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1999PhLB..452...39S

Generalized uncertainty principle in quantum gravity from micro-black hole gedanken experiment

1999-01-01

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

[]

We review versions of the Generalized Uncertainty Principle (GUP) obtained in string theory and in gedanken experiments carried out in quantum gravity. We show how a GUP can be derived from a measure gedanken experiment involving micro-black holes at the Planck scale of spacetime. The model uses only Heisenberg principle and Schwarzschild radius and is independent from particular versions of Quantum Gravity.

[]

https://arxiv.org/pdf/hep-th/9904025.pdf

2019JHEP...12..063A

The entropy of bulk quantum fields and the entanglement wedge of an evaporating black hole

2019-01-01

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

[]

Bulk quantum fields are often said to contribute to the generalized entropy A/4 G<SUB>N</SUB> +S<SUB>bulk</SUB> only at O(1). Nonetheless, in the context of evaporating black holes, O(1/GN ) gradients in S<SUB>bulk</SUB> can arise due to large boosts, introducing a quantum extremal surface far from any classical extremal surface. We examine the effect of such bulk quantum effects on quantum extremal surfaces (QESs) and the resulting entanglement wedge in a simple two-boundary 2d bulk system defined by Jackiw-Teitelboim gravity coupled to a 1+1 CFT. Turning on a coupling between one boundary and a further external auxiliary system which functions as a heat sink allows a two-sided otherwise-eternal black hole to evaporate on one side. We find the generalized entropy of the QES to behave as expected from general considerations of unitarity, and in particular that ingoing information disappears from the entanglement wedge after a scambling time β/2 π logΔS +O (1 ) in accord with expectations for holographic implementations of the Hayden-Preskill protocol. We also find an interesting QES phase transition at what one might call the Page time for our process.

[]

https://arxiv.org/pdf/1905.08762.pdf

2017JHEP...05..118C

Black holes and random matrices

2017-01-01

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

[]

We argue that the late time behavior of horizon fluctuations in large anti-de Sitter (AdS) black holes is governed by the random matrix dynamics characteristic of quantum chaotic systems. Our main tool is the Sachdev-Ye-Kitaev (SYK) model, which we use as a simple model of a black hole. We use an analytically continued partition function | Z( β + it)|<SUP>2</SUP> as well as correlation functions as diagnostics. Using numerical techniques we establish random matrix behavior at late times. We determine the early time behavior exactly in a double scaling limit, giving us a plausible estimate for the crossover time to random matrix behavior. We use these ideas to formulate a conjecture about general large AdS black holes, like those dual to 4D super-Yang-Mills theory, giving a provisional estimate of the crossover time. We make some preliminary comments about challenges to understanding the late time dynamics from a bulk point of view.

[]

https://arxiv.org/pdf/1611.04650.pdf

2004A&A...414..895F

A scheme to unify low-power accreting black holes. Jet-dominated accretion flows and the radio/X-ray correlation

2004-01-01

['astronomy x rays', 'radiation', 'stars winds outflows', 'hydrodynamics', 'black hole physics', 'accretion', 'accretion disks', 'astrophysics']

[]

We explore the evolution in power of black holes of all masses, and their associated jets, within the scheme of an accretion rate-dependent state transition. Below a critical value of the accretion rate all systems are assumed to undergo a transition to a state where the dominant accretion mode is optically thin and radiatively inefficient. In these significantly sub-Eddington systems, the spectral energy distribution is predicted to be dominated by non-thermal emission from a relativistic jet whereas near-Eddington black holes will be dominated instead by emission from the accretion disk. Reasonable candidates for such a sub-Eddington state include X-ray binaries in the hard and quiescent states, the Galactic Center (Sgr A*), LINERs, FR I radio galaxies, and a large fraction of BL Lac objects. Standard jet physics predicts non-linear scaling between the optically thick (radio) and optically thin (optical or X-ray) emission of these systems, which has been confirmed recently in <P />X-ray binaries. We show that this scaling relation is also a function of black hole mass and only slightly of the relativistic Doppler factor. Taking the scaling into account we show that indeed hard and quiescent state X-ray binaries, LINERs, FR I radio galaxies, and BL Lacs can be unified and fall on a common radio/X-ray correlation. This suggests that jet domination is an important stage in the luminosity evolution of accreting black hole systems.

[]

https://arxiv.org/pdf/astro-ph/0305335.pdf

2018A&A...615L..15G

Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole

2018-01-01

['galaxy center', 'gravitation', 'black hole physics', '-', '-', '-']

[]

The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A* is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU ≈ 1400 Schwarzschild radii, the star has an orbital speed of ≈7650 km s<SUP>-1</SUP>, such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z = Δλ / λ ≈ 200 km s<SUP>-1</SUP>/c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f , with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 ± 0.09|<SUB>stat</SUB> ± 0.15|<SUB>sys</SUB>. The S2 data are inconsistent with pure Newtonian dynamics. <P />This paper is dedicated to Tal Alexander, who passed away about a week before the pericentre approach of S2.

[]

https://arxiv.org/pdf/1807.09409.pdf

2009MNRAS.398...53B

Cosmological simulations of the growth of supermassive black holes and feedback from active galactic nuclei: method and tests

2009-01-01

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

[]

We present a method that self-consistently tracks the growth of supermassive black holes (BHs) and the feedback from active galactic nuclei (AGN) in cosmological, hydrodynamical simulations. Our model is a substantially modified version of the one introduced by Springel, Di Matteo &amp; Hernquist implemented in a significantly expanded version of the GADGET III code, which contains new prescriptions for star formation, supernova feedback, radiative cooling and chemodynamics. We simulate the growth of BHs from an initial seed state via Eddington-limited accretion of the surrounding gas, and via mergers with other BHs. Because cosmological simulations at present lack both the resolution and the physics to model the multiphase interstellar medium, they tend to strongly underestimate the Bondi-Hoyle accretion rate. To allow low-mass BHs to grow, it is therefore necessary to increase the predicted Bondi-Hoyle rates in star-forming gas by large factors, either by explicitly multiplying the accretion rate by a numerical correction factor or by using an unresolved, subgrid model for the gas close to the BH. We explore the physical regimes where the use of such multiplicative factors is reasonable, and through this introduce a new prescription for gas accretion by BHs. Feedback from AGN is modelled by coupling a fraction of the rest-mass energy of the accreted gas thermally into the surrounding medium. We describe the implementation as well as the limitations of the model in detail and motivate all the changes relative to previous work. We demonstrate how general physical considerations can be used to choose many of the parameters of the model and demonstrate that the fiducial model reproduces observational constraints. <P />We employ a large suite of cosmological simulations, in which the parameters of the BH model are varied away from their fiducial values, to investigate the robustness of the predictions for the cosmic star formation history and the redshift zero cosmic BH density, BH scaling relations and galaxy-specific star formation rates. We find that the freedom introduced by the need to increase the predicted accretion rates by hand, the standard procedure in the literature, is the most significant source of uncertainty. Our simulations demonstrate that supermassive BHs are able to regulate their growth by releasing a fixed amount of energy for a given halo mass, independent of the assumed efficiency of AGN feedback, which sets the normalization of the BH scaling relations. Regardless of whether BH seeds are initially placed above or below the BH scaling relations, they grow on to the same scaling relations. AGN feedback efficiently suppresses star formation in high-mass galaxies.

[]

https://arxiv.org/pdf/0904.2572.pdf

1999ApJ...518..356P

Hyperaccreting Black Holes and Gamma-Ray Bursts

1999-01-01

['accretion', 'accretion disks', 'black hole physics', 'gamma rays', 'radiation', 'accretion', 'accretion disks', 'black hole physics', 'gamma rays', 'radiation', 'astrophysics']

[]

A variety of current models of gamma-ray bursts (GRBs) suggest a common engine: a black hole of several solar masses accreting matter from a disk at a rate of 0.01 to 10 M<SUB>solar</SUB> s<SUP>-1</SUP>. Using a numerical model for relativistic disk accretion, we have studied steady state accretion at these high rates. Outside about 10<SUP>8</SUP> cm, the disk is advection dominated; energy released by dissipation is carried in by the optically thick gas, and the disk does not cool. Inside this radius, for accretion rates greater than about 0.01 M<SUB>solar</SUB> s<SUP>-1</SUP> a global state of balanced power comes to exist between neutrino losses, chiefly pair capture on nucleons, and dissipation. As a result of these losses, the temperature is reduced, the density is raised, and the disk scale height is reduced compared to the advective solution. The sudden onset of neutrino losses (due to the high temperature dependence) and photodisintegration leads to an abrupt thinning of the disk that may provide a favorable geometry for jet production. The inner disk remains optically thin to neutrinos for accretion rates of up to about 1 M<SUB>solar</SUB> s<SUP>-1</SUP>. The energy emitted in neutrinos is less, and in the case of low accretion rates, very much less, than the maximum efficiency factor for black hole accretion (0.057 for no rotation; 0.42 for extreme Kerr rotation) times the accretion rate, Ṁc<SUP>2</SUP>. Neutrino temperatures at the last stable orbit range from 2 MeV (no rotation, slow accretion) to 13 MeV (Kerr geometry, rapid accretion), and the density ranges from 10<SUP>9</SUP> to 10<SUP>12</SUP> g cm<SUP>-3</SUP>. The efficiency for producing a pair fireball along the rotational axis by neutrino annihilation is calculated and found to be highly variable and very sensitive to the accretion rate. For some of the higher accretion rates studied, it can be several percent or more; for accretion rates less than 0.05 M<SUB>solar</SUB> s<SUP>-1</SUP>, it is essentially zero. The efficiency of the Blandford-Znajek mechanism in extracting rotational energy from the black hole is also estimated. In light of these results, the viability of various gamma-ray burst models is discussed, and the sensitivity of the results to disk viscosity, black hole rotation rate, and black hole mass is explored. A diverse range of GRB energies seems unavoidable, and neutrino annihilation in hyperaccreting black hole systems can explain bursts of up to 10<SUP>52</SUP> ergs. Larger energies can be inferred for beaming systems.

[]

https://arxiv.org/pdf/astro-ph/9807028.pdf

2018CQGra..35f3001S

Primordial black holes—perspectives in gravitational wave astronomy

2018-01-01

['-', '-']

[]

This article reviews current understanding of primordial black holes (PBHs), with particular focus on those massive examples (≳ 10<SUP>15</SUP>~g ) which remain at the present epoch, not having evaporated through Hawking radiation. With the detection of gravitational waves by LIGO, we have gained a completely novel observational tool to search for PBHs, complementary to those using electromagnetic waves. Taking the perspective that gravitational-wave astronomy will make significant progress in the coming decades, the purpose of this article is to give a comprehensive review covering a wide range of topics on PBHs. After discussing PBH formation, as well as several inflation models leading to PBH production, we summarize various existing and future observational constraints. We then present topics on formation of PBH binaries, gravitational waves from PBH binaries, and various observational tests of PBHs using gravitational waves.

[]

https://arxiv.org/pdf/1801.05235.pdf

2004ApJ...613..109H

Present-Day Growth of Black Holes and Bulges: The Sloan Digital Sky Survey Perspective

2004-01-01

['galaxies active', 'galaxies bulges', 'galaxies evolution', 'galaxies nuclei', 'galaxies stellar content', 'astrophysics']

[]

We investigate the accretion-driven growth of supermassive black holes in the low-redshift universe using 23,000 narrow-emission-line (``type 2'') active galactic nuclei (AGNs) and the complete sample of 123,000 galaxies in the Sloan Digital Sky Survey from which they were drawn. We use the stellar velocity dispersions of the early-type galaxies and AGN hosts to estimate their black hole masses, and we use the AGN [O III] λ5007 emission line luminosities to estimate black hole accretion rates. We find that most present-day accretion occurs onto black holes with masses less than 10<SUP>8</SUP> M<SUB>solar</SUB> that reside in moderately massive galaxies (M<SUB>*</SUB>~10<SUP>10</SUP>-10<SUP>11.5</SUP> M<SUB>solar</SUB>) with high stellar surface mass densities (μ<SUB>*</SUB>~10<SUP>8.5</SUP>-10<SUP>9.5</SUP> M<SUB>solar</SUB> kpc<SUP>-2</SUP>) and young stellar populations. The volume-averaged accretion rates of low-mass black holes (&lt;3×10<SUP>7</SUP> M<SUB>solar</SUB>) imply that this population is growing on a timescale that is comparable to the age of the universe. Around half this growth takes place in AGNs that are radiating within a factor of 5 of the Eddington luminosity. Such systems are rare, making up only 0.2% of the low-mass black hole population at the present day. The rest of the growth occurs in lower luminosity AGNs. The growth timescale is more than 2 orders of magnitude longer for the population of the most massive black holes in our sample. The volume-averaged ratio of star formation to black hole accretion in bulge-dominated galaxies is ~1000, in remarkable agreement with the observed ratio of stellar mass to black hole mass in nearby galaxy bulges. We conclude that (1) bulge formation and black hole formation are tightly coupled, even in present-day galaxies, and (2) the evolution of the AGN luminosity function documented in recent optical and X-ray surveys is driven by a decrease in the characteristic mass scale of actively accreting black holes.

[]

https://arxiv.org/pdf/astro-ph/0406218.pdf

2002ApJ...579..530W

Active Galactic Nucleus Black Hole Masses and Bolometric Luminosities

2002-01-01

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

[]

Black hole mass, along with mass accretion rate, is a fundamental property of active galactic nuclei (AGNs). Black hole mass sets an approximate upper limit to AGN energetics via the Eddington limit. We collect and compare all AGN black hole mass estimates from the literature; these 177 masses are mostly based on the virial assumption for the broad emission lines, with the broad-line region size determined from either reverberation mapping or optical luminosity. We introduce 200 additional black hole mass estimates based on properties of the host galaxy bulges, using either the observed stellar velocity dispersion or the fundamental plane relation to infer σ these methods assume that AGN hosts are normal galaxies. We compare 36 cases for which black hole mass has been generated by different methods and find, for individual objects, a scatter as high as a couple of orders of magnitude. The less direct the method, the larger the discrepancy with other estimates, probably due to the large scatter in the underlying correlations assumed. Using published fluxes, we calculate bolometric luminosities for 234 AGNs and investigate the relation between black hole mass and luminosity. In contrast to other studies, we find no significant correlation of black hole mass with luminosity, other than those induced by circular reasoning in the estimation of black hole mass. The Eddington limit defines an approximate upper envelope to the distribution of luminosities, but the lower envelope depends entirely on the sample of AGNs included. For any given black hole mass, there is a range in Eddington ratio of up to 3 orders of magnitude.

[]

https://arxiv.org/pdf/astro-ph/0207249.pdf

2019MNRAS.490.3234N

First results from the TNG50 simulation: galactic outflows driven by supernovae and black hole feedback

2019-01-01

['galaxies evolution', 'galaxies formation', '-', '-', '-']

[]

We present the new TNG50 cosmological, magnetohydrodynamical simulation - the third and final volume of the IllustrisTNG project. This simulation occupies a unique combination of large volume and high resolution, with a 50 Mpc box sampled by 2160<SUP>3</SUP> gas cells (baryon mass of 8 × 10<SUP>4</SUP> M<SUB>⊙</SUB>). The median spatial resolution of star-forming interstellar medium gas is ∼100-140 pc. This resolution approaches or exceeds that of modern `zoom' simulations of individual massive galaxies, while the volume contains ∼20 000 resolved galaxies with M_\star ≳ 10^7 M<SUB>⊙</SUB>. Herein we show first results from TNG50, focusing on galactic outflows driven by supernovae as well as supermassive black hole feedback. We find that the outflow mass loading is a non-monotonic function of galaxy stellar mass, turning over and rising rapidly above 10<SUP>10.5</SUP> M<SUB>⊙</SUB> due to the action of the central black hole (BH). The outflow velocity increases with stellar mass, and at fixed mass it is faster at higher redshift. The TNG model can produce high-velocity, multiphase outflows that include cool, dense components. These outflows reach speeds in excess of 3000 km s<SUP>-1</SUP> out to 20 kpc with an ejective, BH-driven origin. Critically, we show how the relative simplicity of model inputs (and scalings) at the injection scale produces complex behaviour at galactic and halo scales. For example, despite isotropic wind launching, outflows exhibit natural collimation and an emergent bipolarity. Furthermore, galaxies above the star-forming main sequence drive faster outflows, although this correlation inverts at high mass with the onset of quenching, whereby low-luminosity, slowly accreting, massive BHs drive the strongest outflows.

