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2010AJ....140..546W

Eddington-limited Accretion and the Black Hole Mass Function at Redshift 6

2010-01-01

['cosmology observations', 'galaxies quasars', 'galaxies quasars', '-']

[]

We present discovery observations of a quasar in the Canada-France High-z Quasar Survey (CFHQS) at redshift z = 6.44. We also use near-infrared spectroscopy of nine CFHQS quasars at z ~ 6 to determine black hole masses. These are compared with similar estimates for more luminous Sloan Digital Sky Survey quasars to investigate the relationship between black hole mass and quasar luminosity. We find a strong correlation between Mg II FWHM and UV luminosity and that most quasars at this early epoch are accreting close to the Eddington limit. Thus, these quasars appear to be in an early stage of their life cycle where they are building up their black hole mass exponentially. Combining these results with the quasar luminosity function, we derive the black hole mass function at z = 6. Our black hole mass function is ~10<SUP>4</SUP> times lower than at z = 0 and substantially below estimates from previous studies. The main uncertainties which could increase the black hole mass function are a larger population of obscured quasars at high redshift than is observed at low redshift and/or a low quasar duty cycle at z = 6. In comparison, the global stellar mass function is only ~10<SUP>2</SUP> times lower at z = 6 than at z = 0. The difference between the black hole and stellar mass function evolution is due to either rapid early star formation which is not limited by radiation pressure as is the case for black hole growth or inefficient black hole seeding. Our work predicts that the black hole mass-stellar mass relation for a volume-limited sample of galaxies declines rapidly at very high redshift. This is in contrast to the observed increase at 4 &lt; z &lt; 6 from the local relation if one just studies the most massive black holes.

[]

https://arxiv.org/pdf/1006.1342.pdf

2014PhRvD..89l4004G

Photon regions and shadows of Kerr-Newman-NUT black holes with a cosmological constant

2014-01-01

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

[]

We consider the Plebański class of electrovacuum solutions to the Einstein equations with a cosmological constant. These space-times, which are also known as the Kerr-Newman-NUT-(anti-)de Sitter space-times, are characterized by a mass m, a spin a, a parameter β that comprises electric and magnetic charge, a NUT parameter ℓ and a cosmological constant Λ. Based on a detailed discussion of the photon regions in these space-times (i.e., of the regions in which spherical lightlike geodesics exist), we derive an analytical formula for the shadow of a Kerr-Newman-NUT-(anti-)de Sitter black hole for an observer at given Boyer-Lindquist coordinates (r<SUB>O</SUB>,ϑ<SUB>O</SUB>) in the domain of outer communication. We visualize the photon regions and the shadows for various values of the parameters.

[]

https://arxiv.org/pdf/1403.5234.pdf

2011PhRvD..83l4015J

Metric for rapidly spinning black holes suitable for strong-field tests of the no-hair theorem

2011-01-01

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

[]

According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric deviations from the Kerr metric have been suggested to study observational signatures in both the electromagnetic and gravitational-wave spectra that differ from the expected Kerr signals. Because of the no-hair theorem, however, such spacetimes cannot be regular everywhere outside the event horizons, if they are solutions to the Einstein field equations; they are often characterized by naked singularities or closed timelike loops in the regions of the spacetime that are accessible to an external observer. For observational tests of the no-hair theorem that involve phenomena in the vicinity of the circular photon orbit or the innermost stable circular orbit around a black hole, these pathologies limit the applicability of the metrics only to compact objects that do not spin rapidly. In this paper, we construct a Kerr-like metric which depends on a set of free parameters in addition to its mass and spin and which is regular everywhere outside of the event horizon. We derive expressions for the energy and angular momentum of a particle on a circular equatorial orbit around the black hole and compute the locations of the innermost stable circular orbit and the circular photon orbit. We demonstrate that these orbits change significantly for even moderate deviations from the Kerr metric. The properties of our metric make it an ideally suited spacetime to carry out strong-field tests of the no-hair theorem in the electromagnetic spectrum using the properties of accretion flows around astrophysical black holes of arbitrary spin.

[]

https://arxiv.org/pdf/1105.3191.pdf

2004PhRvL..93u1302E

A Supersymmetric Black Ring

2004-01-01

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

[]

A new supersymmetric black hole solution of five-dimensional supergravity is presented. It has an event horizon of topology S<SUP>1</SUP>×S<SUP>2</SUP>. This is the first example of a supersymmetric, asymptotically flat black hole of nonspherical topology. The solution is uniquely specified by its electric charge and two independent angular momenta. These conserved charges can be arbitrarily close, but not exactly equal, to those of a supersymmetric black hole of spherical topology.

[]

https://arxiv.org/pdf/hep-th/0407065.pdf

2006PhRvD..74d1501C

Spinning-black-hole binaries: The orbital hang-up

2006-01-01

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

[]

We present the first fully-nonlinear numerical study of the dynamics of highly-spinning-black-hole binaries. We evolve binaries from quasicircular orbits (as inferred from post-Newtonian theory), and find that the last stages of the orbital motion of black-hole binaries are profoundly affected by their individual spins. In order to cleanly display its effects, we consider two equal-mass holes with individual spin parameters S/m<SUP>2</SUP>=0.757, both aligned and antialigned with the orbital angular momentum (and compare with the spinless case), and with an initial orbital period of 125M. We find that the aligned case completes three orbits and merges significantly after the antialigned case, which completes less than one orbit. The total energy radiated for the former case is ≈7% while for the latter it is only ≈2%. The final Kerr hole remnants have rotation parameters a/M=0.89 and a/M=0.44 respectively, showing the unlikeliness of creating a maximally rotating black hole out of the merger two highly spinning holes.

[]

https://arxiv.org/pdf/gr-qc/0604012.pdf

2006PhRvD..73f4027S

Merger of binary neutron stars to a black hole: Disk mass, short gamma-ray bursts, and quasinormal mode ringing

2006-01-01

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

[]

Three-dimensional simulations for the merger of binary neutron stars are performed in the framework of full general relativity. We pay particular attention to the black hole formation case and to the resulting mass of the surrounding disk for exploring the possibility for formation of the central engine of short-duration gamma-ray bursts (SGRBs). Hybrid equations of state are adopted mimicking realistic, stiff nuclear equations of state (EOSs), for which the maximum allowed gravitational mass of cold and spherical neutron stars, M<SUB>sph</SUB>, is larger than 2M<SUB>⊙</SUB>. Such stiff EOSs are adopted motivated by the recent possible discovery of a heavy neutron star of mass ∼2.1±0.2M<SUB>⊙</SUB>. For the simulations, we focus on binary neutron stars of the ADM mass M≳2.6M<SUB>⊙</SUB>. For an ADM mass larger than the threshold mass M<SUB>thr</SUB>, the merger results in prompt formation of a black hole irrespective of the mass ratio Q<SUB>M</SUB> with 0.65≲Q<SUB>M</SUB>≤1. The value of M<SUB>thr</SUB> depends on the EOSs and is approximately written as 1.3 1.35M<SUB>sph</SUB> for the chosen EOSs. For the black hole formation case, we evolve the space-time using a black hole excision technique and determine the mass of a quasistationary disk surrounding the black hole. The disk mass steeply increases with decreasing the value of Q<SUB>M</SUB> for given ADM mass and EOS. This suggests that a merger with small value of Q<SUB>M</SUB> is a candidate for producing central engine of SGRBs. For M&lt;M<SUB>thr</SUB>, the outcome is a hypermassive neutron star of a large ellipticity. Because of the nonaxisymmetry, angular momentum is transported outward. If the hypermassive neutron star collapses to a black hole after the long-term angular momentum transport, the disk mass may be ≳0.01M<SUB>⊙</SUB> irrespective of Q<SUB>M</SUB>. Gravitational waves are computed in terms of a gauge-invariant wave extraction technique. In the formation of the hypermassive neutron star, quasiperiodic gravitational waves of frequency between 3 and 3.5 kHz are emitted irrespective of EOSs. The effective amplitude of gravitational waves can be ≳5×10<SUP>-21</SUP> at a distance of 50 Mpc, and hence, it may be detected by advanced laser-interferometers. For the black hole formation case, the black hole excision technique enables a long-term computation and extraction of ring-down gravitational waves associated with a black hole quasinormal mode. It is found that the frequency and amplitude are ≈6.5 7kHz and ∼10<SUP>-22</SUP> at a distance of 50 Mpc for the binary of mass M≈2.7 2.9M<SUB>⊙</SUB>.

[]

https://arxiv.org/pdf/astro-ph/0603145.pdf

2014ApJ...783..134F

Binary Black Hole Accretion from a Circumbinary Disk: Gas Dynamics inside the Central Cavity

2014-01-01

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

[]

We present the results of two-dimensional (2D) hydrodynamical simulations of circumbinary disk accretion using the finite-volume code DISCO. This code solves the 2D viscous Navier-Stokes equations on a high-resolution moving mesh which shears with the fluid flow, greatly reducing advection errors in comparison with a fixed grid. We perform a series of simulations for binary mass ratios in the range 0.026 &lt;= q &lt;= 1.0, each lasting longer than a viscous time so that we reach a quasi-steady accretion state. In each case, we find that gas is efficiently stripped from the inner edge of the circumbinary disk and enters the cavity along accretion streams, which feed persistent "mini disks" surrounding each black hole. We find that for q &gt;~ 0.1, the binary excites eccentricity in the inner region of the circumbinary disk, creating an overdense lump which gives rise to enhanced periodicity in the accretion rate. The dependence of the periodicity on mass ratio may provide a method for observationally inferring mass ratios from measurements of the accretion rate. We also find that for all mass ratios studied, the magnitude of the accretion onto the secondary is sufficient to drive the binary toward larger mass ratio. This suggests a mechanism for biasing mass-ratio distributions toward equal mass.

[]

https://arxiv.org/pdf/1310.0492.pdf

2011ApJ...742...84O

The Mass of the Black Hole in Cygnus X-1

2011-01-01

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

[]

Cygnus X-1 is a binary star system that is comprised of a black hole and a massive giant companion star in a tight orbit. Building on our accurate distance measurement reported in the preceding paper, we first determine the radius of the companion star, thereby constraining the scale of the binary system. To obtain a full dynamical model of the binary, we use an extensive collection of optical photometric and spectroscopic data taken from the literature. By using all of the available observational constraints, we show that the orbit is slightly eccentric (both the radial velocity and photometric data independently confirm this result) and that the companion star rotates roughly 1.4 times its pseudosynchronous value. We find a black hole mass of M = 14.8 ± 1.0 M <SUB>⊙</SUB>, a companion mass of M <SUB>opt</SUB> = 19.2 ± 1.9 M <SUB>⊙</SUB>, and the angle of inclination of the orbital plane to our line of sight of i = 27.1 ± 0.8 deg.

[]

https://arxiv.org/pdf/1106.3689.pdf

1998ApJ...499..367B

The Mass Distribution of Stellar Black Holes

1998-01-01

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

[]

We examine the distribution of masses of black holes in transient low-mass X-ray binary systems. A Bayesian analysis suggests that it is probable that six of the seven systems with measured mass functions have black hole masses clustered near seven solar masses. There appears to be a significant gap between the masses of these systems and those of the observed neutron stars. The remaining source, V404 Cyg, has a mass significantly larger than the others, and our analysis suggests that it is probably drawn from a different distribution. Selection effects do not appear to play a role in producing the observed mass distribution, which may be explained by currently unknown details of the supernova explosions and of binary evolution prior to the supernova.

[]

https://arxiv.org/pdf/astro-ph/9708032.pdf

2008PhR...467..117S

The fuzzball proposal for black holes

2008-01-01

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

[]

The fuzzball proposal states that associated with a black hole of entropy S, there are expShorizon-free non-singular solutions that asymptotically look like the black hole but generically differ from the black hole up to the horizon scale. These solutions, the fuzzballs, are considered to be the black hole microstates, while the original black hole represents the average description of the system. The purpose of this report is to review current evidence for the fuzzball proposal, emphasizing the use of AdS/CFT methods in developing and testing the proposal. In particular, we discuss the status of the proposal for 2 and 3 charge black holes in the D1 D5 system, presenting new derivations and streamlining the discussion of their properties. Results to date support the fuzzball proposal, but further progress is likely to require going beyond the supergravity approximation and sharpening the definition of a “stringy fuzzball”. We outline how the fuzzball proposal could resolve longstanding issues in black hole physics, such as Hawking radiation and information loss. Our emphasis throughout is on connecting different developments and identifying open problems and directions for future research.

[]

https://arxiv.org/pdf/0804.0552.pdf

2010ApJ...708..137M

On the Cosmic Evolution of the Scaling Relations Between Black Holes and Their Host Galaxies: Broad-Line Active Galactic Nuclei in the zCOSMOS Survey

2010-01-01

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

[]

We report on the measurement of the physical properties (rest-frame K-band luminosity and total stellar mass) of the hosts of 89 broad-line (type-1) active galactic nuclei (AGNs) detected in the zCOSMOS survey in the redshift range 1 &lt; z &lt; 2.2. The unprecedented multi-wavelength coverage of the survey field allows us to disentangle the emission of the host galaxy from that of the nuclear black hole in their spectral energy distributions (SEDs). We derive an estimate of black hole masses through the analysis of the broad Mg II emission lines observed in the medium-resolution spectra taken with VIMOS/VLT as part of the zCOSMOS project. We found that, as compared to the local value, the average black hole to host-galaxy mass ratio appears to evolve positively with redshift, with a best-fit evolution of the form (1+z)^{0.68 ± 0.12 ^{+0.6}_{-0.3}}, where the large asymmetric systematic errors stem from the uncertainties in the choice of initial mass function, in the calibration of the virial relation used to estimate BH masses and in the mean QSO SED adopted. On the other hand, if we consider the observed rest-frame K-band luminosity, objects tend to be brighter, for a given black hole mass, than those on the local M <SUB>BH</SUB>-M<SUB>K</SUB> relation. This fact, together with more indirect evidence from the SED fitting itself, suggests that the AGN hosts are likely actively star-forming galaxies. A thorough analysis of observational biases induced by intrinsic scatter in the scaling relations reinforces the conclusion that an evolution of the M <SUB>BH</SUB>-M <SUB>*</SUB> relation must ensue for actively growing black holes at early times: either its overall normalization, or its intrinsic scatter (or both) appear to increase with redshift. This can be interpreted as signature of either a more rapid growth of supermassive black holes at high redshift, a change of structural properties of AGN hosts at earlier times, or a significant mismatch between the typical growth times of nuclear black holes and host galaxies. In any case, our results provide important clues on the nature of the early co-evolution of black holes and galaxies and challenging tests for models of AGN feedback and self-regulated growth of structures. <P />Based on observations obtained at the European Southern Observatory (ESO) Very Large Telescope (VLT), Paranal, Chile, as part of the Large Program 175.A-0839 (the zCOSMOS Spectroscopic Redshift Survey). Also based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555; and on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; the National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.; and the Canada-France-Hawaii Telescope with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the National Research Council of Canada, the Canadian Astronomy Data Centre, the Centre National de la Recherche Scientifique de France, TERAPIX, and the University of Hawaii.

