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2011PhRvL.106x1101A

Inspiral-Merger-Ringdown Waveforms for Black-Hole Binaries with Nonprecessing Spins

2011-01-01

['-', '-', '-', 'methods numerical', '-', '-']

[]

We present the first analytical inspiral-merger-ringdown gravitational waveforms from binary black holes (BBHs) with nonprecessing spins, that is based on a description of the late-inspiral, merger and ringdown in full general relativity. By matching a post-Newtonian description of the inspiral to a set of numerical-relativity simulations, we obtain a waveform family with a conveniently small number of physical parameters. These waveforms will allow us to detect a larger parameter space of BBH coalescence, including a considerable fraction of precessing binaries in the comparable-mass regime, thus significantly improving the expected detection rates.

[]

https://arxiv.org/pdf/0909.2867.pdf

2007PhRvB..76n4502H

Theory of the Nernst effect near quantum phase transitions in condensed matter and in dyonic black holes

2007-01-01

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

[]

We present a general hydrodynamic theory of transport in the vicinity of superfluid-insulator transitions in two spatial dimensions described by “Lorentz”-invariant quantum critical points. We allow for a weak impurity scattering rate, a magnetic field B , and a deviation in the density ρ from that of the insulator. We show that the frequency-dependent thermal and electric linear response functions, including the Nernst coefficient, are fully determined by a single transport coefficient (a universal electrical conductivity), the impurity scattering rate, and a few thermodynamic state variables. With reasonable estimates for the parameters, our results predict a magnetic field and temperature dependence of the Nernst signal which resembles measurements in the cuprates, including the overall magnitude. Our theory predicts a “hydrodynamic cyclotron mode” which could be observable in ultrapure samples. We also present exact results for the zero frequency transport coefficients of a supersymmetric conformal field theory (CFT), which is solvable by the anti-de Sitter (AdS)/CFT correspondence. This correspondence maps the ρ and B perturbations of the 2+1 dimensional CFT to electric and magnetic charges of a black hole in the 3+1 dimensional anti-de Sitter space. These exact results are found to be in full agreement with the general predictions of our hydrodynamic analysis in the appropriate limiting regime. The mapping of the hydrodynamic and AdS/CFT results under particle-vortex duality is also described.

[]

https://arxiv.org/pdf/0706.3215.pdf

2015MNRAS.452..575S

The Illustris simulation: the evolving population of black holes across cosmic time

2015-01-01

['methods numerical', 'galaxies formation', 'galaxies quasars', 'cosmology theory', '-', '-']

[]

We study the properties of black holes and their host galaxies across cosmic time in the Illustris simulation. Illustris is a large-scale cosmological hydrodynamical simulation which resolves a (106.5 Mpc)<SUP>3</SUP> volume with more than 12 billion resolution elements and includes state-of-the-art physical models relevant for galaxy formation. We find that the black hole mass density for redshifts z = 0-5 and the black hole mass function at z = 0 predicted by Illustris are in very good agreement with the most recent observational constraints. We show that the bolometric and hard X-ray luminosity functions of active galactic nuclei (AGN) at z = 0 and 1 reproduce observational data very well over the full dynamic range probed. Unless the bolometric corrections are largely underestimated, this requires radiative efficiencies to be on average low, ɛ<SUB>r</SUB> ≲ 0.1, noting however that in our model radiative efficiencies are degenerate with black hole feedback efficiencies. Cosmic downsizing of the AGN population is in broad agreement with the findings from X-ray surveys, but we predict a larger number density of faint AGN at high redshifts than currently inferred. We also study black hole-host galaxy scaling relations as a function of galaxy morphology, colour and specific star formation rate. We find that black holes and galaxies co-evolve at the massive end, but for low mass, blue and star-forming galaxies there is no tight relation with either their central black hole masses or the nuclear AGN activity.

[]

https://arxiv.org/pdf/1408.6842.pdf

2012NewAR..56...93A

What drives the growth of black holes?

2012-01-01

['-', '-']

[]

Massive black holes (BHs) are at once exotic and yet ubiquitous, residing at the centers of massive galaxies in the local Universe. Recent years have seen remarkable advances in our understanding of how these BHs form and grow over cosmic time, during which they are revealed as Active Galactic Nuclei (AGN). However, despite decades of research, we still lack a coherent picture of the physical drivers of BH growth, the connection between the growth of BHs and their host galaxies, the role of large-scale environment on the fueling of BHs, and the impact of BH-driven outflows on the growth of galaxies. In this paper we review our progress in addressing these key issues, motivated by the science presented at the "What drives the growth of black holes?" workshop held at Durham on 26-29th July 2010, and discuss how these questions may be tackled with current and future facilities.

[]

https://arxiv.org/pdf/1112.1949.pdf

1997ApJ...482L.155Z

Black Hole Spin in X-Ray Binaries: Observational Consequences

1997-01-01

['black hole physics', 'astronomy x rays', 'black hole physics', 'astronomy x rays', 'astrophysics']

[]

We discuss the observational consequences of black hole spin in X-ray binaries within the framework of the standard thin accretion disk model. When compared with theoretical flux distribution from the surface of a thin disk surrounding a Kerr black hole, the observed X-ray properties of the Galactic superluminal jet sources, GRO J1655-40 and GRS 1915+105, strongly suggest that each contains a black hole spinning rapidly in the same direction as the accretion disk. We show, however, that some other black hole binaries with an ultrasoft X-ray component probably harbor only non- or slowly spinning black holes, and we argue that those with no detectable ultrasoft component above 1-2 keV in their high luminosity state may contain a fast-spinning black hole but with a retrograde disk. Therefore, all classes of known black hole binaries are united within one scheme. Furthermore, we explore the possibility that spectral state transitions in Cyg X-1 are simply due to temporary disk reversal, which can occur in a wind accretion system.

[]

https://arxiv.org/pdf/astro-ph/9704072.pdf

2002MNRAS.331..795M

On the black hole-bulge mass relation in active and inactive galaxies

2002-01-01

['galaxies active', 'galaxies bulges', 'galaxies nuclei', 'galaxies quasars', 'astrophysics']

[]

New black-hole mass estimates are presented for a sample of 72 AGN covering three decades in optical luminosity. Using a sub-sample of Seyfert galaxies, which have black-hole mass estimates from both reverberation mapping and stellar velocity dispersions, we investigate the geometry of the AGN broad-line region (BLR). It is demonstrated that a model in which the orbits of the line-emitting material have a flattened geometry is favoured over randomly orientated orbits. Using this model we investigate the M_{bh}-L_{bulge} relation for a combined 90-object sample, consisting of the AGN plus a sample of 18 nearby inactive elliptical galaxies with dynamical black-hole mass measurements. It is found that, for all reasonable mass-to-light ratios, the M_{bh}-L_{bulge} relation is equivalent to a linear scaling between bulge and black-hole mass. The best-fitting normalization of the M_{bh}-M_{bulge} relation is found to be M_{bh}=0.0012M_{bulge}, in agreement with recent black-hole mass studies based on stellar velocity dispersions. Furthermore, the scatter around the M_{bh}-L_{bulge} relation for the full sample is found to be significantly smaller than has been previously reported (Delta \log M_{bh}=0.39 dex). Finally, using the nearby inactive elliptical galaxy sample alone, it is shown that the scatter in the M_{bh}-L_{bulge} relation is only 0.33 dex, comparable to that of the M_{bh}-sigma relation. These results indicate that reliable black-hole mass estimates can be obtained for high redshift galaxies.

[]

https://arxiv.org/pdf/astro-ph/0108417.pdf

2011Sci...333..203B

A Possible Relativistic Jetted Outburst from a Massive Black Hole Fed by a Tidally Disrupted Star

2011-01-01

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

[]

Gas accretion onto some massive black holes (MBHs) at the centers of galaxies actively powers luminous emission, but most MBHs are considered dormant. Occasionally, a star passing too near an MBH is torn apart by gravitational forces, leading to a bright tidal disruption flare (TDF). Although the high-energy transient Sw 1644+57 initially displayed none of the theoretically anticipated (nor previously observed) TDF characteristics, we show that observations suggest a sudden accretion event onto a central MBH of mass about 10<SUP>6</SUP> to 10<SUP>7</SUP> solar masses. There is evidence for a mildly relativistic outflow, jet collimation, and a spectrum characterized by synchrotron and inverse Compton processes; this leads to a natural analogy of Sw 1644+57 to a temporary smaller-scale blazar.

[]

https://arxiv.org/pdf/1104.3257.pdf

2006MNRAS.368.1561M

General relativistic magnetohydrodynamic simulations of the jet formation and large-scale propagation from black hole accretion systems

2006-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies jets', 'gamma rays', 'astronomy x rays', 'astrophysics']

[]

The formation and large-scale propagation of Poynting-dominated jets produced by accreting, rapidly rotating black hole systems are studied by numerically integrating the general relativistic magnetohydrodynamic equations of motion to follow the self-consistent interaction between accretion discs and black holes. This study extends previous similar work by studying jets till t~ 10<SUP>4</SUP>GM/c<SUP>3</SUP> out to r~ 10<SUP>4</SUP>GM/c<SUP>2</SUP>, by which the jet is superfast magnetosonic and moves at a lab-frame bulk Lorentz factor of Γ~ 10 with a maximum terminal Lorentz factor of Γ<SUB>∞</SUB>&lt;~ 10<SUP>3</SUP>. The radial structure of the Poynting-dominated jet is piece-wise self-similar, and fits to flow quantities along the field line are provided. Beyond the Alfvén surface at r~ 10-100GM/c<SUP>2</SUP>, the jet becomes marginally unstable to (at least) current-driven instabilities. Such instabilities drive shocks in the jet that limit the efficiency of magnetic acceleration and collimation. These instabilities also induce jet substructure with 3 &lt;~Γ&lt;~ 15. The jet is shown to only marginally satisfy the necessary and sufficient conditions for kink instability, so this may explain how astrophysical jets can extend to large distances without completely disrupting. At large distance, the jet angular structure is Gaussian-like (or uniform within the core with sharp exponential wings) with a half-opening angle of ~5° and there is an extended component out to ~ 27°. Unlike in some hydrodynamic simulations, the environment is found to play a negligible role in jet structure, acceleration, and collimation as long as the ambient pressure of the surrounding medium is small compared to the magnetic pressure in the jet.

[]

https://arxiv.org/pdf/astro-ph/0603045.pdf

2021JPhG...48d3001G

Primordial black holes as a dark matter candidate

2021-01-01

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

[]

The detection of gravitational waves from mergers of tens of Solar mass black hole binaries has led to a surge in interest in primordial black holes (PBHs) as a dark matter candidate. We aim to provide a (relatively) concise overview of the status of PBHs as a dark matter candidate, circa Summer 2020. First we review the formation of PBHs in the early Universe, focussing mainly on PBHs formed via the collapse of large density perturbations generated by inflation. Then we review the various current and future constraints on the present day abundance of PBHs. We conclude with a discussion of the key open questions in this field.

[]

https://arxiv.org/pdf/2007.10722.pdf

2019NatAs...3..524N

Microlensing constraints on primordial black holes with Subaru/HSC Andromeda observations

2019-01-01

['-', '-']

[]

Primordial black holes (PBHs) have long been suggested as a viable candidate for the elusive dark matter. The abundance of such PBHs has been constrained using a number of astrophysical observations, except for a hitherto unexplored mass window of M<SUB>PBH</SUB> = [10<SUP>-14</SUP>, 10<SUP>-9</SUP>] solar masses. Here we carry out a dense-cadence, 7-hour-long observation of M31 with the Subaru Hyper Suprime-Cam (HSC) to search for microlensing of stars in M31 by PBHs lying in the halo regions of the Milky Way and M31. Given our simultaneous monitoring of tens of millions of stars in M31, if such light PBHs make up a significant fraction of dark matter, we expect to find many microlensing events. However, we identify only a single candidate event, which translates into stringent upper bounds on the abundance of PBHs in the mass range M<SUB>PBH</SUB> ≃ [10<SUP>-11</SUP>, 10<SUP>-6</SUP>] solar masses.

[]

https://arxiv.org/pdf/1701.02151.pdf

1999ApJ...522..413F

Mass Limits For Black Hole Formation

1999-01-01

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

[]

We present a series of two-dimensional core-collapse supernova simulations for a range of progenitor masses and different input physics. These models predict a range of supernova energies and compact remnant masses. In particular, we study two mechanisms for black hole formation: prompt collapse and delayed collapse owing to fallback. For massive progenitors (greater than 20 M<SUB>solar</SUB>), after a hydrodynamic time for the helium core (a few minutes to a few hours), fallback drives the compact object beyond the maximum neutron star mass, causing it to collapse into a black hole. With the current accuracy of the models, progenitors more massive than 40 M<SUB>solar</SUB> form black holes directly with no supernova explosion (if rotating, these black holes may be the progenitors of gamma-ray bursts). We calculate the mass distribution of black holes formed and compare these predictions to the observations, which represent a small biased subset of the black hole population. Uncertainties in these estimates are discussed.

[]

https://arxiv.org/pdf/astro-ph/9902315.pdf

2003MNRAS.340.1095D

Quasars, their host galaxies and their central black holes

2003-01-01

['black hole physics', 'galaxies active', 'galaxies photometry', 'galaxies quasars', 'astronomy infrared', 'astrophysics']

[]

We present the final results from our deep Hubble Space Telescope (HST) imaging study of the host galaxies of radio-quiet quasars (RQQs), radio-loud quasars (RLQs) and radio galaxies (RGs). We describe and analyse new Wide Field &amp; Planetary Camera 2 (WFPC2) R-band observations for 14 objects, which when combined with the first tranche of HST imaging reported in McLure et al., provide a complete and consistent set of deep, red, line-free images for statistically matched samples of 13 RQQs, 10 RLQs and 10 RGs in the redshift band 0.1 &lt; z &lt; 0.25. We also report the results of new deep VLA imaging that has yielded a 5-GHz detection of all but one of the 33 active galactic nuclei (AGN) in our sample. <P />Careful modelling of our images, aided by a high dynamic-range point spread function, has allowed us to determine accurately the morphology, luminosity, scalelength and axial ratio of every host galaxy in our sample. Armed with this information we have undertaken a detailed comparison of the properties of the hosts of these three types of powerful AGN, both internally and with the galaxy population in general. <P />We find that spheroidal hosts become more prevalent with increasing nuclear luminosity such that, for nuclear luminosities M<SUB>V</SUB> &lt; -23.5, the hosts of both radio-loud and radio-quiet AGN are virtually all massive ellipticals. Moreover, we demonstrate that the basic properties of these hosts are indistinguishable from those of quiescent, evolved, low-redshift ellipticals of comparable mass. This result rules out the possibility that radio-loudness is determined by host-galaxy morphology, and also sets severe constraints on evolutionary schemes that attempt to link low-z ultraluminous infrared galaxies with RQQs. <P />Instead, we show that our results are as expected given the relationship between black hole and spheroid mass established for nearby galaxies, and apply this relation to estimate the mass of the black hole in each object. The results agree remarkably well with completely independent estimates based on nuclear emission-line widths; all the quasars in our sample have M<SUB>bh</SUB> &gt; 5 × 10<SUP>8</SUP> M<SUB>solar</SUB>, while the radio-loud objects are confined to M<SUB>bh</SUB> &gt; 10<SUP>9</SUP> M<SUB>solar</SUB>. This apparent mass-threshold difference, which provides a natural explanation for why RQQs outnumber RLQs by a factor of 10, appears to reflect the existence of a minimum and a maximum level of black hole radio output, which is a strong function of black hole mass (~M<SUP>2-2.5</SUP><SUB>bh</SUB>). Finally, we use our results to estimate the fraction of massive spheroids/black holes that produce quasar-level activity. This fraction is ~=0.1 per cent at the present day, rising to &gt;10 per cent at z~= 2-3.