[]

https://arxiv.org/pdf/1902.05554.pdf

2003ApJ...596...34B

Formation of the First Supermassive Black Holes

2003-01-01

['black hole physics', 'cosmology theory', 'galaxies formation', 'hydrodynamics', 'galaxies quasars', 'astrophysics', '-']

[]

We consider the physical conditions under which supermassive black holes could have formed inside the first galaxies. Our smoothed particle hydrodynamics simulations indicate that metal-free galaxies with a virial temperature of ~10<SUP>4</SUP> K and suppressed H<SUB>2</SUB> formation (due to an intergalactic UV background) tend to form a binary black hole system that contains a substantial fraction (&gt;~10%) of the total baryonic mass of the host galaxy. Fragmentation into stars is suppressed without substantial H<SUB>2</SUB> cooling. Our simulations follow the condensation of ~5×10<SUP>6</SUP> M<SUB>solar</SUB> around the two centers of the binary down to a scale of &lt;~0.1 pc. Low-spin galaxies form a single black hole instead. These early black holes lead to quasar activity before the epoch of reionization. Primordial black hole binaries lead to gravitational radiation emission at redshifts z&gt;~10 that would be detectable by Laser Interferometer Space Antenna.

[]

https://arxiv.org/pdf/astro-ph/0212400.pdf

2006PhRvD..73f4030B

Gravitational-wave spectroscopy of massive black holes with the space interferometer LISA

2006-01-01

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

[]

Newly formed black holes are expected to emit characteristic radiation in the form of quasinormal modes, called ringdown waves, with discrete frequencies. LISA should be able to detect the ringdown waves emitted by oscillating supermassive black holes throughout the observable Universe. We develop a multimode formalism, applicable to any interferometric detectors, for detecting ringdown signals, for estimating black-hole parameters from those signals, and for testing the no-hair theorem of general relativity. Focusing on LISA, we use current models of its sensitivity to compute the expected signal-to-noise ratio for ringdown events, the relative parameter estimation accuracy, and the resolvability of different modes. We also discuss the extent to which uncertainties on physical parameters, such as the black-hole spin and the energy emitted in each mode, will affect our ability to do black-hole spectroscopy.

[]

https://arxiv.org/pdf/gr-qc/0512160.pdf

2014ApPhL.104j3106K

Electric field effect in ultrathin black phosphorus

2014-01-01

['-']

[]

Black phosphorus exhibits a layered structure similar to graphene, allowing mechanical exfoliation of ultrathin single crystals. Here, we demonstrate few-layer black phosphorus field effect devices on Si/SiO<SUB>2</SUB> and measure charge carrier mobility in a four-probe configuration as well as drain current modulation in a two-point configuration. We find room-temperature mobilities of up to 300 cm<SUP>2</SUP>/Vs and drain current modulation of over 10<SUP>3</SUP>. At low temperatures, the on-off ratio exceeds 10<SUP>5</SUP>, and the device exhibits both electron and hole conduction. Using atomic force microscopy, we observe significant surface roughening of thin black phosphorus crystals over the course of 1 h after exfoliation.

[]

https://arxiv.org/pdf/1402.5718.pdf

2003ApJ...596L..27K

Black Holes, Galaxy Formation, and the M<SUB>BH</SUB>-σ Relation

2003-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies formation', 'galaxies nuclei', 'galaxies quasars', 'astrophysics']

[]

Recent X-ray observations of intense high-speed outflows in quasars suggest that supercritical accretion on to the central black hole may have an important effect on a host galaxy. I revisit some ideas of Silk &amp; Rees and assume that such flows occur in the final stages of building up the black hole mass. It is now possible to model explicitly the interaction between the outflow and the host galaxy. This is found to resemble a momentum-driven stellar wind bubble, implying a relation M<SUB>BH</SUB>=(f<SUB>g</SUB>κ/2πG<SUP>2</SUP>)σ<SUP>4</SUP>~=1.5×10<SUP>8</SUP>σ<SUP>4</SUP><SUB>200</SUB> M<SUB>solar</SUB> between black hole mass and bulge velocity dispersion (f<SUB>g</SUB>=gas fraction of total matter density, κ=electron scattering opacity), without free parameters. This is remarkably close to the observed relation in both slope and normalization. This result suggests that the central black holes in galaxies gain most of their mass in phases of super-Eddington accretion, which are presumably obscured or at high redshift. Observed super-Eddington quasars are apparently late in growing their black hole masses.

[]

https://arxiv.org/pdf/astro-ph/0308342.pdf

2006MNRAS.370..289B

Formation of supermassive black holes by direct collapse in pre-galactic haloes

2006-01-01

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

[]

We describe a mechanism by which supermassive black holes (SMBHs) can form directly in the nuclei of protogalaxies, without the need for `seed' black holes left over from early star formation. Self-gravitating gas in dark matter haloes can lose angular momentum rapidly via runaway, global dynamical instabilities, the so-called `bars within bars' mechanism. This leads to the rapid build-up of a dense, self-gravitating core supported by gas pressure - surrounded by a radiation pressure-dominated envelope - which gradually contracts and is compressed further by subsequent infall. We show that these conditions lead to such high temperatures in the central region that the gas cools catastrophically by thermal neutrino emission, leading to the formation and rapid growth of a central black hole. <P />We estimate the initial mass and growth rate of the black hole for typical conditions in metal-free haloes with T<SUB>vir</SUB> ~ 10<SUP>4</SUP>K, which are the most likely to be susceptible to runaway infall. The initial black hole should have a mass of &lt;~20 M<SUB>solar</SUB>, but in principle could grow at a super-Eddington rate until it reaches ~10<SUP>4</SUP>-10<SUP>6</SUP> M<SUB>solar</SUB>. Rapid growth may be limited by feedback from the accretion process and/or disruption of the mass supply by star formation or halo mergers. Even if super-Eddington growth stops at ~10<SUP>3</SUP>-10<SUP>4</SUP> M<SUB>solar</SUB>, this process would give black holes ample time to attain quasar-size masses by a redshift of 6, and could also provide the seeds for all SMBHs seen in the present Universe.

[]

https://arxiv.org/pdf/astro-ph/0602363.pdf

1994PhRvD..50.2700S

Black hole entropy in canonical quantum gravity and superstring theory

1994-01-01

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

[]

In this paper the entropy of an eternal Schwarzschild black hole is studied in the limit of an infinite black hole mass. The problem is addressed from the point of view of both canonical quantum gravity and superstring theory. The entropy per unit area of a free scalar field propagating in a fixed black hole background is shown to be quadratically divergent near the horizon. It is shown that such quantum corrections to the entropy per unit area are equivalent to the quantum corrections to the gravitational coupling. Unlike field theory, superstring theory provides a set of identifiable configurations which give rise to the classical contribution to the entropy per unit area. These configurations can be understood as open superstrings with both ends attached to the horizon. The entropy per unit area is shown to be finite to all orders in superstring perturbation theory. The importance of these conclusions to the resolution of the problem of black hole information loss is reiterated.

[]

https://arxiv.org/pdf/hep-th/9401070.pdf

2006PhLB..632..547N

Noncommutative geometry inspired Schwarzschild black hole

2006-01-01

['-', '-']

[]

We investigate the behavior of a noncommutative radiating Schwarzschild black hole. It is shown that coordinate noncommutativity cures usual problems encountered in the description of the terminal phase of black hole evaporation. More in detail, we find that: the evaporation end-point is a zero temperature extremal black hole even in the case of electrically neutral, non-rotating, objects; there exists a finite maximum temperature that the black hole can reach before cooling down to absolute zero; there is no curvature singularity at the origin, rather we obtain a regular de Sitter core at short distance.

[]

https://arxiv.org/pdf/gr-qc/0510112.pdf

2019PhRvD.100j4036A

Tests of general relativity with the binary black hole signals from the LIGO-Virgo catalog GWTC-1

2019-01-01

['-']

[]

The detection of gravitational waves by Advanced LIGO and Advanced Virgo provides an opportunity to test general relativity in a regime that is inaccessible to traditional astronomical observations and laboratory tests. We present four tests of the consistency of the data with binary black hole gravitational waveforms predicted by general relativity. One test subtracts the best-fit waveform from the data and checks the consistency of the residual with detector noise. The second test checks the consistency of the low- and high-frequency parts of the observed signals. The third test checks that phenomenological deviations introduced in the waveform model (including in the post-Newtonian coefficients) are consistent with 0. The fourth test constrains modifications to the propagation of gravitational waves due to a modified dispersion relation, including that from a massive graviton. We present results both for individual events and also results obtained by combining together particularly strong events from the first and second observing runs of Advanced LIGO and Advanced Virgo, as collected in the catalog GWTC-1. We do not find any inconsistency of the data with the predictions of general relativity and improve our previously presented combined constraints by factors of 1.1 to 2.5. In particular, we bound the mass of the graviton to be m<SUB>g</SUB>≤4.7 ×10<SUP>-23</SUP> eV /c<SUP>2</SUP> (90% credible level), an improvement of a factor of 1.6 over our previously presented results. Additionally, we check that the four gravitational-wave events published for the first time in GWTC-1 do not lead to stronger constraints on alternative polarizations than those published previously.

[]

https://arxiv.org/pdf/1903.04467.pdf

2005ApJ...620..744G

Stellar Orbits around the Galactic Center Black Hole

2005-01-01

['black hole physics', 'galaxy center', 'galaxy kinematics and dynamics', 'astronomy infrared', 'techniques high angular resolution', 'astrophysics']

[]

We present new diffraction-limited images of the Galactic center, obtained with the W. M. Keck I 10 m telescope. Within 0.4" of the Galaxy's central dark mass, 17 proper-motion stars, with K magnitudes ranging from 14.0 to 16.8, are identified, and 10 of these are new detections (six were also independently discovered by others). In this sample, three newly identified (S0-16, S0-19, and S0-20) and four previously known (S0-1, S0-2, S0-4, and S0-5) sources have measured proper motions that reveal orbital solutions. Orbits are derived simultaneously so that they jointly constrain the central dark object's properties: its mass, its position, and, for the first time using orbits, its motion on the plane of the sky. This analysis pinpoints the Galaxy's central dark mass to within 1.3 mas (10 AU) and limits its proper motion to 1.5+/-0.5 mas yr<SUP>-1</SUP> (or equivalently 60+/-20 km s<SUP>-1</SUP>) with respect to the central stellar cluster. This localization of the central dark mass is consistent with our derivation of the position of the radio source Sgr A* in the infrared reference frame (+/-10 mas) but with an uncertainty that is a factor of 8 times smaller, which greatly facilitates searches for near-infrared counterparts to the central black hole. Consequently, one previous claim for such a counterpart can now be ascribed to a close stellar passage in 1996. Furthermore, we can place a conservative upper limit of 15.5 mag on any steady state counterpart emission. The estimated central dark mass from orbital motions is 3.7(+/-0.2)×10<SUP>6</SUP>[R<SUB>0</SUB>/(8kpc)]<SUP>3</SUP>M<SUB>solar</SUB> this is a more direct measure of mass than those obtained from velocity dispersion measurements, which are as much as a factor of 2 smaller. The Galactic center's distance, which adds an additional 19% uncertainty in the estimated mass, is now the limiting source of uncertainty in the absolute mass. For stars in this sample, the closest approach is achieved by S0-16, which came within a mere 45 AU (=0.0002pc=600R<SUB>s</SUB>) at a velocity of 12,000 km s<SUP>-1</SUP>. This increases the inferred dark mass density by 4 orders of magnitude compared to earlier analyses based on velocity and acceleration vectors, making the Milky Way the strongest existing case for a supermassive black hole at the center of a normal-type galaxy. Well-determined orbital parameters for these seven Sgr A* cluster stars also provide new constraints on how these apparently massive, young (&lt;10 Myr) stars formed in a region that seems to be hostile to star formation. Unlike the more distant He I emission line stars-another population of young stars in the Galactic center-that appear to have coplanar orbits, the Sgr A* cluster stars have orbital properties (eccentricities, angular momentum vectors, and apoapse directions) that are consistent with an isotropic distribution. Therefore, many of the mechanisms proposed for the formation of the He I stars, such as formation from a preexisting disk, are unlikely solutions for the Sgr A* cluster stars. Unfortunately, alternative theories for producing young stars, or old stars that look young, in close proximity to a central supermassive black hole are all also somewhat problematic. Understanding the apparent youth of stars in the Sgr A* cluster, as well as the more distant He I emission line stars, has now become one of the major outstanding issues in the study of the Galactic center.

[]

https://arxiv.org/pdf/astro-ph/0306130.pdf

1998JHEP...12..005M

AdS<SUB>3</SUB> black holes and a stringy exclusion principle

1998-01-01

['-']

[]

The duality relating near-horizon microstates of black holes obtained as orbifolds of a subset of AdS<SUB>3</SUB> to the states of a conformal field theory is analyzed in detail. The SL(2,R)<SUB>L</SUB>SL(2,R)<SUB>R</SUB> invariant vacuum on AdS<SUB>3</SUB> corresponds to the NS-NS vacuum of the conformal field theory. The effect of the orbifolding is to produce a density matrix, the temperature and entropy of which coincide with the black hole. For string theory examples the spectrum of chiral primaries agrees with the spectrum of multi-particle BPS states for particle numbers less than of order the central charge. An upper bound on the BPS particle number follows from the upper bound on the U(1) charge of chiral primaries. This is a stringy exclusion principle which cannot be seen in perturbation theory about AdS<SUB>3</SUB>.

[]

https://arxiv.org/pdf/hep-th/9804085.pdf

2019CQGra..36n3001B

Black holes, gravitational waves and fundamental physics: a roadmap

2019-01-01

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

[]

The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. <P />The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. <P />The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on ‘Black holes, Gravitational waves and Fundamental Physics’.

[]

https://arxiv.org/pdf/1806.05195.pdf

2005ApJ...620L..79S

Black Holes in Galaxy Mergers: The Formation of Red Elliptical Galaxies

2005-01-01

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

[]

We use hydrodynamical simulations to study the color transformations induced by star formation and active galactic nuclei (AGNs) during major mergers of spiral galaxies. Our modeling accounts for radiative cooling, star formation, and supernova feedback. Moreover, we include a treatment of accretion onto supermassive black holes embedded in the nuclei of the merging galaxies. We assume that a small fraction of the bolometric luminosity of an accreting black hole couples thermally to surrounding gas, providing a feedback mechanism that regulates its growth. The encounter and coalescence of the galaxies triggers nuclear gas inflow, which fuels both a powerful starburst and strong black hole accretion. Comparing simulations with and without black holes, we show that AGN feedback can quench star formation and accretion on a short timescale, particularly in large galaxies where the black holes can drive powerful winds once they become sufficiently massive. The color evolution of the remnant differs markedly between mergers with and without central black holes. Without AGNs, gas-rich mergers lead to elliptical galaxies that remain blue owing to residual star formation, even after more than 7 Gyr have elapsed. In contrast, mergers with black holes produce elliptical galaxies that redden much faster, an effect that is more pronounced in massive remnants where a nearly complete termination of star formation occurs, allowing them to redden to u-r~=2.3 in less than 1 Gyr. AGN feedback may thus be required to explain the population of extremely red massive early-type galaxies, and it appears to be an important driver in generating the observed bimodal color distribution of galaxies in the local universe.