[]

https://arxiv.org/pdf/0910.4970.pdf

1999ApJ...512..100L

Extracting Energy from Black Holes: The Relative Importance of the Blandford-Znajek Mechanism

1999-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies magnetic fields', 'galaxies nuclei', 'mhd', 'accretion', 'accretion disks', 'black hole physics', 'galaxies magnetic fields', 'galaxies nuclei', 'mhd', 'astrophysics']

[]

We critically assess the role of the Blandford-Znajek mechanism in the powering of outflows from accretion-disk-fed black holes. We argue that there is no reason to suppose that the magnetic field threading the central spinning black hole differs significantly in strength from that threading the central regions of the disk. In this case, we show that the electromagnetic output from the inner disk regions is expected in general to dominate over that from the hole. Thus the spin (or not) of the hole is probably irrelevant to the expected electromagnetic power output from the system. We also point out that the strength of the poloidal field in the center of a standard accretion disk has been generally overestimated, and we discuss scenarios that might give rise to more significant central poloidal fields.

[]

https://arxiv.org/pdf/astro-ph/9809093.pdf

2019PhRvD..99h3503N

Constraints on Earth-mass primordial black holes from OGLE 5-year microlensing events

2019-01-01

['-']

[]

We constrain the abundance of primordial black holes (PBH) using 2622 microlensing events obtained from 5-years observations of stars in the Galactic bulge by the Optical Gravitational Lensing Experiment (OGLE). The majority of microlensing events display a single or at least continuous population that has a peak around the light curve timescale t<SUB>E</SUB>≃20 days and a wide distribution over the range t<SUB>E</SUB>≃[1 ,300 ] days , while the data also indicates a second population of 6 ultrashort-timescale events in t<SUB>E</SUB>≃[0.1 ,0.3 ] days , which are advocated to be due to free-floating planets. We confirm that the main population of OGLE events can be well modeled by microlensing due to brown dwarfs, main sequence stars and stellar remnants (white dwarfs and neutron stars) in the standard Galactic bulge and disk models for their spatial and velocity distributions. Using the dark matter (DM) model for the Milky Way (MW) halo relative to the Galactic bulge/disk models, we obtain the tightest upper bound on the PBH abundance in the mass range M<SUB>PBH</SUB>≃[10<SUP>-6</SUP>,10<SUP>-3</SUP>] M<SUB>⊙</SUB> (Earth-Jupiter mass range), if we employ the "null hypothesis" that the OGLE data does not contain any PBH microlensing event. More interestingly, we also show that Earth-mass PBHs can well reproduce the 6 ultrashort-timescale events, without the need of free-floating planets, if the mass fraction of PBH to DM is at a per cent level, which is consistent with other constraints such as the microlensing search for Andromeda galaxy (M31) and the longer timescale OGLE events. Our result gives a hint of PBH existence, and can be confirmed or falsified by microlensing search for stars in M31, because M31 is towards the MW halo direction and should therefore contain a much less number of free-floating planets, even if exist, than the direction to the MW center.

[]

https://arxiv.org/pdf/1901.07120.pdf

2010LNP...794...53B

States and Transitions in Black Hole Binaries

2010-01-01

['-']

[]

With the availability of the large database of black-hole transients from the Rossi X-Ray Timing Explorer, the observed phenomenology has become very complex. The original classification of the properties of these systems in a series of static states sorted by mass accretion rate proved not to be able to encompass the new picture. I outline here a summary of the current situation and show that a coherent picture emerges when simple properties such as X-ray spectral hardness and fractional variability are considered. In particular, fast transition in the properties of the fast time variability appear to be crucial to describe the evolution of black-hole transients. Based on this picture, I present a state classification which takes into account the observed transitions. I show that, in addition to transients systems, other black-hole binaries and Active Galactic Nuclei can be interpreted within this framework. The association between these states and the physics of the accretion flow around black holes will be possible only through modeling of the full time evolution of galactic transient systems.

[]

https://arxiv.org/pdf/0909.2474.pdf

1996NuPhB.478..561D

Comparing decay rates for black holes and D-branes

1996-01-01

['-']

[]

We compute the leading order (in coupling) rate of emission of low energy quanta from a slightly non-extremal system of 1-D- and 5-D-branes. We also compute the classical cross-section, and hence the Hawking emission rate, for low energy scalar quanta for the black hole geometry that corresponds to these branes (at sufficiently strong coupling). These rates are found to agree with each other.

[]

https://arxiv.org/pdf/hep-th/9606185.pdf

2002PhRvD..66b4010E

Reissner-Nordström black hole lensing

2002-01-01

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

[]

In this paper we study the strong gravitational lensing scenario where the lens is a Reissner-Nordström black hole. We obtain the basic equations and show that, as in the case of a Schwarzschild black hole, in addition to the primary and secondary images, two infinite sets of relativistic images are formed. We find analytical expressions for the positions and amplifications of the relativistic images. The formalism is applied to the case of a low-mass black hole placed at the galactic halo.

[]

https://arxiv.org/pdf/gr-qc/0203049.pdf

2015JHEAp...7..148K

Tidal disruption of stars by supermassive black holes: Status of observations

2015-01-01

['-', '-']

[]

Stars in the immediate vicinity of supermassive black holes (SMBHs) can be ripped apart by the tidal forces of the black hole. The subsequent accretion of the stellar material causes a spectacular flare of electromagnetic radiation. Here, we provide a review of the observations of tidal disruption events (TDEs), with an emphasis on the important contributions of Swift to this field. TDEs represent a new probe of matter under strong gravity, and have opened up a new window into studying accretion physics under extreme conditions. The events probe relativistic effects, provide a new means of measuring black hole spin, and represent signposts of intermediate-mass BHs, binary BHs and recoiling BHs. Luminous, high-amplitude X-ray flares, matching key predictions of the tidal disruption scenario, have first been discovered with ROSAT, and more recently with other missions and in other wavebands. The Swift discovery of two γ-ray emitting, jetted TDEs, never seen before, has provided us with a unique probe of the early phases of jet formation and evolution, and Swift J1644+75 has the best covered lightcurve of any TDE to date. Further, Swift has made important contributions in providing well-covered lightcurves of TDEs discovered with other instruments, setting constraints on the physics that govern the TDE evolution, and including the discovery of the first candidate binary SMBH identified from a TDE lightcurve. <P />In X-rays, TDEs probe relativistic effects (via emission-line profiles or precession effects in the Kerr metric) and the extremes of accretion physics at high rates and near the last stable orbit, and provide us with a new means of measuring BH spin. <P />Jetted TDEs provide new insight into the formation and early evolution of radio jets, and may shed new light on related issues like the cause of the radio-loud radio-quiet dichotomy of active galactic nuclei (AGN). <P />TDEs, once detected in large numbers, will unveil the population of IMBHs in the universe. <P />TDE rates depend on, and therefore trace, stellar dynamics in galaxy cores on spatial scales which cannot be resolved directly. <P />TDEs are signposts of binary SMBHs and recoiling BHs, because their rates are strongly enhanced under these conditions, and TDEs will occur off-nuclear if the SMBH is recoiling. <P />TDEs in gas-rich environments will illuminate the circum-nuclear material, so that the reprocessed emission lines and their temporal evolution provide us with an unparalleled opportunity of reverberation mapping the cores of quiescent galaxies. <P />Here, we present an overview of the status of observations of TDEs, highlighting the important role plaid by the Swift mission (Gehrels et al., 2004; Gehrels and Cannizzo, in press). An accompanying review by Lodato (in press) will focus on theoretical aspects of tidal disruption.

[]

https://arxiv.org/pdf/1505.01093.pdf

2001ApJ...562L..19E

Missing Link Found? The ``Runaway'' Path to Supermassive Black Holes

2001-01-01

['galaxies starburst', 'galaxies star clusters', 'gravitational waves', 'methods n body', 'astronomy radio', 'astronomy x rays', 'astrophysics']

[]

Observations of stellar kinematics, gasdynamics, and masers around galactic nuclei have now firmly established that many galaxies host central supermassive black holes (SMBHs) with masses in the range of ~10<SUP>6</SUP>-10<SUP>9</SUP> M<SUB>solar</SUB>. However, how these SMBHs formed is not well understood. One reason for this situation is the lack of observations of intermediate-mass BHs (IMBHs), which could bridge the gap between stellar mass BHs and SMBHs. Recently, this missing link (i.e., an IMBH) has been found in observations made by ASCA and Chandra of the central region of the starburst galaxy M82. Subsequent observations by Subaru have revealed that this IMBH apparently coincides with a young compact star cluster. Based on these findings, we suggest a new formation scenario for SMBHs. In this scenario, IMBHs first form in young compact star clusters through runaway merging of massive stars. While these IMBHs are forming, the host star clusters sink toward the galactic nucleus through dynamical friction and upon evaporation deposit their IMBHs near the galactic center. The IMBHs then form binaries and eventually merge via gravitational radiation, forming an SMBH.

[]

https://arxiv.org/pdf/astro-ph/0106252.pdf

2016PhRvD..93j4004A

Shadow of rotating regular black holes

2016-01-01

['-', '-']

[]

We study the shadows cast by the different types of rotating regular black holes viz. Ayón-Beato-García (ABG), Hayward, and Bardeen. These black holes have in addition to the total mass (M ) and rotation parameter (a ), different parameters as electric charge (Q ), deviation parameter (g ), and magnetic charge (g<SUB>*</SUB>). Interestingly, the size of the shadow is affected by these parameters in addition to the rotation parameter. We found that the radius of the shadow in each case decreases monotonically, and the distortion parameter increases when the values of these parameters increase. A comparison with the standard Kerr case is also investigated. We have also studied the influence of the plasma environment around regular black holes to discuss its shadow. The presence of the plasma affects the apparent size of the regular black hole's shadow to be increased due to two effects: (i) gravitational redshift of the photons and (ii) radial dependence of plasma density.

[]

https://arxiv.org/pdf/1604.03809.pdf

1996PhDT.........6M

Black Holes in String Theory

1996-01-01

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

[]

This thesis is devoted to finding a microscopic quantum description of black holes. We consider black holes in string theory which is a quantum theory of gravity. We find that the "area law" black hole entropy for extremal and near-extremal charged black holes arises from counting microscopic configurations. We study black holes in five and four spacetime dimensions. We calculate the Hawking temperature and give a physical picture of the Hawking decay process.

[]

https://arxiv.org/pdf/hep-th/9607235.pdf

2005ApJ...632..799P

Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass

2005-01-01

['galaxies active', 'galaxies nuclei', 'galaxies seyfert', 'galaxies quasars', 'astronomy uv', 'astrophysics']

[]

A reverberation-mapping program on NGC 4395, the least luminous known Seyfert 1 galaxy, undertaken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope yields a measurement of the mass of the central black hole M<SUB>BH</SUB>=(3.6+/-1.1)×10<SUP>5</SUP> M<SUB>solar</SUB>. The observations consist of two visits of five orbits each, in 2004 April and July. During each of these visits, the UV continuum varied by at least 10% (rms), and only C IV λ1549 showed corresponding variations large enough to reliably determine the emission-line lag, which was measured to be of order 1 hr for both visits. The size of the C IV-emitting region is about a factor of 3 smaller than expected if the slope of the broad-line region radius-luminosity relationship is identical to that for the Hβ emission line. NGC 4395 is underluminous even for its small black hole mass; the Eddington ratio of ~1.2×10<SUP>-3</SUP> is lower than that of any other active galactic nucleus for which a black hole mass measurement has been made by emission-line reverberation.

[]

https://arxiv.org/pdf/astro-ph/0506665.pdf

2009PhRvD..79d3002B

Apparent shape of super-spinning black holes

2009-01-01

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

[]

We consider the possibility that astrophysical black holes (BHs) can violate the Kerr bound; i.e., they can have angular momentum greater than BH mass, J&gt;M. We discuss implications on the BH apparent shape. Even if the bound is violated by a small amount, the shadow cast by the BH changes significantly (it is ∼ an order of magnitude smaller) from the case with J≤M and can be used as a clear observational signature in the search for super-spinning BHs. We discuss briefly recent observations in the mm range of the supermassive BH at the center of the Galaxy, speculating on the possibility that it might violate the Kerr bound.

[]

https://arxiv.org/pdf/0812.1328.pdf

2014PhRvD..89h4006P

Inspiral-merger-ringdown waveforms of spinning, precessing black-hole binaries in the effective-one-body formalism

2014-01-01

['-', '-', '-', '-', 'methods numerical', 'methods numerical', '-', 'perturbation theory', '-', '-', '-']

[]

We describe a general procedure to generate spinning, precessing waveforms that include inspiral, merger, and ringdown stages in the effective-one-body (EOB) approach. The procedure uses a precessing frame in which precession-induced amplitude and phase modulations are minimized, and an inertial frame, aligned with the spin of the final black hole, in which we carry out the matching of the inspiral-plunge to merger-ringdown waveforms. As a first application, we build spinning, precessing EOB waveforms for the gravitational modes ℓ=2 such that in the nonprecessing limit those waveforms agree with the EOB waveforms recently calibrated to numerical-relativity waveforms. Without recalibrating the EOB model, we then compare EOB and post-Newtonian precessing waveforms to two numerical-relativity waveforms produced by the Caltech-Cornell-CITA collaboration. The numerical waveforms are strongly precessing and have 35 and 65 gravitational-wave cycles. We find a remarkable agreement between EOB and numerical-relativity precessing waveforms and spins' evolutions. The phase difference is ∼0.2 rad rad at merger, while the mismatches, computed using the advanced-LIGO noise spectral density, are below 2% when maximizing only on the time and phase at coalescence and on the polarization angle.