[]

https://arxiv.org/pdf/astro-ph/0108397.pdf

2001PhRvD..64l4013D

Coalescence of two spinning black holes: An effective one-body approach

2001-01-01

['-', '-', '-', '-', 'waves', '-', 'perturbation theory', '-', '-', 'black hole physics', '-']

[]

We generalize to the case of spinning black holes a recently introduced ``effective one-body'' approach to the general relativistic dynamics of binary systems. We show how to approximately map the conservative part of the third post-Newtonian (3PN) dynamics of two spinning black holes of masses m<SUB>1</SUB>, m<SUB>2</SUB> and spins S<SUB>1</SUB>, S<SUB>2</SUB> onto the dynamics of a non-spinning particle of mass μ≡m<SUB>1</SUB>m<SUB>2</SUB>/(m<SUB>1</SUB>+m<SUB>2</SUB>) in a certain effective metric g<SUP>eff</SUP><SUB>μν</SUB>(x<SUP>λ</SUP>M,ν,a) which can be viewed either as a spin deformation [with the deformation parameter a≡S<SUB>eff</SUB>/M] of the recently constructed 3PN effective metric g<SUP>eff</SUP><SUB>μν</SUB>(x<SUP>λ</SUP>M,ν), or as a ν deformation [with the comparable-mass deformation parameter ν≡m<SUB>1</SUB>m<SUB>2</SUB>/(m<SUB>1</SUB>+m<SUB>2</SUB>)<SUP>2</SUP>] of a Kerr metric of mass M≡m<SUB>1</SUB>+m<SUB>2</SUB> and (effective) spin S<SUB>eff</SUB>≡[1+3m<SUB>2</SUB>/(4m<SUB>1</SUB>)]S<SUB>1</SUB>+[1+3m<SUB>1</SUB>/(4m<SUB>2</SUB>)]S<SUB>2</SUB>. The combination of the effective one-body approach, and of a Padé definition of the crucial effective radial functions, is shown to define a dynamics with much improved post-Newtonian convergence properties, even for black hole separations of the order of 6 GM/c<SUP>2</SUP>. The complete (conservative) phase-space evolution equations of binary spinning black hole systems are written down and their exact and approximate first integrals are discussed. This leads to the approximate existence of a two-parameter family of ``spherical orbits'' (with constant radius), and of a corresponding one-parameter family of ``last stable spherical orbits'' (LSSO). These orbits are of special interest for forthcoming LIGO-VIRGO-GEO gravitational wave observations. The binding energy and total angular momentum of LSSO's are studied in some detail. It is argued that for most (but not all) of the parameter space of two spinning holes the approximate (leading-order) effective one-body approach introduced here gives a reliable analytical tool for describing the dynamics of the last orbits before coalescence. This tool predicts, in a quantitative way, how certain spin orientations increase the binding energy of the LSSO. This leads to a detection bias, in LIGO-VIRGO-GEO observations, favoring spinning black hole systems, and makes it urgent to complete the conservative effective one-body dynamics given here by adding (resummed) radiation reaction effects, and by constructing gravitational waveform templates that include spin effects. Finally, our approach predicts that the spin of the final hole formed by the coalescence of two arbitrarily spinning holes never approaches extremality.

[]

https://arxiv.org/pdf/gr-qc/0103018.pdf

1996PhRvD..54.3915G

Entropy and temperature of black 3-branes

1996-01-01

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

[]

We consider slightly nonextremal black 3-branes of type IIB supergravity and show that their Bekenstein-Hawking entropy agrees, up to a mysterious factor, with an entropy derived by counting non-BPS excitations of the Dirichlet 3-brane. These excitations are described in terms of the statistical mechanics of a (3+1)-dimensional gas of massless open string states. This is essentially the classic problem of blackbody radiation. The blackbody temperature is related to the temperature of the Hawking radiation. We also construct a solution of type IIB supergravity describing a 3-brane with a finite density of longitudinal momentum. For extremal momentum-carrying 3-branes the horizon area vanishes. This is in agreement with the fact that the BPS entropy of the momentum-carrying Dirichlet 3-branes is not an extensive quantity.

[]

https://arxiv.org/pdf/hep-th/9602135.pdf

2023Univ....9...88M

Gravitational Condensate Stars: An Alternative to Black Holes

2023-01-01

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

[]

A new final endpoint of complete gravitational collapse is proposed. By extending the concept of Bose–Einstein condensation to gravitational systems, a static, spherically symmetric solution to Einstein's equations is obtained, characterized by an interior de Sitter region of p=‑ρ gravitational vacuum condensate and an exterior Schwarzschild geometry of arbitrary total mass M. These are separated by a phase boundary with a small but finite thickness ℓ, replacing both the Schwarzschild and de Sitter classical horizons. The resulting collapsed cold, compact object has no singularities, no event horizons, and a globally defined Killing time. Its entropy is maximized under small fluctuations and is given by the standard hydrodynamic entropy of the thin shell, which is of order kBℓMc/ℏ, instead of the Bekenstein–Hawking entropy, SBH=4πkBGM2/ℏc. Unlike BHs, a collapsed star of this kind is consistent with quantum theory, thermodynamically stable, and suffers from no information paradox.

[]

https://arxiv.org/pdf/gr-qc/0109035.pdf

2016PhRvD..93h4029R

Binary black hole mergers from globular clusters: Masses, merger rates, and the impact of stellar evolution

2016-01-01

['-', '-']

[]

The recent discovery of GW150914, the binary black hole merger detected by Advanced LIGO, has the potential to revolutionize observational astrophysics. But to fully utilize this new window into the Universe, we must compare these new observations to detailed models of binary black hole formation throughout cosmic time. Expanding upon our previous work [C. L. Rodriguez, M. Morscher, B. Pattabiraman, S. Chatterjee, C.-J. Haster, and F. A. Rasio, Phys. Rev. Lett. 115, 051101 (2015).], we study merging binary black holes formed in globular clusters using our Monte Carlo approach to stellar dynamics. We have created a new set of 52 cluster models with different masses, metallicities, and radii to fully characterize the binary black hole merger rate. These models include all the relevant dynamical processes (such as two-body relaxation, strong encounters, and three-body binary formation) and agree well with detailed direct N -body simulations. In addition, we have enhanced our stellar evolution algorithms with updated metallicity-dependent stellar wind and supernova prescriptions, allowing us to compare our results directly to the most recent population synthesis predictions for merger rates from isolated binary evolution. We explore the relationship between a cluster's global properties and the population of binary black holes that it produces. In particular, we derive a numerically calibrated relationship between the merger times of ejected black hole binaries and a cluster's mass and radius. With our improved treatment of stellar evolution, we find that globular clusters can produce a significant population of massive black hole binaries that merge in the local Universe. We explore the masses and mass ratios of these binaries as a function of redshift, and find a merger rate of ∼5 Gpc<SUP>-3</SUP>yr<SUP>-1</SUP> in the local Universe, with 80% of sources having total masses from 32 M<SUB>⊙</SUB> to 64 M<SUB>⊙</SUB>. Under standard assumptions, approximately one out of every seven binary black hole mergers in the local Universe will have originated in a globular cluster, but we also explore the sensitivity of this result to different assumptions for binary stellar evolution. If black holes were born with significant natal kicks, comparable to those of neutron stars, then the merger rate of binary black holes from globular clusters would be comparable to that from the field, with approximately 1 /2 of mergers originating in clusters. Finally we point out that population synthesis results for the field may also be modified by dynamical interactions of binaries taking place in dense star clusters which, unlike globular clusters, dissolved before the present day.

[]

https://arxiv.org/pdf/1602.02444.pdf

2019arXiv191111977P

Replica wormholes and the black hole interior

2019-01-01

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

[]

Recent work has shown how to obtain the Page curve of an evaporating black hole from holographic computations of entanglement entropy. We show how these computations can be justified using the replica trick, from geometries with a spacetime wormhole connecting the different replicas. In a simple model, we study the Page transition in detail by summing replica geometries with different topologies. We compute related quantities in less detail in more complicated models, including JT gravity coupled to conformal matter and the SYK model. Separately, we give a direct gravitational argument for entanglement wedge reconstruction using an explicit formula known as the Petz map; again, a spacetime wormhole plays an important role. We discuss an interpretation of the wormhole geometries as part of some ensemble average implicit in the gravity description.

[]

https://arxiv.org/pdf/1911.11977.pdf

2010RAA....10..495K

Primordial black holes

2010-01-01

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

[]

Primordial black holes (PBHs) are a profound signature of primordial cosmological structures and provide a theoretical tool to study nontrivial physics of the early Universe. The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum, or effects of PBH evaporation, are shown to restrict a wide range of particle physics models, predicting an enhancement of the ultraviolet part of the spectrum of density perturbations, early dust-like stages, first order phase transitions and stages of superheavy metastable particle dominance in the early Universe. The mechanism of closed wall contraction can lead, in the inflationary Universe, to a new approach to galaxy formation, involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds.

[]

https://arxiv.org/pdf/0801.0116.pdf

2017PhRvD..95d4028B

Improved effective-one-body model of spinning, nonprecessing binary black holes for the era of gravitational-wave astrophysics with advanced detectors

2017-01-01

['-']

[]

We improve the accuracy of the effective-one-body (EOB) waveforms that were employed during the first observing run of Advanced LIGO for binaries of spinning, nonprecessing black holes by calibrating them to a set of 141 numerical-relativity (NR) waveforms. The NR simulations expand the domain of calibration toward larger mass ratios and spins, as compared to the previous EOBNR model. Merger-ringdown waveforms computed in black-hole perturbation theory for Kerr spins close to extremal provide additional inputs to the calibration. For the inspiral-plunge phase, we use a Markov-chain Monte Carlo algorithm to efficiently explore the calibration space. For the merger-ringdown phase, we fit the NR signals with phenomenological formulae. After extrapolation of the calibrated model to arbitrary mass ratios and spins, the (dominant-mode) EOBNR waveforms have faithfulness—at design Advanced-LIGO sensitivity—above 99% against all the NR waveforms, including 16 additional waveforms used for validation, when maximizing only on initial phase and time. This implies a negligible loss in event rate due to modeling for these binary configurations. We find that future NR simulations at mass ratios ≳4 and double spin ≳0.8 will be crucial to resolving discrepancies between different ways of extrapolating waveform models. We also find that some of the NR simulations that already exist in such region of parameter space are too short to constrain the low-frequency portion of the models. Finally, we build a reduced-order version of the EOBNR model to speed up waveform generation by orders of magnitude, thus enabling intensive data-analysis applications during the upcoming observation runs of Advanced LIGO.

[]

https://arxiv.org/pdf/1611.03703.pdf

2001ApJ...554..548F

Theoretical Black Hole Mass Distributions

2001-01-01

['stars binaries general', 'black hole physics', '-', 'stars luminosity function;mass function', '-', '-', 'astrophysics']

[]

We derive the theoretical distribution function of black hole masses by studying the formation processes of black holes. We use the results of recent two-dimensional simulations of stellar core collapse to obtain the relation between remnant and progenitor masses and fold it with an initial mass function for the progenitors. Thus, we are able to derive the binary black hole mass distribution. We examine how the calculated black hole mass distributions are modified by (1) strong-wind mass loss at different evolutionary stages of the progenitors and (2) the presence of close binary companions to the black hole progenitors. The compact-remnant distribution is dominated by neutron stars in the mass range 1.2-1.6 M<SUB>solar</SUB> and falls off exponentially at higher remnant masses. Our results are most sensitive to mass loss from stellar winds (particularly from Wolf-Rayet stars), and the effects of winds are even more important in close binaries. Wind mass loss leads to flatter black hole mass distributions and limits the maximum possible black hole mass (&lt;~10-15 M<SUB>solar</SUB>). We also study the effects of the uncertainties in the explosion and unbinding energies for different progenitors. The distributions are continuous and extend over a broad range. We find no evidence for a gap at low values (3-5 M<SUB>solar</SUB>) or for a peak at higher values (~7 M<SUB>solar</SUB>) of black hole masses, but we argue that our black hole mass distribution for binaries is consistent with the current sample of measured black hole masses in X-ray transients. We discuss possible biases against the detection or formation of X-ray transients with low-mass black holes. We also comment on the possibility of black hole kicks and their effect on binaries.

[]

https://arxiv.org/pdf/astro-ph/9911312.pdf

1996PhRvL..77.3288R

Black Hole Entropy from Loop Quantum Gravity

1996-01-01

['-']

[]

We study the idea that the statistical entropy governing thermal interactions of a black hole with its exterior is determined by the microstates of the hole having distinct effects on the exterior, and over which a hole in a given macroscopic configuration thermally fluctuates. We argue that for a (macroscopically) Schwarzschild black hole this ensemble is formed by horizons with the same area. We compute the number of states in this ensemble from first principles using nonperturbative loop quantum gravity. We obtain a statistical entropy proportional to the area, as in the Bekenstein-Hawking formula.

[]

https://arxiv.org/pdf/gr-qc/9603063.pdf

1995NuPhB.433..403K

Self-interaction correction to black hole radiance

1995-01-01

['-', '-']

[]

We consider the modification of the formulas for black hole radiation, due to the self-gravitation of the radiation. This is done by truncating the coupled particle-hole system to a small set of modes, that are plausibly the most significant ones, and quantizing the reduced system. In this way we find that the particles no longer move along geodesics, nor is the action along the rays zero for a massless particle. The radiation is no longer thermal, but is corrected in a definite way that we calculate. Our methods can be extended in a straightforward manner to discuss correlations in the radiation, or between incoming particles and the radiation.

[]

https://arxiv.org/pdf/gr-qc/9408003.pdf

2009IJMPA..24.1229N

Noncommutative Black Holes, the Final Appeal to Quantum Gravity: A Review

2009-01-01

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

[]

We present the state of the art regarding the relation between the physics of Quantum Black Holes and Noncommutative Geometry. We start with a review of models proposed in the literature for describing deformations of General Relativity in the presence of noncommutativity, seen as an effective theory of Quantum Gravity. We study the resulting metrics, proposed to replace or at least to improve the conventional black hole solutions of Einstein's equation. In particular, we analyze noncommutative-inspired solutions obtained in terms of quasi-classical noncommutative coordinates: indeed because of their surprising new features, these solutions enable us to circumvent long standing problems with Quantum Field Theory in Curved Space and to cure the singular behavior of gravity at the centers of black holes. As a consequence, for the first time, we get a complete description of what we may call the black hole SCRAM, the shut down of the emission of thermal radiation from the black hole: in place of the conventional scenario of runaway evaporation in the Planck phase, we find a zero temperature final state, a stable black hole remnant, whose size and mass are determined uniquely in terms of the noncommutative parameter $\theta$. This result turns out to be of vital importance for the physics of the forthcoming experiments at the LHC, where mini black hole production is foreseen in extreme energy hadron collisions. Because of this, we devote the final part of this review to higher dimensional solutions and their phenomenological implications for TeV Gravity.

[]

https://arxiv.org/pdf/0807.1939.pdf

2000PhLB..487....1D

Black holes on the brane

2000-01-01

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

[]

We consider exact solutions for static black holes localized on a three-brane in five-dimensional gravity in the Randall-Sundrum scenario. We show that the Reissner-Nördstrom metric is an exact solution of the effective Einstein equations on the brane, re-interpreted as a black hole without electric charge, but with instead a tidal `charge' arising via gravitational effects from the fifth dimension. The tidal correction to the Schwarzschild potential is negative, which is impossible in general relativity, and in this case only one horizon is admitted, located outside the Schwarzschild horizon. The solution satisfies a closed system of equations on the brane, and describes the strong-gravity regime. Current observations do not strongly constrain the tidal charge, and significant tidal corrections could in principle arise in the strong-gravity regime and for primordial black holes.

[]

https://arxiv.org/pdf/hep-th/0003061.pdf

2011Natur.476..421B

Relativistic jet activity from the tidal disruption of a star by a massive black hole

2011-01-01

['-']

[]

Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.

[]

https://arxiv.org/pdf/1104.4787.pdf

2016A&A...588A..50M

A new route towards merging massive black holes

2016-01-01

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

[]

With recent advances in gravitational-wave astronomy, the direct detection of gravitational waves from the merger of two stellar-mass compact objects has become a realistic prospect. Evolutionary scenarios towards mergers of various double compact objects generally invoke so-called common-envelope evolution, which is poorly understood and leads to large uncertainties in the predicted merger rates. Here we explore, as an alternative, the scenario of massive overcontact binary (MOB) evolution, which involves two very massive stars in a very tight binary that remain fully mixed as a result of their tidally induced high spin. While many of these systems merge early on, we find many MOBs that swap mass several times, but survive as a close binary until the stars collapse. The simplicity of the MOB scenario allows us to use the efficient public stellar-evolution code MESA to explore it systematically by means of detailed numerical calculations. We find that, at low metallicity, MOBs produce double-black-hole (BH+BH) systems that will merge within a Hubble time with mass-ratios close to one, in two mass ranges, about 25...60 M<SUB>⊙</SUB> and ≳130M<SUB>⊙</SUB>, with pair-instability supernovae (PISNe) being produced at intermediate masses. Our models are also able to reproduce counterparts of various stages in the MOB scenario in the local Universe, providing direct support for the scenario. We map the initial binary parameter space that produces BH+BH mergers, determine the expected chirp mass distribution, merger times, and expected Kerr parameters, and predict event rates. We find typically one BH+BH merger event for ~1000 core-collapse supernovae for Z ≲ Z<SUB>⊙</SUB>/ 10 . The advanced LIGO (aLIGO) detection rate is more uncertain and depends on the cosmic metallicity evolution. From deriving upper and lower limits from a local and a global approximation for the metallicity distribution of massive stars, we estimate aLIGO detection rates (at the aLIGO design limit) of ~19-550 yr<SUP>-1</SUP> for BH-BH mergers below the PISN gap and of ~2.1-370 yr<SUP>-1</SUP> above the PISN gap. Even with conservative assumptions, we find that aLIGO will probably soon detect BH+BH mergers from the MOB scenario. These could be the dominant source for aLIGO detections.