[]

https://arxiv.org/pdf/astro-ph/0409436.pdf

2010A&ARv..18..279V

Formation of supermassive black holes

2010-01-01

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

[]

Evidence shows that massive black holes reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than the host (~0.1%), are linked to the evolution of galactic structure. In hierarchical cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation had to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for ‘seed’ black holes that are likely to place at early cosmic epochs, and possible observational tests of these scenarios.

[]

https://arxiv.org/pdf/1003.4404.pdf

2000PhRvD..62f4015B

Transition from inspiral to plunge in binary black hole coalescences

2000-01-01

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

[]

Combining recent techniques giving nonperturbative resummed estimates of the damping and conservative parts of the two-body dynamics, we describe the transition between the adiabatic phase and the plunge, in coalescing binary black holes with comparable masses moving on quasicircular orbits. We give initial dynamical data for numerical relativity investigations, with a fraction of an orbit left, and provide, for data analysis purposes, an estimate of the gravitational waveform emitted throughout the inspiral, plunge and coalescence phases.

[]

https://arxiv.org/pdf/gr-qc/0001013.pdf

1996PhRvD..54.6040G

Density perturbations and black hole formation in hybrid inflation

1996-01-01

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

[]

We investigate the recently proposed hybrid inflation models with two stages of inflation. We show that quantum fluctuations at the time corresponding to the phase transition between the two inflationary stages can trigger the formation of a large number of inflating topological defects. In order to study density perturbations in these models we further develop a method to calculate density perturbations in a system of two scalar fields. We show that density perturbations in hybrid inflation models of the new type can be very large on the scale corresponding to the phase transition. The resulting density inhomogeneities lead to a copious production of black holes. This could be an argument against hybrid inflation models with two stages of inflation. However, we find a class of models where this problem can be easily avoided. The number of black holes produced in these models can be made extremely small, but in general it could be sufficiently large to have important cosmological and astrophysical implications. In particular, for certain values of parameters these black holes may constitute the dark matter in the Universe. It is also possible to have hybrid models with two stages of inflation where the black hole production is not suppressed, but where the typical masses of the black holes are very small. Such models lead to a completely different thermal history of the Universe, where postinflationary reheating occurs via black hole evaporation.

[]

https://arxiv.org/pdf/astro-ph/9605094.pdf

2005ApJ...630..122G

Estimating Black Hole Masses in Active Galaxies Using the Hα Emission Line

2005-01-01

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

[]

It has been established that virial masses for black holes in low-redshift active galaxies can be estimated from measurements of the optical continuum strength and the width of the broad Hβ line. Under various circumstances, however, both of these quantities can be challenging to measure or can be subject to large systematic uncertainties. To mitigate these difficulties, we present a new method for estimating black hole masses. From analysis of a new sample of broad-line active galactic nuclei, we find that Hα luminosity scales almost linearly with optical continuum luminosity and that a strong correlation exists between Hα and Hβ line widths. These two empirical correlations allow us to translate the standard virial mass system to a new one based solely on observations of the broad Hα emission line.

[]

https://arxiv.org/pdf/astro-ph/0508335.pdf

2016ApJ...818L..22A

Astrophysical Implications of the Binary Black-hole Merger GW150914

2016-01-01

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

[]

The discovery of the gravitational-wave (GW) source GW150914 with the Advanced LIGO detectors provides the first observational evidence for the existence of binary black hole (BH) systems that inspiral and merge within the age of the universe. Such BH mergers have been predicted in two main types of formation models, involving isolated binaries in galactic fields or dynamical interactions in young and old dense stellar environments. The measured masses robustly demonstrate that relatively “heavy” BHs (≳ 25 {M}<SUB>⊙ </SUB>) can form in nature. This discovery implies relatively weak massive-star winds and thus the formation of GW150914 in an environment with a metallicity lower than about 1/2 of the solar value. The rate of binary-BH (BBH) mergers inferred from the observation of GW150914 is consistent with the higher end of rate predictions (≳ 1 Gpc<SUP>-3</SUP> yr<SUP>-1</SUP>) from both types of formation models. The low measured redshift (z≃ 0.1) of GW150914 and the low inferred metallicity of the stellar progenitor imply either BBH formation in a low-mass galaxy in the local universe and a prompt merger, or formation at high redshift with a time delay between formation and merger of several Gyr. This discovery motivates further studies of binary-BH formation astrophysics. It also has implications for future detections and studies by Advanced LIGO and Advanced Virgo, and GW detectors in space.

[]

https://arxiv.org/pdf/1602.03846.pdf

2001GReGr..33.2101A

The Generalized Uncertainty Principle and Black Hole Remnants

2001-01-01

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

[]

In the current standard viewpoint small black holes are believed to emit black body radiation at the Hawking temperature, at least until they approach Planck size, after which their fate is open to conjecture. A cogent argument against the existence of remnants is that, since no evident quantum number prevents it, black holes should radiate completely away to photons and other ordinary stable particles and vacuum, like any unstable quantum system. Here we argue the contrary, that the generalized uncertainty principle may prevent their total evaporation in exactly the same way that the uncertainty principle prevents the hydrogen atom from total collapse: the collapse is prevented, not by symmetry, but by dynamics, as a minimum size and mass are approached.

[]

https://arxiv.org/pdf/gr-qc/0106080.pdf

2003MNRAS.344...60G

A universal radio-X-ray correlation in low/hard state black hole binaries

2003-01-01

['accretion', 'accretion disks', 'stars binaries general', 'ism jets and outflows', 'astronomy radio', 'astronomy x rays', 'astrophysics']

[]

Several independent lines of evidence now point to a connection between the physical processes that govern radio (i.e. jet) and X-ray emission from accreting X-ray binaries. We present a comprehensive study of (quasi-)simultaneous radio-X-ray observations of stellar black hole binaries during the spectrally hard X-ray state, finding evidence for a strong correlation between these two bands over more than three orders of magnitude in X-ray luminosity. The correlation extends from the quiescent regime up to close to the soft state transition, where radio emission starts to decline, sometimes below detectable levels, probably corresponding to the physical disappearance of the jet. The X-ray transient V404 Cygni is found to display the same functional relationship already reported for GX 339-4 between radio and X-ray flux, namely S<SUB>radio</SUB>~S<SUP>+0.7</SUP><SUB>X</SUB>. In fact, the data for all low/hard state black holes is consistent with a universal relation between the radio and X-ray luminosity of the form L<SUB>radio</SUB>~L<SUP>+0.7</SUP><SUB>X</SUB>. Under the hypothesis of common physics driving the disc-jet coupling in different sources, the observed spread to the best-fitting relation can be interpreted in terms of a distribution in Doppler factors and hence used to constrain the bulk Lorentz factors of both the radio- and X-ray-emitting regions. Monte Carlo simulations show that, assuming little or no X-ray beaming, the measured scatter in radio power is consistent with Lorentz factors &lt;~ 2 for the outflows in the low/hard state, significantly less relativistic than the jets associated with X-ray transients. When combined radio and X-ray beaming is considered, the range of possible jet bulk velocities significantly broadens, allowing highly relativistic outflows, but therefore implying severe X-ray selection effects. If the radio luminosity scales as the total jet power raised to x &gt; 0.7, then there exists an X-ray luminosity below which most of the accretion power will be channelled into the jet, rather than into X-rays. For x= 1.4, as in several optically thick jet models, the power output of `quiescent' black holes may be jet-dominated below L<SUB>X</SUB>~= 4 × 10<SUP>-5</SUP>L<SUB>Edd</SUB>.

[]

https://arxiv.org/pdf/astro-ph/0305231.pdf

2014PhRvL.112v1101H

Kerr Black Holes with Scalar Hair

2014-01-01

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

[]

We present a family of solutions of Einstein's gravity minimally coupled to a complex, massive scalar field, describing asymptotically flat, spinning black holes with scalar hair and a regular horizon. These hairy black holes (HBHs) are supported by rotation and have no static limit. Besides mass M and angular momentum J, they carry a conserved, continuous Noether charge Q measuring the scalar hair. HBHs branch off from the Kerr metric at the threshold of the superradiant instability and reduce to spinning boson stars in the limit of vanishing horizon area. They overlap with Kerr black holes for a set of (M, J) values. A single Killing vector field preserves the solutions, tangent to the null geodesic generators of the event horizon. HBHs can exhibit sharp physical differences when compared to the Kerr solution, such as J/M<SUP>2</SUP>&gt;1, a quadrupole moment larger than J<SUP>2</SUP>/M, and a larger orbital angular velocity at the innermost stable circular orbit. Families of HBHs connected to the Kerr geometry should exist in scalar (and other) models with more general self-interactions.

[]

https://arxiv.org/pdf/1403.2757.pdf

1996NuPhB.472..591C

D-brane approach to black hole quantum mechanics

1996-01-01

['-']

[]

Strominger and Vafa have used D-brane technology to identify and precisely count the degenerate quantum states responsible for the entropy of certain extremal, BPS-saturated black holes. Here we give a Type-II D-brane description of a class of extremal and non-extremal five-dimensional Reissner-Nordström solutions and identify a corresponding set of degenerate D-brane configurations. We use this information to do a string theory calculation of the entropy, radiation rate and ``Hawking'' temperature. The results agree perfectly with standard Hawking results for the corresponding nearly extremal Reissner-Nordström black holes. Although these calculations suffer from open-string strong coupling problems, we give some reasons to believe that they are nonetheless qualitatively reliable. In this optimistic scenario there would be no ``information loss'' in black hole quantum evolution.

[]

https://arxiv.org/pdf/hep-th/9602043.pdf

2016PhRvL.116w1301H

Soft Hair on Black Holes

2016-01-01

['-']

[]

It has recently been shown that Bondi-van der Burg-Metzner-Sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian spacetimes. These laws require black holes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This Letter gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.

[]

https://arxiv.org/pdf/1601.00921.pdf

2004Natur.428..724P

Formation of massive black holes through runaway collisions in dense young star clusters

2004-01-01

['astrophysics']

[]

A luminous X-ray source is associated with MGG 11-a cluster of young stars ~200pc from the centre of the starburst galaxy M 82 (refs 1, 2). The properties of this source are best explained by invoking a black hole with a mass of at least 350 solar masses (350M<SUB>solar</SUB>), which is intermediate between stellar-mass and supermassive black holes. A nearby but somewhat more massive cluster (MGG 9) shows no evidence of such an intermediate-mass black hole, raising the issue of just what physical characteristics of the clusters can account for this difference. Here we report numerical simulations of the evolution and motion of stars within the clusters, where stars are allowed to merge with each other. We find that for MGG 11 dynamical friction leads to the massive stars sinking rapidly to the centre of the cluster, where they participate in a runaway collision. This produces a star of 800-3,000 M<SUB>solar</SUB>, which ultimately collapses to a black hole of intermediate mass. No such runaway occurs in the cluster MGG 9, because the larger cluster radius leads to a mass segregation timescale a factor of five longer than for MGG 11.

[]

https://arxiv.org/pdf/astro-ph/0402622.pdf

1999MNRAS.308L..39F

The obscured growth of massive black holes

1999-01-01

['astrophysics']

[]

The mass density of massive black holes observed locally is consistent with the hard X-ray background provided that most of the radiation produced during their growth was absorbed by surrounding gas. A simple model is proposed here for the formation of galaxy bulges and central black holes in which young spheroidal galaxies have a significant distributed component of cold dusty clouds, which accounts for the absorption. The central accreting black hole is assumed to emit both a quasar-like spectrum, which is absorbed by the surrounding gas, and a slow wind. The power in both is less than the Eddington limit for the black hole. The wind, however, exerts the most force on the gas and, as earlier suggested by Silk &amp; Rees, when the black hole reaches a critical mass it is powerful enough to eject the cold gas from the galaxy, so terminating the growth of both black hole and galaxy. In the present model this point occurs when the Thomson depth in the surrounding gas has dropped to about unity and results in the mass of the black hole being proportional to the mass of the spheroid, with the normalization agreeing with that found for local galaxies by Magorrian et al. for reasonable wind parameters. The model predicts a new population of hard X-ray and submm sources at redshifts above 1, which are powered by black holes in their main growth phase.

[]

https://arxiv.org/pdf/astro-ph/9908064.pdf

2008LRR....11....6E

Black Holes in Higher Dimensions

2008-01-01

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

[]

We review black-hole solutions of higher-dimensional vacuum gravity and higher-dimensional supergravity theories. The discussion of vacuum gravity is pedagogical, with detailed reviews of Myers-Perry solutions, black rings, and solution-generating techniques. We discuss black-hole solutions of maximal supergravity theories, including black holes in anti-de Sitter space. General results and open problems are discussed throughout.

[]

https://arxiv.org/pdf/0801.3471.pdf

1998ApJ...509..678G

High Proper-Motion Stars in the Vicinity of Sagittarius A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy

1998-01-01

['black hole physics', 'galaxy center', 'galaxy kinematics and dynamics', 'astronomy infrared', 'stars kinematics and dynamics', 'techniques image processing', 'black hole physics', 'galaxy center', 'galaxy kinematics and dynamics', 'astronomy infrared', 'stars kinematics and dynamics', 'techniques image processing', 'astrophysics']

[]

Over a 2 year period we have conducted a diffraction-limited imaging study at 2.2 μm of the inner 6" × 6" of the central stellar cluster of the Galaxy using the W. M. Keck 10 m telescope. The K-band images obtained in 1995 June, 1996 June, and 1997 May have the highest angular resolution obtained at near-infrared wavelengths from ground or space (θ<SUB>res</SUB> = 0.05" = 0.002 pc) and reveal a large population of faint stars. We use an unbiased approach for identifying and selecting stars to be included in this proper-motion study, which results in a sample of 90 stars with brightness ranging from K = 9-17 mag and two-dimensional velocities as large as 1400 +/- 100 km s<SUP>-1</SUP>. Compared to earlier work (Eckart et al. 1997; Genzel et al. 1997), the source confusion is reduced by a factor of 9, the number of stars with proper-motion measurement in the central 25 arcsec<SUP>2</SUP> of our Galaxy is doubled, and the accuracy of the velocity measurements in the central 1 arcsec<SUP>2</SUP> is improved by a factor of 4. The peaks of both the stellar surface density and the velocity dispersion are consistent with the position of the unusual radio source and black hole candidate Sgr A*, which suggests that Sgr A* is coincident (+/-0.1") with the dynamical center of the Galaxy. As a function of distance from Sgr A*, the velocity dispersion displays a falloff well-fitted by Keplerian motion (σ<SUB>v</SUB> ~ r<SUP>-0.5+/-0.1</SUP>) about a central dark mass of 2.6 +/- 0.2 × 10<SUP>6</SUP> M<SUB>⊙</SUB> confined to a volume of at most 10<SUP>-6</SUP> pc<SUP>3</SUP>, which is consistent with earlier results. Although uncertainties in the measurements mathematically allow for the matter to be distributed over this volume as a cluster, no realistic cluster is physically tenable. Thus, independent of the presence of Sgr A*, the large inferred central density of at least 10<SUP>12</SUP> M<SUB>⊙</SUB> pc<SUP>-3</SUP>, which exceeds the volume-averaged mass densities found at the center of any other galaxy, leads us to the conclusion that our Galaxy harbors a massive central black hole.

[]

https://arxiv.org/pdf/astro-ph/9807210.pdf

2017CQGra..34f3001K

Black hole chemistry: thermodynamics with Lambda

2017-01-01

['-', '-']

[]

We review recent developments on the thermodynamics of black holes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. In this approach, the mass of the black hole is no longer regarded as internal energy, rather it is identified with the chemical enthalpy. This leads to an extended dictionary for black hole thermodynamic quantities; in particular a notion of thermodynamic volume emerges for a given black hole spacetime. This volume is conjectured to satisfy the reverse isoperimetric inequality—an inequality imposing a bound on the amount of entropy black hole can carry for a fixed thermodynamic volume. New thermodynamic phase transitions naturally emerge from these identifications. Namely, we show that black holes can be understood from the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids, reentrant phase transitions, and triple points. We also review the recent attempts at extending the AdS/CFT dictionary in this setting, discuss the connections with horizon thermodynamics, applications to Lifshitz spacetimes, and outline possible future directions in this field.