[]

https://arxiv.org/pdf/1307.6232.pdf

1999GReGr..31..629A

Non-Singular Charged Black Hole Solution for Non-Linear Source

1999-01-01

['-']

[]

A non-singular exact black hole solution in General Relativity is presented. The source is a non-linear electromagnetic field, which reduces to the Maxwell theory for weak field. The solution corresponds to a charged black hole with |q| \leq 2s_c m \approx 0.6 m, having metric, curvature invariants, and electric field bounded everywhere.

[]

https://arxiv.org/pdf/gr-qc/9911084.pdf

2019ApJ...887...53F

Mind the Gap: The Location of the Lower Edge of the Pair-instability Supernova Black Hole Mass Gap

2019-01-01

['-', 'stars luminosity function;mass function', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

Detections of gravitational waves are now starting to probe the mass distribution of stellar mass black holes (BHs). Robust predictions from stellar models are needed to interpret these. Theory predicts the existence of a gap in the BH mass distribution because of pair-instability supernovae. The maximum BH mass below the gap is the result of pulsational mass loss. We evolve massive helium stars through their late hydrodynamical phases of evolution using the open-source MESA stellar evolution code. We find that the location of the lower edge of the mass gap at 45 {M}<SUB>⊙ </SUB> is remarkably robust against variations in the metallicity (≈3 {M}<SUB>⊙ </SUB>), the treatment of internal mixing (≈1 {M}<SUB>⊙ </SUB>), and stellar wind mass loss (≈4 {M}<SUB>⊙ </SUB>), making it the most robust predictor for the final stages of the evolution of massive stars. The reason is that the onset of the instability is dictated by the near-final core mass, which in turn sets the resulting BH mass. However, varying the {}<SUP>12</SUP>{{C}}{≤ft(α ,γ \right)}<SUP>16</SUP>{{O}} reaction rate within its 1σ uncertainties shifts the location of the gap between 40 {M}<SUB>⊙ </SUB> and 56 {M}<SUB>⊙ </SUB>. We provide updated analytic fits for population synthesis simulations. Our results imply that the detection of merging BHs can provide constraints on nuclear astrophysics. Furthermore, the robustness against metallicity suggests that there is a universal maximum for the location of the lower edge of the gap, which is insensitive to the formation environment and redshift for first-generation BHs. This is promising for the possibility to use the location of the gap as a “standard siren” across the universe.

[]

https://arxiv.org/pdf/1910.12874.pdf

2013PhRvD..88h4045H

Extended phase space thermodynamics and P-V criticality of black holes with a nonlinear source

2013-01-01

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

[]

In this paper, we consider the solutions of Einstein gravity in the presence of a generalized Maxwell theory, namely power Maxwell invariant. First, we investigate the analogy of nonlinear charged black hole solutions with the Van der Waals liquid-gas system in the extended phase space where the cosmological constant appear as pressure. Then, we plot isotherm P-V diagram and study the thermodynamics of AdS black hole in the (grand canonical) canonical ensemble in which (potential) charge is fixed at infinity. Interestingly, we find the phase transition occurs in the both of canonical and grand canonical ensembles in contrast to Reissner-Nordström black hole in Maxwell theory which only admits canonical ensemble phase transition. Moreover, we calculate the critical exponents and find their values are the same as those in mean field theory. Besides, we find in the grand canonical ensembles universal ratio (P<SUB>c</SUB>v<SUB>c</SUB>)/(T<SUB>c</SUB>) is independent of spacetime dimensions.

[]

https://arxiv.org/pdf/1212.6128.pdf

1999A&A...344..573R

Gamma-ray bursts from accreting black holes in neutron star mergers

1999-01-01

['elementary particles', 'hydrodynamics', 'stars binaries close', '-', 'gamma rays', 'astrophysics']

[]

By means of three-dimensional hydrodynamic simulations with a Eulerian PPM code we investigate the formation and the properties of the accretion torus around the stellar mass black hole which we assume to originate from the remnant of a neutron star merger within the dynamical time scale of a few milliseconds. The simulations are performed with four nested cartesian grids which allow for both a good resolution near the central black hole and a large computational volume. They include the use of a physical equation of state as well as the neutrino emission from the hot matter of the torus. The gravity of the black hole is described with a Newtonian and alternatively with a Paczyński-Wiita potential. In a post-processing step, we evaluate our models for the energy deposition by nu bar nu annihilation around the accretion torus. We find that the torus formed after neutron star merging has a mass between several 10(-2} M_{sun) and a few 10(-1} M_{sun) with maximum densities around 10(12) g cm(-3) and maximum temperatures of about 10 MeV (entropies around 5 k_B per nucleon). Correspondingly, the neutrino emission is huge with a total luminosity near 10(53) erg s(-1) . Neutrino-antineutrino annihilation deposits energy in the vicinity of the torus at a rate of (3-5)x 10(50) erg s(-1) . It is most efficient near the rotation axis where 10 to 30% of this energy or up to a total of 10(49) erg are dumped within an estimated emission period of 0.02-0.1 s in a region with a low integral baryonic mass of about 10(-5} M_{sun) . This baryon pollution is still dangerously high, and the estimated maximum relativistic Lorentz factors Gamma -1 are around unity. The conversion of neutrino energy into a pair plasma, however, is sufficiently powerful to blow out the baryons along the axis so that a clean funnel should be produced within only milliseconds. Our models show that accretion on the black hole formed after neutron star merging can yield enough energy by nu bar nu annihilation to account for weak, short gamma-ray bursts, if moderate beaming is involved. In fact, the barrier of the dense baryonic gas of the torus suggests that the low-density e(+/-gamma ) plasma is beamed as axial jets into a fraction f_Ω = 2delta Omega /(4pi ) between 1/100 and 1/10 of the sky, corresponding to opening half-angles of roughly ten to several tens of degrees. Thus gamma -burst energies of E_γ~ E_{nu bar nu }/f_Ω&lt;~ 10(50) -10(51) erg seem to be within the reach of accreting black holes formed in neutron star mergers (if the source is interpreted as radiating isotropically), corresponding to luminosities around 10(51) erg s(-1) for typical burst durations of 0.1-1 s. Gravitational capture of radiation by the black hole, redshift and ray bending do not reduce the jet energy significantly, because most of the neutrino emission comes from parts of the torus at distances of several Schwarzschild radii from the black hole. Effects associated with the Kerr character of the rapidly rotating black hole, however, could increase the gamma -burst energy considerably, and effects due to magnetic fields might even be required to get the energies for long complex gamma-ray bursts.

[]

https://arxiv.org/pdf/astro-ph/9809280.pdf

2017MNRAS.464L..36A

MOCCA-SURVEY Database - I. Coalescing binary black holes originating from globular clusters

2017-01-01

['gravitational waves', 'methods numerical', 'stars binaries general', 'stars black holes', 'clusters globular', '-', '-']

[]

In this first of a series of papers, we utilize results for around 2000 star cluster models simulated using the MOCCA code for star cluster evolution (Survey Database I) to determine the astrophysical properties and local merger rate densities for coalescing binary black holes (BBHs) originating from globular clusters (GCs). We extracted information for all coalescing BBHs that escape the cluster models and subsequently merge within a Hubble time along with BBHs that are retained in our GC models and merge inside the cluster via gravitational wave emission. By obtaining results from a substantial number of realistic star cluster models that cover different initial parameters, we have an extremely large statistical sample of BBHs with stellar mass and massive stellar BH (≲100 M<SUB>⊙</SUB>) components that merge within a Hubble time. Using these data, we estimate local merger rate densities for these BBHs originating from GCs to be at least 5.4 Gpc<SUP>-3</SUP> yr<SUP>-1</SUP>.

[]

https://arxiv.org/pdf/1608.02520.pdf

2017PhRvD..96h2004A

Echoes from the abyss: Tentative evidence for Planck-scale structure at black hole horizons

2017-01-01

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

[]

In classical general relativity (GR), an observer falling into an astrophysical black hole is not expected to experience anything dramatic as she crosses the event horizon. However, tentative resolutions to problems in quantum gravity, such as the cosmological constant problem, or the black hole information paradox, invoke significant departures from classicality in the vicinity of the horizon. It was recently pointed out that such near-horizon structures can lead to late-time echoes in the black hole merger gravitational wave signals that are otherwise indistinguishable from GR. We search for observational signatures of these echoes in the gravitational wave data released by the advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), following the three black hole merger events GW150914, GW151226, and LVT151012. In particular, we look for repeating damped echoes with time delays of 8 M log M (+spin corrections, in Planck units), corresponding to Planck-scale departures from GR near their respective horizons. Accounting for the "look elsewhere" effect due to uncertainty in the echo template, we find tentative evidence for Planck-scale structure near black hole horizons at false detection probability of 1% (corresponding to 2.5 σ

[]

https://arxiv.org/pdf/1612.00266.pdf

2000ApJ...543L.111L

On Black Hole Masses and Radio Loudness in Active Galactic Nuclei

2000-01-01

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

[]

The distribution of radio to optical fluxes in active galactic nuclei (AGNs) is bimodal. The physical origin for this bimodality is not understood. In this Letter I describe observational evidence, based on the Boroson &amp; Green Palomar-Green quasar sample, that the radio loudness bimodality is strongly related to the black hole mass (M<SUB>BH</SUB>). Nearly all PG quasars with M<SUB>BH</SUB>&gt;10<SUP>9</SUP> M<SUB>solar</SUB> are radio-loud, while quasars with M<SUB>BH</SUB>&lt;3×10<SUP>8</SUP> M<SUB>solar</SUB> are practically all radio-quiet. This result is consistent with the dependence of quasar host galaxy morphology on radio loudness. There is no simple physical explanation for this result, but it may provide a clue as to how jets are formed near massive black holes. The radio loudness-black hole mass relationship suggests that the properties of various types of AGN may be largely set by three basic parameters: M<SUB>BH</SUB>, L/L<SUB>Edd</SUB>, and inclination angle.

[]

https://arxiv.org/pdf/astro-ph/0009192.pdf

2007CQGra..24.4169K

Near-horizon symmetries of extremal black holes

2007-01-01

['-', '-']

[]

Recent work has demonstrated an attractor mechanism for extremal rotating black holes subject to the assumption of a near-horizon SO(2, 1) symmetry. We prove the existence of this symmetry for any extremal black hole with the same number of rotational symmetries as known four- and five-dimensional solutions (including black rings). The result is valid for a general two-derivative theory of gravity coupled to Abelian vectors and uncharged scalars, allowing for a non-trivial scalar potential. We prove that it remains valid in the presence of higher-derivative corrections. We show that SO(2, 1)-symmetric near-horizon solutions can be analytically continued to give SU(2)-symmetric black hole solutions. For example, the near-horizon limit of an extremal 5D Myers Perry black hole is related by analytic continuation to a non-extremal cohomogeneity-1 Myers Perry solution.

[]

https://arxiv.org/pdf/0705.4214.pdf

2005NJPh....7..203P

Hawking radiation and black hole thermodynamics

2005-01-01

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

[]

An inexhaustive review of Hawking radiation and black hole thermodynamics is given, focusing especially upon some of the historical aspects as seen from the biased viewpoint of a minor player in the field on and off for the past 30 years. <P />Preprint Alberta-Thy-18-04, hep-th/0409024.

[]

https://arxiv.org/pdf/hep-th/0409024.pdf

2008PhRvD..78h4033B

Accurate evolutions of inspiralling neutron-star binaries: Prompt and delayed collapse to a black hole

2008-01-01

['-', '-', '-', '-', 'waves', 'relativity', 'hydrodynamics', 'neutron', '-', 'astrophysics']

[]

Binary neutron-star systems represent primary sources for the gravitational-wave detectors that are presently operating or are close to being operating at the target sensitivities. We present a systematic investigation in full general relativity of the dynamics and gravitational-wave emission from binary neutron stars which inspiral and merge, producing a black hole surrounded by a torus. Our results represent the state of the art from several points of view: (i) We use high-resolution shock-capturing methods for the solution of the hydrodynamics equations and high-order finite-differencing techniques for the solution of the Einstein equations; (ii) We employ adaptive mesh-refinement techniques with “moving boxes” that provide high-resolution around the orbiting stars; (iii) We use as initial data accurate solutions of the Einstein equations for a system of binary neutron stars in irrotational quasicircular orbits; (iv) We exploit the isolated-horizon formalism to measure the properties of the black holes produced in the merger; (v) Finally, we use two approaches, based either on gauge-invariant perturbations or on Weyl scalars, to calculate the gravitational waves emitted by the system. Within our idealized treatment of the matter, these techniques allow us to perform accurate evolutions on time scales never reported before (i.e. ∼30ms) and to provide the first complete description of the inspiral and merger of a neutron-star binary leading to the prompt or delayed formation of a black hole and to its ringdown. We consider either a polytropic equation of state or that of an ideal fluid and show that already with this idealized treatment a very interesting phenomenology can be described. In particular, we show that while higher-mass polytropic binaries lead to the prompt formation of a rapidly rotating black hole surrounded by a dense torus, lower-mass binaries give rise to a differentially rotating star, which undergoes large oscillations and emits large amounts of gravitational radiation. Eventually, also the hyper-massive neutron star collapses to a rotating black hole surrounded by a torus. Finally, we also show that the use of a nonisentropic equation of state leads to significantly different evolutions, giving rise to a delayed collapse also with high-mass binaries, as well as to a more intense emission of gravitational waves and to a geometrically thicker torus.

[]

https://arxiv.org/pdf/0804.0594.pdf

1999PhRvD..60h4002S

Black hole formation in the Friedmann universe: Formulation and computation in numerical relativity

1999-01-01

['-', '-', '-', 'methods numerical', 'cosmology dark matter', 'black hole physics', '-']

[]

We study the formation of black holes in the Friedmann universe. We present a formulation of the Einstein equations under the constant mean curvature time-slicing condition. Our formalism not only gives us the analytic solution of the perturbation equations for nonlinear density and metric fluctuations on superhorizon scales, but also allows us to carry out a numerical relativity simulation for black hole formation after the scale of the density fluctuations is well within the Hubble horizon scale. We perform a numerical simulation of spherically symmetric black hole formation in the radiation-dominated spatially flat background universe for a realistic initial condition supplied from the analytic solution. It is found that the initial metric perturbation has to be nonlinear (the maximum value of three-dimensional conformal factor ψ<SUB>0</SUB> at t=0 should be larger than ~1.4) for a black hole to be formed, but the threshold amplitude for black hole formation and the final black hole mass considerably depend on the initial density (or metric) profile of the perturbation: The threshold value of ψ<SUB>0</SUB> at t=0 for formation of a black hole is smaller for a high density peak surrounded by a low density region than for that surrounded by the average density region of the flat universe. This suggests that it is necessary to take into account the spatial correlation of density fluctuations in the study of primordial black hole formation.