[]

https://arxiv.org/pdf/1601.03718.pdf

2006ApJ...652..216R

The Feedback-regulated Growth of Black Holes and Bulges through Gas Accretion and Starbursts in Cluster Central Dominant Galaxies

2006-01-01

['galaxies cooling flows', 'galaxies active', 'galaxies clusters', 'astronomy x rays', 'astronomy x rays', 'astrophysics']

[]

We present an analysis of the growth of black holes through accretion and bulges through star formation in 33 galaxies at the centers of cooling flows. Most of these systems show evidence of cavities in the intracluster medium (ICM) inflated by radio jets emanating from their active galactic nuclei (AGNs). We present a new and extensive analysis of X-ray cavities in these systems. We find that AGNs are energetically able to balance radiative losses (cooling) from the ICM in more than half of our sample. We examine the relationship between cooling and star formation and find that the star formation rates are approaching or are comparable to X-ray and far-UV limits on the rates of gas condensation onto the central galaxy. The vast gulf between radiative losses and the sink of cooling material, which has been the primary objection to cooling flows, has narrowed significantly. Using the cavity (jet) powers, we place strong lower limits on the rate of growth of the central black holes, and we find that they are growing at an average rate of ~0.1 M<SUB>solar</SUB> yr<SUP>-1</SUP>, with some systems growing as quickly as ~1 M<SUB>solar</SUB> yr<SUP>-1</SUP>. We find a trend between bulge growth (star formation) and black hole growth that is approximately in accordance with the slope of the local (Magorrian) relation between black hole and bulge mass, but the scatter suggests that bulges and black holes do not necessarily grow in lockstep. Bondi accretion can power the low-luminosity sources, provided the nuclear gas density rises as ~r<SUP>-1</SUP> to the Bondi radius, but is probably too feeble to fuel the most powerful outbursts.

[]

https://arxiv.org/pdf/astro-ph/0605323.pdf

1997NuPhB.500...75F

Black holes and critical points in moduli space

1997-01-01

['-']

[]

We study the stabilization of scalars near a supersymmetric black hole horizon using the equation of motion of a particle moving in a potential and background metric. When the relevant 4-dimensional theory is described by special geometry, the generic properties of the critical points of this potential can be studied. We find that the extremal value of the central charge provides the minimal value of the BPS mass and of the potential under the condition that the moduli space metric is positive at the critical point. This is a property of a regular special geometry. We also study the critical points in all N &gt;= 2 supersymmetric theories. We relate these ideas to the Weinhold and Ruppeiner metrics introduced in the geometric approach to thermodynamics and used for the study of critical phenomena.

[]

https://arxiv.org/pdf/hep-th/9702103.pdf

2009JHEP...01..055E

Fluid dynamics of R-charged black holes

2009-01-01

['-']

[]

We construct electrically charged AdS<SUB>5</SUB> black hole solutions whose charge, mass and boost-parameters vary slowly with the space-time coordinates. From the perspective of the dual theory, these are equivalent to hydrodynamic configurations with varying chemical potential, temperature and velocity fields. We compute the boundary theory transport coefficients associated with a derivative expansion of the energy momentum tensor and R-charge current up to second order. In particular, for the current we find a first order transport coefficient associated with the vorticity of the fluid.

[]

https://arxiv.org/pdf/0809.2488.pdf

2002NuPhB.623..342L

AdS/CFT duality and the black hole information paradox

2002-01-01

['-', '-']

[]

Near-extremal black holes are obtained by exciting the Ramond sector of the D1-D5 CFT, where the ground state is highly degenerate. We find that the dual geometries for these ground states have throats that end in a way that is characterized by the CFT state. Below the black hole threshold we find a detailed agreement between propagation in the throat and excitations of the CFT. We study the breakdown of the semiclassical approximation and relate the results to the proposal of gr-qc/0007011 for resolving the information paradox: semiclassical evolution breaks down if hypersurfaces stretch too much during an evolution. We find that a volume V stretches to a maximum throat depth of V/2G .

[]

https://arxiv.org/pdf/hep-th/0109154.pdf

2018PhRvL.120m1104S

Spontaneous Scalarization of Black Holes and Compact Stars from a Gauss-Bonnet Coupling

2018-01-01

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

[]

We identify a class of scalar-tensor theories with coupling between the scalar and the Gauss-Bonnet invariant that exhibit spontaneous scalarization for both black holes and compact stars. In particular, these theories formally admit all of the stationary solutions of general relativity, but these are not dynamically preferred if certain conditions are satisfied. Remarkably, black holes exhibit scalarization if their mass lies within one of many narrow bands. We find evidence that scalarization can occur in neutron stars as well.

[]

https://arxiv.org/pdf/1711.02080.pdf

2000PhRvD..62d3008B

Renormalization group improved black hole spacetimes

2000-01-01

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

[]

We study the quantum gravitational effects in spherically symmetric black hole spacetimes. The effective quantum spacetime felt by a pointlike test mass is constructed by ``renormalization group improving'' the Schwarzschild metric. The key ingredient is the running Newton constant which is obtained from the exact evolution equation for the effective average action. The conformal structure of the quantum spacetime depends on its ADM mass M and it is similar to that of the classical Reissner-Nordström black hole. For M larger than, equal to, and smaller than a certain critical mass M<SUB>cr</SUB> the spacetime has two, one, and no horizon(s), respectively. Its Hawking temperature, specific heat capacity, and entropy are computed as a function of M. It is argued that the black hole evaporation stops when M approaches M<SUB>cr</SUB> which is of the order of the Planck mass. In this manner a ``cold'' soliton-like remnant with the near-horizon geometry of AdS<SUB>2</SUB>×S<SUP>2</SUP> is formed. As a consequence of the quantum effects, the classical singularity at r=0 is either removed completely or it is at least much milder than classically; in the first case the quantum spacetime has a smooth de Sitter core which would be in accord with the cosmic censorship hypothesis even if M&lt;M<SUB>cr</SUB>.

[]

https://arxiv.org/pdf/hep-th/0002196.pdf

2017ApJ...835..165B

Rapid and Bright Stellar-mass Binary Black Hole Mergers in Active Galactic Nuclei

2017-01-01

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

[]

The Laser Interferometer Gravitational-wave Observatory (LIGO) found direct evidence for double black hole binaries emitting gravitational waves. Galactic nuclei are expected to harbor the densest population of stellar-mass black holes. A significant fraction (∼ 30 % ) of these black holes can reside in binaries. We examine the fate of the black hole binaries in active galactic nuclei, which get trapped in the inner region of the accretion disk around the central supermassive black hole. We show that binary black holes can migrate into and then rapidly merge within the disk well within a Salpeter time. The binaries may also accrete a significant amount of gas from the disk, well above the Eddington rate. This could lead to detectable X-ray or gamma-ray emission, but would require hyper-Eddington accretion with a few percent radiative efficiency, comparable to thin disks. We discuss implications for gravitational-wave observations and black hole population studies. We estimate that Advanced LIGO may detect ∼20 such gas-induced binary mergers per year.

[]

https://arxiv.org/pdf/1602.03831.pdf

2008ApJ...676...33D

Direct Cosmological Simulations of the Growth of Black Holes and Galaxies

2008-01-01

['cosmology theory', 'galaxies active', 'galaxies evolution', 'galaxies formation', 'hydrodynamics', 'galaxies quasars', 'astrophysics']

[]

We investigate the coupled formation and evolution of galaxies and their embedded supermassive black holes using state-of-the-art hydrodynamic simulations of cosmological structure formation. For the first time, we self-consistently follow the dark matter dynamics, radiative gas cooling, and star formation, as well as BH growth and associated feedback processes, starting directly from initial conditions appropriate for the ΛCDM cosmology. Our modeling of the black hole physics is based on an approach that we have developed in simulations of isolated galaxy mergers. Here we examine (1) the predicted global history of BH mass assembly, (2) the evolution of the local black hole-host mass correlations, and (3) the conditions that allow rapid growth of the first quasars, and the properties of their hosts and descendants today. We find a total BH mass density in good agreement with observational estimates. The BH accretion rate density peaks at lower redshift and evolves more strongly at high redshift than the star formation rate density, but the ratio of black hole to stellar mass density shows only a moderate evolution at low redshifts. We find strong correlations between BH masses and properties of the stellar systems, agreeing well with the measured local M<SUB>BH</SUB>-σ and M<SUB>BH</SUB>-M<SUB>*</SUB> relationships, but also suggesting (dependent on the mass range) a weak evolution with redshift in the normalization and the slope. Our simulations also produce massive black holes at high redshift, due to extended periods of exponential growth in regions that collapse early and exhibit strong gas inflows. These first supermassive BH systems, however, are not necessarily the most massive ones today, since they are often overtaken in growth by quasars that form later.

[]

https://arxiv.org/pdf/0705.2269.pdf

2001ApJS..132..377H

Correlated X-Ray Spectral and Timing Behavior of the Black Hole Candidate XTE J1550-564: A New Interpretation of Black Hole States

2001-01-01

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

[]

We present an analysis of data of the black hole candidate and X-ray transient XTE J1550-564, taken with the Rossi X-Ray Timing Explorer between 1998 November 22 and 1999 May 20. During this period the source went through several different states, which could be divided into soft and hard states based on the relative strength of the high-energy spectral component. These states showed up as distinct branches in the color-color and hardness-intensity diagrams, connecting to form a structure with a comblike topology, the branch corresponding to the soft state forming the spine and the branches corresponding to the various hard states forming the teeth of the comb. The power spectral properties of the source were strongly correlated with its position on the branches. The broadband noise became stronger and changed from power law-like to band-limited, as the spectrum became harder. Three types of quasi-periodic oscillations (QPOs) were found: 1-18 Hz and 102-284 Hz QPOs on the hard branches, and 16-18 Hz QPOs on and near the soft branch. The 1-18 Hz QPOs on the hard branches could be divided into three subtypes. The frequencies of the high- and low-frequency QPOs on the hard branches were correlated with each other and were anticorrelated with spectral hardness. The changes in QPO frequency suggest that the inner disk radius only increases by a factor of 3-4 as the source changes from a soft to a hard state. Our results on XTE J1550-564 strongly favor a two-dimensional description of black hole behavior, where the regions near the spine of the comb in the color-color diagram can be identified with the high state, and the teeth with transitions from the high state, via the intermediate state (which includes the very high state) to the low state, and back. The two physical parameters underlying this two-dimensional behavior vary to a large extent independently and could for example be the accretion rate through the disk and the size of the Comptonizing region causing the hard tail. The difference between the various teeth is then associated with the mass accretion rate through the disk, suggesting that high state&lt;--&gt;low state transitions can occur at any disk mass accretion rate and that these transitions are primarily caused by another, independent parameter. We discuss how this picture could tie in with the canonical, one-dimensional behavior of black hole candidates that has usually been observed.

[]

https://arxiv.org/pdf/astro-ph/0001163.pdf

2002NuPhB.628..295C

Black hole thermodynamics and negative entropy in de Sitter and anti-de Sitter Einstein-Gauss-Bonnet gravity

2002-01-01

['-', '-']

[]

We investigate the charged Schwarzschild-anti-de Sitter (SAdS) BH thermodynamics in 5d Einstein-Gauss-Bonnet gravity with electromagnetic field. The Hawking-Page phase transitions between SAdS BH and pure AdS space are studied. The corresponding phase diagrams (with critical line defined by GB term coefficient and electric charge) are drawn. The possibility to account for higher derivative Maxwell terms is mentioned. In frames of proposed dS/CFT correspondence it is demonstrated that brane gravity maybe localized similarly to AdS/CFT. SdS BH thermodynamics in 5d Einstein and Einstein-Gauss-Bonnet gravity is considered. The corresponding (complicated) surface counterterms are found and used to get the conserved BH mass, free energy and entropy. The interesting feature of higher derivative gravity is the possibility for negative (or zero) SdS (or SAdS) BH entropy which depends on the parameters of higher derivative terms. We speculate that the appearance of negative entropy may indicate a new type instability where a transition between SdS (SAdS) BH with negative entropy to SAdS (SdS) BH with positive entropy would occur.

[]

https://arxiv.org/pdf/hep-th/0112045.pdf

2005PhRvL..95l0404F

Alice Falls into a Black Hole: Entanglement in Noninertial Frames

2005-01-01

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

[]

Two observers determine the entanglement between two free bosonic modes by each detecting one of the modes and observing the correlations between their measurements. We show that a state which is maximally entangled in an inertial frame becomes less entangled if the observers are relatively accelerated. This phenomenon, which is a consequence of the Unruh effect, shows that entanglement is an observer-dependent quantity in noninertial frames. In the high acceleration limit, our results can be applied to a nonaccelerated observer falling into a black hole while the accelerated one barely escapes. If the observer escapes with infinite acceleration, the state’s distillable entanglement vanishes.

[]

https://arxiv.org/pdf/quant-ph/0410172.pdf

2013ApJ...767...25G

Hydrodynamical Simulations to Determine the Feeding Rate of Black Holes by the Tidal Disruption of Stars: The Importance of the Impact Parameter and Stellar Structure

2013-01-01

['accretion', 'accretion disks', 'black hole physics', 'gravitation', 'hydrodynamics', 'methods numerical', '-']

[]

The disruption of stars by supermassive black holes has been linked to more than a dozen flares in the cores of galaxies out to redshift z ~ 0.4. Modeling these flares properly requires a prediction of the rate of mass return to the black hole after a disruption. Through hydrodynamical simulation, we show that aside from the full disruption of a solar mass star at the exact limit where the star is destroyed, the common assumptions used to estimate \dot{M}(t), the rate of mass return to the black hole, are largely invalid. While the analytical approximation to tidal disruption predicts that the least-centrally concentrated stars and the deepest encounters should have more quickly-peaked flares, we find that the most-centrally concentrated stars have the quickest-peaking flares, and the trend between the time of peak and the impact parameter for deeply penetrating encounters reverses beyond the critical distance at which the star is completely destroyed. We also show that the most-centrally concentrated stars produced a characteristic drop in \dot{M}(t) shortly after peak when a star is only partially disrupted, with the power law index n being as extreme as -4 in the months immediately following the peak of a flare. Additionally, we find that n asymptotes to ~= - 2.2 for both low- and high-mass stars for approximately half of all stellar disruptions. Both of these results are significantly steeper than the typically assumed n = -5/3. As these precipitous decay rates are only seen for events in which a stellar core survives the disruption, they can be used to determine if an observed tidal disruption flare produced a surviving remnant. We provide fitting formulae for four fundamental quantities of tidal disruption as functions of the star's distance to the black hole at pericenter and its stellar structure: the total mass lost, the time of peak, the accretion rate at peak, and the power-law index shortly after peak. These results should be taken into consideration when flares arising from tidal disruptions are modeled.

[]

https://arxiv.org/pdf/1206.2350.pdf

2013LRR....16....1A

Foundations of Black Hole Accretion Disk Theory

2013-01-01

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

[]

This review covers the main aspects of black hole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of black holes themselves. In this light we discuss how accretion disks might reveal some of the unique signatures of strong gravity: the event horizon, the innermost stable circular orbit, and the ergosphere. We then review, from a first-principles perspective, the physical processes at play in accretion disks. This leads us to the four primary accretion disk models that we review: Polish doughnuts (thick disks), Shakura-Sunyaev (thin) disks, slim disks, and advection-dominated accretion flows (ADAFs). After presenting the models we discuss issues of stability, oscillations, and jets. Following our review of the analytic work, we take a parallel approach in reviewing numerical studies of black hole accretion disks. We finish with a few select applications that highlight particular astrophysical applications: measurements of black hole mass and spin, black hole vs. neutron star accretion disks, black hole accretion disk spectral states, and quasi-periodic oscillations (QPOs).

[]

https://arxiv.org/pdf/1104.5499.pdf

2008ApJ...680..169S

Biases in Virial Black Hole Masses: An SDSS Perspective

2008-01-01

['black hole physics', 'galaxies active', 'galaxies fundamental parameters', 'galaxies photometry', 'galaxies quasars', 'surveys', 'astrophysics']

[]

We compile black hole (BH) masses for ~60,000 quasars in the redshift range 0.1lesssim zlesssim 4.5 included in the Fifth Data Release of the Sloan Digital Sky Survey, using virial BH mass estimators based on the Hβ, Mg II, and C IV emission lines. Within our sample, the widths of the three lines follow lognormal distributions, with means and dispersions that do not depend strongly on luminosity or redshift. The Mg II- and Hβ-estimated BH masses are consistent with one another, but there is a positive bias between the C IV- and Mg II-estimated BH masses correlated with the C IV-Mg II blueshift, suggesting that the C IV estimator is more severely affected by a disk wind. If the underlying BH mass distribution decreases with mass and the Eddington ratio distribution at fixed true BH mass has nonzero width, we show that the measured virial BH mass and Eddington ratio distributions within finite luminosity bins are subject to Malmquist bias. We present a model that reproduces the observed virial mass distribution, quasar luminosity function, and line width distribution of our sample; it has an underlying BH mass distribution dN/dlog M propto M<SUP>-2.6</SUP> and a lognormal true Eddington ratio distribution at fixed true mass with dispersion 0.4 dex and mean dependent on BH mass. In this model, the observed virial mass (Eddington ratio) distribution for the SDSS sample is biased high (low) by ~0.6 dex within finite luminosity bins. Finally, we compare virial BH masses of radio and broad absorption line quasars with ordinary quasars matched in redshift and luminosity.