[]

https://arxiv.org/pdf/1608.06147.pdf

2008Natur.455...78D

Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre

2008-01-01

['astrophysics']

[]

The cores of most galaxies are thought to harbour supermassive black holes, which power galactic nuclei by converting the gravitational energy of accreting matter into radiation. Sagittarius A* (SgrA*), the compact source of radio, infrared and X-ray emission at the centre of the Milky Way, is the closest example of this phenomenon, with an estimated black hole mass that is 4,000,000 times that of the Sun. A long-standing astronomical goal is to resolve structures in the innermost accretion flow surrounding SgrA*, where strong gravitational fields will distort the appearance of radiation emitted near the black hole. Radio observations at wavelengths of 3.5mm and 7mm have detected intrinsic structure in SgrA*, but the spatial resolution of observations at these wavelengths is limited by interstellar scattering. Here we report observations at a wavelength of 1.3mm that set a size of microarcseconds on the intrinsic diameter of SgrA*. This is less than the expected apparent size of the event horizon of the presumed black hole, suggesting that the bulk of SgrA* emission may not be centred on the black hole, but arises in the surrounding accretion flow.

[]

https://arxiv.org/pdf/0809.2442.pdf

2020ARNPS..70..355C

Primordial Black Holes as Dark Matter: Recent Developments

2020-01-01

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

[]

Although the dark matter is usually assumed to be made up of some form of elementary particle, primordial black holes (PBHs) could also provide some of it. However, various constraints restrict the possible mass windows to 10<SUP>16</SUP>–10<SUP>17</SUP> g, 10<SUP>20</SUP>–10<SUP>24</SUP> g, and 10–10<SUP>3</SUP>M<SUB>⊙</SUB>. The last possibility is contentious but of special interest in view of the recent detection of black hole mergers by LIGO/Virgo. PBHs might have important consequences and resolve various cosmological conundra even if they account for only a small fraction of the dark matter density. In particular, those larger than 10<SUP>3</SUP>M<SUB>⊙</SUB> could generate cosmological structures through the seed or Poisson effect, thereby alleviating some problems associated with the standard cold dark matter scenario, and sufficiently large PBHs might provide seeds for the supermassive black holes in galactic nuclei. More exotically, the Planck-mass relics of PBH evaporations or stupendously large black holes bigger than 10<SUP>12</SUP>M<SUB>⊙</SUB> could provide an interesting dark component.

[]

https://arxiv.org/pdf/2006.02838.pdf

2015Natur.518..512W

An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30

2015-01-01

['-']

[]

So far, roughly 40 quasars with redshifts greater than z = 6 have been discovered. Each quasar contains a black hole with a mass of about one billion solar masses (10<SUP>9</SUP> ). The existence of such black holes when the Universe was less than one billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies. Here we report the discovery of an ultraluminous quasar, SDSS J010013.02+280225.8, at redshift z = 6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z &gt; 6 quasars. On the basis of the deep absorption trough on the blue side of the Lyman-α emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be about 26 million light years, larger than found with other z &gt; 6.1 quasars with lower luminosities. We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of ~1.2 × 10<SUP>10</SUP> , which is consistent with the 1.3 × 10<SUP>10</SUP> derived by assuming an Eddington-limited accretion rate.

[]

https://arxiv.org/pdf/1502.07418.pdf

2010ApJ...725.1918O

The Black Hole Mass Distribution in the Galaxy

2010-01-01

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

[]

We use dynamical mass measurements of 16 black holes in transient low-mass X-ray binaries to infer the stellar black hole mass distribution in the parent population. We find that the observations are best described by a narrow mass distribution at 7.8 ± 1.2 M <SUB>sun</SUB>. We identify a selection effect related to the choice of targets for optical follow-ups that results in a flux-limited sample. We demonstrate, however, that this selection effect does not introduce a bias in the observed distribution and cannot explain the absence of black holes in the 2-5 M <SUB>sun</SUB> mass range. On the high-mass end, we argue that the rapid decline in the inferred distribution may be the result of the particular evolutionary channel followed by low-mass X-ray binaries. This is consistent with the presence of high-mass black holes in the persistent, high-mass X-ray binary sources. If the paucity of low-mass black holes is caused by a sudden decrease of the supernova explosion energy with increasing progenitor mass, this would have observable implications for ongoing transient surveys that target core-collapse supernovae. Our results also have significant implications for the calculation of event rates from the coalescence of black hole binaries for gravitational wave detectors.

[]

https://arxiv.org/pdf/1006.2834.pdf

2012JHEP...11..110G

Extended phase space thermodynamics for charged and rotating black holes and Born-Infeld vacuum polarization

2012-01-01

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

[]

We investigate the critical behaviour of charged and rotating AdS black holes in d spacetime dimensions, including effects from non-linear electrodynamics via the Born-Infeld action, in an extended phase space in which the cosmological constant is interpreted as thermodynamic pressure. For Reissner-Nördstrom black holes we find that the analogy with the Van der Walls liquid-gas system holds in any dimension greater than three, and that the critical exponents coincide with those of the Van der Waals system. We find that neutral slowly rotating black holes in four space-time dimensions also have the same qualitative behaviour. However charged and rotating black holes in three spacetime dimensions do not exhibit critical phenomena. For Born-Infeld black holes we define a new thermodynamic quantity B conjugate to the Born-Infeld parameter b that we call Born-Infeld vacuum polarization. We demonstrate that this quantity is required for consistency of both the first law of thermodynamics and the corresponding Smarr relation.

[]

https://arxiv.org/pdf/1208.6251.pdf

2021PhRvD.103l2002A

Tests of general relativity with binary black holes from the second LIGO-Virgo gravitational-wave transient catalog

2021-01-01

['-', '-']

[]

Gravitational waves enable tests of general relativity in the highly dynamical and strong-field regime. Using events detected by LIGO-Virgo up to 1 October 2019, we evaluate the consistency of the data with predictions from the theory. We first establish that residuals from the best-fit waveform are consistent with detector noise, and that the low- and high-frequency parts of the signals are in agreement. We then consider parametrized modifications to the waveform by varying post-Newtonian and phenomenological coefficients, improving past constraints by factors of ∼2 ; we also find consistency with Kerr black holes when we specifically target signatures of the spin-induced quadrupole moment. Looking for gravitational-wave dispersion, we tighten constraints on Lorentz-violating coefficients by a factor of ∼2.6 and bound the mass of the graviton to m<SUB>g</SUB>≤1.76 ×10<SUP>-23</SUP> eV /c<SUP>2</SUP> with 90% credibility. We also analyze the properties of the merger remnants by measuring ringdown frequencies and damping times, constraining fractional deviations away from the Kerr frequency to δ f<SUB>^220</SUB>=0.0 3<SUB>-0.35</SUB><SUP>+0.38</SUP> for the fundamental quadrupolar mode, and δ f<SUB>^221</SUB>=0.0 4<SUB>-0.32</SUB><SUP>+0.27</SUP> for the first overtone; additionally, we find no evidence for postmerger echoes. Finally, we determine that our data are consistent with tensorial polarizations through a template-independent method. When possible, we assess the validity of general relativity based on collections of events analyzed jointly. We find no evidence for new physics beyond general relativity, for black hole mimickers, or for any unaccounted systematics.

[]

https://arxiv.org/pdf/2010.14529.pdf

2013JHEP...05..014H

Time evolution of entanglement entropy from black hole interiors

2013-01-01

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

[]

We compute the time-dependent entanglement entropy of a CFT which starts in relatively simple initial states. The initial states are the thermofield double for thermal states, dual to eternal black holes, and a particular pure state, dual to a black hole formed by gravitational collapse. The entanglement entropy grows linearly in time. This linear growth is directly related to the growth of the black hole interior measured along "nice" spatial slices. These nice slices probe the spacelike direction in the interior, at a fixed special value of the interior time. In the case of a two-dimensional CFT, we match the bulk and boundary computations of the entanglement entropy. We briefly discuss the long time behavior of various correlators, computed via classical geodesics or surfaces, and point out that their exponential decay comes about for similar reasons. We also present the time evolution of the wavefunction in the tensor network description.

[]

https://arxiv.org/pdf/1303.1080.pdf

2016PhRvD..93d4006H

Frequency-domain gravitational waves from nonprecessing black-hole binaries. I. New numerical waveforms and anatomy of the signal

2016-01-01

['-']

[]

In this paper we discuss the anatomy of frequency-domain gravitational-wave signals from nonprecessing black-hole coalescences with the goal of constructing accurate phenomenological waveform models. We first present new numerical-relativity simulations for mass ratios up to 18, including spins. From a comparison of different post-Newtonian approximants with numerical-relativity data we select the uncalibrated SEOBNRv2 model as the most appropriate for the purpose of constructing hybrid post-Newtonian/numerical-relativity waveforms, and we discuss how we prepare time-domain and frequency-domain hybrid data sets. We then use our data together with results in the literature to calibrate simple explicit expressions for the final spin and radiated energy. Equipped with our prediction for the final state we then develop a simple and accurate merger-ringdown model based on modified Lorentzians in the gravitational-wave amplitude and phase, and we discuss a simple method to represent the low frequency signal augmenting the TaylorF2 post-Newtonian approximant with terms corresponding to higher orders in the post-Newtonian expansion. We finally discuss different options for modelling the small intermediate frequency regime between inspiral and merger ringdown. A complete phenomenological model based on the present work is presented in a companion paper [S. Khan et al., following paper, Phys. Rev. D 93 044007 (2016)].

[]

https://arxiv.org/pdf/1508.07250.pdf

2003PhRvD..68b4018K

Quasinormal behavior of the D-dimensional Schwarzschild black hole and the higher order WKB approach

2003-01-01

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

[]

We study characteristic (quasinormal) modes of a D-dimensional Schwarzschild black hole. It is shown that the real parts of the complex quasinormal modes, representing the real oscillation frequencies, are proportional to the product of the number of dimensions and inverse horizon radius ∼Dr<SUP>-1</SUP><SUB>0</SUB>. The asymptotic formula for large multipole number l and arbitrary D is derived. In addition, the WKB formula for computing QN modes, developed to the third order beyond the eikonal approximation, is extended to the sixth order here. This gives us an accurate and economic way to compute quasinormal frequencies.

[]

https://arxiv.org/pdf/gr-qc/0303052.pdf

2011PhRvD..84b4037C

Black hole enthalpy and an entropy inequality for the thermodynamic volume

2011-01-01

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

[]

In a theory where the cosmological constant Λ or the gauge coupling constant g arises as the vacuum expectation value, its variation should be included in the first law of thermodynamics for black holes. This becomes dE=TdS+Ω<SUB>i</SUB>dJ<SUB>i</SUB>+Φ<SUB>α</SUB>dQ<SUB>α</SUB>+ΘdΛ, where E is now the enthalpy of the spacetime, and Θ, the thermodynamic conjugate of Λ, is proportional to an effective volume V=-(16πΘ)/(D-2) “inside the event horizon.” Here we calculate Θ and V for a wide variety of D-dimensional charged rotating asymptotically anti-de Sitter (AdS) black hole spacetimes, using the first law or the Smarr relation. We compare our expressions with those obtained by implementing a suggestion of Kastor, Ray, and Traschen, involving Komar integrals and Killing potentials, which we construct from conformal Killing-Yano tensors. We conjecture that the volume V and the horizon area A satisfy the inequality R≡((D-1)V/A<SUB>D-2</SUB>)<SUP>1/(D-1)</SUP>(A<SUB>D-2</SUB>/A)<SUP>1/(D-2)</SUP>≥1, where A<SUB>D-2</SUB> is the volume of the unit (D-2) sphere, and we show that this is obeyed for a wide variety of black holes, and saturated for Schwarzschild-AdS. Intriguingly, this inequality is the “inverse” of the isoperimetric inequality for a volume V in Euclidean (D-1) space bounded by a surface of area A, for which R≤1. Our conjectured reverse isoperimetric inequality can be interpreted as the statement that the entropy inside a horizon of a given ”volume” V is maximized for Schwarzschild-AdS. The thermodynamic definition of V requires a cosmological constant (or gauge coupling constant). However, except in seven dimensions, a smooth limit exists where Λ or g goes to zero, providing a definition of V even for asymptotically flat black holes.

[]

https://arxiv.org/pdf/1012.2888.pdf

1998Natur.395A..14R

Supermassive black holes and the evolution of galaxies.

1998-01-01

['astrophysics']

[]

Black holes - an extreme consequence of the mathematics of General Relativity - have long been suspected of being the main energy source for quasars, which emit more energy than any other objects in the Universe. Recent evidence indicates that supermassive black holes reside at the centres of most galaxies, where they are probably the remnants of quasars that have been starved of fuel. As our knowledge of the demographics of supermassive black holes improves, we see clues that they participated in the formation of galaxies, and strongly influenced the evolution towards the present-day structure of their surrounding hosts.

[]

https://arxiv.org/pdf/astro-ph/9810378.pdf

2011ApJ...730...70O

Black Hole Formation in Failing Core-Collapse Supernovae

2011-01-01

['black hole physics', 'thermodynamics', 'hydrodynamics', 'neutrinos', '-', 'stars luminosity function;mass function', '-', 'stars novae;cataclysmic variables', '-', '-', '-']

[]

We present results of a systematic study of failing core-collapse supernovae and the formation of stellar-mass black holes (BHs). Using our open-source general-relativistic 1.5D code GR1D equipped with a three-species neutrino leakage/heating scheme and over 100 presupernova models, we study the effects of the choice of nuclear equation of state (EOS), zero-age main sequence (ZAMS) mass and metallicity, rotation, and mass-loss prescription on BH formation. We find that the outcome, for a given EOS, can be estimated, to first order, by a single parameter, the compactness of the stellar core at bounce. By comparing protoneutron star (PNS) structure at the onset of gravitational instability with solutions of the Tolman-Oppenheimer-Volkof equations, we find that thermal pressure support in the outer PNS core is responsible for raising the maximum PNS mass by up to 25% above the cold NS value. By artificially increasing neutrino heating, we find the critical neutrino heating efficiency required for exploding a given progenitor structure and connect these findings with ZAMS conditions, establishing, albeit approximately, for the first time based on actual collapse simulations, the mapping between ZAMS parameters and the outcome of core collapse. We also study the effect of progenitor rotation and find that the dimensionless spin of nascent BHs may be robustly limited below a* = Jc/GM <SUP>2</SUP> = 1 by the appearance of nonaxisymmetric rotational instabilities.

[]

https://arxiv.org/pdf/1010.5550.pdf

1998PhRvL..81.4293H

Bohr's Correspondence Principle and the Area Spectrum of Quantum Black Holes

1998-01-01

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

[]

During the last twenty-five years evidence has been mounting that a black-hole surface area has a discrete spectrum. Moreover, it is widely believed that area eigenvalues are uniformly spaced. There is, however, no general agreement on the spacing of the levels. In this Letter we use Bohr's correspondence principle to provide this missing link. We conclude that the area spacing of a black hole is 4ħln3. This is the unique spacing consistent both with the area-entropy thermodynamic relation for black holes, with the Boltzmann-Einstein formula in statistical physics, and with Bohr's correspondence principle.