[]

https://arxiv.org/pdf/gr-qc/9905064.pdf

1999PhRvD..59l4013N

Dynamics of primordial black hole formation

1999-01-01

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

[]

We present a numerical investigation of the gravitational collapse of horizon-size density fluctuations to primordial black holes (PBHs) during the radiation-dominated phase of the early Universe. The collapse dynamics of three different families of initial perturbation shapes, imposed at the time of horizon crossing, is computed. The perturbation threshold for black hole formation, needed for estimations of the cosmological PBH mass function, is found to be δ<SUB>c</SUB>~0.7 rather than the generally employed δ<SUB>c</SUB>~1/3 if δ is defined as ΔM/M<SUB>h</SUB>, the relative excess mass within the initial horizon volume. In order to study the accretion onto the newly formed black holes, we use a numerical scheme that allows us to follow the evolution for long times after formation of the event horizon. In general, small black holes (compared to the horizon mass at the onset of the collapse) give rise to a fluid bounce that effectively shuts off accretion onto the black hole, while large ones do not. In both cases, the growth of the black hole mass owing to accretion is insignificant. Furthermore, the scaling of black hole mass with the distance from the formation threshold, known to occur in near-critical gravitational collapse, is demonstrated to apply to primordial black hole formation.

[]

https://arxiv.org/pdf/astro-ph/9901292.pdf

2020JHEP...08..044M

Transcending the ensemble: baby universes, spacetime wormholes, and the order and disorder of black hole information

2020-01-01

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

[]

In the 1980's, work by Coleman and by Giddings and Strominger linked the physics of spacetime wormholes to `baby universes' and an ensemble of theories. We revisit such ideas, using features associated with a negative cosmological constant and asymptotically AdS boundaries to strengthen the results, introduce a change in perspective, and connect with recent replica wormhole discussions of the Page curve. A key new feature is an emphasis on the role of null states. We explore this structure in detail in simple topological models of the bulk that allow us to compute the full spectrum of associated boundary theories. The dimension of the asymptotically AdS Hilbert space turns out to become a random variable Z , whose value can be less than the naive number k of independent states in the theory. For k &gt; Z , consistency arises from an exact degeneracy in the inner product defined by the gravitational path integral, so that many a priori independent states differ only by a null state. We argue that a similar property must hold in any consistent gravitational path integral. We also comment on other aspects of extrapolations to more complicated models, and on possible implications for the black hole information problem in the individual members of the above ensemble.

[]

https://arxiv.org/pdf/2002.08950.pdf

2018PhRvD..97b3501B

Primordial black hole dark matter from single field inflation

2018-01-01

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

[]

We propose a model of inflation capable of generating a population of light black holes (about 10<SUP>-16</SUP>- 10<SUP>-14</SUP> solar masses) that might account for a significant fraction of the dark matter in the Universe. The effective potential of the model features an approximate inflection point arising from two-loop order logarithmic corrections in well-motivated and perturbative particle physics examples. This feature decelerates the inflaton before the end of inflation, enhancing the primordial spectrum of scalar fluctuations and triggering efficient black hole production with a peaked mass distribution. At larger field values, inflation occurs thanks to a generic small coupling between the inflaton and the curvature of spacetime. We compute accurately the peak mass and abundance of the primordial black holes using the Press-Schechter and Mukhanov-Sasaki formalisms, showing that the slow-roll approximation fails to reproduce the correct results by orders of magnitude. We study as well a qualitatively similar implementation of the idea, where the approximate inflection point is due to competing terms in a generic polynomial potential. In both models, requiring a significant part of the dark matter abundance to be in the form of black holes implies a small blue scalar tilt with a sizable negative running and a tensor spectrum that may be detected by the next-generation probes of the cosmic microwave background. We also comment on previous works on the topic.

[]

https://arxiv.org/pdf/1709.05565.pdf

2005PhR...419...65A

Stellar processes near the massive black hole in the Galactic center [review article]

2005-01-01

['astrophysics']

[]

A massive black hole resides in the center of most, perhaps all galaxies. The one in the center of our home galaxy, the Milky Way, provides a uniquely accessible laboratory for studying in detail the connections and interactions between a massive black hole and the stellar system in which it grows; for investigating the effects of extreme density, velocity and tidal fields on stars; and for using stars to probe the central dark mass and to probe post-Newtonian gravity in the weak- and strong-field limits. Recent results, open questions and future prospects are reviewed in the wider context of the theoretical framework and physical processes that underlie them.

[]

https://arxiv.org/pdf/astro-ph/0508106.pdf

2019JCAP...06..028B

Steepest growth of the power spectrum and primordial black holes

2019-01-01

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

[]

We derive analytic bounds on the shape of the primordial power spectrum in the context of single-field inflation. In particular, the steepest possible growth has a spectral index of n<SUB>s</SUB> - 1 = 4 once transients have died down. Its primary implication is that any constraint on the power spectrum at a particular scale can be extrapolated to an upper bound over an extended range of scales. This is important for models which generate relics due to an enhanced amplitude of the primordial scalar perturbations, such as primordial black holes. In order to generate them, the power spectrum needs to grow many orders of magnitude larger than its observed value on CMB scales—typically achieved through a phase of ultra slow-roll inflation—and is thus subject to additional constraints at small scales. We plot all relevant constraints including CMB spectral distortions and gravitational waves sourced by scalar perturbations at second order. We show how this limits the allowed mass of PBHs, especially for the large masses of interest following recent detections by LIGO and prospects for constraining them further with future observations. We show that any transition from approximately constant epsilon slow-roll inflation to a phase where the power spectrum rapidly rises necessarily implies an intervening dip in power. We also show how to reconstruct a potential that can reproduce an arbitrary time-varying epsilon, offering a complementary perspective on how ultra slow-roll can be achieved.

[]

https://arxiv.org/pdf/1811.11158.pdf

1996PhRvD..54.4891C

Black plane solutions in four-dimensional spacetimes

1996-01-01

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

[]

The static, plane symmetric solutions and cylindrically symmetric solutions of Einstein-Maxwell equations with a negative cosmological constant are investigated. These black configurations are asymptotically anti-de Sitter-type not only in the transverse directions, but also in the membrane or string directions. Their causal structure is similar to that of Reissner-Nordström black holes, but their Hawking temperature goes with M<SUP>1/3</SUP>, where M is the ADM mass density. We also discuss the static plane solutions in Einstein-Maxwell-dilaton gravity with a Liouville-type dilaton potential. The presence of the dilaton field changes drastically the structure of solutions. They are asymptotically ``anti-de Sitter-'' or ``de Sitter-type'' depending on the parameters in the theory.

[]

https://arxiv.org/pdf/gr-qc/9609065.pdf

2008MNRAS.383.1079V

The evolution of massive black hole seeds

2008-01-01

['black hole physics', 'galaxies evolution', 'galaxies quasars', 'cosmology miscellaneous', 'astrophysics']

[]

We investigate the evolution of high-redshift seed black hole masses at late times and their observational signatures. The massive black hole seeds studied here form at extremely high redshifts from the direct collapse of pre-galactic gas discs. Populating dark matter haloes with seeds formed in this way, we follow the mass assembly of these black holes to the present time using a Monte Carlo merger tree. Using this machinery, we predict the black hole mass function at high redshifts and at the present time, the integrated mass density of black holes and the luminosity function of accreting black holes as a function of redshift. These predictions are made for a set of three seed models with varying black hole formation efficiency. Given the accuracy of present observational constraints, all three models can be adequately fitted. Discrimination between the models appears predominantly at the low-mass end of the present-day black hole mass function which is not observationally well constrained. However, all our models predict that low surface brightness, bulgeless galaxies with large discs are least likely to be sites for the formation of massive seed black holes at high redshifts. The efficiency of seed formation at high redshifts has a direct influence on the black hole occupation fraction in galaxies at z = 0. This effect is more pronounced for low-mass galaxies. This is the key discriminant between the models studied here and the Population III remnant seed model. We find that there exist a population of low-mass galaxies that do not host nuclear black holes. Our prediction of the shape of the M<SUB>BH</SUB>-σ relation at the low-mass end is in agreement with the recent observational determination from the census of low-mass galaxies in the Virgo cluster.

[]

https://arxiv.org/pdf/0709.0529.pdf

2001JHEP...08..018G

The evolution of unstable black holes in anti-de Sitter space

2001-01-01

['-']

[]

We examine the thermodynamic stability of large black holes in four-dimensional anti-de Sitter space, and we demonstrate numerically that black holes which lack local thermodynamic stability often also lack stability against small perturbations. This shows that no-hair theorems do not apply in anti-de Sitter space. A heuristic argument, based on thermodynamics only, suggests that if there are any violations of Cosmic Censorship in the evolution of unstable black holes in anti-de Sitter space, they are beyond the reach of a perturbative analysis.

[]

https://arxiv.org/pdf/hep-th/0011127.pdf

1999PhLB..451..309C

Corrections to macroscopic supersymmetric black-hole entropy

1999-01-01

['-', '-']

[]

We determine the corrections to the entropy of extremal black holes arising from terms quadratic in the Riemann tensor in N=2, D=4 supergravity theories. We follow Wald's proposal to modify the Bekenstein-Hawking area law. The new entropy formula, whose value only depends on the electric/magnetic charges, is expressed in terms of a single holomorphic function and is consistent with electric-magnetic duality. For string effective field theories arising from Calabi-Yau compactifications, our result for the entropy of a certain class of extremal black-hole solutions fully agrees with the counting of microstates performed some time ago by Maldacena, Strominger, Witten and by Vafa.

[]

https://arxiv.org/pdf/hep-th/9812082.pdf

1999NuPhB.553..317B

Non-extreme black holes of five-dimensional N=2 AdS supergravity

1999-01-01

['-']

[]

We consider static black holes of D=5, N=2 gauged supergravity with general spatial curvature k and show that the modifications due to the gauging as well as k enter only the non-extremality function. Therefore, one can promote any (known) black hole solution of ungauged supergravity with k=+1 to a solution of gauged supergravity with an arbitrary k. As an example we discuss a solution for the STU model of gauged supergravity which is incidentally also a solution of D=5 N=4 and N=8 gauged supergravity. This solution is specified by three charges, the asymptotic negative cosmological constant (minimum of the potential) and a non-extremality parameter. While its BPS-saturated limit has a naked singularity, we find a lower bound on the non-extremality parameter (or equivalently on the ADM mass) for which the non-extreme solutions are regular. When this bound is saturated the extreme (non-supersymmetric) solution has zero Hawking temperature and finite entropy. Analogous qualitative features are expected to emerge for black hole solutions in D=4 gauged supergravity as well.

[]

https://arxiv.org/pdf/hep-th/9810227.pdf

2004JHEP...02..014F

The black hole singularity in AdS/CFT

2004-01-01

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

[]

We explore physics behind the horizon in eternal AdS Schwarzschild black holes. In dimension d &gt; 3 , where the curvature grows large near the singularity, we find distinct but subtle signals of this singularity in the boundary CFT correlators. Building on previous work, we study correlation functions of operators on the two disjoint asymptotic boundaries of the spacetime by investigating the spacelike geodesics that join the boundaries. These dominate the correlators for large mass bulk fields. We show that the Penrose diagram for d &gt; 3 is not square. As a result, the real geodesic connecting the two boundary points becomes almost null and bounces off the singularity at a finite boundary time t<SUB>c</SUB>\not=0. If this geodesic were to dominate the correlator there would be a ``light cone" singularity at t<SUB>c</SUB>. However, general properties of the boundary theory rule this out. In fact, we argue that the correlator is actually dominated by a complexified geodesic, whose properties yield the large mass quasinormal mode frequencies previously found for this black hole. We find a branch cut in the correlator at small time (in the limit of large mass), arising from coincidence of three geodesics. The t<SUB>c</SUB> singularity, a signal of the black hole singularity, occurs on a secondary sheet of the analytically continued correlator. Its properties are computationally accessible. The t<SUB>c</SUB> singularity persists to all orders in the 1/m expansion, for finite alpha', and to all orders in g<SUB>s</SUB>. Certain leading nonperturbative effects can also be studied. The behavior of these boundary theory quantities near t<SUB>c</SUB> gives, in principle, significant information about stringy and quantum behavior in the vicinity of the black hole singularity.

[]

https://arxiv.org/pdf/hep-th/0306170.pdf

1997PhRvL..78..417D

Universality of Low Energy Absorption Cross Sections for Black Holes

1997-01-01

['-', '-']

[]

In this paper we compute the low energy absorption cross section for minimally coupled massles scalars and spin- 1/2 particles into a general spherically symmetric black hole in arbitrary dimensions. The scalars have a cross section equal to the area of the black hole, while the spin- 1/2 particles give the area measured in a flat spatial metric conformally related to the true metric.

[]

https://arxiv.org/pdf/hep-th/9609052.pdf

2006A&A...455..173P

On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies

2006-01-01

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

[]

We investigate the relation between X-ray nuclear emission, optical emission line luminosities and black hole masses for a sample of 47 Seyfert galaxies. The sample, which has been selected from the Palomar optical spectroscopic survey of nearby galaxies (Ho et al. 1997a, ApJS, 112, 315), covers a wide range of nuclear powers, from L<SUB>2-10 keV</SUB> ~ 10<SUP>43</SUP> erg/s down to very low luminosities (L<SUB>2-10 keV</SUB> ~ 10<SUP>38</SUP> erg/s). Best available data from Chandra, XMM-Newton and, in a few cases, ASCA observations have been considered. Thanks to the good spatial resolution available from these observations and a proper modeling of the various spectral components, it has been possible to obtain accurate nuclear X-ray luminosities not contaminated by off-nuclear sources and/or diffuse emission. X-ray luminosities have then been corrected taking into account the likely candidate Compton thick sources, which are a high fraction (&gt;30%) among type 2 Seyferts in our sample. The main result of this study is that we confirm strong linear correlations between 2-10 keV, [OIII]λ5007, Hα luminosities which show the same slope as quasars and luminous Seyfert galaxies, independent of the level of nuclear activity displayed. Moreover, despite the wide range of Eddington ratios (L/L_Edd) tested here (six orders of magnitude, from 0.1 down to ~10<SUP>-7</SUP>), no correlation is found between the X-ray or optical emission line luminosities and the black hole mass. Our results suggest that Seyfert nuclei in our sample are consistent with being a scaled-down version of more luminous AGN.