[]

https://arxiv.org/pdf/0709.3098.pdf

1995CQGra..12.2853C

TOPICAL REVIEW: The (2 + 1)-dimensional black hole

1995-01-01

['-', '-']

[]

I review the classical and quantum properties of the (2+1)-dimensional black hole of Ba{ñ}ados, Teitelboim, and Zanelli. This solution of the Einstein field equations in three spacetime dimensions shares many of the characteristics of the Kerr black hole: it has an event horizon, an inner horizon, and an ergosphere; it occurs as an endpoint of gravitational collapse; it exhibits mass inflation; and it has a nonvanishing Hawking temperature and interesting thermodynamic properties. At the same time, its structure is simple enough to allow a number of exact computations, particularly in the quantum realm, that are impractical in 3+1 dimensions.

[]

https://arxiv.org/pdf/gr-qc/9506079.pdf

2007MNRAS.377.1187P

Supercritically accreting stellar mass black holes as ultraluminous X-ray sources

2007-01-01

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

[]

We derive the luminosity-temperature relation for the supercritically accreting black holes (BHs) and compare it to the data on ultraluminous X-ray sources (ULXs). At super-Eddington accretion rates, an outflow forms within the spherization radius. We construct the accretion disc model accounting for the advection and the outflow, and compute characteristic disc temperatures. The bolometric luminosity exceeds the Eddington luminosity L<SUB>Edd</SUB> by a logarithmic factor (where is the accretion rate in Eddington units) and the wind kinetic luminosity is close to L<SUB>Edd</SUB>. The apparent luminosity for the face-on observer is 2-7 times higher because of geometrical beaming. Such an observer has a direct view of the inner hot accretion disc, which has a peak temperature T<SUB>max</SUB> of a few keV in stellar mass BHs. The emitted spectrum extends as a power law F<SUB>E</SUB> ~ E<SUP>-1</SUP> down to the temperature at the spherization radius . We associate T<SUB>max</SUB> with a few keV spectral components and T<SUB>sp</SUB> with the soft, 0.1-0.2 keV components observed in ULXs. An edge-on observer sees only the soft emission from the extended envelope, with the photosphere radius exceeding the spherization radius by orders of magnitude. The dependence of the photosphere temperature on luminosity is consistent with that observed in the super-Eddington accreting BHs SS 433 and V4641 Sgr. Strong outflows combined with the large intrinsic X-ray luminosity of the central BH explain naturally the presence of the photoionized nebulae around ULXs. An excellent agreement between the model and the observational data strongly argues in favour of ULXs being supercritically accreting, stellar mass BHs similar to SS 433, but viewed close to the symmetric axis.

[]

https://arxiv.org/pdf/astro-ph/0609274.pdf

2006ApJ...652.1028B

Constraining Black Hole Spin via X-Ray Spectroscopy

2006-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies', 'galaxies nuclei', 'galaxies seyfert', 'astronomy x rays', 'astrophysics']

[]

We present an analysis of the observed broad iron line feature and putative warm absorber in the long 2001 XMM-Newton observation of the Seyfert 1.2 galaxy MCG -06-30-15. The new kerrdisk model we have designed for simulating line emission from accretion disk systems allows black hole spin to be a free parameter in the fit, enabling the user to formally constrain the angular momentum of a black hole, among other physical parameters of the system. In an important extension of previous work, we derive constraints on the black hole spin in MCG -06-30-15 using a self-consistent model for X-ray reflection from the surface of the accretion disk while simultaneously accounting for absorption by dusty photoionized material along the line of sight (the warm absorber). Even including these complications, the XMM-Newton EPIC pn data require extreme relativistic broadening of the X-ray reflection spectrum; assuming no emission from within the radius of marginal stability, we derive a formal constraint on the dimensionless black hole spin parameter of a=0.989<SUP>+0.009</SUP><SUB>-0.002</SUB> at 90% confidence. The principal unmodeled effect that can significantly reduce the inferred black hole spin is powerful emission from within the radius of marginal stability. Although significant theoretical developments are required to fully understand this region, we argue that the need for a rapidly spinning black hole is robust to physically plausible levels of emission from within the radius of marginal stability. In particular, we show that a nonrotating black hole is strongly ruled out.

[]

https://arxiv.org/pdf/astro-ph/0608502.pdf

2018PhRvL.120m1103D

New Gauss-Bonnet Black Holes with Curvature-Induced Scalarization in Extended Scalar-Tensor Theories

2018-01-01

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

[]

In the present Letter, we consider a class of extended scalar-tensor-Gauss-Bonnet (ESTGB) theories for which the scalar degree of freedom is excited only in the extreme curvature regime. We show that in the mentioned class of ESTGB theories there exist new black-hole solutions that are formed by spontaneous scalarization of the Schwarzschild black holes in the extreme curvature regime. In this regime, below certain mass, the Schwarzschild solution becomes unstable and a new branch of solutions with a nontrivial scalar field bifurcates from the Schwarzschild one. As a matter of fact, more than one branch with a nontrivial scalar field can bifurcate at different masses, but only the first one is supposed to be stable. This effect is quite similar to the spontaneous scalarization of neutron stars. In contrast to the standard spontaneous scalarization of neutron stars, which is induced by the presence of matter, in our case, the scalarization is induced by the curvature of the spacetime.

[]

https://arxiv.org/pdf/1711.01187.pdf

2003PhR...377..389R

Fluorescent iron lines as a probe of astrophysical black hole systems

2003-01-01

['astrophysics', '-']

[]

With most physicists and astrophysicists in agreement that black holes do indeed exist, the focus of astrophysical black hole research has shifted to the detailed properties of these systems. Nature has provided us with an extremely useful probe of the region very close to an accreting black hole-X-ray irradiation of relatively cold material in the vicinity of the black hole can imprint characteristic features into the X-ray spectra of black hole systems, most notably the /Kα fluorescent line of iron. Detailed X-ray spectroscopy of these features can be used to study Doppler and gravitational redshifts, thereby providing key information on the location and kinematics of the cold material. This is a powerful tool that allows us to probe within a few gravitational radii, or less, of the event horizon. <P />Here, we present a comprehensive review of relativistic iron line studies for both accreting stellar mass black holes (i.e., galactic black hole candidate systems, GBHCs), and accreting supermassive black holes (i.e., active galactic nuclei, AGN). We begin with a pedagogical introduction to astrophysical black holes, GBHCs, AGN, and accretion disks (including a brief discussion of recent work on the magnetohydrodynamical properties of accretion disks). We then discuss studies of relativistic iron lines in the AGN context, and show how differences between classes of AGN can be diagnosed using X-ray spectroscopy. Furthermore, through a detailed discussion of one particular object (MCG-6-30-15), we illustrate how the exotic physics of black hole spin, such as the Penrose and Blandford-Znajek processes, are now open to observational study. We proceed to discuss GBHCs, which turn out to possess rather more complicated X-ray spectra, making robust conclusions more difficult to draw. However, even in these cases, modern X-ray observatories are now providing convincing evidence for relativistic effects. We conclude by discussing the science that can be addressed by future X-ray observatories.

[]

https://arxiv.org/pdf/astro-ph/0212065.pdf

2009ApJ...690...20S

Self-Consistent Models of the AGN and Black Hole Populations: Duty Cycles, Accretion Rates, and the Mean Radiative Efficiency

2009-01-01

['cosmology theory', 'galaxies evolution', 'galaxies quasars', 'astrophysics']

[]

We construct evolutionary models of the populations of active galactic nuclei (AGNs) and supermassive black holes, in which the black hole mass function grows at the rate implied by the observed luminosity function, given assumptions about the radiative efficiency and the luminosity in Eddington units. We draw on a variety of recent X-ray and optical measurements to estimate the bolometric AGN luminosity function and compare to X-ray background data and the independent estimate of Hopkins et al. to assess remaining systematic uncertainties. The integrated AGN emissivity closely tracks the cosmic star-formation history, suggesting that star formation and black hole growth are closely linked at all redshifts. We discuss observational uncertainties in the local black hole mass function, which remain substantial, with estimates of the integrated black hole mass density ρ<SUB>•</SUB> spanning the range 3-5.5 × 10<SUP>5</SUP> M <SUB>sun</SUB> Mpc<SUP>-3</SUP>. We find good agreement with estimates of the local mass function for a reference model where all active black holes have a fixed efficiency epsilon = 0.065 and L <SUB>bol</SUB>/L <SUB>Edd</SUB> ≈ 0.4 (shifting to epsilon = 0.09, L <SUB>bol</SUB>/L <SUB>Edd</SUB> ≈ 0.9 for the Hopkins et al. luminosity function). In our reference model, the duty cycle of 10<SUP>9</SUP> M <SUB>sun</SUB> black holes declines from 0.07 at z = 3 to 0.004 at z = 1 and 10<SUP>-4</SUP> at z = 0. The decline is shallower for less massive black holes, a signature of "downsizing" evolution in which more massive black holes build their mass earlier. The predicted duty cycles and AGN clustering bias in this model are in reasonable accord with observational estimates. If the typical Eddington ratio declines at z &lt; 2, then the "downsizing" of black hole growth is less pronounced. Models with reduced Eddington ratios at low redshift or black hole mass predict fewer low-mass black holes (M <SUB>•</SUB> lsim 10<SUP>8</SUP> M <SUB>sun</SUB>) in the local universe, while models with black hole mergers predict more black holes at M <SUB>•</SUB> &gt; 10<SUP>9</SUP> M <SUB>sun</SUB>. Matching the integrated AGN emissivity to the local black hole mass density implies epsilon = 0.075 × (ρ<SUB>•</SUB>/4.5 × 10<SUP>5</SUP> M <SUB>sun</SUB> Mpc<SUP>-3</SUP>)<SUP>-1</SUP> for our standard luminosity function estimate, or 25% higher for Hopkins et al.'s estimate. It is difficult to reconcile current observations with a model in which most black holes have the high efficiencies epsilon ≈ 0.16-0.20 predicted by MHD simulations of disk accretion. We provide electronic tabulations of our bolometric luminosity function and our reference model predictions for black hole mass functions and duty cycles as a function of redshift.

[]

https://arxiv.org/pdf/0710.4488.pdf

2010PhR...487....1R

Electron-positron pairs in physics and astrophysics: From heavy nuclei to black holes

2010-01-01

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

[]

Due to the interaction of physics and astrophysics we are witnessing in these years a splendid synthesis of theoretical, experimental and observational results originating from three fundamental physical processes. They were originally proposed by Dirac, by Breit and Wheeler and by Sauter, Heisenberg, Euler and Schwinger. For almost seventy years they have all three been followed by a continued effort of experimental verification on Earth-based experiments. The Dirac process, e<SUP>+</SUP>e<SUP>-</SUP>→2γ, has been by far the most successful. It has obtained extremely accurate experimental verification and has led as well to an enormous number of new physics in possibly one of the most fruitful experimental avenues by introduction of storage rings in Frascati and followed by the largest accelerators worldwide: DESY, SLAC etc. The Breit-Wheeler process, 2γ→e<SUP>+</SUP>e<SUP>-</SUP>, although conceptually simple, being the inverse process of the Dirac one, has been by far one of the most difficult to be verified experimentally. Only recently, through the technology based on free electron X-ray laser and its numerous applications in Earth-based experiments, some first indications of its possible verification have been reached. The vacuum polarization process in strong electromagnetic field, pioneered by Sauter, Heisenberg, Euler and Schwinger, introduced the concept of critical electric field E<SUB>c</SUB>=me2c<SUP>3</SUP>/(eħ). It has been searched without success for more than forty years by heavy-ion collisions in many of the leading particle accelerators worldwide. The novel situation today is that these same processes can be studied on a much more grandiose scale during the gravitational collapse leading to the formation of a black hole being observed in Gamma Ray Bursts (GRBs). This report is dedicated to the scientific race. The theoretical and experimental work developed in Earth-based laboratories is confronted with the theoretical interpretation of space-based observations of phenomena originating on cosmological scales. What has become clear in the last ten years is that all the three above mentioned processes, duly extended in the general relativistic framework, are necessary for the understanding of the physics of the gravitational collapse to a black hole. Vice versa, the natural arena where these processes can be observed in mutual interaction and on an unprecedented scale, is indeed the realm of relativistic astrophysics. We systematically analyze the conceptual developments which have followed the basic work of Dirac and Breit-Wheeler. We also recall how the seminal work of Born and Infeld inspired the work by Sauter, Heisenberg and Euler on effective Lagrangian leading to the estimate of the rate for the process of electron-positron production in a constant electric field. In addition to reviewing the intuitive semi-classical treatment of quantum mechanical tunneling for describing the process of electron-positron production, we recall the calculations in Quantum Electro-Dynamics of the Schwinger rate and effective Lagrangian for constant electromagnetic fields. We also review the electron-positron production in both time-alternating electromagnetic fields, studied by Brezin, Itzykson, Popov, Nikishov and Narozhny, and the corresponding processes relevant for pair production at the focus of coherent laser beams as well as electron-beam-laser collision. We finally report some current developments based on the general JWKB approach which allows us to compute the Schwinger rate in spatially varying and time varying electromagnetic fields. We also recall the pioneering work of Landau and Lifshitz, and Racah on the collision of charged particles as well as the experimental success of AdA and ADONE in the production of electron-positron pairs. We then turn to the possible experimental verification of these phenomena. We review: (A) the experimental verification of the e<SUP>+</SUP>e<SUP>-</SUP>→2γ process studied by Dirac. We also briefly recall the very successful experiments of e<SUP>+</SUP>e<SUP>-</SUP> annihilation to hadronic channels, in addition to the Dirac electromagnetic channel; (B) ongoing Earth-based experiments to detect electron-positron production in strong fields by focusing coherent laser beams and by electron-beam-laser collisions; and (C) the multiyear attempts to detect electron-positron production in Coulomb fields for a large atomic number Z&gt;137 in heavy-ion collisions. These attempts follow the classical theoretical work of Popov and Zeldovich, and Greiner and their schools. We then turn to astrophysics. We first review the basic work on the energetics and electrodynamical properties of an electromagnetic black hole and the application of the Schwinger formula around Kerr-Newman black holes as pioneered by Damour and Ruffini. We only focus on black hole masses larger than the critical mass of neutron stars, for convenience assumed to coincide with the Rhoades and Ruffini upper limit of 3.2 M<SUB>⊙</SUB>. In this case the electron Compton wavelength is much smaller than the space-time curvature and all previous results invariantly expressed can be applied following well established rules of the equivalence principle. We derive the corresponding rate of electron-positron pair production and introduce the concept of dyadosphere. We review the recent progress in describing the evolution of optically thick electron-positron plasma in the presence of supercritical electric field, which is relevant both in astrophysics as well as in ongoing laser beam experiments. In particular we review the recent progress based on the Vlasov-Boltzmann-Maxwell equations to study the feedback of the created electron-positron pairs on the original constant electric field. We evidence the existence of plasma oscillations and its interaction with photons leading to energy and number equipartition of photons, electrons and positrons. We finally review the recent progress obtained by using the Boltzmann equations to study the evolution of an electron-positron-photon plasma towards thermal equilibrium and determination of its characteristic timescales. The crucial difference introduced by the correct evaluation of the role of two- and three-body collisions, direct and inverse, is especially evidenced. We then present some general conclusions. The results reviewed in this report are going to be submitted to decisive tests in the forthcoming years both in physics and astrophysics. To mention only a few of the fundamental steps in testing in physics we recall, the setting up of experimental facilities at the National Ignition Facility at the Lawrence Livermore National Laboratory as well as the corresponding French Laser Mega Joule project. In astrophysics these results will be tested in galactic and extragalactic black holes observed in binary X-ray sources, active galactic nuclei, microquasars and in the process of gravitational collapse to a neutron star and also of two neutron stars to a black hole giving rise to GRBs. The astrophysical description of the stellar precursors and the initial physical conditions leading to a gravitational collapse process will be the subject of a forthcoming report. As of today no theoretical description has yet been found to explain either the emission of the remnant for supernova or the formation of a charged black hole for GRBs. Important current progress toward the understanding of such phenomena as well as of the electrodynamical structure of neutron stars, the supernova explosion and the theories of GRBs will be discussed in the above mentioned forthcoming report. What is important to recall at this stage is only that both the supernovae and GRBs processes are among the most energetic and transient phenomena ever observed in the Universe: a supernova can attain an energy of ∼10<SUP>54</SUP> ergs on a timescale of a few months and GRBs can have emission of up to ∼10<SUP>54</SUP> ergs in a timescale as short as a few seconds. The central role of neutron stars in the description of supernovae, as well as of black holes and the electron-positron plasma, in the description of GRBs, pioneered by one of us (RR) in 1975, are widely recognized. Only the theoretical basis to address these topics are discussed in the present report.