[]

https://arxiv.org/pdf/gr-qc/9812002.pdf

2019A&A...625L..10G

A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty

2019-01-01

['black hole physics', 'astrometry', 'galaxy nucleus', '-']

[]

We present a 0.16% precise and 0.27% accurate determination of R<SUB>0</SUB>, the distance to the Galactic center. Our measurement uses the star S2 on its 16-year orbit around the massive black hole Sgr A* that we followed astrometrically and spectroscopically for 27 years. Since 2017, we added near-infrared interferometry with the VLTI beam combiner GRAVITY, yielding a direct measurement of the separation vector between S2 and Sgr A* with an accuracy as good as 20 μas in the best cases. S2 passed the pericenter of its highly eccentric orbit in May 2018, and we followed the passage with dense sampling throughout the year. Together with our spectroscopy, in the best cases with an error of 7 km s<SUP>-1</SUP>, this yields a geometric distance estimate of R<SUB>0</SUB> = 8178 ± 13<SUB>stat.</SUB> ± 22<SUB>sys.</SUB> pc. This work updates our previous publication, in which we reported the first detection of the gravitational redshift in the S2 data. The redshift term is now detected with a significance level of 20σ with f<SUB>redshift</SUB> = 1.04 ± 0.05. <P />GRAVITY has been developed by a collaboration of the Max Planck Institute for Extraterrestrial Physics, LESIA of Paris Observatory/CNRS/UPMC/Univ. Paris Diderot and IPAG of Université Grenoble Alpes/CNRS, the Max Planck Institute for Astronomy, the University of Cologne, the Centro de Astrofísica e Gravitaçâo, and the European Southern Observatory.

[]

https://arxiv.org/pdf/1904.05721.pdf

2001PhRvD..63d4005B

Regular magnetic black holes and monopoles from nonlinear electrodynamics

2001-01-01

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

[]

It is shown that general relativity coupled to nonlinear electrodynamics (NED) with the Lagrangian L(F), F=F<SUB>μν</SUB>F<SUP>μν</SUP> having a correct weak field limit, leads to nontrivial spherically symmetric solutions with a globally regular metric if and only if the electric charge is zero and L(F) tends to a finite limit as F--&gt;∞. The properties and examples of such solutions, which include magnetic black holes and solitonlike objects (monopoles), are discussed. Magnetic solutions are compared with their electric counterparts. A duality between solutions of different theories specified in two alternative formulations of NED (called the FP duality) is used as a tool for this comparison.

[]

https://arxiv.org/pdf/gr-qc/0006014.pdf

2021ApJ...915L...5A

Observation of Gravitational Waves from Two Neutron Star-Black Hole Coalescences

2021-01-01

['-']

[]

We report the observation of gravitational waves from two compact binary coalescences in LIGO's and Virgo's third observing run with properties consistent with neutron star-black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115; the first was observed by LIGO Livingston and Virgo and the second by all three LIGO-Virgo detectors. The source of GW200105 has component masses $8.{9}_{-1.5}^{+1.2}$ and $1.{9}_{-0.2}^{+0.3}\,{M}_{\odot }$ , whereas the source of GW200115 has component masses $5.{7}_{-2.1}^{+1.8}$ and $1.{5}_{-0.3}^{+0.7}\,{M}_{\odot }$ (all measurements quoted at the 90% credible level). The probability that the secondary's mass is below the maximal mass of a neutron star is 89%-96% and 87%-98%, respectively, for GW200105 and GW200115, with the ranges arising from different astrophysical assumptions. The source luminosity distances are ${280}_{-110}^{+110}$ and ${300}_{-100}^{+150}\,\mathrm{Mpc}$ , respectively. The magnitude of the primary spin of GW200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. For GW200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. We are unable to constrain the spin or tidal deformation of the secondary component for either event. We infer an NSBH merger rate density of ${45}_{-33}^{+75}\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ when assuming that GW200105 and GW200115 are representative of the NSBH population or ${130}_{-69}^{+112}\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ under the assumption of a broader distribution of component masses.

[]

https://arxiv.org/pdf/2106.15163.pdf

2000ApJ...528L..17P

Black Hole Mergers in the Universe

2000-01-01

['stars binaries close', 'galaxy globular clusters', 'gravitation', 'methods n body', '-', 'stars kinematics and dynamics', 'stars binaries close', 'galaxy globular clusters', 'gravitation', 'methods n body', '-', 'stars kinematics and dynamics', 'astrophysics']

[]

Mergers of black hole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates that are too low to be of observational interest. In this Letter, we explore the possibility that black holes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, black holes become the most massive objects within a few tens of millions of years; dynamical relaxation then causes them to sink to the cluster core, where they form binaries. These black hole binaries become more tightly bound by superelastic encounters with other cluster members and are ultimately ejected from the cluster. The majority of escaping black hole binaries have orbital periods short enough and eccentricities high enough that the emission of gravitational radiation causes them to coalesce within a few billion years. We predict a black hole merger rate of about 1.6×10<SUP>-7</SUP> yr<SUP>-1</SUP> Mpc<SUP>-3</SUP>, implying gravity-wave detection rates substantially greater than the corresponding rates from neutron star mergers. For the first-generation Laser Interferometer Gravitational-Wave Observatory (LIGO-I), we expect about one detection during the first 2 years of operation. For its successor LIGO-II, the rate rises to roughly one detection per day. The uncertainties in these numbers are large. Event rates may drop by about an order of magnitude if the most massive clusters eject their black hole binaries early in their evolution.

[]

https://arxiv.org/pdf/astro-ph/9910061.pdf

1998CQGra..15.1767V

Acoustic black holes: horizons, ergospheres and Hawking radiation

1998-01-01

['-', '-']

[]

It is a deceptively simple question to ask how acoustic disturbances propagate in a non-homogeneous flowing fluid. This question can be answered by invoking the language of Lorentzian differential geometry: If the fluid is barotropic and inviscid, and the flow is irrotational (though possibly time dependent), then the equation of motion for the velocity potential describing a sound wave is identical to that for a minimally coupled massless scalar field propagating in a (3+1)-dimensional Lorentzian geometry. The acoustic metric governing the propagation of sound depends algebraically on the density, flow velocity, and local speed of sound. This rather simple physical system is the basis underlying a deep and fruitful analogy between the black holes of Einstein gravity and supersonic fluid flows. Many results and definitions can be carried over directly from one system to another. For example, I will show how to define the ergosphere, trapped regions, acoustic apparent horizon, and acoustic event horizon for a supersonic fluid flow, and will exhibit the close relationship between the acoustic metric for the fluid flow surrounding a point sink and the Painleve-Gullstrand form of the Schwarzschild metric for a black hole. This analysis can be used either to provide a concrete non-relativistic model for black hole physics, up to and including Hawking radiation, or to provide a framework for attacking acoustics problems with the full power of Lorentzian differential geometry.

[]

https://arxiv.org/pdf/gr-qc/9712010.pdf

2014PhRvL.113o1101H

Simple Model of Complete Precessing Black-Hole-Binary Gravitational Waveforms

2014-01-01

['-', '-', '-', '-', 'waves', '-', 'perturbation theory', '-', '-', '-', 'stars luminosity function;mass function', '-', '-']

[]

The construction of a model of the gravitational-wave (GW) signal from generic configurations of spinning-black-hole binaries, through inspiral, merger, and ringdown, is one of the most pressing theoretical problems in the buildup to the era of GW astronomy. We present the first such model in the frequency domain, PhenomP, which captures the basic phenomenology of the seven-dimensional parameter space of binary configurations with only three key physical parameters. Two of these (the binary's mass ratio and an effective total spin parallel to the orbital angular momentum, which determines the inspiral rate) define an underlying nonprecessing-binary model. The nonprecessing-binary waveforms are then twisted up with approximate expressions for the precessional motion, which require only one additional physical parameter, an effective precession spin, χ<SUB>p</SUB>. All other parameters (total mass, sky location, orientation and polarization, and initial phase) can be specified trivially. The model is constructed in the frequency domain, which will be essential for efficient GW searches and source measurements. We have tested the model's fidelity for GW applications by comparison against hybrid post-Newtonian-numerical-relativity waveforms at a variety of configurations—although we did not use these numerical simulations in the construction of the model. Our model can be used to develop GW searches, to study the implications for astrophysical measurements, and as a simple conceptual framework to form the basis of generic-binary waveform modeling in the advanced-detector era.

[]

https://arxiv.org/pdf/1308.3271.pdf

1994PhRvD..49.6587J

On black hole entropy

1994-01-01

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

[]

Two techniques for computing black hole entropy in generally covariant gravity theories including arbitrary higher derivative interactions are studied. The techniques are Wald's Noether charge approach introduced recently, and a field redefinition method developed in this paper. Wald's results are extended by establishing that his local geometric expression for the black hole entropy gives the same result when evaluated on an arbitrary cross section of a Killing horizon (rather than just the bifurcation surface). Further, we show that his expression for the entropy is not affected by ambiguities which arise in the Noether construction. Using the Noether charge expression, the entropy is evaluated explicitly for black holes in a wide class of generally covariant theories. For a Lagrangian of the functional form L~=L~(ψ<SUB>m</SUB>, ∇<SUB>a</SUB>ψ<SUB>m</SUB>,g<SUB>ab</SUB>,R<SUB>abcd</SUB>, ∇<SUB>e</SUB>R<SUB>abcd</SUB>), it is found that the entropy is given by S=-2π∮(Y<SUP>abcd</SUP>-∇<SUB>e</SUB>Z<SUP>e:abcd</SUP>) ɛ^<SUB>ab</SUB>ɛ^<SUB>cd</SUB>ɛ¯, where the integral is over an arbitrary cross section of the Killing horizon, ɛ^<SUB>ab</SUB> is the binormal to the cross section, Y<SUP>abcd</SUP>=∂L~/∂R<SUB>abcd</SUB>, and Z<SUP>e:abcd</SUP>=∂L~/∂∇<SUB>e</SUB>R<SUB>abcd</SUB>. Further, it is shown that the Killing horizon and surface gravity of a stationary black hole metric are invariant under field redefinitions of the metric of the form g¯<SUB>ab</SUB>≡g<SUB>ab</SUB>+Δ<SUB>ab</SUB>, where Δ<SUB>ab</SUB> is a stationary tensor field that vanishes at infinity and is regular on the horizon (including the bifurcation surface). Using this result, a technique is developed for evaluating the black hole entropy in a given theory in terms of that of another theory related by field redefinitions. Remarkably, it is established that certain perturbative, first order, results obtained with this method are in fact exact. A particular result established in this fashion is that a scalar matter term of the form ∇<SUP>2p</SUP>φ∇<SUP>2q</SUP>φ in the Lagrangian makes no contribution to the black hole entropy. The possible significance of these results for the problem of finding the statistical origin of black hole entropy is discussed.

[]

https://arxiv.org/pdf/gr-qc/9312023.pdf

2011CQGra..28w5017D

Pressure and volume in the first law of black hole thermodynamics

2011-01-01

['-', '-']

[]

The mass of a black hole is interpreted, in terms of thermodynamic potentials, as being the enthalpy, with the pressure given by the cosmological constant. The volume is then defined as being the Legendre transform of the pressure, and the resulting relation between volume and pressure is explored in the case of positive pressure. A virial expansion is developed and a van der Waals like critical point determined. The first law of black hole thermodynamics includes a PdV term which modifies the maximal efficiency of a Penrose process. It is shown that, in four-dimensional spacetime with a negative cosmological constant, an extremal charged rotating black hole can have an efficiency of up to 75%, while for an electrically neutral rotating black hole this figure is reduced to 52%, compared to the corresponding values of 50% and 29% respectively when the cosmological constant is zero.

[]

https://arxiv.org/pdf/1106.6260.pdf

1999ApJ...519...89C

The Nature of Accreting Black Holes in Nearby Galaxy Nuclei

1999-01-01

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

[]

We have found compact X-ray sources in the center of 21 (54%) of 39 nearby face-on spiral and elliptical galaxies with available ROSAT HRI data. ROSAT X-ray luminosities (0.2-2.4 keV) of these compact X-ray sources are ~10<SUP>37</SUP>-10<SUP>40</SUP> ergs s<SUP>-1</SUP> (with a mean of 3×10<SUP>39</SUP> ergs s<SUP>-1</SUP>). The mean displacement between the location of the compact X-ray source and the optical photometric center of the galaxy is ~390 pc. The fact that compact nuclear sources were found in nearly all (five of six) galaxies with previous evidence for a black hole or an active galactic nucleus (AGN) indicates that at least some of the X-ray sources are accreting supermassive black holes. ASCA spectra of six of the 21 galaxies show the presence of a hard component with relatively steep (Γ~2.5) spectral slope. A multicolor disk blackbody model fits the data from the spiral galaxies well, suggesting that the X-ray object in these galaxies may be similar to a black hole candidate in its soft (high) state. ASCA data from the elliptical galaxies indicate that hot (kT~0.7 keV) gas dominates the emission. <P />The fact that (for both spiral and elliptical galaxies) the spectral slope is steeper than in normal type 1 AGNs and that relatively low absorbing columns (N<SUB>H</SUB>~10<SUP>21</SUP> cm<SUP>-2</SUP>) were found to the power-law component indicates that these objects are somehow geometrically and/or physically different from AGNs in normal active galaxies. The X-ray sources in the spiral and elliptical galaxies may be black hole X-ray binaries, low-luminosity AGNs, or possibly young X-ray luminous supernovae. Assuming the sources in the spiral galaxies are accreting black holes in their soft state, we estimate black hole masses ~10<SUP>2</SUP>-10<SUP>4</SUP> M<SUB>solar</SUB>.

[]

https://arxiv.org/pdf/astro-ph/9901023.pdf

1994PhRvD..49.6467H

General laws of black-hole dynamics

1994-01-01

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

[]

A general definition of a black hole is given, and general ``laws of black-hole dynamics'' derived. The definition involves something similar to an apparent horizon, a trapping horizon, defined as a hypersurface foliated by marginal surfaces of one of four nondegenerate types, described as future or past, and outer or inner. If the boundary of an inextendible trapped region is suitably regular, then it is a (possibly degenerate) trapping horizon. The future outer trapping horizon provides the definition of a black hole. Outer marginal surfaces have spherical or planar topology. Trapping horizons are null only in the instantaneously stationary case, and otherwise outer trapping horizons are spatial and inner trapping horizons are Lorentzian. Future outer trapping horizons have nondecreasing area form, constant only in the null case: the ``second law.'' A definition of the trapping gravity of an outer trapping horizon is given, generalizing surface gravity. The total trapping gravity of a compact outer marginal surface has an upper bound, attained if and only if the trapping gravity is constant: the ``zeroth law.'' The variation of the area form along an outer trapping horizon is determined by the trapping gravity and an energy flux: the ``first law.''

[]

https://arxiv.org/pdf/gr-qc/9303006.pdf

2003CQGra..20.1187K

Quintessence and black holes

2003-01-01

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

[]

We present new static spherically symmetric exact solutions of the Einstein equations for quintessential matter surrounding a black hole, charged or uncharged, as well as for the case without a black hole. A condition of additivity and linearity in the energy-momentum tensor is introduced which allows one to obtain correct limits to known solutions for the electromagnetic static field, implying the relativistic relation between the energy density and pressure, as well as for the extraordinary case of the cosmological constant, i.e. de Sitter space. We classify the horizons, which evidently reveal themselves in static coordinates, and derive the Gibbons-Hawking temperatures. An example of quintessence with state parameter w = -2/3 is discussed in detail.

