-Strominger solution or in a more conventional way, depending on the value of the magnetic charge q. Moreover, we find that for magnetic charge above a critical value, the temperature of the black hole has a maximum and goes to zero for a finite value of the mass. This indicates that the conventional Hawking evaporation law is modified by string theory at a classical level.

[]

https://arxiv.org/pdf/hep-th/9212146.pdf

2016PhRvD..93f4015K

General parametrization of axisymmetric black holes in metric theories of gravity

2016-01-01

['-', '-', '-']

[]

Following previous work of ours in spherical symmetry, we here propose a new parametric framework to describe the spacetime of axisymmetric black holes in generic metric theories of gravity. In this case, the metric components are functions of both the radial and the polar angular coordinates, forcing a double expansion to obtain a generic axisymmetric metric expression. In particular, we use a continued-fraction expansion in terms of a compactified radial coordinate to express the radial dependence, while we exploit a Taylor expansion in terms of the cosine of the polar angle for the polar dependence. These choices lead to a superior convergence in the radial direction and to an exact limit on the equatorial plane. As a validation of our approach, we build parametrized representations of Kerr, rotating dilaton, and Einstein-dilaton-Gauss-Bonnet black holes. The match is already very good at lowest order in the expansion and improves as new orders are added. We expect a similar behavior for any stationary and axisymmetric black-hole metric.

[]

https://arxiv.org/pdf/1602.02378.pdf

1999MNRAS.307..637S

Mass function of dormant black holes and the evolution of active galactic nuclei

1999-01-01

['astrophysics']

[]

Under the assumption that accretion on to massive black holes (BHs) powers active galactic nuclei (AGNs), the mass function (MF) of the BHs responsible for their past activity is estimated. For this, we take into account not only the activity related to the optically selected AGNs, but also that required to produce the hard X-ray background (HXRB). The MF of the massive dark objects (MDOs) in nearby quiescent galaxies is computed by means of the most recent results on their demography. The two mass functions match well under the assumption that the activity is concentrated in a single significant burst with lambdaLL_Edd being a weakly increasing function of luminosity. This behaviour may be indicative of some level of recurrence and/or of accretion rates insufficient to maintain the Eddington rates in low-luminosity/low-redshift objects. Our results support the scenario in which the early phase of intense nuclear activity occurred mainly in early-type galaxies (E/S0) during the relatively short period in which they still had an abundant interstellar medium. Only recently, with the decline of the quasi-stellar object (QSO) luminosities, did the activity in late-type galaxies (Sa/Sab) become statistically significant.

[]

https://arxiv.org/pdf/astro-ph/9811102.pdf

1992PhRvD..46.1340H

Rotating dilaton black holes

1992-01-01

['-', '-', '-', 'black hole physics', '-', '-']

[]

It is shown that an arbitrarily small amount of angular momentum can qualitatively change the properties of extremal charged black holes coupled to a dilaton. In addition, the gyromagnetic ratio of these black holes is computed and an exact rotating black string solution is presented.

[]

https://arxiv.org/pdf/hep-th/9203083.pdf

1996MNRAS.283L.111R

The `quiescent' black hole in M87

1996-01-01

['accretion', 'accretion disks', 'galaxies active', 'galaxies', 'astrophysics']

[]

It is believed that most giant elliptical galaxies possess nuclear black holes with masses in excess of 10^8 M_solar. Bondi accretion from the interstellar medium might then be expected to produce quasar-like luminosities from the nuclei of even quiescent elliptical galaxies. It is a puzzle that such luminosities are not observed. Motivated by this problem, Fabian &amp; Rees have recently suggested that the final stages of accretion in these objects occurs in an advection-dominated mode with a correspondingly small radiative efficiency. Despite possessing a long-known active nucleus and dynamical evidence for a black hole, the low radiative and kinetic luminosities of the core of M87 provide the best illustration of this problem. We examine an advection-dominated model for the nucleus of M87, and show that accretion at the Bondi rate is compatible with the best-known estimates for the core flux from radio through to X-ray wavelengths. The success of this model prompts us to propose that Fanaroff-Riley (FR)I radio galaxies and quiescent elliptical galaxies accrete in an advection-dominated mode whereas FRII-type radio-loud nuclei possess radiatively efficient thin accretion discs.