[]

https://arxiv.org/pdf/0910.0974.pdf

2009Natur.460...73F

An intermediate-mass black hole of over 500 solar masses in the galaxy ESO243-49

2009-01-01

['-', '-']

[]

Ultraluminous X-ray sources are extragalactic objects located outside the nucleus of the host galaxy with bolometric luminosities exceeding 10<SUP>39</SUP>ergs<SUP>-1</SUP>. These extreme luminosities-if the emission is isotropic and below the theoretical (Eddington) limit, where the radiation pressure is balanced by the gravitational pressure-imply the presence of an accreting black hole with a mass of ~10<SUP>2</SUP>-10<SUP>5</SUP> solar masses (). The existence of such intermediate-mass black holes is in dispute, and though many candidates have been proposed, none are widely accepted as definitive. Here we report the detection of a variable X-ray source with a maximum 0.2-10keV luminosity of up to 1.1×10<SUP>42</SUP>ergs<SUP>-1</SUP> in the edge-on spiral galaxy ESO243-49, with an implied conservative lower limit for the mass of the black hole of ~500.

[]

https://arxiv.org/pdf/1001.0567.pdf

1996PhLB..383...39S

Macroscopic entropy of N = 2 extremal black holes

1996-01-01

['-']

[]

Extremal BPS-saturated black holes in N = 2, d = 4 supergravity can carry electric and magnetic charges (q<SUP>Λ</SUP><SUB>(m)</SUB>, q<SUP>(e)</SUP><SUB>Λ</SUB>). It is shown that in smooth cases the moduli fields at the horizon take a fixed ``rational'' value X<SUP>Λ</SUP> (q<SUB>(m)</SUB>, q<SUP>(e)</SUP>) which is determined by the charges and is independent of the asymptotic values of the moduli fields. A universal formula for the Bekenstein-Hawking entropy is derived in terms of the charges and the moduli space geometry at X<SUP>Λ</SUP> (q<SUB>(m)</SUB>, q<SUP>(e)</SUP>). This work extends previous results of Ferrara, Kallosh and the author for the pure magnetic case.

[]

https://arxiv.org/pdf/hep-th/9602111.pdf

1999PhLB..464...25A

New regular black hole solution from nonlinear electrodynamics

1999-01-01

['-', '-']

[]

Using a nonlinear electrodynamics coupled to General Relativity a new regular exact black hole solution is found. The nonlinear theory reduces to the Maxwell one in the weak limit, and the solution corresponds to a charged black hole for |q| \leq 2s_c m \approx 1.05 m, with metric, curvature invariants, and electric field regular everywhere.

[]

https://arxiv.org/pdf/hep-th/9911174.pdf

2000ApJ...543L...5G

Black Hole Mass Estimates from Reverberation Mapping and from Spatially Resolved Kinematics

2000-01-01

['black hole physics', 'galaxies active', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'galaxies seyfert', 'astrophysics']

[]

Black hole (BH) masses that have been measured by reverberation mapping in active galaxies fall significantly below the correlation between bulge luminosity and BH mass determined from spatially resolved kinematics of nearby normal galaxies. This discrepancy has created concern that one or both techniques suffer from systematic errors. We show that BH masses from reverberation mapping are consistent with the recently discovered relationship between BH mass and galaxy velocity dispersion. Therefore, the bulge luminosities are the probable source of the disagreement, not problems with either method of mass measurement. This result underscores the utility of the BH mass-velocity dispersion relationship. Reverberation mapping can now be applied with increased confidence to galaxies whose active nuclei are too bright or whose distances are too large for BH searches based on spatially resolved kinematics.

[]

https://arxiv.org/pdf/astro-ph/0007123.pdf

2004MNRAS.349.1435M

A light bending model for the X-ray temporal and spectral properties of accreting black holes

2004-01-01

['accretion', 'accretion disks', 'black hole physics', 'relativity', 'galaxies active', 'astronomy x rays', 'astronomy x rays', 'astrophysics', '-']

[]

Some of the X-ray temporal and spectral properties of accreting black holes represent a challenge for current theoretical models. In particular, uncorrelated variability between direct continuum and reflection components (including the iron line, if present) has been reported in many cases. Here, we explore a light bending model in which we assume a primary source of X-rays located close to a central, maximally rotating Kerr black hole and illuminating both the observer at infinity and the accretion disc. We show that, due to strong light bending, the observed flux can vary by more than one order of magnitude as the height of the primary source above the accretion disc varies, even if its intrinsic luminosity is constant. We identify three different regimes in which the reflection-dominated component (and the iron line) is correlated, anticorrelated or almost independent with respect to the direct continuum. These regimes correspond to low, high and intermediate flux states of the X-ray source. As a general rule, the reflection component varies with much smaller amplitude than the continuum. X-ray observations of the Seyfert galaxy MCG-6-30-15 and of the Galactic black hole candidate XTE J1650-500 reveal that a series of predictions of our model is actually observed; the consistent behaviour of the iron line flux and equivalent width with respect to the direct continuum, as well as the increase of the relative strength of disc reflection as the flux drops, all match very well our predictions. The iron line profile is predicted to be narrower in high flux states and broader in (reflection-dominated) low flux states, in fairly good agreement with observations of the best-studied case of MCG-6-30-15. Observations of some other narrow-line Seyfert 1 galaxies (e.g. NGC 4051) also seem to support our model, which may explain what are otherwise puzzling characteristics of some sources. We also show that beaming along the equatorial plane can enhance the re-emission of narrow reflection features from distant material during low flux states providing a possible contribution to the observed X-ray Baldwin effect.

[]

https://arxiv.org/pdf/astro-ph/0309064.pdf

2010MNRAS.407.1529H

How do massive black holes get their gas?

2010-01-01

['galaxies active', 'galaxies evolution', 'galaxies quasars', 'cosmology theory', '-', '-', '-']

[]

We use multiscale smoothed particle hydrodynamic simulations to study the inflow of gas from galactic scales (~10kpc) down to &lt;~ 0.1pc, at which point the gas begins to resemble a traditional, Keplerian accretion disc. The key ingredients of the simulations are gas, stars, black holes (BHs), self-gravity, star formation and stellar feedback (via a subgrid model); BH feedback is not included. We use ~100 simulations to survey a large parameter space of galaxy properties and subgrid models for the interstellar medium physics. We generate initial conditions for our simulations of galactic nuclei (&lt;~ 300pc) using galaxy-scale simulations, including both major galaxy mergers and isolated bar-(un)stable disc galaxies. For sufficiently gas-rich, disc-dominated systems, we find that a series of gravitational instabilities generates large accretion rates of up to ~ 1-10 M<SUB>solar</SUB> yr<SUP>-1</SUP> on to the BH (i.e. at &lt;~ 0.1pc) this is comparable to what is needed to fuel the most luminous quasars. The BH accretion rate is highly time variable for a given set of conditions in the galaxy at ~kpc. At radii of &gt;rsim 10 pc, our simulations resemble the `bars-within-bars' model of Shlosman et al., but we show that the gas can have a diverse array of morphologies, including spirals, rings, clumps and bars; the duty cycle of these features is modest, complicating attempts to correlate BH accretion with the morphology of gas in galactic nuclei. At ~ 1-10 pc, the gravitational potential becomes dominated by the BH and bar-like modes are no longer present. However, we show that the gas can become unstable to a standing, eccentric disc or a single-armed spiral mode (m = 1), in which the stars and gas precess at different rates, driving the gas to sub-pc scales (again for sufficiently gas-rich, disc-dominated systems). A proper treatment of this mode requires including star formation and the self-gravity of both the stars and gas (which has not been the case in many previous calculations). Our simulations predict a correlation between the BH accretion rate and the star formation rate at different galactic radii. We find that nuclear star formation is more tightly coupled to active galactic nucleus activity than the global star formation rate of a galaxy, but a reasonable correlation remains even for the latter.

[]

https://arxiv.org/pdf/0912.3257.pdf

2002PhRvD..66d4011E

Classical black hole production in high-energy collisions

2002-01-01

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

[]

We investigate the classical formation of a D-dimensional black hole in a high-energy collision of two particles. The existence of an apparent horizon is related to the solution of an unusual boundary-value problem for Poisson's equation in flat space. For a sufficiently small impact parameter, we construct solutions giving such apparent horizons in D=4. These supply improved estimates of the classical cross section for black hole production, and of the mass of the resulting black holes. We also argue that a horizon can be found in a region of weak curvature, suggesting that these solutions are valid starting points for a semiclassical analysis of quantum black hole formation.

[]

https://arxiv.org/pdf/gr-qc/0201034.pdf

2002ApJ...565...78B

Black Hole Mass and Eddington Ratio as Drivers for the Observable Properties of Radio-loud and Radio-quiet QSOs

2002-01-01

['galaxies nuclei', 'galaxies seyfert', 'galaxies quasars', 'astrophysics']

[]

Recent studies of black holes in the nuclei of both active and normal galaxies have yielded relationships that permit a physical interpretation of the principal components of the spectra of QSOs. It is shown that principal component (or eigenvector) 1 (PC1) is driven predominantly by L/L<SUB>Edd</SUB>, and principal component 2 (PC2) is driven by accretion rate. This results in a PC2 versus PC1 diagram in which lines of constant black hole mass are diagonal. Using a sample consisting of the low-redshift PG objects supplemented by 75 radio-loud QSOs, it is shown that such a diagram effectively distinguishes radio-loud from radio-quiet objects and demonstrates that both narrow-line Seyfert 1 galaxies and broad absorption line QSOs lie at the high L/L<SUB>Edd</SUB> extreme, although these two types of objects are well separated in the PC2 direction. A simple picture that ties together physical parameters (black hole mass and Eddington ratio) and classification of active galactic nuclei is presented. Based on the location of core-dominated and lobe-dominated radio-loud QSOs, orientation can be modeled as a third parameter in this scheme, implying an enhancement in the radio flux of core-dominated objects.

[]

https://arxiv.org/pdf/astro-ph/0109317.pdf

2017A&A...601A.143F

AGN wind scaling relations and the co-evolution of black holes and galaxies

2017-01-01

['galaxies active', 'galaxies evolution', 'galaxies quasars', '-']

[]

Context. Feedback from accreting supermassive black holes (SMBHs) is often identified as the main mechanism responsible for regulating star formation in active galactic nucleus (AGN) host galaxies. However, the relationships between AGN activity, radiation, winds, and star formation are complex and still far from being understood. <BR /> Aims: We study scaling relations between AGN properties, host galaxy properties, and AGN winds. We then evaluate the wind mean impact on the global star formation history, taking into account the short AGN duty cycle with respect to that of star formation. <BR /> Methods: We first collect AGN wind observations for 94 AGN with detected massive winds at sub-pc to kpc spatial scales. We then fold AGN wind scaling relations with AGN luminosity functions, to evaluate the average AGN wind mass-loading factor as a function of cosmic time. <BR /> Results: We find strong correlations between the AGN molecular and ionised wind mass outflow rates and the AGN bolometric luminosity. The power law scaling is steeper for ionised winds (slope 1.29 ± 0.38) than for molecular winds (0.76 ± 0.06), meaning that the two rates converge at high bolometric luminosities. The molecular gas depletion timescale and the molecular gas fraction of galaxies hosting powerful AGN driven winds are 3-10 times shorter and smaller than those of main sequence galaxies with similar star formation rate (SFR), stellar mass, and redshift. These findings suggest that, at high AGN bolometric luminosity, the reduced molecular gas fraction may be due to the destruction of molecules by the wind, leading to a larger fraction of gas in the atomic ionised phase. The AGN wind mass-loading factor η = Ṁ<SUB>OF</SUB>/SFR is systematically higher than that of starburst driven winds. <BR /> Conclusions: Our analysis shows that AGN winds are, on average, powerful enough to clean galaxies from their molecular gas only in massive systems at z ≲ 2, I.e. a strong form of co-evolution between SMBHs and galaxies appears to break down for the least massive galaxies.

[]

https://arxiv.org/pdf/1702.04507.pdf

1999ApJ...526..152F

Formation Rates of Black Hole Accretion Disk Gamma-Ray Bursts

1999-01-01

['stars binaries close', 'black hole physics', 'gamma rays', '-', 'stars binaries close', 'black hole physics', 'gamma rays', '-', 'astrophysics']

[]

The cosmological origin of at least an appreciable fraction of classical gamma-ray bursts (GRBs) is now supported by redshift measurements for a half-dozen faint host galaxies. Still, the nature of the central engine (or engines) that provide the burst energy remains unclear. While many models have been proposed, those currently favored are all based upon the formation of and/or rapid accretion into stellar-mass black holes. Here we discuss a variety of such scenarios and estimate the probability of each. Population synthesis calculations are carried out using a Monte Carlo approach in which the many uncertain parameters intrinsic to such calculations are varied. We estimate the event rate for each class of model as well as the propagation distances for those having significant delay between formation and burst production, i.e., double neutron star (DNS) mergers and black hole-neutron star (BH/NS) mergers. One conclusion is a 1-2 order of magnitude decrease in the rate of DNS and BH/NS mergers compared to that previously calculated using invalid assumptions about common envelope evolution. Other major uncertainties in the event rates and propagation distances include the history of star formation in the universe, the masses of the galaxies in which merging compact objects are born, and the radii of the hydrogen-stripped cores of massive stars. For reasonable assumptions regarding each, we calculate a daily event rate in the universe for (1) merging neutron stars: ~100 day<SUP>-1</SUP> (2) neutron star-black hole mergers: ~450 day<SUP>-1</SUP> (3) collapsars: ~10<SUP>4</SUP> day<SUP>-1</SUP> (4) helium star black hole mergers: ~1000 day<SUP>-1</SUP> and (5) white dwarf-black hole mergers: ~20 day<SUP>-1</SUP>. The range of uncertainty in these numbers, however, is very large, typically 2-3 orders of magnitude. These rates must additionally be multiplied by any relevant beaming factor (f<SUB>Ω</SUB>&lt;1) and sampling fraction (if the entire universal set of models is not being observed). Depending upon the mass of the host galaxy, one-half of the DNS mergers will happen within 60 kpc (for a galaxy with a mass comparable to that of the Milky Way) to 5 Mpc (for a galaxy with negligible mass) from the Galactic center. The same numbers characterize BH/NS mergers. Because of the delay time, neutron star and black hole mergers will happen at a redshift 0.5-0.8 times that of the other classes of models. Information is still lacking regarding the hosts of short, hard bursts, but we suggest that they are due to DNS and BH/NS mergers and thus will ultimately be determined to lie outside of galaxies and at a closer mean distance than long complex bursts (which we attribute to collapsars). In the absence of a galactic site, the distance to these bursts may be difficult to determine.

[]

https://arxiv.org/pdf/astro-ph/9904122.pdf

2007ApJ...659L...5C

Large Merger Recoils and Spin Flips from Generic Black Hole Binaries

2007-01-01

['black hole physics', 'galaxies nuclei', 'gravitation', 'gravitational waves', 'relativity', '-', 'astrophysics']

[]

We report the first results from the evolution of generic black hole binaries, i.e., binaries containing unequal-mass black holes with misaligned spins. Our configuration, which has a mass ratio of 2:1, consists of an initially nonspinning hole orbiting a larger, rapidly spinning hole (specific spin a/m=0.885), with the spin direction oriented -45° with respect to the orbital plane. We track the inspiral and merger for ~2 orbits and find that the remnant receives a substantial kick of 454 km s<SUP>-1</SUP>, more than twice as large as the maximum kick from nonspinning binaries. The remnant spin direction is flipped by 103° with respect to the initial spin direction of the larger hole. We performed a second run with antialigned spins, a/m=+/-0.5 lying in the orbital plane that produces a kick of ~1830 km s<SUP>-1</SUP> off the orbital plane. This value scales to nearly 4000 km s<SUP>-1</SUP> for maximally spinning holes. Such a large recoil velocity opens up the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy.

[]

https://arxiv.org/pdf/gr-qc/0701164.pdf

2011ApJ...741..103F

The Mass Distribution of Stellar-mass Black Holes

2011-01-01

['methods data analysis', 'astronomy x rays', '-']

[]

We perform a Bayesian analysis of the mass distribution of stellar-mass black holes using the observed masses of 15 low-mass X-ray binary systems undergoing Roche lobe overflow and 5 high-mass, wind-fed X-ray binary systems. Using Markov Chain Monte Carlo calculations, we model the mass distribution both parametrically—as a power law, exponential, Gaussian, combination of two Gaussians, or log-normal distribution—and non-parametrically—as histograms with varying numbers of bins. We provide confidence bounds on the shape of the mass distribution in the context of each model and compare the models with each other by calculating their relative Bayesian evidence as supported by the measurements, taking into account the number of degrees of freedom of each model. The mass distribution of the low-mass systems is best fit by a power law, while the distribution of the combined sample is best fit by the exponential model. This difference indicates that the low-mass subsample is not consistent with being drawn from the distribution of the combined population. We examine the existence of a "gap" between the most massive neutron stars and the least massive black holes by considering the value, M <SUB>1%</SUB>, of the 1% quantile from each black hole mass distribution as the lower bound of black hole masses. Our analysis generates posterior distributions for M <SUB>1%</SUB>; the best model (the power law) fitted to the low-mass systems has a distribution of lower bounds with M <SUB>1%</SUB>&gt;4.3 M <SUB>sun</SUB> with 90% confidence, while the best model (the exponential) fitted to all 20 systems has M <SUB>1%</SUB>&gt;4.5 M <SUB>sun</SUB> with 90% confidence. We conclude that our sample of black hole masses provides strong evidence of a gap between the maximum neutron star mass and the lower bound on black hole masses. Our results on the low-mass sample are in qualitative agreement with those of Ozel et al., although our broad model selection analysis more reliably reveals the best-fit quantitative description of the underlying mass distribution. The results on the combined sample of low- and high-mass systems are in qualitative agreement with Fryer &amp; Kalogera, although the presence of a mass gap remains theoretically unexplained.