[]

https://arxiv.org/pdf/astro-ph/0605236.pdf

2012Natur.481...51G

A gas cloud on its way towards the supermassive black hole at the Galactic Centre

2012-01-01

['-']

[]

Measurements of stellar orbits provide compelling evidence that the compact radio source Sagittarius A* at the Galactic Centre is a black hole four million times the mass of the Sun. With the exception of modest X-ray and infrared flares, Sgr A* is surprisingly faint, suggesting that the accretion rate and radiation efficiency near the event horizon are currently very low. Here we report the presence of a dense gas cloud approximately three times the mass of Earth that is falling into the accretion zone of Sgr A*. Our observations tightly constrain the cloud's orbit to be highly eccentric, with an innermost radius of approach of only ~3,100 times the event horizon that will be reached in 2013. Over the past three years the cloud has begun to disrupt, probably mainly through tidal shearing arising from the black hole's gravitational force. The cloud's dynamic evolution and radiation in the next few years will probe the properties of the accretion flow and the feeding processes of the supermassive black hole. The kilo-electronvolt X-ray emission of Sgr A* may brighten significantly when the cloud reaches pericentre. There may also be a giant radiation flare several years from now if the cloud breaks up and its fragments feed gas into the central accretion zone.

[]

https://arxiv.org/pdf/1112.3264.pdf

1994PhRvD..50.4853C

Black hole relics and inflation: Limits on blue perturbation spectra

1994-01-01

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

[]

Blue primordial power spectra have spectral index n&gt;1 and arise naturally in the recently proposed hybrid inflationary scenario. An observational upper limit on n is derived by normalizing the spectrum at the quadrupole scale and considering the possible overproduction of Planck mass relics formed in the final stage of primordial black hole evaporation. In the inflationary Universe with the maximum reheating temperature compatible with the observed quadrupole anisotropy, the upper limit is n=1.4, but it is slightly weaker for lower reheat temperatures. This limit applies over 57 decades of mass and is therefore insensitive to cosmic variance and any gravitational wave contribution to the quadrupole anisotropy. It is also independent of the dark matter content of the Universe and therefore the bias parameter. In some circumstances, there may be an extended dustlike phase between the end of inflation and reheating. In this case, primordial black holes form more abundantly and the upper limit is n=1.3.

[]

https://arxiv.org/pdf/astro-ph/9405027.pdf

2012Entrp..14.1717D

Black Holes, Cosmological Solutions, Future Singularities, and Their Thermodynamical Properties in Modified Gravity Theories

2012-01-01

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

[]

Along this review, we focus on the study of several properties of modified gravity theories, in particular on black-hole solutions and its comparison with those solutions in General Relativity, and on Friedmann-Lemaître-Robertson-Walker metrics. The thermodynamical properties of fourth order gravity theories are also a subject of this investigation with special attention on local and global stability of paradigmatic f ( R ) models. In addition, we revise some attempts to extend the Cardy-Verlinde formula, including modified gravity, where a relation between entropy bounds is obtained. Moreover, a deep study on cosmological singularities, which appear as a real possibility for some kind of modified gravity theories, is performed, and the validity of the entropy bounds is studied.

[]

https://arxiv.org/pdf/1207.2663.pdf

1997PhRvD..56.3600B

Thermodynamics of (3+1)-dimensional black holes with toroidal or higher genus horizons

1997-01-01

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

[]

We examine counterparts of the Reissner-Nordström-anti-de Sitter black hole spacetimes in which the two-sphere has been replaced by a surface Σ of constant negative or zero curvature. When horizons exist, the spacetimes are black holes with an asymptotically locally anti-de Sitter infinity, but the infinity topology differs from that in the asymptotically Minkowski case, and the horizon topology is not S<SUP>2</SUP>. Maximal analytic extensions of the solutions are given. The local Hawking temperature is found. When Σ is closed, we derive the first law of thermodynamics using a Brown-York-type quasilocal energy at a finite boundary, and we identify the entropy as one-quarter of the horizon area, independent of the horizon topology. The heat capacities with constant charge and constant electrostatic potential are shown to be positive definite. With the boundary pushed to infinity, we consider thermodynamical ensembles that fix the renormalized temperature and either the charge or the electrostatic potential at infinity. Both ensembles turn out to be thermodynamically stable, and dominated by a unique classical solution.

[]

https://arxiv.org/pdf/gr-qc/9705012.pdf

2012MNRAS.425..460M

Intermediate mass black holes in AGN discs - I. Production and growth

2012-01-01

['accretion disks', '-', '-', 'stars binaries close', 'galaxies active', 'galaxies nuclei', '-', '-']

[]

Here we propose a mechanism for efficiently growing intermediate mass black holes (IMBH) in discs around supermassive black holes. Stellar mass objects can efficiently agglomerate when facilitated by the gas disc. Stars, compact objects and binaries can migrate, accrete and merge within discs around supermassive black holes. While dynamical heating by cusp stars excites the velocity dispersion of nuclear cluster objects (NCOs) in the disc, gas in the disc damps NCO orbits. If gas damping dominates, NCOs remain in the disc with circularized orbits and large collision cross-sections. IMBH seeds can grow extremely rapidly by collisions with disc NCOs at low relative velocities, allowing for super-Eddington growth rates. Once an IMBH seed has cleared out its feeding zone of disc NCOs, growth of IMBH seeds can become dominated by gas accretion from the active galactic nucleus (AGN) disc. However, the IMBH can migrate in the disc and expand its feeding zone, permitting a super-Eddington accretion rate to continue. Growth of IMBH seeds via NCO collisions is enhanced by a pile-up of migrators. <P />We highlight the remarkable parallel between the growth of IMBH in AGN discs with models of giant planet growth in protoplanetary discs. If an IMBH becomes massive enough it can open a gap in the AGN disc. IMBH migration in AGN discs may stall, allowing them to survive the end of the AGN phase and remain in galactic nuclei. Our proposed mechanisms should be more efficient at growing IMBH in AGN discs than the standard model of IMBH growth in stellar clusters. Dynamical heating of disc NCOs by cusp stars is transferred to the gas in an AGN disc helping to maintain the outer disc against gravitational instability. Model predictions, observational constraints and implications are discussed in a companion paper (Paper II).

[]

https://arxiv.org/pdf/1206.2309.pdf

2001PhRvL..88b1303F

Black Hole Production by Cosmic Rays

2001-01-01

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

[]

Ultrahigh energy cosmic rays create black holes in scenarios with extra dimensions and TeV-scale gravity. In particular, cosmic neutrinos will produce black holes deep in the atmosphere, initiating quasihorizontal showers far above the standard model rate. At the Auger Observatory, hundreds of black hole events may be observed, providing evidence for extra dimensions and the first opportunity for experimental study of microscopic black holes. If no black holes are found, the fundamental Planck scale must be above 2 TeV for any number of extra dimensions.

[]

https://arxiv.org/pdf/hep-ph/0109106.pdf

2019PhRvR...1c3015V

Surrogate models for precessing binary black hole simulations with unequal masses

2019-01-01

['-', '-']

[]

Only numerical relativity simulations can capture the full complexities of binary black hole mergers. These simulations, however, are prohibitively expensive for direct data analysis applications such as parameter estimation. We present two fast and accurate surrogate models for the outputs of these simulations: the first model, NRSur7dq4, predicts the gravitational waveform and the second model, NRSur7dq4Remnant, predicts the properties of the remnant black hole. These models extend previous seven-dimensional, noneccentric precessing models to higher mass ratios and have been trained against 1528 simulations with mass ratios q ≤4 and spin magnitudes χ<SUB>1</SUB>,χ<SUB>2</SUB>≤0.8 , with generic spin directions. The waveform model, NRSur7dq4, which begins about 20 orbits before merger, includes all ℓ ≤4 spin-weighted spherical harmonic modes, as well as the precession frame dynamics and spin evolution of the black holes. The final black hole model, NRSur7dq4Remnant, models the mass, spin, and recoil kick velocity of the remnant black hole. In their training parameter range, both models are shown to be more accurate than existing models by at least an order of magnitude, with errors comparable to the estimated errors in the numerical relativity simulations. We also show that the surrogate models work well even when extrapolated outside their training parameter space range, up to mass ratios q =6 .

[]

https://arxiv.org/pdf/1905.09300.pdf

2004JHEP...02..008H

The black hole final state

2004-01-01

['black hole physics', '-']

[]

We propose that in quantum gravity one needs to impose a final state boundary condition at black hole singularities. This resolves the apparent contradiction between string theory and semiclassical arguments over whether black hole evaporation is unitary.

[]

https://arxiv.org/pdf/hep-th/0310281.pdf

2004ApJ...610..722G

Active Galactic Nuclei with Candidate Intermediate-Mass Black Holes

2004-01-01

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

[]

We present an initial sample of 19 intermediate-mass black hole candidates in active galactic nuclei culled from the first data release of the Sloan Digital Sky Survey. Using the line width-luminosity mass scaling relation established for broad-line active nuclei, we estimate black hole masses in the range of M<SUB>BH</SUB>~8×(10<SUP>4</SUP>-10<SUP>6</SUP>)M<SUB>solar</SUB>, a regime in which only two objects are currently known. The absolute magnitudes are faint for active galactic nuclei, ranging from M<SUB>g</SUB>~-15 to -18 mag, while the bolometric luminosities are all close to the Eddington limit. The entire sample formally satisfies the line width criterion for so-called narrow-line Seyfert 1 galaxies; however, they display a wider range of Fe II and [O III] λ5007 line strengths than is typically observed in this class of objects. Although the available imaging data are of insufficient quality to ascertain the detailed morphologies of the host galaxies, it is likely that the majority of the hosts are relatively late-type systems. The host galaxies have estimated g-band luminosities ~1 mag fainter than M<SUP>*</SUP> for the general galaxy population at z~0.1. Beyond simply extending the known mass range of central black holes in galactic nuclei, these objects provide unique observational constraints on the progenitors of supermassive black holes. They are also expected to contribute significantly to the integrated signal for future gravitational wave experiments.

[]

https://arxiv.org/pdf/astro-ph/0404110.pdf

2008PhRvL.100n1301M

Physical Interpretation of the Spectrum of Black Hole Quasinormal Modes

2008-01-01

['-', '-', '-', '-', 'quantum theory', '-', '-', '-']

[]

When a classical black hole is perturbed, its relaxation is governed by a set of quasinormal modes with complex frequencies ω=ω<SUB>R</SUB>+iω<SUB>I</SUB>. We show that this behavior is the same as that of damped harmonic oscillators whose real frequencies are (ω<SUB>R</SUB><SUP>2</SUP>+ω<SUB>I</SUB><SUP>2</SUP>)<SUP>1/2</SUP>, rather than simply ω<SUB>R</SUB>. Since, for highly excited modes, ω<SUB>I</SUB>≫ω<SUB>R</SUB>, this observation changes drastically the physical understanding of the black hole spectrum and forces a reexamination of various results in the literature. In particular, adapting a derivation by Hod, we find that the area of the horizon of a Schwarzschild black hole is quantized in units ΔA=8πl<SUB>Pl</SUB><SUP>2</SUP>, in contrast with the original result ΔA=4log⁡(3)l<SUB>Pl</SUB><SUP>2</SUP>.

[]

https://arxiv.org/pdf/0711.3145.pdf

2004PThPh.111...29K

Master Equations for Perturbations of Generalized Static Black Holes with Charge in Higher Dimensions

2004-01-01

['-', '-']

[]

We extend the formulation for perturbations of maximally symmetric black holes in higher dimensions developed by the present authors in a previous paper to a charged black hole background whose horizon is described by an Einstein manifold. For charged black holes, perturbations of electromagnetic fields are coupled to the vector and scalar modes of metric perturbations non-trivially. We show that by taking appropriate combinations of gauge-invariant variables for these perturbations, the perturbation equations for the Einstein-Maxwell system are reduced to two decoupled second-order wave equations describing the behaviour of the electromagnetic mode and the gravitational mode, for any value of the cosmologiconstant. These wave equations are transformed into Schrödinger-type ODEs through a Fourier transformation with respect to time. Using these equations, we investigate the stability of generalised black holes with charge. We also give explicit expressions for the source terms of these master equations with application to the emission problem of gravitational waves in mind.

[]

https://arxiv.org/pdf/hep-th/0308128.pdf

2005LRR.....8....8M

Massive Black Hole Binary Evolution

2005-01-01

['astrophysics']

[]

Coalescence of binary supermassive black holes (SBHs) would constitute the strongest sources of gravitational waves to be observed by LISA. While the formation of binary SBHs during galaxy mergers is almost inevitable, coalescence requires that the separation between binary components first drop by a few orders of magnitude, due presumably to interaction of the binary with stars and gas in a galactic nucleus. This article reviews the observational evidence for binary SBHs and discusses how they would evolve. No completely convincing case of a bound, binary SBH has yet been found, although a handful of systems (e.g. interacting galaxies; remnants of galaxy mergers) are now believed to contain two SBHs at projected separations of &lt;~ 1kpc. N-body studies of binary evolution in gas-free galaxies have reached large enough particle numbers to reproduce the slow, "diffusive" refilling of the binary's loss cone that is believed to characterize binary evolution in real galactic nuclei. While some of the results of these simulations - e.g. the binary hardening rate and eccentricity evolution - are strongly N-dependent, others - e.g. the "damage" inflicted by the binary on the nucleus - are not. Luminous early-type galaxies often exhibit depleted cores with masses of ~ 1-2 times the mass of their nuclear SBHs, consistent with the predictions of the binary model. Studies of the interaction of massive binaries with gas are still in their infancy, although much progress is expected in the near future. Binary coalescence has a large influence on the spins of SBHs, even for mass ratios as extreme as 10:1, and evidence of spin-flips may have been observed.