[]

https://arxiv.org/pdf/astro-ph/9610097.pdf

2013PhRvD..87l3524C

Constraints on primordial black holes as dark matter candidates from capture by neutron stars

2013-01-01

['-', '-', 'cosmology dark matter', '-', '-', '-']

[]

We investigate constraints on primordial black holes (PBHs) as dark matter candidates that arise from their capture by neutron stars (NSs). If a PBH is captured by a NS, the star is accreted onto the PBH and gets destroyed in a very short time. Thus, mere observations of NSs put limits on the abundance of PBHs. High DM densities and low velocities are required to constrain the fraction of PBHs in DM. Such conditions may be realized in the cores of globular clusters if the latter are of a primordial origin. Assuming that cores of globular clusters possess the DM densities exceeding several hundred GeV/cm<SUP>3</SUP> would imply that PBHs are excluded as comprising all of the dark matter in the mass range 3×10<SUP>18</SUP>≲m<SUB>BH</SUB>≲10<SUP>24</SUP>g. At the DM density of 2×10<SUP>3</SUP>GeV/cm<SUP>3</SUP> that has been found in simulations in the corresponding models, less than 5% of the DM may consist of PBH for these PBH masses.

[]

https://arxiv.org/pdf/1301.4984.pdf

2021PhRvL.126e1303V

Did NANOGrav See a Signal from Primordial Black Hole Formation?

2021-01-01

['-']

[]

We show that the recent NANOGrav result can be interpreted as a stochastic gravitational wave signal associated to formation of primordial black holes from high-amplitude curvature perturbations. The indicated amplitude and power of the gravitational wave spectrum agrees well with formation of primordial seeds for supermassive black holes.

[]

https://arxiv.org/pdf/2009.07832.pdf

1994PhRvL..72..957B

Black hole entropy and the dimensional continuation of the Gauss-Bonnet theorem

1994-01-01

['-', '-', '-', '-', '-', 'thermodynamics', 'black hole physics', '-']

[]

The Euclidean black hole has topology gerR<SUP>2</SUP>×scrS<SUP>d-2</SUP>. It is shown that, in Einstein's theory the deficit angle of a cusp at any point in gerR<SUP>2</SUP> and the area of the scrS<SUP>d-2</SUP> are canonical conjugates. The black hole entropy emerges as the Euler class of a small disk centered at the horizon multiplied by the area of the scrS<SUP>d-2</SUP> there. These results are obtained through dimensional continuation of the Gauss-Bonnet theorem. The extension to the most general action yielding second order field equations for the metric in any spacetime dimension is given.

[]

https://arxiv.org/pdf/gr-qc/9309026.pdf

1996PhRvD..54.5059M

No hair for spherical black holes: Charged and nonminimally coupled scalar field with self-interaction

1996-01-01

['-', '-', '-', '-', '-', 'black hole physics', '-', 'astrophysics', '-']

[]

We prove three theorems in general relativity which rule out classical scalar hair of static, spherically symmetric, possibly electrically charged black holes. We first generalize Bekenstein's no-hair theorem for a multiplet of minimally coupled real scalar fields with not necessarily quadratic action to the case of a charged black hole. We then use a conformal map of the geometry to convert the problem of a charged (or neutral) black hole with hair in the form of a neutral self-interacting scalar field nonminimally coupled to gravity to the preceding problem, thus establishing a no-hair theorem for the cases with a nonminimal coupling parameter ξ&lt;0 or ξ&gt;=1/2. The proof also makes use of a causality requirement on the field configuration. Finally, from the required behavior of the fields at the horizon and infinity we exclude hair of a charged black hole in the form of a charged self-interacting scalar field nonminimally coupled to gravity for any ξ.