[]

https://arxiv.org/pdf/1011.1459.pdf

2001A&A...374L..19A

A precise determination of black hole spin in GRO J1655-40

2001-01-01

['thermodynamics', 'relativity', 'stars black holes', 'astronomy x rays', 'astrophysics']

[]

We note that the recently discovered 450 Hz frequency in the X-ray flux of the black hole candidate GRO J1655-40 is in a 3:2 ratio to the previously known 300 Hz frequency of quasi-periodic oscillations (QPO) in the same source. If the origin of high frequency QPOs in black hole systems is a resonance between orbital and epicyclic motion of accreting matter, as suggested previously, the angular momentum of the black hole can be accurately determined, given its mass. We find that the dimensionless angular momentum is in the range 0.2&lt;j&lt;0.67 if the mass is in the (corresponding) range of 5.5 to 7.9 solar masses.

[]

https://arxiv.org/pdf/astro-ph/0105077.pdf

2015PhRvD..91h4011A

Discovering the QCD axion with black holes and gravitational waves

2015-01-01

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

[]

Advanced LIGO may be the first experiment to detect gravitational waves. Through superradiance of stellar black holes, it may also be the first experiment to discover the QCD axion with decay constant above the grand unification scale. When an axion's Compton wavelength is comparable to the size of a black hole, the axion binds to the black hole, forming a "gravitational atom." Through the superradiance process, the number of axions occupying the bound levels grows exponentially, extracting energy and angular momentum from the black hole. Axions transitioning between levels of the gravitational atom and axions annihilating to gravitons can produce observable gravitational wave signals. The signals are long lasting, monochromatic, and can be distinguished from ordinary astrophysical sources. We estimate up to O (1 ) transition events at aLIGO for an axion between 1 0<SUP>-11</SUP> and 1 0<SUP>-10</SUP> eV and up to 1 0<SUP>4</SUP> annihilation events for an axion between 1 0<SUP>-13</SUP> and 1 0<SUP>-11</SUP> eV . In the event of a null search, aLIGO can constrain the axion mass for a range of rapidly spinning black hole formation rates. Axion annihilations are also promising for much lighter masses at future lower-frequency gravitational wave observatories; the rates have large uncertainties, dominated by supermassive black hole spin distributions. Our projections for aLIGO are robust against perturbations from the black hole environment and account for our updated exclusion on the QCD axion of 6 ×1 0<SUP>-13</SUP> eV &lt;μ<SUB>a</SUB>&lt;2 ×1 0<SUP>-11</SUP> eV suggested by stellar black hole spin measurements.

[]

https://arxiv.org/pdf/1411.2263.pdf

2004PhRvD..70j6007O

Black hole attractors and the topological string

2004-01-01

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

[]

A simple relationship of the form Z<SUB>BH</SUB>=|Z<SUB>top</SUB>|<SUP>2</SUP> is conjectured, where Z<SUB>BH</SUB> is a supersymmetric partition function for a four-dimensional BPS black hole in a Calabi-Yau compactification of Type II superstring theory and Z<SUB>top</SUB> is a second-quantized topological string partition function evaluated at the attractor point in moduli space associated to the black hole charges. Evidence for the conjecture in a perturbation expansion about large graviphoton charge is given. The microcanonical ensemble of BPS black holes can be viewed as the Wigner function associated to the wave function defined by the topological string partition function.

[]

https://arxiv.org/pdf/hep-th/0405146.pdf

2001ApJ...547..140M

The M<SUB>•</SUB>-σ Relation for Supermassive Black Holes

2001-01-01

['black hole physics', 'galaxies kinematics and dynamics', 'methods data analysis', 'astrophysics']

[]

We investigate the differences in the M<SUB>•</SUB>-σ relation derived recently by Ferrarese &amp; Merritt and by Gebhardt and collaborators. The shallower slope found by the latter authors (3.75 vs. 4.8) is due partly to the use of a regression algorithm that ignores measurement errors and partly to the value of the velocity dispersion adopted for a single galaxy, the Milky Way. A steeper relation is shown to provide a better fit to black hole masses derived from reverberation mapping studies. Combining the stellar dynamical, gasdynamical, and reverberation mapping mass estimates, we derive a best-fit relation M<SUB>•</SUB>=1.30(+/-0.36)×10<SUP>8</SUP> M<SUB>solar</SUB>(σ<SUB>c</SUB>/200 km s<SUP>-1</SUP>)<SUP>4.72(+/-0.36)</SUP>.

[]

https://arxiv.org/pdf/astro-ph/0008310.pdf

2009PhRvL.103k1102B

Kerr Black Holes as Particle Accelerators to Arbitrarily High Energy

2009-01-01

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

[]

We show that intermediate mass black holes conjectured to be the early precursors of supermassive black holes and surrounded by relic cold dark matter density spikes can act as particle accelerators with collisions, in principle, at arbitrarily high center-of-mass energies in the case of Kerr black holes. While the ejecta from such interactions will be highly redshifted, we may anticipate the possibility of a unique probe of Planck-scale physics.

[]

https://arxiv.org/pdf/0909.0169.pdf

2017PDU....18...47G

Primordial black holes from single field models of inflation

2017-01-01

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

[]

Primordial black holes (PBH) have been shown to arise from high peaks in the matter power spectra of multi-field models of inflation. Here we show, with a simple toy model, that it is also possible to generate a peak in the curvature power spectrum of single-field inflation. We assume that the effective dynamics of the inflaton field presents a near-inflection point which slows down the field right before the end of inflation and gives rise to a prominent spike in the fluctuation power spectrum at scales much smaller than those probed by Cosmic Microwave Background (CMB) and Large Scale Structure (LSS) observations. This peak will give rise, upon reentry during the radiation era, to PBH via gravitational collapse. The mass and abundance of these PBH is such that they could constitute the totality of the Dark Matter today. We satisfy all CMB and LSS constraints and predict a very broad range of PBH masses. Some of these PBH are light enough that they will evaporate before structure formation, leaving behind a large curvature fluctuation on small scales. This broad mass distribution of PBH as Dark Matter will be tested in the future by AdvLIGO and LISA interferometers.

[]

https://arxiv.org/pdf/1702.03901.pdf

2009MNRAS.395.2127O

Gravitational waves from scattering of stellar-mass black holes in galactic nuclei

2009-01-01

['black hole physics', 'gravitational waves', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'astrophysics', '-']

[]

Stellar-mass black holes (BHs) are expected to segregate and form a steep density cusp around supermassive black holes (SMBHs) in galactic nuclei. We follow the evolution of a multimass system of BHs and stars by numerically integrating the Fokker-Planck energy diffusion equations for a variety of BH mass distributions. We find that the BHs `self-segregate', and that the rarest, most massive BHs dominate the scattering rate closest to the SMBH (&lt;~10<SUP>-1</SUP>pc). BH-BH binaries form out of gravitational wave emission during BH encounters. We find that the expected rate of BH coalescence events detectable by Advanced LIGO is ~1-10<SUP>2</SUP>yr<SUP>-1</SUP>, depending on the initial mass function of stars in galactic nuclei and the mass of the most massive BHs. We find that the actual merger rate is likely ~10 times larger than this due to the intrinsic scatter of stellar densities in many different galaxies. The BH binaries that form this way in galactic nuclei have significant eccentricities as they enter the LIGO band (90 per cent with e &gt; 0.9), and are therefore distinguishable from other binaries, which circularize before becoming detectable. We also show that eccentric mergers can be detected to larger distances and greater BH masses than circular mergers, up to ~700M<SUB>solar</SUB>. Future ground-based gravitational wave observatories will be able to constrain both the mass function of BHs and stars in galactic nuclei.

[]

https://arxiv.org/pdf/0807.2638.pdf

2003PhRvD..67h4023A

Gauge conditions for long-term numerical black hole evolutions without excision

2003-01-01

['-', '-', '-', '-', 'methods numerical', 'waves', '-', 'black hole physics', '-']

[]

Numerical relativity has faced the problem that standard 3+1 simulations of black hole spacetimes without singularity excision and with singularity avoiding lapse and vanishing shift fail early on due to the so-called slice stretching. We discuss lapse and shift conditions for the nonexcision case that effectively cure slice stretching and allow run times of 1000M and more.

[]

https://arxiv.org/pdf/gr-qc/0206072.pdf

2011JHEP...01..094B

Hydrodynamics from charged black branes

2011-01-01

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

[]

We extend the recent work on fluid-gravity correspondence to charged black-branes by determining the metric duals to arbitrary charged fluid configuration up to second order in the boundary derivative expansion. We also derive the energy-momentum tensor and the charge current for these configurations up to second order in the boundary derivative expansion. We find a new term in the charge current when there is a bulk Chern-Simons interaction thus resolving an earlier discrepancy between thermodynamics of charged rotating black holes and boundary hydrodynamics. We have also confirmed that all our expressions are covariant under boundary Weyl-transformations as expected.

[]

https://arxiv.org/pdf/0809.2596.pdf

2002ApJ...571...30S

First Stars, Very Massive Black Holes, and Metals

2002-01-01

['black hole physics', 'cosmology theory', 'galaxies formation', 'galaxies intergalactic medium', 'astrophysics']

[]

Recent studies suggest that the initial mass function (IMF) of the first stars (Population III) is likely to have been extremely top-heavy, unlike what is observed at present. We propose a scenario to generate fragmentation to lower masses once the first massive stars have formed and derive constraints on the primordial IMF. We estimate the mass fraction of pair-unstable supernovae (SN<SUB>γγ</SUB>), shown to be the dominant sources of the first heavy elements. These metals enrich the surrounding gas up to ~10<SUP>-4</SUP> Z<SUB>solar</SUB>, when a transition to efficient cooling-driven fragmentation producing &lt;~1 M<SUB>solar</SUB> clumps occurs. We argue that the remaining fraction of the first stars ends up in ~100 M<SUB>solar</SUB> VMBHs (very massive black holes). If we further assume that all these VMBHs are likely to end up in the centers of galactic nuclei constituting the observed supermassive black holes (SMBHs), then ~6% of the first stars contributed to the initial metal enrichment and the IMF remained top-heavy down to a redshift z~18.5%. Interestingly, this is the epoch at which the cool metals detected in the Lyα forest at z~3 must have been ejected from galaxies. At the other extreme, if none of these VMBHs has as yet ended up in SMBHs, we expect them to be either (1) en route toward galactic nuclei, thereby accounting for the X-ray-bright off-center sources detected locally by ROSAT, or (2) the dark matter candidate composing the entire baryonic halos of galaxies. For case 1 we expect all but a negligible fraction of the primordial stars to produce metals, causing the transition at the maximum possible redshift of &gt;~22.1, and for case 2, ~3×10<SUP>5</SUP>, a very negligible fraction of the initial stars produce the metals and the transition redshift occurs at z<SUB>f</SUB>&gt;~5.4. In this paper, we present a framework (albeit one that is not stringently constrained at present) that relates the first episode of star formation to the fate of their remnants at late times. Clearly, further progress in understanding the formation and fragmentation of Population III stars within the cosmological context will provide tighter constraints in the future. We conclude with a discussion of several hitherto unexplored implications of a high-mass-dominated star formation mode in the early universe.

[]

https://arxiv.org/pdf/astro-ph/0111341.pdf

2016MNRAS.458.2634M

Merging binary black holes formed through chemically homogeneous evolution in short-period stellar binaries

2016-01-01

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

[]

We explore a newly proposed channel to create binary black holes of stellar origin. This scenario applies to massive, tight binaries where mixing induced by rotation and tides transports the products of hydrogen burning throughout the stellar envelopes. This slowly enriches the entire star with helium, preventing the build-up of an internal chemical gradient. The stars remain compact as they evolve nearly chemically homogeneously, eventually forming two black holes, which we estimate typically merge 4-11 Gyr after formation. Like other proposed channels, this evolutionary pathway suffers from significant theoretical uncertainties, but could be constrained in the near future by data from advanced ground-based gravitational-wave detectors. We perform Monte Carlo simulations of the expected merger rate over cosmic time to explore the implications and uncertainties. Our default model for this channel yields a local binary black hole merger rate of about 10 Gpc<SUP>-3</SUP> yr<SUP>-1</SUP> at redshift z = 0, peaking at twice this rate at z = 0.5. This means that this channel is competitive, in terms of expected rates, with the conventional formation scenarios that involve a common-envelope phase during isolated binary evolution or dynamical interaction in a dense cluster. The events from this channel may be distinguished by the preference for nearly equal-mass components and high masses, with typical total masses between 50 and 110 M<SUB>⊙</SUB>. Unlike the conventional isolated binary evolution scenario that involves shrinkage of the orbit during a common-envelope phase, short time delays are unlikely for this channel, implying that we do not expect mergers at high redshift.

[]

https://arxiv.org/pdf/1601.00007.pdf

2013JHEP...09..005C

P-V criticality in the extended phase space of Gauss-Bonnet black holes in AdS space

2013-01-01

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

[]

We study the P - V criticality and phase transition in the extended phase space of charged Gauss-Bonnet black holes in anti-de Sitter space, where the cosmological constant appears as a dynamical pressure of the system and its conjugate quantity is the thermodynamic volume of the black holes. The black holes can have a Ricci flat ( k = 0), spherical ( k = 1), or hyperbolic ( k = -1) horizon. We find that for the Ricci flat and hyperbolic Gauss-Bonnet black holes, no P - V criticality and phase transition appear, while for the black holes with a spherical horizon, even when the charge of the black hole is absent, the P - V criticality and the small black hole/large black hole phase transition will appear, but it happens only in d = 5 dimensions; when the charge does not vanish, the P - V criticality and the small black hole/large phase transition always appear in d = 5 dimensions; in the case of d ≥ 6, to have the P - V criticality and the small black hole/large black hole phase transition, there exists an upper bound for the parameter , where is the Gauss-Bonnet coefficient and Q is the charge of the black hole. We calculate the critical exponents at the critical point and find that for all cases, they are the same as those in the van der Waals liquid-gas system.

[]

https://arxiv.org/pdf/1306.6233.pdf

2013ApJ...775..116R

Dwarf Galaxies with Optical Signatures of Active Massive Black Holes

2013-01-01

['galaxies active', 'galaxies dwarf', 'galaxies nuclei', 'galaxies seyfert', '-', '-']

[]

We present a sample of 151 dwarf galaxies (10<SUP>8.5</SUP> &lt;~ M <SUB>sstarf</SUB> &lt;~ 10<SUP>9.5</SUP> M <SUB>⊙</SUB>) that exhibit optical spectroscopic signatures of accreting massive black holes (BHs), increasing the number of known active galaxies in this stellar-mass range by more than an order of magnitude. Utilizing data from the Sloan Digital Sky Survey Data Release 8 and stellar masses from the NASA-Sloan Atlas, we have systematically searched for active BHs in ~25,000 emission-line galaxies with stellar masses comparable to the Magellanic Clouds and redshifts z &lt; 0.055. Using the narrow-line [O III]/Hβ versus [N II]/Hα diagnostic diagram, we find photoionization signatures of BH accretion in 136 galaxies, a small fraction of which also exhibit broad Hα emission. For these broad-line active galactic nucleus (AGN) candidates, we estimate BH masses using standard virial techniques and find a range of 10<SUP>5</SUP> &lt;~ M <SUB>BH</SUB> &lt;~ 10<SUP>6</SUP> M <SUB>⊙</SUB> and a median of M <SUB>BH</SUB> ~ 2 × 10<SUP>5</SUP> M <SUB>⊙</SUB>. We also detect broad Hα in 15 galaxies that have narrow-line ratios consistent with star-forming galaxies. Follow-up observations are required to determine if these are true type 1 AGN or if the broad Hα is from stellar processes. The median absolute magnitude of the host galaxies in our active sample is M<SUB>g</SUB> = -18.1 mag, which is ~1-2 mag fainter than previous samples of AGN hosts with low-mass BHs. This work constrains the smallest galaxies that can form a massive BH, with implications for BH feedback in low-mass galaxies and the origin of the first supermassive BH seeds.