[]

https://arxiv.org/pdf/astro-ph/0410364.pdf

2017JHEP...05..161H

Superrotation charge and supertranslation hair on black holes

2017-01-01

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

[]

It is shown that black hole spacetimes in classical Einstein gravity are characterized by, in addition to their ADM mass M, momentum \overrightarrow{P} , angular momentum \overrightarrow{J} and boost charge \overrightarrow{K} , an infinite head of supertranslation hair. The distinct black holes are distinguished by classical superrotation charges measured at infinity. Solutions with super-translation hair are diffeomorphic to the Schwarzschild spacetime, but the diffeomorphisms are part of the BMS subgroup and act nontrivially on the physical phase space. It is shown that a black hole can be supertranslated by throwing in an asymmetric shock wave. A leading-order Bondi-gauge expression is derived for the linearized horizon supertranslation charge and shown to generate, via the Dirac bracket, supertranslations on the linearized phase space of gravitational excitations of the horizon. The considerations of this paper are largely classical augmented by comments on their implications for the quantum theory.

[]

https://arxiv.org/pdf/1611.09175.pdf

2018PhRvL.120o1101R

Post-Newtonian Dynamics in Dense Star Clusters: Highly Eccentric, Highly Spinning, and Repeated Binary Black Hole Mergers

2018-01-01

['-', '-']

[]

We present models of realistic globular clusters with post-Newtonian dynamics for black holes. By modeling the relativistic accelerations and gravitational-wave emission in isolated binaries and during three- and four-body encounters, we find that nearly half of all binary black hole mergers occur inside the cluster, with about 10% of those mergers entering the LIGO/Virgo band with eccentricities greater than 0.1. In-cluster mergers lead to the birth of a second generation of black holes with larger masses and high spins, which, depending on the black hole natal spins, can sometimes be retained in the cluster and merge again. As a result, globular clusters can produce merging binaries with detectable spins regardless of the birth spins of black holes formed from massive stars. These second-generation black holes would also populate any upper mass gap created by pair-instability supernovae.

[]

https://arxiv.org/pdf/1712.04937.pdf

2010ApJ...712.1129M

The Quasar Accretion Disk Size-Black Hole Mass Relation

2010-01-01

['accretion', 'accretion disks', 'cosmology dark matter', 'gravitational lensing', 'gravitational lensing', 'galaxies quasars', '-']

[]

We use the microlensing variability observed for 11 gravitationally lensed quasars to show that the accretion disk size at a rest-frame wavelength of 2500 Å is related to the black hole mass by log(R <SUB>2500</SUB>/cm) = (15.78 ± 0.12) + (0.80 ± 0.17)log(M <SUB>BH</SUB>/10<SUP>9</SUP> M <SUB>sun</SUB>). This scaling is consistent with the expectation from thin-disk theory (R vprop M <SUP>2/3</SUP> <SUB>BH</SUB>), but when interpreted in terms of the standard thin-disk model (T vprop R <SUP>-3/4</SUP>), it implies that black holes radiate with very low efficiency, log(η) = -1.77 ± 0.29 + log(L/L <SUB>E</SUB>), where η =L/(\dot{M}c^2). Only by making the maximum reasonable shifts in the average inclination, Eddington factors, and black hole masses can we raise the efficiency estimate to be marginally consistent with typical efficiency estimates (η ≈ 10%). With one exception, these sizes are larger by a factor of ~4 than the size needed to produce the observed 0.8 μm quasar flux by thermal radiation from a thin disk with the same T vprop R <SUP>-3/4</SUP> temperature profile. While scattering a significant fraction of the disk emission on large scales or including a large fraction of contaminating line emission can reduce the size discrepancy, resolving it also appears to require that accretion disks have flatter temperature/surface brightness profiles. <P />Based on observations obtained with the Small and Moderate Aperture Research Telescope System (SMARTS) 1.3 m, which is operated by the SMARTS Consortium, the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium, the WIYN Observatory which is owned and operated by the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories (NOAO), the 6.5 m Magellan Baade telescope, which is a collaboration between the observatories of the Carnegie Institution of Washington (OCIW), University of Arizona, Harvard University, University of Michigan, and Massachusetts Institute of Technology, and observations made with the NASA/ESA Hubble Space Telescope for program HST-GO-9744 of the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

[]

https://arxiv.org/pdf/1002.4160.pdf

2001ApJ...555L..79F

Supermassive Black Holes in Active Galactic Nuclei. I. The Consistency of Black Hole Masses in Quiescent and Active Galaxies

2001-01-01

['galaxies active', 'galaxies seyfert', 'astrophysics']

[]

We report the first results of a program to measure accurate stellar velocity dispersions in the bulges of the host galaxies of active galactic nuclei for which accurate black hole (BH) masses have been determined via reverberation mapping. We find good agreement between BH masses obtained from reverberation mapping and from the M<SUB>•</SUB>-σ relation as defined by quiescent galaxies, indicating a common relationship between active and quiescent black holes and their larger scale environments.

[]

https://arxiv.org/pdf/astro-ph/0104380.pdf

2013PhRvL.111x1104M

Catalog of 174 Binary Black Hole Simulations for Gravitational Wave Astronomy

2013-01-01

['-', '-', '-', 'methods numerical', '-', 'perturbation theory', '-', '-', '-']

[]

This Letter presents a publicly available catalog of 174 numerical binary black hole simulations following up to 35 orbits. The catalog includes 91 precessing binaries, mass ratios up to 8∶1, orbital eccentricities from a few percent to 10<SUP>-5</SUP>, black hole spins up to 98% of the theoretical maximum, and radiated energies up to 11.1% of the initial mass. We establish remarkably good agreement with post-Newtonian precession of orbital and spin directions for two new precessing simulations, and we discuss other applications of this catalog. Formidable challenges remain: e.g., precession complicates the connection of numerical and approximate analytical waveforms, and vast regions of the parameter space remain unexplored.

[]

https://arxiv.org/pdf/1304.6077.pdf

2020ApJ...897L..14Y

Pōniuā'ena: A Luminous z = 7.5 Quasar Hosting a 1.5 Billion Solar Mass Black Hole

2020-01-01

['cosmology early universe', '-', 'galaxies intergalactic medium', 'galaxies quasars', '-', 'galaxies quasars', '-', '-', '-', '-', '-', '-', '-']

[]

We report the discovery of a luminous quasar, J1007+2115 at z = 7.515 ("Pōniuā'ena"), from our wide-field reionization-era quasar survey. J1007+2115 is the second quasar now known at z &gt; 7.5, deep into the reionization epoch. The quasar is powered by a (1.5 ± 0.2) × 10<SUP>9</SUP> M<SUB>⊙</SUB> supermassive black hole (SMBH), based on its broad Mg II emission-line profile from Gemini and Keck near-IR spectroscopy. The SMBH in J1007+2115 is twice as massive as that in quasar J1342+0928 at z = 7.54, the current quasar redshift record holder. The existence of such a massive SMBH just 700 million years after the Big Bang significantly challenges models of the earliest SMBH growth. Model assumptions of Eddington-limited accretion and a radiative efficiency of 0.1 require a seed black hole of ≳10<SUP>4</SUP> M<SUB>⊙</SUB> at z = 30. This requirement suggests either a massive black hole seed as a result of direct collapse or earlier periods of rapid black hole growth with hyper-Eddington accretion and/or a low radiative efficiency. We measure the damping wing signature imprinted by neutral hydrogen absorption in the intergalactic medium (IGM) on J1007+2115's Lyα line profile, and find that it is weaker than that of J1342+0928 and two other z ≳ 7 quasars. We estimate an IGM volume-averaged neutral fraction $\langle {X}_{{\rm{H}}{\rm{I}}}\rangle ={0.39}_{-0.13}^{+0.22}$ . This range of values suggests a patchy reionization history toward different IGM sightlines. We detect the 158 μm [C II] emission line in J1007+2115 with the Atacama Large Millimeter/submillimeter Array; this line centroid yields a systemic redshift of z = 7.5149 ± 0.0004 and indicates a star formation rate of ∼210 M<SUB>⊙</SUB> yr<SUP>-1</SUP> in its host galaxy.

[]

https://arxiv.org/pdf/2006.13452.pdf

2015PhR...603....1C

Black hole remnants and the information loss paradox

2015-01-01

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

[]

Forty years after the discovery of Hawking radiation, its exact nature remains elusive. If Hawking radiation does not carry any information out from the ever shrinking black hole, it seems that unitarity is violated once the black hole completely evaporates. On the other hand, attempts to recover information via quantum entanglement lead to the firewall controversy. Amid the confusions, the possibility that black hole evaporation stops with a "remnant" has remained unpopular and is often dismissed due to some "undesired properties" of such an object. Nevertheless, as in any scientific debate, the pros and cons of any proposal must be carefully scrutinized. We fill in the void of the literature by providing a timely review of various types of black hole remnants, and provide some new thoughts regarding the challenges that black hole remnants face in the context of the information loss paradox and its latest incarnation, namely the firewall controversy. The importance of understanding the role of curvature singularity is also emphasized, after all there remains a possibility that the singularity cannot be cured even by quantum gravity. In this context a black hole remnant conveniently serves as a cosmic censor. We conclude that a remnant remains a possible end state of Hawking evaporation, and if it contains large interior geometry, may help to ameliorate the information loss paradox and the firewall controversy. We hope that this will raise some interests in the community to investigate remnants more critically but also more thoroughly.

[]

https://arxiv.org/pdf/1412.8366.pdf

2020PhRvL.124y1102G

Candidate Electromagnetic Counterpart to the Binary Black Hole Merger Gravitational-Wave Event S190521g<SUP>*</SUP>

2020-01-01

['-', '-']

[]

We report the first plausible optical electromagnetic counterpart to a (candidate) binary black hole merger. Detected by the Zwicky Transient Facility, the electromagnetic flare is consistent with expectations for a kicked binary black hole merger in the accretion disk of an active galactic nucleus [B. McKernan, K. E. S. Ford, I. Bartos et al., Astrophys. J. Lett. 884, L50 (2019), 10.3847/2041-8213/ab4886] and is unlikely [&lt;O (0.01 %) )] due to intrinsic variability of this source. The lack of color evolution implies that it is not a supernova and instead is strongly suggestive of a constant temperature shock. Other false-positive events, such as microlensing or a tidal disruption event, are ruled out or constrained to be &lt;O (0.1 %) . If the flare is associated with S190521g, we find plausible values of total mass M<SUB>BBH</SUB>∼100 M<SUB>⊙</SUB>, kick velocity v<SUB>k</SUB>∼200 km s<SUP>-1</SUP> at θ ∼6 0 ° in a disk with aspect ratio H /a ∼0.01 (i.e., disk height H at radius a ) and gas density ρ ∼10<SUP>-10</SUP> g cm<SUP>-3</SUP> . The merger could have occurred at a disk migration trap (a ∼700 r<SUB>g</SUB>; r<SUB>g</SUB>≡G M<SUB>SMBH</SUB>/c<SUP>2</SUP>, where M<SUB>SMBH</SUB> is the mass of the active galactic nucleus supermassive black hole). The combination of parameters implies a significant spin for at least one of the black holes in S190521g. The timing of our spectroscopy prevents useful constraints on broad-line asymmetry due to an off-center flare. We predict a repeat flare in this source due to a reencountering with the disk in ∼1.6 yr (M<SUB>SMBH</SUB>/10<SUP>8</SUP> M<SUB>⊙</SUB>)(a /10<SUP>3</SUP>r<SUB>g</SUB>)<SUP>3 /2</SUP> .

[]

https://arxiv.org/pdf/2006.14122.pdf

2009PhRvD..79h4043Y

Dynamical Chern-Simons modified gravity: Spinning black holes in the slow-rotation approximation

2009-01-01

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

[]

The low-energy limit of string theory contains an anomaly-canceling correction to the Einstein-Hilbert action, which defines an effective theory: Chern-Simons (CS) modified gravity. The CS correction consists of the product of a scalar field with the Pontryagin density, where the former can be treated as a background field (nondynamical formulation) or as an evolving field (dynamical formulation). Many solutions of general relativity persist in the modified theory; a notable exception is the Kerr metric, which has sparked a search for rotating black hole solutions. Here, for the first time, we find a solution describing a rotating black hole within the dynamical framework, and in the small-coupling/slow-rotation limit. The solution is axisymmetric and stationary, constituting a deformation of the Kerr metric with dipole scalar “hair,” whose effect on geodesic motion is to weaken the frame-dragging effect and shift the location of the innermost stable circular orbit outwards (inwards) relative to Kerr for corotating (counterrotating) geodesics. We further show that the correction to the metric scales inversely with the fourth power of the radial distance to the black hole, suggesting it will escape any meaningful bounds from weak-field experiments. For example, using binary pulsar data we can only place an initial bound on the magnitude of the dynamical coupling constant of ξ<SUP>1/4</SUP>≲10<SUP>4</SUP>km. More stringent bounds will require observations of inherently strong-field phenomena.

[]

https://arxiv.org/pdf/0902.4669.pdf

2008PhRvD..78h6007G

Mimicking the QCD equation of state with a dual black hole

2008-01-01

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

[]

We present numerical and analytical studies of the equation of state of translationally invariant black hole solutions to five-dimensional gravity coupled to a single scalar. As an application, we construct a family of black holes that closely mimics the equation of state of quantum chromodynamics at zero chemical potential.

[]

https://arxiv.org/pdf/0804.0434.pdf

2004MNRAS.354..355J

The distances to Galactic low-mass X-ray binaries: consequences for black hole luminosities and kicks

2004-01-01

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

[]

We investigated the reported distances of Galactic black hole (BH) and neutron star low-mass X-ray binaries (LMXBs). Comparing the distances derived for the neutron stars Cyg X-2 and XTE J2123-058 using the observed Eddington limited photospheric radius expansion bursts with the distances derived using the observed radius and effective temperature of the companion star, we find that the latter are smaller by approximately a factor of 1.5-2. The latter method is often employed to determine the distance to BH LMXBs. A possible explanation for this discrepancy is that the stellar absorption lines in fast rotating companion stars are different from those in the slowly rotating template stars as was found before for early-type stars. This could lead to a systematic mis-classification of the spectral type of the companion star, which in turn would yield a systematic error in the distance. Further, we derive a distance of 4.0<SUP>+2.0</SUP><SUB>-1.2</SUB> kpc for V404 Cyg, using parameters available in the literature. The interstellar extinction seems to have been overestimated for XTE J1550-564 and possibly for two other BH sources (H 1705-25 and GS 2000+25) as well. As a result of this, the distance to XTE J1550-564 may have been underestimated by as much as a factor three. We find that, using the new distances for XTE J1550-564 and V404 Cyg, the maximum outburst luminosity for at least five, but perhaps even seven, of the 15 BH soft X-ray transients exceed the Eddington luminosity for a 10-M<SUB>solar</SUB> BH - showing that these systems would be classified as ultra-luminous X-ray sources had we observed them in other Galaxies. This renders support for the idea that many ultra-luminous X-ray sources are stellar-mass rather than intermediate-mass BHs. We find that the rms-value of the distance to the Galactic plane for BHs is consistent with that of neutron star LMXBs. This suggests that BHs could also receive a kick-velocity during their formation, although this has to be investigated in more detail. We find that the Galactic neutron star and BH l- and b-distributions are consistent with being the same. The neutron star and BH distribution is asymmetric in l with an excess of systems between -30° &lt; l &lt; 0° over systems with 0° &lt; l &lt; 30°.