[]

https://arxiv.org/pdf/gr-qc/0210040.pdf

2003ApJ...586L.127G

The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy's Central Black Hole: A Paradox of Youth

2003-01-01

['black hole physics', 'galaxy center', 'galaxy kinematics and dynamics', 'astronomy infrared', 'techniques high angular resolution', 'techniques spectroscopic', 'astrophysics']

[]

We have obtained the first detection of spectral absorption lines in one of the high-velocity stars in the vicinity of the Galaxy's central supermassive black hole. Both Brγ (2.1661 μm) and He I (2.1126 μm) are seen in absorption in S0-2 with equivalent widths (2.8+/-0.3 and 1.7+/-0.4 Å) and an inferred stellar rotational velocity (220+/-40 km s<SUP>-1</SUP>) that are consistent with that of an O8-B0 dwarf, which suggests that it is a massive (~15 M<SUB>solar</SUB>) young (less than 10 Myr) main-sequence star. This presents a major challenge to star formation theories, given the strong tidal forces that prevail over all distances reached by S0-2 in its current orbit (130-1900 AU) and the difficulty in migrating this star inward during its lifetime from farther out where tidal forces should no longer preclude star formation. The radial velocity measurements (z&gt;=-510+/-40 km s<SUP>-1</SUP>) and our reported proper motions for S0-2 strongly constrain its orbit, providing a direct measure of the black hole mass of 4.1(+/-0.6)×10<SUP>6</SUP>(R<SUB>0</SUB>/8 kpc)<SUP>3 </SUP>M<SUB>solar</SUB>. The Keplerian orbit parameters have uncertainties that are reduced by a factor of 2-3 compared to previously reported values and include, for the first time, an independent solution for the dynamical center; this location, while consistent with the nominal infrared position of Sgr A*, is localized to a factor of 5 more precisely (+/-2 mas). Furthermore, the ambiguity in the inclination of the orbit is resolved with the addition of the radial velocity measurement, indicating that the star is behind the black hole at the time of closest approach and counterrevolving against the Galaxy. With further radial velocity measurements in the next few years, the orbit of S0-2 will provide the most robust estimate of the distance to the Galactic center.

[]

https://arxiv.org/pdf/astro-ph/0302299.pdf

1996PhRvD..54.5049K

Dilatonic black holes in higher curvature string gravity

1996-01-01

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

[]

We give analytical arguments and demonstrate numerically the existence of black hole solutions of the 4D effective superstring action in the presence of Gauss-Bonnet quadratic curvature terms. The solutions possess nontrivial dilaton hair. The hair, however, is of ``secondary type,'' in the sense that the dilaton charge is expressed in terms of the black hole mass. Our solutions are not covered by the assumptions of existing proofs of the ``no-hair'' theorem. We also find some alternative solutions with singular metric behavior, but finite energy. The absence of naked singularities in this system is pointed out.

[]

https://arxiv.org/pdf/hep-th/9511071.pdf

1995ApJ...455..623C

Spectral Properties of Accretion Disks around Galactic and Extragalactic Black Holes

1995-01-01

['accretion', 'accretion disks', 'black hole physics', 'radiation', 'shock waves', '-', 'astrophysics']

[]

We study the spectral properties of a very general class of accretion disks which can be decomposed into three distinct components apart from a shock at r = r<SUB>s</SUB>: (1) An optically thick Keplerian disk on the equatorial plane (r &gt; r<SUB>s</SUB>); (2) a sub-Keplerian optically thin halo above and below this disk r &gt; r<SUB>s</SUB> and (3) a hot, optically slim τ ∼ 1 postshock region r &lt; r<SUB>s</SUB> ∼ 5-10r<SUB>g</SUB> where r<SUB>g</SUB> is the Schwarzschild radius. The postshock halo intercepts soft photons from the Keplerian component and reradiates them as hard X-rays and γ rays after Comptonization. We solve two-temperature equations in the postshock region with Coulomb energy exchange between protons and electrons, and incorporating radiative processes such as bremsstrahlung and Comptonization. We also present the exact prescription to compute the reflection of the hard X-rays from the cool disk. We produce radiated spectra from both the disk components as functions of the accretion rates and compare them with the spectra of Galactic and extragalactic black hole candidates. We find that the transition from hard state to soft state is smoothly initiated by a single parameter, namely the mass accretion rate of the disk. In the soft state, when the postshock region is very optically thick and cooled down, bulk motion of the converging flow determines the spectral index to be about 1.5 in agreement with observations.

[]

https://arxiv.org/pdf/astro-ph/9510005.pdf

2016PhRvD..93h6006B

Complexity, action, and black holes

2016-01-01

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

[]

Our earlier paper "Complexity Equals Action" conjectured that the quantum computational complexity of a holographic state is given by the classical action of a region in the bulk (the "Wheeler-DeWitt" patch). We provide calculations for the results quoted in that paper, explain how it fits into a broader (tensor) network of ideas, and elaborate on the hypothesis that black holes are the fastest computers in nature.

[]

https://arxiv.org/pdf/1512.04993.pdf

2011CQGra..28l5020D

The cosmological constant and black-hole thermodynamic potentials

2011-01-01

['-', '-']

[]

The thermodynamics of black holes in various dimensions are described in the presence of a negative cosmological constant which is treated as a thermodynamic variable, interpreted as a pressure in the equation of state. The black hole mass is then identified with the enthalpy, rather than the internal energy, and heat capacities are calculated at constant pressure not at constant volume. The Euclidean action is associated with a bridge equation for the Gibbs free energy and not the Helmholtz free energy. Quantum corrections to the enthalpy and the equation of state of the BTZ black hole are studied.

[]

https://arxiv.org/pdf/1008.5023.pdf

2016PhRvD..94h4002Y

Theoretical physics implications of the binary black-hole mergers GW150914 and GW151226

2016-01-01

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

[]

The gravitational wave observations GW150914 and GW151226 by Advanced LIGO provide the first opportunity to learn about physics in the extreme gravity environment of coalescing binary black holes. The LIGO Scientific Collaboration and the Virgo Collaboration have verified that this observation is consistent with Einstein's theory of general relativity, constraining the presence of certain parametric anomalies in the signal. This paper expands their analysis to a larger class of anomalies, highlighting the inferences that can be drawn on nonstandard theoretical physics mechanisms that could otherwise have affected the observed signals. We find that these gravitational wave events constrain a plethora of mechanisms associated with the generation and propagation of gravitational waves, including the activation of scalar fields, gravitational leakage into large extra dimensions, the variability of Newton's constant, the speed of gravity, a modified dispersion relation, gravitational Lorentz violation and the strong equivalence principle. Though other observations limit many of these mechanisms already, GW150914 and GW151226 are unique in that they are direct probes of dynamical strong-field gravity and of gravitational wave propagation. We also show that GW150914 constrains inferred properties of exotic compact object alternatives to Kerr black holes. We argue, however, that the true potential for GW150914 to both rule out exotic objects and constrain physics beyond general relativity is severely limited by the lack of understanding of the coalescence regime in almost all relevant modified gravity theories. This event thus significantly raises the bar that these theories have to pass, both in terms of having a sound theoretical underpinning and reaching the minimal level of being able to solve the equations of motion for binary merger events. We conclude with a discussion of the additional inferences that can be drawn if the lower-confidence observation of an electromagnetic counterpart to GW150914 holds true, or such a coincidence is observed with future events; this would provide dramatic constraints on the speed of gravity and gravitational Lorentz violation.

[]

https://arxiv.org/pdf/1603.08955.pdf

2001LRR.....4....6W

The Thermodynamics of Black Holes

2001-01-01

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

[]

We review the present status of black hole thermodynamics. Our review includes discussion of classical black hole thermodynamics, Hawking radiation from black holes, the generalized second law, and the issue of entropy bounds. A brief survey also is given of approaches to the calculation of black hole entropy. We conclude with a discussion of some unresolved open issues.

[]

https://arxiv.org/pdf/gr-qc/9912119.pdf

2015ApJ...813...82R

Relations between Central Black Hole Mass and Total Galaxy Stellar Mass in the Local Universe

2015-01-01

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

[]

Scaling relations between central black hole (BH) mass and host galaxy properties are of fundamental importance to studies of BH and galaxy evolution throughout cosmic time. Here we investigate the relationship between BH mass and host galaxy total stellar mass using a sample of 262 broad-line active galactic nuclei (AGNs) in the nearby universe (z &lt; 0.055), as well as 79 galaxies with dynamical BH masses. The vast majority of our AGN sample is constructed using Sloan Digital Sky Survey spectroscopy and searching for Seyfert-like narrow-line ratios and broad Hα emission. BH masses are estimated using standard virial techniques. We also include a small number of dwarf galaxies with total stellar masses M<SUB>stellar</SUB> ≲ 10<SUP>9.5</SUP> M<SUB>⊙</SUB> and a subsample of the reverberation-mapped AGNs. Total stellar masses of all 341 galaxies are calculated in the most consistent manner feasible using color-dependent mass-to-light ratios. We find a clear correlation between BH mass and total stellar mass for the AGN host galaxies, with M<SUB>BH</SUB> ∝ M<SUB>stellar</SUB>, similar to that of early-type galaxies with dynamically detected BHs. However, the relation defined by the AGNs has a normalization that is lower by more than an order of magnitude, with a BH-to-total stellar mass fraction of M<SUB>BH</SUB>/M<SUB>stellar</SUB> ∼ 0.025% across the stellar mass range 10<SUP>8</SUP> ≤ M<SUB>stellar</SUB>/M<SUB>⊙</SUB> ≤ 10<SUP>12</SUP>. This result has significant implications for studies at high redshift and cosmological simulations in which stellar bulges cannot be resolved.

[]

https://arxiv.org/pdf/1508.06274.pdf

2014ApJ...782...76G

Improved Reflection Models of Black Hole Accretion Disks: Treating the Angular Distribution of X-Rays

2014-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies', 'line formation', 'radiative transfer', 'astronomy x rays', '-']

[]

X-ray reflection models are used to constrain the properties of the accretion disk, such as the degree of ionization of the gas and the elemental abundances. In combination with general relativistic ray tracing codes, additional parameters like the spin of the black hole and the inclination to the system can be determined. However, current reflection models used for such studies only provide angle-averaged solutions for the flux reflected at the surface of the disk. Moreover, the emission angle of the photons changes over the disk due to relativistic light bending. To overcome this simplification, we have constructed an angle-dependent reflection model with the XILLVER code and self-consistently connected it with the relativistic blurring code RELLINE. The new model, relxill, calculates the proper emission angle of the radiation at each point on the accretion disk and then takes the corresponding reflection spectrum into account. We show that the reflected spectra from illuminated disks follow a limb-brightening law highly dependent on the ionization of disk and yet different from the commonly assumed form Ivpropln (1 + 1/μ). A detailed comparison with the angle-averaged model is carried out in order to determine the bias in the parameters obtained by fitting a typical relativistic reflection spectrum. These simulations reveal that although the spin and inclination are mildly affected, the Fe abundance can be overestimated by up to a factor of two when derived from angle-averaged models. The fit of the new model to the Suzaku observation of the Seyfert galaxy Ark 120 clearly shows a significant improvement in the constraint of the physical parameters, in particular by enhancing the accuracy in the inclination angle and the spin determinations.

[]

https://arxiv.org/pdf/1312.3231.pdf

2015IJMPD..2442014H

Asymptotically flat black holes with scalar hair: A review

2015-01-01

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

[]

We consider the status of black hole (BH) solutions with nontrivial scalar fields but no gauge fields, in four-dimensional asymptotically flat spacetimes, reviewing both classical results and recent developments. We start by providing a simple illustration on the physical difference between BHs in electro-vacuum and scalar-vacuum. Next, we review no-scalar-hair theorems. In particular, we detail an influential theorem by Bekenstein and stress three key assumptions: (1) The type of scalar field equation; (2) the spacetime symmetry inheritance by the scalar field and (3) an energy condition. Then, we list regular (on and outside the horizon), asymptotically flat BH solutions with scalar hair, organizing them by the assumption which is violated in each case and distinguishing primary from secondary hair. We provide a table summary of the state-of-the-art.

[]

https://arxiv.org/pdf/1504.08209.pdf

1995PhRvD..51.2827U

Sonic analogue of black holes and the effects of high frequencies on black hole evaporation

1995-01-01

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

[]

The naive calculation of black hole evaporation makes the thermal emission depend on the arbitrary high frequency behavior of the theory where the theory is certainly wrong. Using the sonic analogue to black holes, ``dumb holes,'' I show numerically that a change in the dispersion relation at high frequencies does not seem to alter the evaporation process, lending weight to the reality of the black hole evaporation process. I also suggest a reason for the insensitivity of the process to the high frequency regime.

[]

https://arxiv.org/pdf/gr-qc/9409008.pdf

1995NuPhB.451...96S

Massless black holes and conifolds in string theory

1995-01-01

['-']

[]

Low-energy effective field theories arising from Calabi-Yau string compactifications are generically inconsistent or ill-defined at the classical level because of conifold singularities in the moduli space. It is shown, given a plausible assumption on the degenaracies of black hole states, that for type II theories this inconsistency can be cured by nonperturbative quantum effects: the singularities are resolved by the appearance of massless Ramond-Ramond black holes. The Wilsonian effective action including these light black holes is smooth near the conifold, and the singularity is reproduced when they are integrated out. In order for a quantum effect to cure a classical inconsistency, it can not be suppressed by the usual string coupling g<SUB>s</SUB>. It is shown how the required g<SUB>s</SUB> dependence arises as a result of the peculiar couplings of Ramond-Ramond gauge fields to the dilaton.

[]

https://arxiv.org/pdf/hep-th/9504090.pdf

2020PhRvD.102d3015A

GW190412: Observation of a binary-black-hole coalescence with asymmetric masses

2020-01-01

['-', '-']

[]

We report the observation of gravitational waves from a binary-black-hole coalescence during the first two weeks of LIGO's and Virgo's third observing run. The signal was recorded on April 12, 2019 at 05∶30∶44 UTC with a network signal-to-noise ratio of 19. The binary is different from observations during the first two observing runs most notably due to its asymmetric masses: a ∼30 M<SUB>⊙</SUB> black hole merged with a ∼8 M<SUB>⊙</SUB> black hole companion. The more massive black hole rotated with a dimensionless spin magnitude between 0.22 and 0.60 (90% probability). Asymmetric systems are predicted to emit gravitational waves with stronger contributions from higher multipoles, and indeed we find strong evidence for gravitational radiation beyond the leading quadrupolar order in the observed signal. A suite of tests performed on GW190412 indicates consistency with Einstein's general theory of relativity. While the mass ratio of this system differs from all previous detections, we show that it is consistent with the population model of stellar binary black holes inferred from the first two observing runs.

[]

https://arxiv.org/pdf/2004.08342.pdf

2002ApJ...576..899P

The Runaway Growth of Intermediate-Mass Black Holes in Dense Star Clusters

2002-01-01

['stars binaries close', 'galaxies bulges', 'galaxies star clusters', 'galaxy globular clusters', 'methods n body', 'stars kinematics and dynamics', 'astrophysics']

[]

We study the growth rate of stars via stellar collisions in dense star clusters, calibrating our analytic calculations with direct N-body simulations of up to 65,536 stars, performed on the GRAPE family of special-purpose computers. We find that star clusters with initial half-mass relaxation times &lt;~25 Myr are dominated by stellar collisions, the first collisions occurring at or near the point of core collapse, which is driven by the segregation of the most massive stars to the cluster center, where they end up in hard binaries. The majority of collisions occur with the same star, resulting in the runaway growth of a supermassive object. This object can grow up to ~0.1% of the mass of the entire star cluster and could manifest itself as an intermediate-mass black hole (IMBH). The phase of runaway growth lasts until mass loss by stellar evolution arrests core collapse. Star clusters older than about 5 Myr and with present-day half-mass relaxation times &lt;~100 Myr are expected to contain an IMBH.

[]

https://arxiv.org/pdf/astro-ph/0201055.pdf

2003Natur.425..934G

Near-infrared flares from accreting gas around the supermassive black hole at the Galactic Centre

2003-01-01

['astrophysics']

[]

Recent measurements of stellar orbits provide compelling evidence that the compact radio source Sagittarius A* (refs 4, 5) at the Galactic Centre is a 3.6-million-solar-mass black hole. Sgr A* is remarkably faint in all wavebands other than the radio region, however, which challenges current theories of matter accretion and radiation surrounding black holes. The black hole's rotation rate is not known, and therefore neither is the structure of space-time around it. Here we report high-resolution infrared observations of Sgr A* that reveal `quiescent' emission and several flares. The infrared emission originates from within a few milliarcseconds of the black hole, and traces very energetic electrons or moderately hot gas within the innermost accretion region. Two flares exhibit a 17-minute quasi-periodic variability. If the periodicity arises from relativistic modulation of orbiting gas, the emission must come from just outside the event horizon, and the black hole must be rotating at about half of the maximum possible rate.