[]

https://arxiv.org/pdf/1308.0328.pdf

2002MNRAS.330..232C

Production of intermediate-mass black holes in globular clusters

2002-01-01

['accretion', 'accretion disks', 'black hole physics', 'stars binaries close', 'clusters globular', 'galaxies starburst', 'astrophysics']

[]

The discovery of numerous non-nuclear X-ray point sources with luminosities in several starburst galaxies has stimulated speculation about their nature and origin. The strong variability seen in several sources points to massive black holes as the central engines. If the flux is isotropic, the luminosities range up to ~10<SUP>41</SUP> ergs<SUP>-1</SUP> , implying masses of if the luminosity is sub-Eddington. Here we explore a model for these sources. We suggest that in some tens of per cent of globular clusters a very massive black hole, , is formed. This black hole sinks in &lt;~10<SUP>6</SUP> yr to the centre of the cluster, where in the ~10<SUP>10</SUP> yr lifetime of the cluster it accretes ~10<SUP>3</SUP> M<SUB>solar</SUB> , primarily in the form of lighter black holes. Unlike less-massive black holes in binaries, which are flung from clusters by recoil before they can merge gravitationally, a &gt;~50M<SUB>solar</SUB> black hole has enough inertia that it remains bound to the cluster. We suggest that ~10<SUP>3</SUP> M<SUB>solar</SUB> black holes may be common in the centres of dense globular clusters, and may therefore exist in some tens of per cent of current globulars. If the cluster later merges with its host galaxy, accretion from young star clusters in molecular clouds by the black hole can generate luminosity consistent with that observed. We also consider the detectability of massive black holes in globular clusters with gravitational wave detectors , and speculate on future observations that may test our predictions.

[]

https://arxiv.org/pdf/astro-ph/0106188.pdf

2001AIPC..586..363K

Supermassive black holes in galactic nuclei

2001-01-01

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

[]

We review the motivation and search for supermassive black holes (BHs) in galaxies. Energetic nuclear activity provides indirect but compelling evidence for BH engines. Ground-based dynamical searches for central dark objects are reviewed in Kormendy &amp; Richstone (1995, ARA&amp;A, 33, 581). Here we provide an update of results from the Hubble Space Telescope (HST). This has greatly accelerated the detection rate. As of 2001 March, dynamical BH detections are available for at least 37 galaxies. The demographics of these objects lead to the following conclusions: (1) BH mass correlates with the luminosity of the bulge component of the host galaxy, albeit with considerable scatter. The median BH mass fraction is 0.13% of the mass of the bulge. (2) BH mass correlates with the mean velocity dispersion of the bulge inside its effective radius, i.e., with how strongly the bulge stars are gravitationally bound to each other. For the best mass determinations, the scatter is consistent with the measurement errors. (3) BH mass correlates with the luminosity of the high-density central component in disk galaxies independent of whether this is a real bulge (a mini-elliptical, believed to form via a merger-induced dissipative collapse and starburst) or a ``pseudobulge'' (believed to form by inward transport of disk material). (4) BH mass does not correlate with the luminosity of galaxy disks. If pure disks contain BHs (and active nuclei imply that some do), then their masses are much smaller than 0.13% of the mass of the disk. We conclude that present observations show no dependence of BH mass on the details of whether BH feeding happens rapidly during a collapse or slowly via secular evolution of the disk. The above results increasingly support the hypothesis that the major events that form a bulge or elliptical galaxy and the main growth phases of its BH-when it shone like a quasar-were the same events. .

[]

https://arxiv.org/pdf/astro-ph/0105230.pdf

2005JHEP...05..014A

Hawking radiation as tunneling for extremal and rotating black holes

2005-01-01

['space science', '-']

[]

The issue concerning semi-classical methods recently developed in deriving the conditions for Hawking radiation as tunneling, is revisited and applied also to rotating black hole solutions as well as to the extremal cases. It is noticed how the tunneling method fixes the temperature of extremal black hole to be zero, unlike the euclidean regularity method that allows an arbitrary compactification period. A comparison with other approaches is presented.

[]

https://arxiv.org/pdf/hep-th/0503081.pdf

2000PhRvD..61f5007C

Brane-world black holes

2000-01-01

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

[]

Gravitational collapse of matter trapped on a brane will produce a black hole on the brane. We discuss such black holes in the models of Randall and Sundrum where our universe is viewed as a domain wall in five-dimensional anti-de Sitter space. We present evidence that a non-rotating uncharged black hole on the domain wall is described by a ``black cigar'' solution in five dimensions.

[]

https://arxiv.org/pdf/hep-th/9909205.pdf

1993hep.th....9145S

Some Speculations about Black Hole Entropy in String Theory

1993-01-01

['-']

[]

The classical Bekenstein entropy of a black hole is argued to arise from configurations of strings with ends which are frozen on the horizon. Quantum corrections to this entropy are probably finite unlike the case in quantum field theory. Finally it is speculated that all black holes are single string states. The level density of strings is of the right order of magnitude to reproduce the Bekenstein entropy.

[]

https://arxiv.org/pdf/hep-th/9309145.pdf

2011LRR....14....8S

Entanglement Entropy of Black Holes

2011-01-01

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

[]

The entanglement entropy is a fundamental quantity, which characterizes the correlations between sub-systems in a larger quantum-mechanical system. For two sub-systems separated by a surface the entanglement entropy is proportional to the area of the surface and depends on the UV cutoff, which regulates the short-distance correlations. The geometrical nature of entanglement-entropy calculation is particularly intriguing when applied to black holes when the entangling surface is the black-hole horizon. I review a variety of aspects of this calculation: the useful mathematical tools such as the geometry of spaces with conical singularities and the heat kernel method, the UV divergences in the entropy and their renormalization, the logarithmic terms in the entanglement entropy in four and six dimensions and their relation to the conformal anomalies. The focus in the review is on the systematic use of the conical singularity method. The relations to other known approaches such as 't Hooft's brick-wall model and the Euclidean path integral in the optical metric are discussed in detail. The puzzling behavior of the entanglement entropy due to fields, which non-minimally couple to gravity, is emphasized. The holographic description of the entanglement entropy of the blackhole horizon is illustrated on the two- and four-dimensional examples. Finally, I examine the possibility to interpret the Bekenstein-Hawking entropy entirely as the entanglement entropy.

[]

https://arxiv.org/pdf/1104.3712.pdf

2010ApJ...711...50T

Black Hole Spin and The Radio Loud/Quiet Dichotomy of Active Galactic Nuclei

2010-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies jets', 'galaxies nuclei', 'mhd', 'galaxies quasars', 'relativity', '-', '-']

[]

Radio loud active galactic nuclei (AGNs) are on average 1000 times brighter in the radio band compared to radio quiet AGNs. We investigate whether this radio loud/quiet dichotomy can be due to differences in the spin of the central black holes (BHs) that power the radio-emitting jets. Using general relativistic magnetohydrodynamic simulations, we construct steady state axisymmetric numerical models for a wide range of BH spins (dimensionless spin parameter 0.1 &lt;= a &lt;= 0.9999) and a variety of jet geometries. We assume that the total magnetic flux through the BH horizon at radius r <SUB>H</SUB>(a) is held constant. If the BH is surrounded by a thin accretion disk, we find that the total BH power output depends approximately quadratically on the angular frequency of the hole, P vprop Ω<SUP>2</SUP> <SUB>H</SUB> vprop (a/r <SUB>H</SUB>)<SUP>2</SUP>. We conclude that, in this scenario, differences in the BH spin can produce power variations of only a few tens at most. However, if the disk is thick such that the jet subtends a narrow solid angle around the polar axis, then the power dependence becomes much steeper, P vprop Ω<SUP>4</SUP> <SUB>H</SUB> or even vpropΩ<SUP>6</SUP> <SUB>H</SUB>. Power variations of 1000 are then possible for realistic BH spin distributions. We derive an analytic solution that accurately reproduces the steeper scaling of jet power with Ω<SUB>H</SUB> and we provide a numerical fitting formula that reproduces all our simulation results. We discuss other physical effects that might contribute to the observed radio loud/quiet dichotomy of AGNs.

[]

https://arxiv.org/pdf/0911.2228.pdf

2020ARA&A..58...27I

The Assembly of the First Massive Black Holes

2020-01-01

['-', '-']

[]

The existence of ∼10<SUP>9</SUP>M<SUB>⊙</SUB> supermassive black holes (SMBHs) within the first billion years of the Universe has stimulated numerous ideas for the prompt formation and rapid growth of black holes (BHs) in the early Universe. Here, we review ways in which the seeds of massive BHs may have first assembled, how they may have subsequently grown as massive as ∼10<SUP>9</SUP>M<SUB>⊙</SUB>, and how multimessenger observations could distinguish between different SMBH assembly scenarios. We conclude the following: The ultrarare ∼10<SUP>9</SUP> M<SUB>⊙</SUB> SMBHs represent only the tip of the iceberg. Early BHs likely fill a continuum from the stellar-mass (∼10M<SUB>⊙</SUB>) to the supermassive (∼10<SUP>9</SUP>) regimes, reflecting a range of initial masses and growth histories. Stellar-mass BHs were likely left behind by the first generation of stars at redshifts as high as ∼30, but their initial growth typically was stunted due to the shallow potential wells of their host galaxies. Conditions in some larger, metal-poor galaxies soon became conducive to the rapid formation and growth of massive seed holes, via gas accretion and by mergers in dense stellar clusters. BH masses depend on the environment (such as the number and properties of nearby radiation sources and the local baryonic streaming velocity) and on the metal enrichment and assembly history of the host galaxy. Distinguishing between assembly mechanisms will be difficult, but a combination of observations by the Laser Interferometer Space Antenna (probing massive BH growth via mergers) and by deep multiwavelength electromagnetic observations (probing growth via gas accretion) is particularly promising.

[]

https://arxiv.org/pdf/1911.05791.pdf

2018PhRvL.120m1102A

Evasion of No-Hair Theorems and Novel Black-Hole Solutions in Gauss-Bonnet Theories

2018-01-01

['-', '-']

[]

We consider a general Einstein-scalar-Gauss-Bonnet theory with a coupling function f (ϕ ) . We demonstrate that black-hole solutions appear as a generic feature of this theory since a regular horizon and an asymptotically flat solution may be easily constructed under mild assumptions for f (ϕ ). We show that the existing no-hair theorems are easily evaded, and a large number of regular black-hole solutions with scalar hair are then presented for a plethora of coupling functions f (ϕ ).

[]

https://arxiv.org/pdf/1711.03390.pdf

2005CQGra..22.1503G

The first law of thermodynamics for Kerr anti-de Sitter black holes

2005-01-01

['-', '-']

[]

We obtain expressions for the mass and angular momenta of rotating black holes in anti-de Sitter backgrounds in four, five and higher dimensions. We verify explicitly that our expressions satisfy the first law of thermodynamics, thus allowing an unambiguous identification of the entropy of these black holes with \ft14 of the area. We find that the associated thermodynamic potential equals the background-subtracted Euclidean action multiplied by the temperature. Our expressions differ from many given in the literature. We find that in more than four dimensions, only our expressions satisfy the first law of thermodynamics. Moreover, in all dimensions we show that our expression for the mass coincides with that given by the conformal conserved charge introduced by Ashtekar, Magnon and Das. We indicate the relevance of these results to the AdS/CFT correspondence.

[]

https://arxiv.org/pdf/hep-th/0408217.pdf

2006A&A...456...75C

Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei: Eddington ratio and inclination

2006-01-01

['galaxies quasars', 'galaxies nuclei', 'galaxies seyfert', 'astrophysics']

[]

Context: .Scatter around the relationship between central black hole masses in active galactic nuclei (AGNs) obtained by reverberation-mapping methods and host-galaxy bulge velocity dispersion indicates that the masses are uncertain typically by a factor of about three.<BR /> Aims: .In this paper, we try to identify the sources and systematics of this uncertainty.<BR /> Methods: .We characterize the broad Hβ emission-line profiles by the ratio of their full-width at half maximum (FWHM) to their line dispersion, i.e., the second moment of the line profile. We use this parameter to separate the reverberation-mapped AGNs into two populations, the first with narrower Hβ lines that tend to have relatively extended wings, and the second with broader lines that are relatively flat-topped. The first population is characterized by higher Eddington ratios than the second. Within each population, we calibrate the black-hole mass scale by comparison of the reverberation-based mass with that predicted by the bulge velocity dispersion. We also use the distribution of ratios of the reverberation-based mass to the velocity-dispersion mass prediction in a comparison with a "generalized thick disk" model in order to see if inclination can plausibly account for the observed distribution.<BR /> Results: .We find that the line dispersion is a less biased parameter in general than FWHM for black hole mass estimation, although we show that it is possible to empirically correct for the bias introduced by using FWHM to characterize the emission-line width. We also argue that inclination effects are apparent only in some small subset of the reverberation-based mass measurements; it is primarily the objects with the narrowest emission lines that seem to be most strongly affected.<BR /> Conclusions: .Our principal conclusion is that the Hβ profile is sensitive primarily to Eddington ratio, but that inclination effects play a role in some cases.

[]

https://arxiv.org/pdf/astro-ph/0603460.pdf

2005JHEP...09..038S

Black hole entropy function and the attractor mechanism in higher derivative gravity

2005-01-01

['-', '-']

[]

We study extremal black hole solutions in D dimensions with near horizon geometry AdS<SUB>2</SUB> × S<SUP>D-2</SUP> in higher derivative gravity coupled to other scalar, vector and anti-symmetric tensor fields. We define an entropy function by integrating the lagrangian density over S<SUP>D-2</SUP> for a general AdS<SUB>2</SUB> × S<SUP>D-2</SUP> background, taking the Legendre transform of the resulting function with respect to the parameters labelling the electric fields, and multiplying the result by a factor of 2π. We show that the values of the scalar fields at the horizon as well as the sizes of AdS<SUB>2</SUB> and S<SUP>D-2</SUP> are determined by extremizing this entropy function with respect to the corresponding parameters, and the entropy of the black hole is given by the value of the entropy function at this extremum. Our analysis relies on the analysis of the equations of motion and does not directly make use of supersymmetry or specific structure of the higher derivative terms.

[]

https://arxiv.org/pdf/hep-th/0506177.pdf

2002PhRvL..88o1301B

Conformal Field Theory Interpretation of Black Hole Quasinormal Modes

2002-01-01

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

[]

We obtain exact expressions for the quasinormal modes of various spin for the Bañados-Teitelboim-Zanelli black hole. These modes determine the relaxation time of black hole perturbations. Exact agreement is found between the quasinormal frequencies and the location of the poles of the retarded correlation function of the corresponding perturbations in the dual conformal field theory. This then provides a new quantitative test of the anti-de Sitter/conformal field theory correspondence.

[]

https://arxiv.org/pdf/hep-th/0112055.pdf

1996NewA....1...35Q

The dynamical evolution of massive black hole binaries I. Hardening in a fixed stellar background

1996-01-01

['astrophysics']

[]

The stellar ejection rate and the rates of change of the binary semimajor axis and eccentricity are derived from scattering experiments for the restricted three-body problem. They are used to study the evolution of binaries in simple models for galactic nuclei, starting soon after the black holes become bound and continuing until the evolution is dominated by the emission of gravitational radiation or until the ejected mass is too large for the galaxy to be considered fixed. The eccentricity growth is found to be unimportant unless the binary forms with a large eccentricity. The scattering results suggest that a binary with masses m <SUB>1</SUB> ≥ m <SUB>2</SUB> should not be considered hard until its orbital velocity exceeds the background velocity dispersion by a factor that scales as (1 +m <SUB>1</SUB>/m <SUB>2</SUB><SUP>1/2</SUP>). The results are compared with predictions from Chandrasekhar's dynamical-friction formula and with previous work on the capture and scattering of comets by planetary systems.

[]

https://arxiv.org/pdf/astro-ph/9601092.pdf

2009MNRAS.400.2070S

Optical flares from the tidal disruption of stars by massive black holes

2009-01-01

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

[]

A star that wanders too close to a massive black hole (BH) is shredded by the BH's tidal gravity. Stellar gas falls back to the BH at a rate initially exceeding the Eddington rate, releasing a flare of energy. In anticipation of upcoming transient surveys, we predict the light curves and spectra of tidal flares as a function of time, highlighting the unique signatures of tidal flares at optical and near-infrared wavelengths. A reasonable fraction of the gas initially bound to the BH is likely blown away when the fallback rate is super-Eddington at early times. This outflow produces an optical luminosity comparable to that of a supernova; such events have durations of ~10 d and may have been missed in supernova searches that exclude the nuclear regions of galaxies. When the fallback rate subsides below Eddington, the gas accretes onto the BH via a thin disc whose emission peaks in the ultraviolet to soft X-rays. Some of this emission is reprocessed by the unbound stellar debris, producing a spectrum of very broad emission lines (with no corresponding narrow forbidden lines). These lines are the strongest for BHs with M<SUB>BH</SUB> ~ 10<SUP>5</SUP>-10<SUP>6</SUP>M<SUB>solar</SUB> and thus optical surveys are particularly sensitive to the lowest mass BHs in galactic nuclei. Calibrating our models to ROSAT and Galaxy Evolution Explorer (GALEX) observations, we predict detection rates for Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), the Palomar Transient Factory (PTF) and the Large Synoptic Survey Telescope (LSST) and highlight some of the observational challenges associated with studying tidal disruption events in the optical. Upcoming surveys such as Pan-STARRS should detect at least several events per year, and may detect many more if current models of outflows during super-Eddington accretion are reasonably accurate. These surveys will significantly improve our knowledge of stellar dynamics in galactic nuclei, the physics of super-Eddington accretion, the demography of intermediate mass BHs and the role of tidal disruption in the growth of massive BHs.