[]

https://arxiv.org/pdf/astro-ph/0407168.pdf

2015Natur.518...74G

A possible close supermassive black-hole binary in a quasar with optical periodicity

2015-01-01

['-', '-']

[]

Quasars have long been known to be variable sources at all wavelengths. Their optical variability is stochastic and can be due to a variety of physical mechanisms; it is also well-described statistically in terms of a damped random walk model. The recent availability of large collections of astronomical time series of flux measurements (light curves) offers new data sets for a systematic exploration of quasar variability. Here we report the detection of a strong, smooth periodic signal in the optical variability of the quasar PG 1302-102 with a mean observed period of 1,884 +/- 88 days. It was identified in a search for periodic variability in a data set of light curves for 247,000 known, spectroscopically confirmed quasars with a temporal baseline of about 9 years. Although the interpretation of this phenomenon is still uncertain, the most plausible mechanisms involve a binary system of two supermassive black holes with a subparsec separation. Such systems are an expected consequence of galaxy mergers and can provide important constraints on models of galaxy formation and evolution.

[]

https://arxiv.org/pdf/1501.01375.pdf

2003MNRAS.341..385P

On the formation and evolution of black hole binaries

2003-01-01

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

[]

We present the results of a systematic study of the formation and evolution of binaries containing black holes and normal-star companions with a wide range of masses. We first reexamine the standard formation scenario for close black hole binaries, where the progenitor system, a binary with at least one massive component, experienced a common-envelope phase and where the spiral-in of the companion in the envelope of the massive star caused the ejection of the envelope. We estimate the formation rates for different companion masses and different assumptions about the common-envelope structure and other model parameters. We find that black hole binaries with intermediate- and high-mass secondaries can form for a wide range of assumptions, while black hole binaries with low-mass secondaries can only form with apparently unrealistic assumptions (in agreement with previous studies). <P />We then present detailed binary evolution sequences for black hole binaries with secondaries of 2 to 17 M<SUB>solar</SUB> and demonstrate that in these systems the black hole can accrete appreciably even if accretion is Eddington-limited (up to 7 M<SUB>solar</SUB> for an initial black hole mass of 10 M<SUB>solar</SUB>) and that the black holes can be spun up significantly in the process. We discuss the implications of these calculations for well-studied black hole binaries (in particular GRS 1915+105) and ultraluminous X-ray sources of which GRS 1915+105 appears to represent a typical Galactic counterpart. We also present a detailed evolutionary model for Cygnus X-1, a massive black hole binary, which suggests that at present the system is most likely in a wind mass-transfer phase following an earlier Roche-lobe overflow phase. Finally, we discuss how some of the assumptions in the standard model could be relaxed to allow the formation of low-mass, short-period black hole binaries, which appear to be very abundant in nature.

[]

https://arxiv.org/pdf/astro-ph/0207153.pdf

2016ApJS..222...15T

WATCHDOG: A Comprehensive All-sky Database of Galactic Black Hole X-ray Binaries

2016-01-01

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

[]

With the advent of more sensitive all-sky instruments, the transient universe is being probed in greater depth than ever before. Taking advantage of available resources, we have established a comprehensive database of black hole (and black hole candidate) X-ray binary (BHXB) activity between 1996 and 2015 as revealed by all-sky instruments, scanning surveys, and select narrow-field X-ray instruments on board the INTErnational Gamma-Ray Astrophysics Laboratory, Monitor of All-Sky X-ray Image, Rossi X-ray Timing Explorer, and Swift telescopes; the Whole-sky Alberta Time-resolved Comprehensive black-Hole Database Of the Galaxy or WATCHDOG. Over the past two decades, we have detected 132 transient outbursts, tracked and classified behavior occurring in 47 transient and 10 persistently accreting BHs, and performed a statistical study on a number of outburst properties across the Galactic population. We find that outbursts undergone by BHXBs that do not reach the thermally dominant accretion state make up a substantial fraction (∼40%) of the Galactic transient BHXB outburst sample over the past ∼20 years. Our findings suggest that this “hard-only” behavior, observed in transient and persistently accreting BHXBs, is neither a rare nor recent phenomenon and may be indicative of an underlying physical process, relatively common among binary BHs, involving the mass-transfer rate onto the BH remaining at a low level rather than increasing as the outburst evolves. We discuss how the larger number of these “hard-only” outbursts and detected outbursts in general have significant implications for both the luminosity function and mass-transfer history of the Galactic BHXB population.

[]

https://arxiv.org/pdf/1512.00778.pdf

1995PhR...260..329B

A primer for black hole quantum physics.

1995-01-01

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

[]

The mechanisms which give rise to Hawking radiation are revealed by analyzing in detail pair production in the presence of horizons. In preparation for the black hole problem, three preparatory problems are dwelt with at length: pair production in an external electric field, thermalization of a uniformly accelerated detector and accelerated mirrors. In the light of these examples, the black hole evaporation problem is then presented. The leitmotif is the singular behavior of modes on the horizon which gives rise to a steady rate of production. Special emphasis is put on how each produced particle contributes to the mean albeit arising from a particular vacuum fluctuation. It is the mean which drives the semiclassical back reaction. This aspect is analyzed in more detail than heretofore and in particular its drawbacks are emphasized. It is the semiclassical theory which gives rise to Hawking's famous equation for the loss of mass of the black hole due to evaporation dM/dt ≅ -1/M<SUP>2</SUP>. Black hole thermodynamics is derived from the evaporation process whereupon the reservoir character of the black hole is manifest. The relation to the thermodynamics of the eternal black hole through the Hartle-Hawking vacuum and the Killing identity are displayed. It is through the analysis of the fluctuations of the field configurations which give rise to a particular Hawking photon that the dubious character of the semiclassical theory is manifest. The present frontier of research revolves around this problem and is principally concerned with the fact that one calls upon energy scales that are greater than Planckian and the possibility of a non unitary evolution as well. These last subjects are presented in qualitative fashion only, so that this review stops at the threshold of quantum gravity.

[]

https://arxiv.org/pdf/0710.4345.pdf

2010JHEP...08..078G

Holography of charged dilaton black holes

2010-01-01

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

[]

We study charged dilaton black branes in AdS <SUB>4</SUB>. Our system involves a dilaton ϕ coupled to a Maxwell field F <SUB> μν </SUB> with dilaton-dependent gauge coupling, 1/{{g^2}} = {f^2}left( φ right) . First, we find the solutions for extremal and near extremal branes through a combination of analytical and numerical techniques. The near horizon geometries in the simplest cases, where f( ϕ) = e <SUP> αϕ </SUP>, are Lifshitz-like, with a dynamical exponent z determined by α. The black hole thermodynamics varies in an interesting way with α, but in all cases the entropy is vanishing and the specific heat is positive for the near extremal solutions. We then compute conductivity in these backgrounds. We find that somewhat surprisingly, the AC conductivity vanishes like ω <SUP>2</SUP> at T = 0 independent of α. We also explore the charged black brane physics of several other classes of gauge-coupling functions f( ϕ). In addition to possible applications in AdS/CMT, the extremal black branes are of interest from the point of view of the attractor mechanism. The near horizon geometries for these branes are universal, independent of the asymptotic values of the moduli, and describe generic classes of endpoints for attractor flows which are different from AdS <SUB>2</SUB> × R <SUP>2</SUP>.

[]

https://arxiv.org/pdf/0911.3586.pdf

2010PhRvD..82b4008C

Hidden conformal symmetry of the Kerr black hole

2010-01-01

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

[]

Extreme and very-near-extreme spin J Kerr black holes have been conjectured to be holographically dual to two-dimensional (2D) conformal field theories (CFTs) with left and right central charges c<SUB>L</SUB>=c<SUB>R</SUB>=12J. In this paper it is observed that the 2D conformal symmetry of the scalar wave equation at low frequencies persists for generic nonextreme values of the mass M≠J. Interestingly, this conformal symmetry is not derived from a conformal symmetry of the spacetime geometry except in the extreme limit. The 2π periodic identification of the azimuthal angle ϕ is shown to correspond to a spontaneous breaking of the conformal symmetry by left and right temperatures T<SUB>L</SUB>=M<SUP>2</SUP>/2πJ and T<SUB>R</SUB>=M<SUP>4</SUP>-J<SUP>2</SUP>/2πJ. The well-known low-frequency scalar-Kerr scattering amplitudes coincide with correlators of a 2D CFT at these temperatures. Moreover, the CFT microstate degeneracy inferred from the Cardy formula agrees exactly with the Bekenstein-Hawking area law for all M and J. These observations provide evidence for the conjecture that the Kerr black hole is dual to a c<SUB>L</SUB>=c<SUB>R</SUB>=12J 2D CFT at temperatures (T<SUB>L</SUB>,T<SUB>R</SUB>) for every value of M and J.

[]

https://arxiv.org/pdf/1004.0996.pdf

2004PhRvL..93q1102G

Rotating Black Holes in Higher Dimensions with a Cosmological Constant

2004-01-01

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

[]

We present the metric for a rotating black hole with a cosmological constant and with arbitrary angular momenta in all higher dimensions. The metric is given in both Kerr-Schild and the Boyer-Lindquist form. In the Euclidean-signature case, we also obtain smooth compact Einstein spaces on associated S<SUP>D-2</SUP> bundles over S<SUP>2</SUP>, infinitely many for each odd D≥5. Applications to string theory and M-theory are indicated.

[]

https://arxiv.org/pdf/hep-th/0409155.pdf

2003LRR.....6....6S

Analytic Black Hole Perturbation Approach to Gravitational Radiation

2003-01-01

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

[]

We review the analytic methods used to perform the post-Newtonian expansion of gravitational waves induced by a particle orbiting a massive, compact body, based on black hole perturbation theory. There exist two different methods of performing the post-Newtonian expansion. Both are based on the Teukolsky equation. In one method, the Teukolsky equation is transformed into a Regge-Wheeler type equation that reduces to the standard Klein Gordon equation in the flat-space limit, while in the other method (which was introduced by Mano, Suzuki, and Takasugi relatively recently, the Teukolsky equation is used directly in its original form. The former's advantage is that it is intuitively easy to understand how various curved space effects come into play. However, it becomes increasingly complicated when one goes to higher and higher post-Newtonian orders. In contrast, the latter's advantage is that a systematic calculation to higher post-Newtonian orders can be implemented relatively easily, but otherwise, it is so mathematical that it is hard to understand the interplay of higher order terms. In this paper, we review both methods so that their pros and cons may be seen clearly. We also review some results of calculations of gravitational radiation emitted by a particle orbiting a black hole.

[]

https://arxiv.org/pdf/gr-qc/0306120.pdf

2007ApJ...661L.147B

Alignment of the Spins of Supermassive Black Holes Prior to Coalescence

2007-01-01

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

[]

Recent numerical relativistic simulations of black hole coalescence suggest that in certain alignments the emission of gravitational radiation can produce a kick of several thousand kilometers per second. This exceeds galactic escape speeds; hence, unless there is a mechanism to prevent this, one would expect many galaxies that had merged to be without a central black hole. Here we show that in most galactic mergers, torques from accreting gas suffice to align the orbit and spins of both black holes with the large-scale gas flow. Such a configuration has a maximum kick speed &lt;200 km s<SUP>-1</SUP>, safely below galactic escape speeds. We predict, however, that in mergers of galaxies without much gas, the remnant will be kicked out several percent of the time. We also discuss other predictions of our scenario, including implications for jet alignment angles and X-type radio sources.

[]

https://arxiv.org/pdf/astro-ph/0703054.pdf

2016ApJ...832L...2R

Illuminating Black Hole Binary Formation Channels with Spins in Advanced LIGO

2016-01-01

['stars binaries general', 'gravitational waves', 'stars black holes', 'stars novae;cataclysmic variables', '-']

[]

The recent detections of the binary black hole mergers GW150914 and GW151226 have inaugurated the field of gravitational-wave astronomy. For the two main formation channels that have been proposed for these sources, isolated binary evolution in galactic fields and dynamical formation in dense star clusters, the predicted masses and merger rates overlap significantly, complicating any astrophysical claims that rely on measured masses alone. Here, we examine the distribution of spin-orbit misalignments expected for binaries from the field and from dense star clusters. Under standard assumptions for black hole natal kicks, we find that black hole binaries similar to GW150914 could be formed with significant spin-orbit misalignment only through dynamical processes. In particular, these heavy-black hole binaries can only form with a significant spin-orbit anti-alignment in the dynamical channel. Our results suggest that future detections of merging black hole binaries with measurable spins will allow us to identify the main formation channel for these systems.

[]

https://arxiv.org/pdf/1609.05916.pdf

2001Natur.414..522G

An unusually massive stellar black hole in the Galaxy

2001-01-01

['astrophysics']

[]

The X-ray source known as GRS1915+105 belongs to a group dubbed `microquasars'. These objects are binary systems which sporadically eject matter at speeds that appear superluminal, as is the case for some quasars. GRS1915+105 is also one of only two known binary sources thought to contain a maximally spinning black hole. Determining the basic parameters of GRS195+105, such as the masses of the components, will help us to understand jet formation in this system, as well as providing links to other objects which exhibit jets. Using X-ray data, indirect methods have previously been used to infer a variety of masses for the accreting compact object in the range 10-30 solar masses (M<SUB>⊙</SUB>). Here we report a direct measurement of the orbital period and mass function of GRS1915+105, which allow us to deduce a mass of 14 +/- 4M<SUB>⊙</SUB> for the black hole. Black holes with masses &gt;5-7M<SUB>⊙</SUB> challenge the conventional picture of black-hole formation in binary systems. Based on the mass estimate, we interpret the distinct X-ray variability of GRS1915+105 as arising from instabilities in an accretion disk that is dominated by radiation pressure, and radiating near the Eddington limit (the point where radiation pressure supports matter against gravity). Also, the mass estimate constrains most models which relate observable X-ray properties to the spin of black holes in microquasars.