[]

https://arxiv.org/pdf/gr-qc/9602057.pdf

2006ApJ...645.1152H

Resonant Relaxation near a Massive Black Hole: The Stellar Distribution and Gravitational Wave Sources

2006-01-01

['black hole physics', 'galaxy center', 'gravitational waves', 'stars kinematics and dynamics', 'astrophysics', '-']

[]

Resonant relaxation (RR) of orbital angular momenta occurs near massive black holes (MBHs) where the potential is spherical and stellar orbits are nearly Keplerian and so do not precess significantly. The resulting coherent torques efficiently change the magnitude of the angular momenta and rotate the orbital inclination in all directions. As a result, many of the tightly bound stars very near the MBH are rapidly destroyed by falling into the MBH on low angular momentum orbits, while the orbits of the remaining stars are efficiently randomized. We solve numerically the Fokker-Planck equation in energy for the steady state distribution of a single-mass population with an RR sink term. We find that the steady state current of stars, which sustains the accelerated drainage close to the MBH, can be &lt;~10 larger than that due to noncoherent two-body relaxation alone. RR mostly affects tightly bound stars, and so it increases only moderately the total tidal disruption rate, which is dominated by stars originating from less bound orbits farther away. We show that the event rate of gravitational wave (GW) emission from inspiraling stars, originating much closer to the MBH, is dominated by RR dynamics. The GW event rate depends on the uncertain efficiency of RR. The efficiency indicated by the few available simulations implies rates &lt;~10 times higher than those predicted by two-body relaxation, which would improve the prospects of detecting such events by future GW detectors, such as LISA. However, a higher, but still plausible, RR efficiency can lead to the drainage of all tightly bound stars and strong suppression of GW events from inspiraling stars. We apply our results to the Galactic MBH and show that the observed dynamical properties of stars there are consistent with RR.

[]

https://arxiv.org/pdf/astro-ph/0601161.pdf

2010PThPh.123..867S

Gravitational-Wave Constraints on the Abundance of Primordial Black Holes

2010-01-01

['-']

[]

We investigate the features of gravitational waves (GWs) induced by primordial density fluctuations with a large amplitude peak associated with the formation of primordial black holes (PBHs). It is shown that the spectrum of induced GW is insensitive to the width of the peak in wavenumber space provided it is below a certain value, but the amplitude of the spectrum decreases at the peak frequency and decreases faster at low frequencies for a larger width. A correspondence between the GW amplitude and PBH abundance is also investigated incorporating the peak width. We find that PBHs with masses of 10^{20-26} g can be probed using space-based laser interferometers and atomic interferometers even if the peak width is large. Moreover we obtain constraints on the abundance of the supermassive PBHs by comparing a low-frequency tail of the GW spectrum with CMB observations.

[]

https://arxiv.org/pdf/0912.5317.pdf

2006PhRvD..73h3005B

Spacetime structure of an evaporating black hole in quantum gravity

2006-01-01

['-', '-', '-', 'black hole physics', '-', '-', '-', 'astrophysics']

[]

The impact of the leading quantum gravity effects on the dynamics of the Hawking evaporation process of a black hole is investigated. Its spacetime structure is described by a renormalization group improved Vaidya metric. Its event horizon, apparent horizon, and timelike limit surface are obtained by taking the scale dependence of Newton’s constant into account. The emergence of a quantum ergosphere is discussed. The final state of the evaporation process is a cold, Planck size remnant.

[]

https://arxiv.org/pdf/hep-th/0602159.pdf

2012ApJS..201...23E

A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes

2012-01-01

['galaxies active', 'line profiles', 'galaxies quasars', 'galaxies quasars', '-']

[]

We have carried out a systematic search for subparsec supermassive black hole (BH) binaries among z &lt;~ 0.7 Sloan Digital Sky Survey quasars. These are predicted by models of supermassive BH and host galaxy coevolution, therefore their census and population properties constitute an important test of these models. In our working hypothesis, one of the two BHs accretes at a much higher rate than the other and carries with it the only broad emission line region of the system, making the system analogous to a single-lined spectroscopic binary star. Accordingly, we used spectroscopic principal component analysis to search for broad Hβ emission lines that are displaced from the quasar rest frame by |Δ v| &gt;~ 1000 km s<SUP>-1</SUP>. This method also yields candidates for rapidly recoiling BHs. Of the 88 candidates, several were previously reported in the literature. We found a correlation between the peak offset and skewness of the broad Hβ profiles, suggesting a common physical explanation for these profiles. We carried out follow-up spectroscopic observations of 68 objects to search for changes in the peak velocities of the Hβ lines. We measured statistically significant changes in 14 objects, with implied accelerations between -120 and +120 km s<SUP>-1</SUP> yr<SUP>-1</SUP>. Interpreting the offset broad emission lines as signatures of supermassive binaries is subject to many caveats. Many more follow-up observations over a long temporal baseline are needed to characterize the variability pattern of the broad lines and test that it is consistent with orbital motion. The possibility that some of the objects in this sample are rapidly recoiling BHs remains open.