[]

https://arxiv.org/pdf/astro-ph/0310821.pdf

2004CQGra..21.5245M

Black-hole entropy in loop quantum gravity

2004-01-01

['-']

[]

We calculate the black-hole entropy in loop quantum gravity as a function of the horizon area and provide the exact formula for the leading and sub-leading terms. By comparison with the Bekenstein Hawking formula, we uniquely fix the value of the 'quantum of area' in the theory.

[]

https://arxiv.org/pdf/gr-qc/0407052.pdf

1998PhRvD..57.4535F

Measuring gravitational waves from binary black hole coalescences. I. Signal to noise for inspiral, merger, and ringdown

1998-01-01

['-', '-', '-', '-', '-', 'methods numerical', 'waves', '-', 'stars luminosity function;mass function', '-', '-', 'astrophysics']

[]

We estimate the expected signal-to-noise ratios (SNRs) from the three phases (inspiral, merger, and ringdown) of coalescing binary black holes (BBHs) for initial and advanced ground-based interferometers (LIGO-VIRGO) and for the space-based interferometer LISA. Ground-based interferometers can do moderate SNR (a few tens), moderate accuracy studies of BBH coalescences in the mass range of a few to about 2000 solar masses; LISA can do high SNR (of order 10<SUP>4</SUP>), high accuracy studies in the mass range of about 10<SUP>5</SUP>-10<SUP>8</SUP> solar masses. BBHs might well be the first sources detected by LIGO-VIRGO: they are visible to much larger distances-up to 500 Mpc by initial interferometers-than coalescing neutron star binaries (heretofore regarded as the ``bread and butter'' workhorse source for LIGO-VIRGO, visible to about 30 Mpc by initial interferometers). Low-mass BBHs (up to 50M<SUB>solar</SUB> for initial LIGO interferometers, 100M<SUB>solar</SUB> for advanced, 10<SUP>6</SUP>M<SUB>solar</SUB> for LISA) are best searched for via their well-understood inspiral waves; higher mass BBHs must be searched for via their poorly understood merger waves and/or their well-understood ringdown waves. A matched filtering search for massive BBHs based on ringdown waves should be capable of finding BBHs in the mass range of about 100M<SUB>solar</SUB>-700M<SUB>solar</SUB> out to ~200 Mpc for initial LIGO interferometers, and in the mass range of ~200M<SUB>solar</SUB> to ~3000M<SUB>solar</SUB> out to about z=1 for advanced interferometers. The required number of templates is of the order of 6000 or less. Searches based on merger waves could increase the number of detected massive BBHs by a factor of the order of 10 over those found from inspiral and ringdown waves, without detailed knowledge of the waveform shapes, using a noise monitoring search algorithm which we describe. A full set of merger templates from numerical relativity simulations could further increase the number of detected BBHs by an additional factor of up to ~4.

[]

https://arxiv.org/pdf/gr-qc/9701039.pdf

2002ApJ...578...90F

Beyond the Bulge: A Fundamental Relation between Supermassive Black Holes and Dark Matter Halos

2002-01-01

['black hole physics', 'cosmology dark matter', 'galaxies halos', 'galaxies nuclei', 'astrophysics']

[]

The possibility that the masses M<SUB>BH</SUB> of supermassive black holes (SBHs) correlate with the total gravitational mass of their host galaxy, or the mass M<SUB>DM</SUB> of the dark matter halo in which they presumably formed, is investigated using a sample of 16 spiral and 20 elliptical galaxies. The bulge velocity dispersion σ<SUB>c</SUB>, typically defined within an aperture of size R&lt;~0.5 kpc, is found to correlate tightly with the galaxy's circular velocity v<SUB>c</SUB>, the latter measured at distances from the Galactic center at which the rotation curve is flat, R~20-80 kpc. By using the well-known M<SUB>BH</SUB>-σ<SUB>c</SUB> relation for SBHs and a prescription to relate v<SUB>c</SUB> to the mass of the dark matter halo M<SUB>DM</SUB> in a standard ΛCDM cosmology, the correlation between σ<SUB>c</SUB> and v<SUB>c</SUB> is equivalent to one between M<SUB>BH</SUB> and M<SUB>DM</SUB>. Such a correlation is found to be nonlinear, with the ratio M<SUB>BH</SUB>/M<SUB>DM</SUB> decreasing from 2×10<SUP>-4</SUP> for M<SUB>DM</SUB>~10<SUP>14</SUP> M<SUB>solar</SUB> to 10<SUP>-5</SUP> for M<SUB>DM</SUB>~10<SUP>12</SUP> M<SUB>solar</SUB>. Preliminary evidence suggests that halos of mass smaller than ~5×10<SUP>11</SUP> M<SUB>solar</SUB> are increasingly less efficient at forming SBHs-perhaps even unable to form them.

[]

https://arxiv.org/pdf/astro-ph/0203469.pdf

1999NuPhB.558...96C

Embedding AdS black holes in ten and eleven dimensions

1999-01-01

['-']

[]

We construct the non-linear Kaluza-Klein ansätze describing the embeddings of the U(1) <SUP>3</SUP>, U(1) <SUP>4</SUP> and U(1) <SUP>2</SUP> truncations of D = 5, D = 4 and D = 7 gauged supergravities into the type IIB string and M-theory. These enable one to oxidise any associated lower-dimensional solutions to D = 10 or D = 11. In particular, we use these general ansätze to embed the charged AdS <SUB>5</SUB>, AdS <SUB>4</SUB> and AdS <SUB>7</SUB> black hole solutions in ten and eleven dimensions. The charges for the black holes with toroidal horizons may be interpreted as the angular momenta of D3-branes, M2-branes and M5-branes spinning in the transverse dimensions, in their near-horizon decoupling limits. The horizons of the black holes coincide with the world-volumes of the branes. The Kaluza-Klein ansätze also allow the black holes with spherical or hyperbolic horizons to be reinterpreted in D = 10 or D = 11.

[]

https://arxiv.org/pdf/hep-th/9903214.pdf

2007ARNPS..57...95S

Viscosity, Black Holes, and Quantum Field Theory

2007-01-01

['-']

[]

We review recent progress in applying the AdS/CFT correspondence to finite-temperature field theory. In particular, we show how the hydrodynamic behavior of field theory is reflected in the low-momentum limit of correlation functions computed through a real-time AdS/CFT prescription, which we formulate. We also show how the hydrodynamic modes in field theory correspond to the low-lying quasi-normal modes of the AdS black p-brane metric. We provide proof of the universality of the viscosity/entropy ratio within a class of theories with gravity duals and formulate a viscosity bound conjecture. Possible implications for real systems are mentioned.

[]

https://arxiv.org/pdf/0704.0240.pdf

2010ApJ...714.1217B

On the Maximum Mass of Stellar Black Holes

2010-01-01

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

[]

We present the spectrum of compact object masses: neutron stars and black holes (BHs) that originate from single stars in different environments. In particular, we calculate the dependence of maximum BH mass on metallicity and on some specific wind mass loss rates (e.g., Hurley et al. and Vink et al.). Our calculations show that the highest mass BHs observed in the Galaxy M <SUB>bh</SUB> ~ 15 M <SUB>sun</SUB> in the high metallicity environment (Z = Z <SUB>sun</SUB> = 0.02) can be explained with stellar models and the wind mass loss rates adopted here. To reach this result we had to set luminous blue variable mass loss rates at the level of ~10<SUP>-4</SUP> M <SUB>sun</SUB> yr<SUP>-1</SUP> and to employ metallicity-dependent Wolf-Rayet winds. With such winds, calibrated on Galactic BH mass measurements, the maximum BH mass obtained for moderate metallicity (Z = 0.3 Z <SUB>sun</SUB> = 0.006) is M <SUB>bh,max</SUB> = 30 M <SUB>sun</SUB>. This is a rather striking finding as the mass of the most massive known stellar BH is M <SUB>bh</SUB> = 23-34 M <SUB>sun</SUB> and, in fact, it is located in a small star-forming galaxy with moderate metallicity. We find that in the very low (globular cluster-like) metallicity environment the maximum BH mass can be as high as M <SUB>bh,max</SUB> = 80 M <SUB>sun</SUB> (Z = 0.01 Z <SUB>sun</SUB> = 0.0002). It is interesting to note that X-ray luminosity from Eddington-limited accretion onto an 80 M <SUB>sun</SUB> BH is of the order of ~10<SUP>40</SUP> erg s<SUP>-1</SUP> and is comparable to luminosities of some known ultra-luminous X-ray sources. We emphasize that our results were obtained for single stars only and that binary interactions may alter these maximum BH masses (e.g., accretion from a close companion). This is strictly a proof-of-principle study which demonstrates that stellar models can naturally explain even the most massive known stellar BHs.

[]

https://arxiv.org/pdf/0904.2784.pdf

2001Natur.413...45B

Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre

2001-01-01

['astrophysics']

[]

The nuclei of most galaxies are now believed to harbour supermassive black holes. The motions of stars in the central few light years of our Milky Way Galaxy indicate the presence of a dark object with a mass of about 2.6 × 10<SUP>6</SUP>solar masses (refs 2, 3). This object is spatially coincident with the compact radio source Sagittarius A* (SgrA*) at the dynamical centre of the Galaxy, and the radio emission is thought to be powered by the gravitational potential energy released by matter as it accretes onto a supermassive black hole. SgrA* is, however, much fainter than expected at all wavelengths, especially in X-rays, which has cast some doubt on this model. The first strong evidence for X-ray emission was found only recently. Here we report the discovery of rapid X-ray flaring from the direction of SgrA*, which, together with the previously reported steady X-ray emission, provides compelling evidence that the emission is coming from the accretion of gas onto a supermassive black hole at the Galactic Centre.

[]

https://arxiv.org/pdf/astro-ph/0109367.pdf

2004ApJ...615..645O

Supermassive Black Holes in Active Galactic Nuclei. II. Calibration of the Black Hole Mass-Velocity Dispersion Relationship for Active Galactic Nuclei

2004-01-01

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

[]

We calibrate reverberation-based black hole (BH) masses in active galactic nuclei (AGNs) by using the correlation between BH mass, M<SUB>BH</SUB>, and bulge/spheroid stellar velocity dispersion, σ<SUB>*</SUB>. We use new measurements of σ<SUB>*</SUB> for six AGNs and published velocity dispersions for 10 others, in conjunction with improved reverberation-mapping results, to determine the scaling factor required to bring reverberation-based BH masses into agreement with the quiescent galaxy M<SUB>BH</SUB>-σ<SUB>*</SUB> relationship. The scatter in the AGN BH masses is found to be less than a factor of 3. The current observational uncertainties preclude the use of the scaling factor to discriminate between broad-line region models.

[]

https://arxiv.org/pdf/astro-ph/0407297.pdf

2011PhRvD..83d4026A

Exploring the string axiverse with precision black hole physics

2011-01-01

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

[]

It has recently been suggested that the presence of a plenitude of light axions, an Axiverse, is evidence for the extra dimensions of string theory. We discuss the observational consequences of these axions on astrophysical black holes through the Penrose superradiance process. When an axion Compton wavelength is comparable to the size of a black hole, the axion binds to the black hole “nucleus” forming a gravitational atom in the sky. The occupation number of superradiant atomic levels, fed by the energy and angular momentum of the black hole, grows exponentially. The black hole spins down and an axion Bose-Einstein condensate cloud forms around it. When the attractive axion self-interactions become stronger than the gravitational binding energy, the axion cloud collapses, a phenomenon known in condensed matter physics as “bosenova”. The existence of axions is first diagnosed by gaps in the mass vs spin plot of astrophysical black holes. For young black holes the allowed values of spin are quantized, giving rise to “Regge trajectories” inside the gap region. The axion cloud can also be observed directly either through precision mapping of the near-horizon geometry or through gravitational waves coming from the bosenova explosion, as well as axion transitions and annihilations in the gravitational atom. Our estimates suggest that these signals are detectable in upcoming experiments, such as Advanced LIGO, AGIS, and LISA. Current black hole spin measurements imply an upper bound on the QCD axion decay constant of 2×10<SUP>17</SUP>GeV, while Advanced LIGO can detect signals from a QCD axion cloud with a decay constant as low as the GUT scale. We finally discuss the possibility of observing the γ-rays associated with the bosenova explosion and, perhaps, the radio waves from axion-to-photon conversion for the QCD axion.

[]

https://arxiv.org/pdf/1004.3558.pdf

2017PDU....15..142C

The clustering of massive Primordial Black Holes as Dark Matter: Measuring their mass distribution with advanced LIGO

2017-01-01

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

[]

The recent detection by Advanced LIGO of gravitational waves (GW) from the merging of a binary black hole system sets new limits on the merging rates of massive primordial black holes (PBH) that could be a significant fraction or even the totality of the dark matter in the Universe. aLIGO opens the way to the determination of the distribution and clustering of such massive PBH. If PBH clusters have a similar density to the one observed in ultra-faint dwarf galaxies, we find merging rates comparable to aLIGO expectations. Massive PBH dark matter predicts the existence of thousands of those dwarf galaxies where star formation is unlikely because of gas accretion onto PBH, which would possibly provide a solution to the missing satellite and too-big-to-fail problems. Finally, we study the possibility of using aLIGO and future GW antennas to measure the abundance and mass distribution of PBH in the range [5-200] M<SUB>⊙</SUB> to 10% accuracy.

[]

https://arxiv.org/pdf/1603.05234.pdf

1997PhLB..391...93B

D-branes and spinning black holes

1997-01-01

['-']

[]

We obtain a new class of spinning charged extremal black holes in five dimensions, considered both as classical configurations and in the Dirichlet (D)-brane representation. The degeneracy of states is computed from the D-brane side and the entropy agrees perfectly with that obtained from the black hole side.

[]

https://arxiv.org/pdf/hep-th/9602065.pdf

1997JHEP...12..002M

Black hole entropy in M-Theory

1997-01-01

['-']

[]

Extremal black holes in M-theory compactification on M × S<SUP>1</SUP> are microscopically represented by fivebranes wrapping P × S<SUP>1</SUP>, where M is a Calabi-Yau threefold and P is a four-cycle in M. Additional spacetime charges arise from momentum around the S<SUP>1</SUP> and expectation values for the self-dual three-form field strength in the fivebrane. The microscopic entropy of the fivebrane as a function of all the charges is determined from a two-dimensional (0,4) sigma model whose target space includes the fivebrane moduli space. This entropy is compared to the macroscopic formula. Precise agreement is found for both the tree-level and one-loop expressions.

[]

https://arxiv.org/pdf/hep-th/9711053.pdf

1998CQGra..15.3147H

Unified first law of black-hole dynamics and relativistic thermodynamics

1998-01-01

['-']

[]

A unified first law of black-hole dynamics and relativistic thermodynamics is derived in spherically symmetric general relativity. This equation expresses the gradient of the active gravitational energy E according to the Einstein equation, divided into energy-supply and work terms. Projecting the equation along the flow of thermodynamic matter and along the trapping horizon of a black hole yield, respectively, first laws of relativistic thermodynamics and black-hole dynamics. In the black-hole case, this first law has the same form as the first law of black-hole statics, with static perturbations replaced by the derivative along the horizon. In particular, there is the expected term involving the area and surface gravity, where the dynamic surface gravity is defined by substituting the Kodama vector and trapping horizon for the Killing vector and Killing horizon in the standard definition of static surface gravity. The remaining work term is consistent with, for instance, electromagnetic work in special relativity. The dynamic surface gravity vanishes for degenerate trapping horizons and satisfies certain inequalities involving the area and energy which have the same form as for stationary black holes. Turning to the thermodynamic case, the quasi-local first law has the same form, apart from a relativistic factor, as the classical first law of thermodynamics, involving heat supply and hydrodynamic work, but with E replacing the internal energy. Expanding E in the Newtonian limit shows that it incorporates the Newtonian mass, kinetic energy, gravitational potential energy and thermal energy (internal energy with fixed zero). There is also a weak type of unified zeroth law: a Gibbs-like definition of thermal equilibrium requires constancy of an effective temperature, generalizing the Tolman condition and the particular case of Hawking radiation, while gravithermal equilibrium further requires constancy of surface gravity. Finally, it is suggested that the energy operator of spherically symmetric quantum gravity is determined by the Kodama vector, which encodes a dynamic time related to E.