[]

https://arxiv.org/pdf/0905.3735.pdf

1999CQGra..16.1197B

Topological black holes in anti-de Sitter space

1999-01-01

['-']

[]

We consider a class of black hole solutions to Einstein's equations in d dimensions with a negative cosmological constant. These solutions have the property that the horizon is a (d - 2)-dimensional Einstein manifold of positive, zero or negative curvature. The mass, temperature and entropy are calculated. Using the correspondence with conformal field theory, the phase structure of the solutions is examined, and used to determine the correct mass dependence of the Bekenstein-Hawking entropy.

[]

https://arxiv.org/pdf/hep-th/9808032.pdf

1998PhLB..441...96A

Black holes and sub-millimeter dimensions

1998-01-01

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

[]

Recently, a new framework for solving the hierarchy problem was proposed which does not rely on low energy supersymmetry or technicolor. The fundamental Planck mass is at a TeV and the observed weakness of gravity at long distances is due the existence of new sub-millimeter spatial dimensions. In this letter, we study how the properties of black holes are altered in these theories. Small black holes-with Schwarzschild radii smaller than the size of the new spatial dimensions-are quite different. They are bigger, colder, and longer-lived than a usual (3+1)-dimensional black hole of the same mass. Furthermore, they primarily decay into harmless bulk graviton modes rather than standard-model degrees of freedom. We discuss the interplay of our scenario with the holographic principle. Our results also have implications for the bounds on the spectrum of primordial black holes (PBHs) derived from the photo-dissociation of primordial nucleosynthesis products, distortion of the diffuse gamma-ray spectrum, overclosure of the universe, gravitational lensing, as well as the phenomenology of black hole production. For example, the bound on the spectral index of the primordial spectrum of density perturbations is relaxed from 1.25 to 1.45-1.60 depending on the epoch of the PBH formation. In these scenarios PBHs provide interesting dark matter candidates; for 6 extra dimensions MACHO candidates with mass ~0.1M<SUB>solar</SUB> can arise. For 2 or 3 extra dimensions PBHs with mass ~10<SUP>4</SUP>M<SUB>solar</SUB> can occur and may act as both dark matter and seeds for early galaxy and QSO formation.

[]

https://arxiv.org/pdf/hep-th/9808138.pdf

2015PhRvL.115u1102C

Shadows of Kerr Black Holes with Scalar Hair

2015-01-01

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

[]

Using backwards ray tracing, we study the shadows of Kerr black holes with scalar hair (KBHSH). KBHSH interpolate continuously between Kerr BHs and boson stars (BSs), so we start by investigating the lensing of light due to BSs. Moving from the weak to the strong gravity region, BSs—which by themselves have no shadows—are classified, according to the lensing produced, as (i) noncompact, which yield not multiple images, (ii) compact, which produce an increasing number of Einstein rings and multiple images of the whole celestial sphere, and (iii) ultracompact, which possess light rings, yielding an infinite number of images with (we conjecture) a self-similar structure. The shadows of KBHSH, for Kerr-like horizons and noncompact BS-like hair, are analogous to, but distinguishable from, those of comparable Kerr BHs. But for non-Kerr-like horizons and ultracompact BS-like hair, the shadows of KBHSH are drastically different: novel shapes arise, sizes are considerably smaller, and multiple shadows of a single BH become possible. Thus, KBHSH provide quantitatively and qualitatively new templates for ongoing (and future) very large baseline interferometry observations of BH shadows, such as those of the Event Horizon Telescope.

[]

https://arxiv.org/pdf/1509.00021.pdf

2020A&A...636L...5G

Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole

2020-01-01

['black hole physics', 'galaxy nucleus', 'gravitation', 'relativity', '-', '-', '-']

[]

The star S2 orbiting the compact radio source Sgr A* is a precision probe of the gravitational field around the closest massive black hole (candidate). Over the last 2.7 decades we have monitored the star's radial velocity and motion on the sky, mainly with the SINFONI and NACO adaptive optics (AO) instruments on the ESO VLT, and since 2017, with the four-telescope interferometric beam combiner instrument GRAVITY. In this Letter we report the first detection of the General Relativity (GR) Schwarzschild Precession (SP) in S2's orbit. Owing to its highly elliptical orbit (e = 0.88), S2's SP is mainly a kink between the pre-and post-pericentre directions of motion ≈±1 year around pericentre passage, relative to the corresponding Kepler orbit. The superb 2017-2019 astrometry of GRAVITY defines the pericentre passage and outgoing direction. The incoming direction is anchored by 118 NACO-AO measurements of S2's position in the infrared reference frame, with an additional 75 direct measurements of the S2-Sgr A* separation during bright states ("flares") of Sgr A*. Our 14-parameter model fits for the distance, central mass, the position and motion of the reference frame of the AO astrometry relative to the mass, the six parameters of the orbit, as well as a dimensionless parameter f<SUB>SP</SUB> for the SP (f<SUB>SP</SUB> = 0 for Newton and 1 for GR). From data up to the end of 2019 we robustly detect the SP of S2, δϕ ≈ 12' per orbital period. From posterior fitting and MCMC Bayesian analysis with different weighting schemes and bootstrapping we find f<SUB>SP</SUB> = 1.10 ± 0.19. The S2 data are fully consistent with GR. Any extended mass inside S2's orbit cannot exceed ≈0.1% of the central mass. Any compact third mass inside the central arcsecond must be less than about 1000 M<SUB>⊙</SUB>.

[]

https://arxiv.org/pdf/2004.07187.pdf

2006MNRAS.371.1813L

Supermassive black hole formation during the assembly of pre-galactic discs

2006-01-01

['accretion', 'accretion disks', 'accretion disks', 'black hole physics', 'hydrodynamics', 'instabilities', 'galaxies formation', 'cosmology theory', 'astrophysics']

[]

In this paper, we discuss the evolution of gravitationally unstable pre-galactic discs that result from the collapse of haloes at high redshift z ~ 10 or so, which have not yet been enriched by metals. In cases where molecular hydrogen formation is suppressed, the discs are maintained at a temperature of a few thousand Kelvin. However, when molecular hydrogen is present, cooling can proceed down to a few hundred Kelvin. Analogous to the case of the larger-scale protogalactic discs, we assume that the evolution of these discs is mainly driven by angular momentum redistribution induced by the development of gravitational instabilities in the disc. We also properly take into account the possibility of disc fragmentation. We thus show that this simple model naturally predicts the formation of supermassive black holes in the nuclei of such discs and provides a robust determination of their mass distribution as a function of halo properties. We estimate that roughly 5 per cent of discs resulting from the collapse of haloes with M ~ 10<SUP>7</SUP>M<SUB>solar</SUB> should host a massive black hole with a mass M<SUB>BH</SUB> ~ 10<SUP>5</SUP>M<SUB>solar</SUB>. We confirm our arguments with time-dependent calculations of the evolution of the surface density and of the accretion rate in these primordial discs. The luminosity of the outer, colder disc is expected to be very low (in the range of a few thousand L<SUB>solar</SUB>), while the formation of the black hole is expected to produce a burst with a luminosity of a few times 10<SUP>9</SUP>L<SUB>solar</SUB>. This mechanism offers an efficient way to form seed black holes at high redshift. The predicted masses for our black hole seeds enable the comfortable assembly of 10<SUP>9</SUP>-M<SUB>solar</SUB> black holes powering the luminous quasars detected by the Sloan Digital Sky Survey at z = 6 for a concordance cosmology.

[]

https://arxiv.org/pdf/astro-ph/0606159.pdf

2005A&A...440..207B

The evolution of the timing properties of the black-hole transient GX 339-4 during its 2002/2003 outburst

2005-01-01

['accretion', 'accretion disks', 'black hole physics', 'stars oscillations', 'astronomy x rays', 'astrophysics']

[]

We present the results of the timing and color analysis of more than two hundred RXTE/PCA observations of the bright black-hole transient GX 339-4 obtained during its 2002/2003 outburst. The color-intensity evolution of the system, coupled to the properties of its fast time variability, allow the identification of four separate states. Depending on the state, strong noise is detected, together with a variety of quasi-periodic oscillations at frequencies from 0.2 to 8 Hz. We present a characterization of the timing parameters of these states and compare them to what has been observed in other systems. These results, together with those obtained from energy spectra, point towards a common evolution of black-hole transients through their outbursts.

[]

https://arxiv.org/pdf/astro-ph/0504577.pdf

2001MNRAS.322...31F

Powerful jets from black hole X-ray binaries in low/hard X-ray states

2001-01-01

['black hole physics', 'stars binaries close', 'ism jets and outflows', 'astronomy radio', 'astronomy x rays', 'astrophysics']

[]

Four persistent (Cygnus X-1, GX 339-4, GRS 1758-258 and 1E 1740.7-2942) and three transient (GS 2023+38, GRO J0422+32 and GS 1354-64) black hole X-ray binary systems have been extensively observed at radio wavelengths during extended periods in the low/hard X-ray state, which is characterized in X-rays by a hard power-law spectrum and strong variability. All seven systems show a persistent flat or inverted (in the sense that α&gt;~0, where S<SUB>ν</SUB>~ν<SUP>α</SUP>) radio spectrum in this state, markedly different from the optically thin radio spectra exhibited by most X-ray transients within days of outburst. Furthermore, in none of the systems is a high-frequency cut-off to this spectral component detected, and there is evidence that it extends to near-infrared or optical regimes. Luminous persistent hard X-ray states in the black hole system GRS 1915+105 produce a comparable spectrum. This spectral component is considered to arise in synchrotron emission from a conical, partially self-absorbed jet, of the same genre as those originally considered for active galactic nuclei. Whatever the physical origin of the low/hard X-ray states, these self-similar outflows are an ever-present feature. The power in the jet component is likely to be a significant (&gt;=5per cent) and approximately fixed fraction of the total accretion luminosity. The correlation between hard X-ray and synchrotron emission in all the sources implies that the jets are intimately related to the Comptonization process, and do not have very large bulk Lorentz factors, unless the hard X-ray emission is also beamed by the same factor.

[]

https://arxiv.org/pdf/astro-ph/0008447.pdf

2015PhRvD..92b3524C

Massive primordial black holes from hybrid inflation as dark matter and the seeds of galaxies

2015-01-01

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

[]

In this paper we present a new scenario where massive primordial black holes (PBHs) are produced from the collapse of large curvature perturbations generated during a mild-waterfall phase of hybrid inflation. We determine the values of the inflaton potential parameters leading to a PBH mass spectrum peaking on planetarylike masses at matter-radiation equality and producing abundances comparable to those of dark matter today, while the matter power spectrum on scales probed by cosmic microwave background (CMB) anisotropies agrees with Planck data. These PBHs could have acquired large stellar masses today, via merging, and the model passes both the constraints from CMB distortions and microlensing. This scenario is supported by Chandra observations of numerous BH candidates in the central region of Andromeda. Moreover, the tail of the PBH mass distribution could be responsible for the seeds of supermassive black holes at the center of galaxies, as well as for ultraluminous x-ray sources. We find that our effective hybrid potential can originate e.g. from D-term inflation with a Fayet-Iliopoulos term of the order of the Planck scale but sub-Planckian values of the inflaton field. Finally, we discuss the implications of quantum diffusion at the instability point of the potential, able to generate a Swiss-cheese-like structure of the Universe, eventually leading to apparent accelerated cosmic expansion.

[]

https://arxiv.org/pdf/1501.07565.pdf

2004IJMPD..13....1M

Intermediate-Mass Black Holes

2004-01-01

['black hole physics', '-', 'gravitational waves', 'stars kinematics and dynamics', 'astronomy x rays', 'astrophysics']

[]

The mathematical simplicity of black holes, combined with their links to some of the most energetic events in the universe, means that black holes are key objects for fundamental physics and astrophysics. Until recently, it was generally believed that black holes in nature appear in two broad mass ranges: stellar-mass (M~3 20 M<SUB>⊙</SUB>), which are produced by the core collapse of massive stars, and supermassive (M~10<SUP>6</SUP> 10<SUP>10</SUP> M<SUB>⊙</SUB>), which are found in the centers of galaxies and are produced by a still uncertain combination of processes. In the last few years, however, evidence has accumulated for an intermediate-mass class of black holes, with M~10<SUP>2</SUP> 10<SUP>4</SUP> M<SUB>⊙</SUB>. If such objects exist they have important implications for the dynamics of stellar clusters, the formation of supermassive black holes, and the production and detection of gravitational waves. We review the evidence for intermediate-mass black holes and discuss future observational and theoretical work that will help clarify numerous outstanding questions about these objects.

[]

https://arxiv.org/pdf/astro-ph/0308402.pdf

2016PhRvD..93b4003K

Science with the space-based interferometer eLISA: Supermassive black hole binaries

2016-01-01

['-', '-']

[]

We compare the science capabilities of different eLISA mission designs, including four-link (two-arm) and six-link (three-arm) configurations with different arm lengths, low-frequency noise sensitivities and mission durations. For each of these configurations we consider a few representative massive black hole formation scenarios. These scenarios are chosen to explore two physical mechanisms that greatly affect eLISA rates, namely (i) black hole seeding, and (ii) the delays between the merger of two galaxies and the merger of the black holes hosted by those galaxies. We assess the eLISA parameter estimation accuracy using a Fisher matrix analysis with spin-precessing, inspiral-only waveforms. We quantify the information present in the merger and ringdown by rescaling the inspiral-only Fisher matrix estimates using the signal-to-noise ratio from nonprecessing inspiral-merger-ringdown phenomenological waveforms, and from a reduced set of precessing numerical relativity/post-Newtonian hybrid waveforms. We find that all of the eLISA configurations considered in our study should detect some massive black hole binaries. However, configurations with six links and better low-frequency noise will provide much more information on the origin of black holes at high redshifts and on their accretion history, and they may allow the identification of electromagnetic counterparts to massive black hole mergers.

[]

https://arxiv.org/pdf/1511.05581.pdf

2014PhRvL.112y1102S

Black Hole Hair in Generalized Scalar-Tensor Gravity

2014-01-01

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

[]

The most general action for a scalar field coupled to gravity that leads to second-order field equations for both the metric and the scalar—Horndeski's theory—is considered, with the extra assumption that the scalar satisfies shift symmetry. We show that in such theories, the scalar field is forced to have a nontrivial configuration in black hole spacetimes, unless one carefully tunes away a linear coupling with the Gauss-Bonnet invariant. Hence, black holes for generic theories in this class will have hair. This contradicts a recent no-hair theorem which seems to have overlooked the presence of this coupling.

[]

https://arxiv.org/pdf/1312.3622.pdf

2010ForPh..58..528D

Black holes and large N species solution to the hierarchy problem

2010-01-01

['-']

[]

We provide the perturbative and non-perturbative arguments showing that theories with large number of species of the quantum fields, imply an inevitable hierarchy between the masses of the species and the Planck scale, shedding a different light on the hierarchy problem. In particular, using the black hole physics, we prove that any consistent theory that includes N number of the Z_2-conserved species of the quantum fields of mass \Lambda, puts a lower bound on the Planck mass, which in large N limit is given by N\Lambda^2. An useful byproduct of this proof is that any exactly conserved quantum charge, not associated with a long-range classical field, must be defined maximum modulo N, bounded by the the ratio of the Planck to the unit charge masses squared. For example, a continuous global U(1) `baryon number' symmetry, must be explicitly broken by gravity, at least down to a Z_N subgroup, with N bounded by the ratio of the Planck to baryon masses squared. The same constraint applies to any discrete gauge symmetry, as well as to other quantum-mechanically detectable black hole charges that are associated with the massive quantum hair of the black hole. We show that the gravitationally-coupled N-species sector that solves the gauge hirearchy problem, should be probed by LHC.

[]

https://arxiv.org/pdf/0706.2050.pdf

1999JHEP...04..024C

Phases of R-charged black holes, spinning branes and strongly coupled gauge theories

1999-01-01

['-']

[]

We study the thermodynamic stability of charged black holes in gauged supergravity theories in D = 5, D = 4 and D = 7. We find explicitly the location of the Hawking-Page phase transition between charged black holes and the pure anti-de Sitter space-time, both in the grand-canonical ensemble, where electric potentials are held fixed, and in the canonical ensemble, where total charges are held fixed. We also find the explicit local thermodynamic stability constraints for black holes with one non-zero charge. In the grand-canonical ensemble, there is in general a region of phase space where neither the anti-de Sitter space-time is dynamically preferred, nor are the charged black holes thermodynamically stable. But in the canonical ensemble, anti-de Sitter space-time is always dynamically preferred in the domain where black holes are unstable. We demonstrate the equivalence of large R-charged black holes in D = 5, D = 4 and D = 7 with spinning near-extreme D3-, M2- and M5-branes, respectively. The mass, the charges and the entropy of such black holes can be mapped into the energy above extremality, the angular momenta and the entropy of the corresponding branes. We also note a peculiar numerological sense in which the grand-canonical stability constraints for large charge black holes in D = 4 and D = 7 are dual, and in which the D = 5 constraints are self-dual.

[]

https://arxiv.org/pdf/hep-th/9902195.pdf