[]

https://arxiv.org/pdf/1106.2952.pdf

2012PhRvD..85b3519M

Constraints on scalar asymmetric dark matter from black hole formation in neutron stars

2012-01-01

['-', '-', 'cosmology dark matter', 'particles', '-', '-']

[]

We consider possibly observable effects of asymmetric dark matter (ADM) in neutron stars. Since dark matter does not self-annihilate in the ADM scenario, dark matter accumulates in neutron stars, eventually reaching the Chandrasekhar limit and forming a black hole. We focus on the case of scalar ADM, where the constraints from Bose-Einstein condensation and subsequent black hole formation are most severe due to the absence of Fermi degeneracy pressure. We also note that in some portions of this constrained parameter space, nontrivial effects from Hawking radiation can modify our limits. We find that for scalar ADM with mass between 5 MeV and 13 GeV, the constraint from nearby neutron stars on the scattering cross section with neutrons ranges from σ<SUB>n</SUB>≲10<SUP>-45</SUP>cm<SUP>2</SUP> to 10<SUP>-47</SUP>cm<SUP>2</SUP>.

[]

https://arxiv.org/pdf/1103.5472.pdf

2019ApJ...871...91Z

Eccentric Black Hole Mergers in Dense Star Clusters: The Role of Binary-Binary Encounters

2019-01-01

['stars binaries close', 'black hole physics', 'clusters globular', 'gravitational waves', 'methods numerical', 'stars kinematics and dynamics', '-', '-']

[]

We present the first systematic study of strong binary-single and binary-binary black hole (BH) interactions with the inclusion of general relativity. By including general relativistic effects in the equations of motion during strong encounters, the dissipation of orbital energy from the emission of gravitational waves (GWs) can lead to captures and subsequent inspirals with appreciable eccentricities when entering the sensitive frequency ranges of the LIGO and Virgo GW detectors. It has been shown that binary-single interactions significantly contribute to the rate of eccentric mergers, but no studies have looked exclusively into the contribution from binary-binary interactions. To this end, we perform binary-binary and binary-single scattering experiments with general relativistic dynamics up through the 2.5 post-Newtonian order included, both in a controlled setting to gauge the importance of non-dissipative post-Newtonian terms and derive scaling relations for the cross section of GW captures, as well as experiments tuned to the strong interactions from state-of-the art globular cluster (GC) models to assess the relative importance of the binary-binary channel in facilitating GW captures and the resultant eccentricity distributions of inspiral from channel. Although binary-binary interactions are 10-100 times less frequent in GCs than binary-single interactions, their longer lifetime and more complex dynamics leads to a higher probability for GW captures to occur during the encounter. We find that binary-binary interactions contribute 25%-45% of the eccentric mergers that occur during strong BH encounters in GCs, regardless of the properties of the cluster environment. The inclusion of higher multiplicity encounters in dense star clusters therefore have major implications on the predicted rates of highly eccentric binaries potentially detectable by the LIGO/Virgo network. Because gravitational waveforms of eccentric inspirals are distinct from those generated by merging binaries that have circularized, measurements of eccentricity in such systems would highly constrain their formation scenario.

[]

https://arxiv.org/pdf/1810.00901.pdf

2015PhRvL.114q1601L

Black Holes in Higher Derivative Gravity

2015-01-01

['-', '-', '-', '-', '-', '-']

[]

Extensions of Einstein gravity with higher-order derivative terms arise in string theory and other effective theories, as well as being of interest in their own right. In this Letter we study static black-hole solutions in the example of Einstein gravity with additional quadratic curvature terms. A Lichnerowicz-type theorem simplifies the analysis by establishing that they must have vanishing Ricci scalar curvature. By numerical methods we then demonstrate the existence of further black-hole solutions over and above the Schwarzschild solution. We discuss some of their thermodynamic properties, and show that they obey the first law of thermodynamics.

[]

https://arxiv.org/pdf/1502.01028.pdf