[]

https://arxiv.org/pdf/gr-qc/9710089.pdf

2006Natur.444..730M

Active galactic nuclei as scaled-up Galactic black holes

2006-01-01

['astrophysics']

[]

A long-standing question is whether active galactic nuclei (AGN) vary like Galactic black hole systems when appropriately scaled up by mass. If so, we can then determine how AGN should behave on cosmological timescales by studying the brighter and much faster varying Galactic systems. As X-ray emission is produced very close to the black holes, it provides one of the best diagnostics of their behaviour. A characteristic timescale-which potentially could tell us about the mass of the black hole-is found in the X-ray variations from both AGN and Galactic black holes, but whether it is physically meaningful to compare the two has been questioned. Here we report that, after correcting for variations in the accretion rate, the timescales can be physically linked, revealing that the accretion process is exactly the same for small and large black holes. Strong support for this linkage comes, perhaps surprisingly, from the permitted optical emission lines in AGN whose widths (in both broad-line AGN and narrow-emission-line Seyfert 1 galaxies) correlate strongly with the characteristic X-ray timescale, exactly as expected from the AGN black hole masses and accretion rates. So AGN really are just scaled-up Galactic black holes.

[]

https://arxiv.org/pdf/astro-ph/0612273.pdf

2004MNRAS.352.1390M

The cosmological evolution of quasar black hole masses

2004-01-01

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

[]

Virial black hole mass estimates are presented for 12698 quasars in the redshift interval 0.1 &lt;=z&lt;= 2.1, based on modelling of spectra from the Sloan Digital Sky Survey (SDSS) first data release. The black hole masses of the SDSS quasars are found to lie between ~=10<SUP>7</SUP> M<SUB>solar</SUB> and an upper limit of ~=3 × 10<SUP>9</SUP> M<SUB>solar</SUB>, entirely consistent with the largest black hole masses found to date in the local Universe. The estimated Eddington ratios of the broad-line quasars (full width at half-maximum &gt;= 2000 km s<SUP>-1</SUP>) show a clear upper boundary at L<SUB>bol</SUB>/L<SUB>Edd</SUB>~= 1, suggesting that the Eddington luminosity is still a relevant physical limit to the accretion rate of luminous broad-line quasars at z&lt;= 2. By combining the black hole mass distribution of the SDSS quasars with the two degree field (2dF) quasar luminosity function, the number density of active black holes at z~= 2 is estimated as a function of mass. In addition, we independently estimate the local black hole mass function for early-type galaxies using the M<SUB>bh</SUB>-σ and M<SUB>bh</SUB>-L<SUB>bulge</SUB> correlations. Based on the SDSS velocity dispersion function and the Two Micron All Sky Survey (2MASS) K-band luminosity function, both estimates are found to be consistent at the high-mass end (M<SUB>bh</SUB>&gt;= 10<SUP>8</SUP> M<SUB>solar</SUB>). By comparing the estimated number density of active black holes at z~= 2 with the local mass density of dormant black holes, we set lower limits on the quasar lifetimes and find that the majority of black holes with mass &gt;=10<SUP>8.5</SUP> M<SUB>solar</SUB> are in place by ~=2.

[]

https://arxiv.org/pdf/astro-ph/0310267.pdf

2000PhRvL..85.4643G

Sonic Analog of Gravitational Black Holes in Bose-Einstein Condensates

2000-01-01

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

[]

It is shown that, in dilute-gas Bose-Einstein condensates, there exist both dynamically stable and unstable configurations which, in the hydrodynamic limit, exhibit a behavior resembling that of gravitational black holes. The dynamical instabilities involve creation of quasiparticle pairs in positive and negative energy states, as in the well-known suggested mechanism for black-hole evaporation. We propose a scheme to generate a stable sonic black hole in a ring trap.

[]

https://arxiv.org/pdf/gr-qc/0002015.pdf

1997PhRvD..55.6189H

Correspondence principle for black holes and strings

1997-01-01

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

[]

For most black holes in string theory, the Schwarzschild radius in string units decreases as the string coupling is reduced. We formulate a correspondence principle, which states that (i) when the size of the horizon drops below the size of a string, the typical black hole state becomes a typical state of strings and D-branes with the same charges, and (ii) the mass does not change abruptly during the transition. This provides a statistical interpretation of black hole entropy. This approach does not yield the numerical coefficient, but gives the correct dependence on mass and charge in a wide range of cases, including neutral black holes.

[]

https://arxiv.org/pdf/hep-th/9612146.pdf

2005ApJ...630..705H

Black Holes in Galaxy Mergers: Evolution of Quasars

2005-01-01

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

[]

Based on numerical simulations of gas-rich galaxy mergers, we discuss a model in which quasar activity is tied to the self-regulated growth of supermassive black holes in galaxies. The nuclear inflow of gas attending a galaxy collision triggers a starburst and feeds black hole growth, but for most of the duration of the starburst, the black hole is ``buried,'' being heavily obscured by surrounding gas and dust, limiting the visibility of the quasar, especially at optical and ultraviolet wavelengths. As the black hole grows, feedback energy from accretion heats the gas and eventually expels it in a powerful wind, leaving behind a ``dead quasar.'' Between the buried and dead phases, there is a window in time during which the galaxy would be seen as a luminous quasar. Because the black hole mass, radiative output, and distribution of obscuring gas and dust all evolve strongly with time, the duration of this phase of observable quasar activity depends on both the waveband and imposed luminosity threshold. We determine the observed and intrinsic lifetimes as a function of luminosity and frequency, and calculate observable lifetimes ~10 Myr for bright quasars in the optical B band, in good agreement with empirical estimates and much smaller than our estimated black hole growth timescales ~100 Myr, naturally producing a substantial population of buried quasars. However, the observed and intrinsic energy outputs converge in the IR and hard X-ray bands as attenuation becomes weaker and chances of observation greatly increase. We also obtain the distribution of column densities along sight lines in which the quasar is seen above a given luminosity, and find that our result agrees remarkably well with observed estimates of the column density distribution from the SDSS for the appropriate luminosity thresholds. Our model reproduces a wide range of quasar phenomena, including observed quasar lifetimes, intrinsic lifetimes, column density distributions, and differences between optical and X-ray samples, having properties consistent with observations across more than 5 orders of magnitude in bolometric luminosity from 10<SUP>9</SUP> to 10<SUP>14</SUP> L<SUB>solar</SUB> (-17&lt;~M<SUB>B</SUB>&lt;~-30).

[]

https://arxiv.org/pdf/astro-ph/0504190.pdf

2004ApJ...611..977M

A Measurement of the Electromagnetic Luminosity of a Kerr Black Hole

2004-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'hydrodynamics', 'turbulence', 'astrophysics']

[]

Some active galactic nuclei, microquasars, and gamma-ray bursts may be powered by the electromagnetic braking of a rapidly rotating black hole. We investigate this possibility via axisymmetric numerical simulations of a black hole surrounded by a magnetized plasma. The plasma is described by the equations of general relativistic magnetohydrodynamics, and the effects of radiation are neglected. The evolution is followed for 2000GM/c<SUP>3</SUP>, and the computational domain extends from inside the event horizon to typically 40GM/c<SUP>2</SUP>. We compare our results to two analytic steady state models, including the force-free magnetosphere of Blandford &amp; Znajek. Along the way we present a self-contained rederivation of the Blandford-Znajek model in Kerr-Schild (horizon penetrating) coordinates. We find that (1) low-density polar regions of the numerical models agree well with the Blandford-Znajek model, (2) many of our models have an outward Poynting flux on the horizon in the Kerr-Schild frame, (3) none of our models have a net outward energy flux on the horizon, and (4) one of our models, in which the initial disk has net magnetic flux, shows a net outward angular momentum flux on the horizon. We conclude with a discussion of the limitations of our model, astrophysical implications, and problems to be addressed by future numerical experiments.

[]

https://arxiv.org/pdf/astro-ph/0404512.pdf

2020ARA&A..58..257G

Intermediate-Mass Black Holes

2020-01-01

['-']

[]

We describe ongoing searches for intermediate-mass black holes with M<SUB>BH</SUB> ≈ 10-10<SUP>5</SUP> M<SUB>⊙</SUB>. We review a range of search mechanisms, both dynamical and those that rely on accretion signatures. We find the following conclusions: Dynamical and accretion signatures alike point to a high fraction of 10<SUP>9</SUP>-10<SUP>10</SUP> M<SUB>⊙</SUB> galaxies hosting black holes with M<SUB>BH</SUB>∼ 10<SUP>5</SUP> M<SUB>⊙</SUB>. In contrast, there are no solid detections of black holes in globular clusters. There are few observational constraints on black holes in any environment with M<SUB>BH</SUB> ≈ 100-10<SUP>4</SUP> M<SUB>⊙</SUB>. Considering low-mass galaxies with dynamical black hole masses and constraining limits, we find that the M<SUB>BH</SUB>-σ<SUB>*</SUB> relation continues unbroken to M<SUB>BH</SUB> ∼10<SUP>5</SUP> M<SUB>⊙</SUB>, albeit with large scatter. We believe the scatter is at least partially driven by a broad range in black hole masses, because the occupation fraction appears to be relatively high in these galaxies. We fold the observed scaling relations with our empirical limits on occupation fraction and the galaxy mass function to put observational bounds on the black hole mass function in galaxy nuclei. We are pessimistic that local demographic observations of galaxy nuclei alone could constrain seeding mechanisms, although either high-redshift luminosity functions or robust measurements of off-nuclear black holes could begin to discriminate models.

[]

https://arxiv.org/pdf/1911.09678.pdf

2006ApJ...652..518M

The Spin of the Near-Extreme Kerr Black Hole GRS 1915+105

2006-01-01

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

[]

Based on a spectral analysis of the X-ray continuum that employs a fully relativistic accretion disk model, we conclude that the compact primary of the binary X-ray source GRS 1915+105 is a rapidly rotating Kerr black hole. We find a lower limit on the dimensionless spin parameter of a<SUB>*</SUB>&gt;0.98. Our result is robust in the sense that it is independent of the details of the data analysis and insensitive to the uncertainties in the mass and distance of the black hole. Furthermore, our accretion disk model includes an advanced treatment of spectral hardening. Our data selection relies on a rigorous and quantitative definition of the thermal state of black hole binaries, which we used to screen all of the available RXTE and ASCA data for the thermal state of GRS 1915+105. In addition, we focus on those data for which the accretion disk luminosity is less than 30% of the Eddington luminosity. We argue that these low-luminosity data are most appropriate for the thin α-disk model that we employ. We assume that there is zero torque at the inner edge of the disk, as is likely when the disk is thin, although we show that the presence of a significant torque does not affect our results. Our model and the model of the relativistic jets observed for this source constrain the distance and black hole mass and could thus be tested by determining a VLBA parallax distance and improving the measurement of the mass function. Finally, we comment on the significance of our results for relativistic jet and core-collapse models and for the detection of gravitational waves.

[]

https://arxiv.org/pdf/astro-ph/0606076.pdf

2020ApJ...900L..13A

Properties and Astrophysical Implications of the 150 M<SUB>⊙</SUB> Binary Black Hole Merger GW190521

2020-01-01

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

[]

The gravitational-wave signal GW190521 is consistent with a binary black hole (BBH) merger source at redshift 0.8 with unusually high component masses, ${85}_{-14}^{+21}$ M<SUB>⊙</SUB> and ${66}_{-18}^{+17}$ M<SUB>⊙</SUB>, compared to previously reported events, and shows mild evidence for spin-induced orbital precession. The primary falls in the mass gap predicted by (pulsational) pair-instability supernova theory, in the approximate range 65-120 M<SUB>⊙</SUB>. The probability that at least one of the black holes in GW190521 is in that range is 99.0%. The final mass of the merger ( ${142}_{-16}^{+28}$ M<SUB>⊙</SUB>) classifies it as an intermediate-mass black hole. Under the assumption of a quasi-circular BBH coalescence, we detail the physical properties of GW190521's source binary and its post-merger remnant, including component masses and spin vectors. Three different waveform models, as well as direct comparison to numerical solutions of general relativity, yield consistent estimates of these properties. Tests of strong-field general relativity targeting the merger-ringdown stages of the coalescence indicate consistency of the observed signal with theoretical predictions. We estimate the merger rate of similar systems to be ${0.13}_{-0.11}^{+0.30}\,{{\rm{Gpc}}}^{-3}\,{{\rm{yr}}}^{-1}$ . We discuss the astrophysical implications of GW190521 for stellar collapse and for the possible formation of black holes in the pair-instability mass gap through various channels: via (multiple) stellar coalescences, or via hierarchical mergers of lower-mass black holes in star clusters or in active galactic nuclei. We find it to be unlikely that GW190521 is a strongly lensed signal of a lower-mass black hole binary merger. We also discuss more exotic possible sources for GW190521, including a highly eccentric black hole binary, or a primordial black hole binary.

[]

https://arxiv.org/pdf/2009.01190.pdf

2003ApJ...594..812G

The Stellar Cusp around the Supermassive Black Hole in the Galactic Center

2003-01-01

['black hole physics', 'galaxies nuclei', 'galaxy center', 'stars fundamental parameters', 'astrophysics']

[]

We analyze deep near-IR adaptive optics imaging (taken with NAOS/CONICA on the Very Large Telescope at the European Southern Observatory, Chile), as well as new proper-motion data of the nuclear star cluster of the Milky Way. The surface density distribution of faint (H&lt;=20, K<SUB>s</SUB>&lt;=19) stars peaks within 0.2" of the black hole candidate Sgr A*. The radial density distribution of this stellar ``cusp'' follows a power law of exponent α~1.3-1.4. The K-band luminosity function of the overall nuclear stellar cluster (within 9<SUP>''</SUP> of Sgr A*) resembles that of the large-scale Galactic bulge but shows an excess of stars at K<SUB>s</SUB>&lt;=14. It fits population synthesis models of an old, metal-rich stellar population with a contribution from young, early, and late-type stars at the bright end. In contrast, the cusp within &lt;=1.5" of Sgr A* appears to have a featureless luminosity function, suggesting that old, low-mass, horizontal-branch/red-clump stars are lacking. Likewise, there appear to be fewer late-type giants. The innermost cusp also contains a group of moderately bright, early-type stars that are tightly bound to the black hole. We interpret these results as evidence that the stellar properties change significantly from the outer cluster (&gt;=a few arcseconds) to the dense innermost region around the black hole. We find that most of the massive early-type stars at distances of 1"-10" from Sgr A* are located in two rotating and geometrically thin disks. These disks are inclined at large angles and counterrotate with respect to each other. Their stellar content is essentially the same, indicating that they formed at the same time. We conclude that of the possible formation scenarios for these massive stars the most probable one is that 5-8 million years ago two clouds fell into the center, collided, were shock compressed, and then formed two rotating (accretion) disks orbiting the central black hole. For the OB stars in the central arcsecond, on the other hand, a stellar merger model is the most appealing explanation. These stars may thus be ``super-blue stragglers,'' formed and ``rejuvenated'' through mergers of lower mass stars in the very dense (&gt;=10<SUP>8</SUP> M<SUB>solar</SUB> pc<SUP>-3</SUP>) environment of the cusp. The ``collider model'' also accounts for the lack of giants within the central few arcseconds. The star closest to Sgr A* in 2002, S2, exhibits a 3.8 μm excess. We propose that the mid-IR emission comes either from the accretion flow around the black hole itself or from dust in the accretion flow that is heated by the ultraviolet emission of S2.

[]

https://arxiv.org/pdf/astro-ph/0305423.pdf