[]

https://arxiv.org/pdf/astro-ph/0111538.pdf

2003PThPh.110..901I

Stability of Higher-Dimensional Schwarzschild Black Holes

2003-01-01

['-', '-']

[]

Our strategy for treating the stability problem is also applicable to other higher-dimensional maximally symmetric black holes with a non-vanishing cosmological constant. We show that all possible types of maximally symmetric black holes (including the higher-dimensional Schwarzschild-de Sitter and Schwarzschild-anti-de Sitter black holes) are stable with respect to tensor and vector perturbations.

[]

https://arxiv.org/pdf/hep-th/0305185.pdf

1996PhLB..383..151H

Nonextremal black hole microstates and U-duality

1996-01-01

['-', '-']

[]

A six-parameter family of five-dimensional black hole solutions is constructed which are labeled by their mass, two asymptotic scalar fields and three charges. It is shown that the Bekenstein-Hawking entropy is exactly matched, arbitrarily far from extremality, by a simple but mysterious duality-invariant extension of previously derived formulae for the number of D-brane states in string theory.

[]

https://arxiv.org/pdf/hep-th/9603109.pdf

1996IJMPA..11.4623T

The Scattering Matrix Approach for the Quantum Black Hole:. AN Overview

1996-01-01

['-']

[]

If one assumes the validity of conventional quantum field theory in the vicinity of the horizon of a black hole, one does not find a quantum-mechanical description of the entire black hole that even remotely resembles that of conventional forms of matter; in contrast with matter made out of ordinary particles one finds that, even if embedded in a finite volume, a black hole would be predicted to have a strictly continuous spectrum. <P />Dissatisfied with such a result, which indeed hinges on assumptions concerning the horizon that may well be wrong, various investigators have now tried to formulate alternative approaches to the problem of “quantizing” the black hole. We here review the approach based on the assumption of quantum-mechanical purity and unitarity as a starting point, as has been advocated by the present author for some time, concentrating on the physics of the states that should live on a black hole horizon. The approach is shown to be powerful in producing not only promising models for the quantum black hole, but also new insights concerning the dynamics of physical degrees of freedom in ordinary flat space-time.

[]

https://arxiv.org/pdf/gr-qc/9607022.pdf

2005Natur.436..819G

A dark jet dominates the power output of the stellar black hole Cygnus X-1

2005-01-01

['astrophysics']

[]

Black holes undergoing accretion are thought to emit the bulk of their power in the X-ray band by releasing the gravitational potential energy of the infalling matter. At the same time, they are capable of producing highly collimated jets of energy and particles flowing out of the system with relativistic velocities. Here we show that the 10-solar-mass (10M<SUB>solar</SUB>) black hole in the X-ray binary Cygnus X-1 (refs 3-5) is surrounded by a large-scale (~5pc in diameter) ring-like structure that appears to be inflated by the inner radio jet. We estimate that in order to sustain the observed emission of the ring, the jet of Cygnus X-1 has to carry a kinetic power that can be as high as the bolometric X-ray luminosity of the binary system. This result may imply that low-luminosity stellar-mass black holes as a whole dissipate the bulk of the liberated accretion power in the form of `dark', radiatively inefficient relativistic outflows, rather than locally in the X-ray-emitting inflow.

[]

https://arxiv.org/pdf/astro-ph/0508228.pdf

1995CQGra..12..297G

Higher-dimensional resolution of dilatonic black-hole singularities

1995-01-01

['-', '-']

[]

We show that the four-dimensional extreme dilaton black hole with dilaton coupling constant $a= \sqrt{p/(p+2)}$ can be interpreted as a {\it completely non-singular}, non-dilatonic, black $p$-brane in $(4+p)$ dimensions provided that $p$ is {\it odd}. Similar results are obtained for multi-black holes and dilatonic extended objects in higher spacetime dimensions. The non-singular black $p$-brane solutions include the self-dual three brane of ten-dimensional N=2B supergravity and a multi-fivebrane solution of eleven-dimensional supergravity. In the case of a supersymmetric non-dilatonic $p$-brane solution of a supergravity theory, we show that it saturates a bound on the energy per unit $p$-volume.

[]

https://arxiv.org/pdf/hep-th/9410073.pdf

2005ApJ...630..152E

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

2005-01-01

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

[]

Using high-resolution SPH numerical simulations, we investigate the effects of gas on the in-spiral and merger of a massive black hole binary. This study is motivated by the very massive nuclear gas disks observed in the central regions of merging galaxies. Here we present results that expand on the treatment in a previous work by studying models in which the gas is in a disk. We run a variety of models, ranging from simulations with a relatively smooth gas disk to cases in which the gas has a more clumpy spatial distribution. We also vary the inclination angle between the plane of the binary and the plane of the disk, and the mass ratio between the MBHs and the gaseous disk. We find that, as in our previous work, in the early evolution of the system the binary separation diminishes mainly due to dynamical friction exerted by the background gas, and in the later stages the gaseous medium responds by forming an ellipsoidal density enhancement whose axis lags behind the binary axis. This offset produces a gravitational torque on the binary that causes continuing loss of angular momentum and is able to reduce the separation to distances at which gravitational radiation is efficient. The main difference is that between these two regimes we now find a new transition regime that was not apparent in our previous paper, in which the evolution is temporarily slowed down when neither of these mechanisms is fully effective. In the variety of simulations that we perform, we find that the coalescence timescale for the MBH binary varies between 5×10<SUP>6</SUP> and 2.5×10<SUP>7</SUP> yr for typical ULIRGs. For MBHs that satisfy the observed ``m-σ<SUB>c</SUB>'' relation, our simulations suggest that in a merger of galaxies that have at least 1% of their total mass in gas, the MBHs will coalesce soon after the galaxies merge.

[]

https://arxiv.org/pdf/astro-ph/0406304.pdf

2004ApJ...602..312G

Black Hole Spin Evolution

2004-01-01

['accretion', 'accretion disks', 'black hole physics', 'methods numerical', 'mhd', 'astrophysics', '-']

[]

We consider a subset of the physical processes that determine the spin j≡a/M of astrophysical black holes. These include (1) Initial conditions. Recent models suggest that the collapse of a supermassive star is likely to produce a black hole with j~0.7. (2) Major mergers. The outcome of a nearly equal mass black hole-black hole merger is not yet known, but we review the current best guesses and analytic bounds. (3) Minor mergers. We recover the result of Blandford &amp; Hughes that accretion of small companions with isotropically distributed orbital angular momenta results in spin-down, with j~M<SUP>-7/3</SUP>. (4) Accretion. We present new results from fully relativistic magnetohydrodynamic (MHD) accretion simulations. These show that, at least for one sequence of flow models, spin equilibrium (dj/dt=0) is reached for j~0.9, far less than the canonical value 0.998 of Thorne that was derived in the absence of MHD effects. This equilibrium value may be inapplicable to some accretion flows, particularly thin disks. Nevertheless, it opens the possibility that black holes that have grown primarily through accretion are not maximally rotating.

[]

https://arxiv.org/pdf/astro-ph/0310886.pdf

2000PhRvD..61j4013M

Charged rotating black hole in three spacetime dimensions

2000-01-01

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

[]

The generalization of the black hole in three-dimensional spacetime to include an electric charge Q in addition to the mass M and the angular momentum J is given. The field equations are first solved explicitly when Q is small and the general form of the field at large distances is established. The total ``hairs'' M, J and Q are exhibited as boundary terms at infinity. It is found that the inner horizon of the rotating uncharged black hole is unstable under the addition of a small electric charge. Next it is shown that when Q=0 the spinning black hole may be obtained from the one with J=0 by a Lorentz boost in the φ-t plane. This boost is an ``illegitimate coordinate transformation'' because it changes the physical parameters of the solution. The extreme black hole appears as the analog of a particle moving with the speed of light. The same boost may be used when Q≠0 to generate a solution with angular momentum from that with J=0, although the geometrical meaning of the transformation is much less transparent since in the charged case the black holes are not obtained by identifying points in anti-de Sitter space. The metric is given explicitly in terms of three parameters, M~, Q~ and ω which are the ``rest mass'' and ``rest charge'' and the angular velocity of the boost. These parameters are related to M, J and Q through the solution of an algebraic cubic equation. Altogether, even without angular momentum, the electrically charged 2+1 black hole is somewhat pathological since (i) it exists for arbitrarily negative values of the mass, and (ii) there is no upper bound on the electric charge.

[]

https://arxiv.org/pdf/hep-th/9912259.pdf

2002ApJ...578..775B

The Kozai Mechanism and the Evolution of Binary Supermassive Black Holes

2002-01-01

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

[]

We consider the dynamical evolution of bound, hierarchical triples of supermassive black holes that might be formed in the nuclei of galaxies undergoing sequential mergers. The tidal force of the outer black hole on the inner binary produces eccentricity oscillations through the Kozai mechanism, and this can substantially reduce the gravitational wave merger time of the inner binary. We numerically calculate the merger time for a wide range of initial conditions and black hole mass ratios, including the effects of octupole interactions in the triple as well as general relativistic periastron precession in the inner binary. The semimajor axes and the mutual inclination of the inner and outer binaries are the most important factors affecting the merger time. We find that for a random distribution of inclination angles and approximately equal mass black holes, it is possible to reduce the merger time of a near circular inner binary by more than a factor of 10 in over 50% of all cases. We estimate that a typical exterior quadrupole moment from surrounding matter in the galaxy may also be sufficient to excite eccentricity oscillations in supermassive black hole binaries and to accelerate black hole mergers.

[]

https://arxiv.org/pdf/astro-ph/0203370.pdf

2013CQGra..30n5009M

Primordial black hole formation in the early universe: critical behaviour and self-similarity

2013-01-01

['-', '-']

[]

Following on after three previous papers discussing the formation of primordial black holes during the radiative era of the early universe, we present here a further investigation of the critical nature of the process involved, aimed at making contact with some of the basic underlying ideas from the literature on critical collapse. We focus on the intermediate state, which we have found appearing in cases with perturbations close to the critical limit, and examine the connection between this and the similarity solutions which play a fundamental role in the standard picture of critical collapse. We have derived a set of self-similar equations for the null-slicing form of the metric which we are using for our numerical calculations, and have then compared the results obtained by integrating these with the ones coming from our simulations for the collapse of cosmological perturbations within an expanding universe. We find that the similarity solution is asymptotically approached in a region which grows to cover both the contracting matter and part of the semi-void which forms outside it. Our main interest is in the situation relevant for primordial black hole formation in the radiative era of the early universe, where the relation between the pressure p and the energy density e can be reasonably approximated by an expression of the form p = we with w = 1/3. However, we have also looked at other values of w, both because these have been considered in the previous literature and also because they can be helpful for giving further insight into situations relevant for primordial black hole formation. As in our previous work, we have started our simulations with initial supra-horizon scale perturbations of a type which could have come from inflation.

[]

https://arxiv.org/pdf/1201.2379.pdf

2003ApJ...585L..37M

X-Ray Spectroscopic Evidence for Intermediate-Mass Black Holes: Cool Accretion Disks in Two Ultraluminous X-Ray Sources

2003-01-01

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

[]

We have analyzed an XMM-Newton observation of the nearby spiral galaxy NGC 1313, which contains two ``ultraluminous'' X-ray (ULX) sources. We measure isotropic luminosities of L<SUB>X</SUB>=2.0×10<SUP>40</SUP> ergs s<SUP>-1</SUP> and L<SUB>X</SUB>=6.6×10<SUP>39</SUP> ergs s<SUP>-1</SUP> for NGC 1313 X-1 and X-2 (0.2-10.0 keV, assuming a distance of 3.7 Mpc). The spectra statistically require soft and hard spectral components to describe the continuum emission; some prior studies of ULX sources have claimed cool soft components with lower statistics. The improvement over several single-component models exceeds the 8 σ level of confidence for X-1 the improvement for X-2 is significant at the 3 σ level. The soft components in these ULX spectra are well fitted by multicolor disk blackbody models with color temperatures of kT~=150 eV. This temperature differs markedly from those commonly measured in the spectra of stellar mass (10 M<SUB>solar</SUB>) black holes in their brightest states (kT~=1 keV). It is expected that the temperature of an accretion disk orbiting a black hole should decrease with increasing black hole mass. If the soft components we measure are due to emission from the inner region of an accretion disk, and disks extend close to the innermost stable circular orbit at the accretion rates being probed, the low color temperatures may be interpreted as spectroscopic evidence of black holes with intermediate masses: M<SUB>BH</SUB>~=10<SUP>3</SUP> M<SUB>solar</SUB>. Simple Eddington scaling arguments suggest a minimum mass of M<SUB>BH</SUB>~10<SUP>2</SUP> M<SUB>solar</SUB>. NGC 1313 X-1 and X-2 are found in optical nebulae, which may indicate that anisotropic emission geometries are unlikely to account for the fluxes observed.

[]

https://arxiv.org/pdf/astro-ph/0211178.pdf

2007Sci...316.1874M

Rapid Formation of Supermassive Black Hole Binaries in Galaxy Mergers with Gas

2007-01-01

['-', 'astrophysics']

[]

Supermassive black holes (SMBHs) are a ubiquitous component of the nuclei of galaxies. It is normally assumed that after the merger of two massive galaxies, a SMBH binary will form, shrink because of stellar or gas dynamical processes, and ultimately coalesce by emitting a burst of gravitational waves. However, so far it has not been possible to show how two SMBHs bind during a galaxy merger with gas because of the difficulty of modeling a wide range of spatial scales. Here we report hydrodynamical simulations that track the formation of a SMBH binary down to scales of a few light years after the collision between two spiral galaxies. A massive, turbulent, nuclear gaseous disk arises as a result of the galaxy merger. The black holes form an eccentric binary in the disk in less than 1 million years as a result of the gravitational drag from the gas rather than from the stars.

[]

https://arxiv.org/pdf/0706.1562.pdf

2000ApJ...540L..13P

Evidence for Supermassive Black Holes in Active Galactic Nuclei from Emission-Line Reverberation

2000-01-01

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

[]

Emission-line variability data for Seyfert 1 galaxies provide strong evidence for the existence of supermassive black holes in the nuclei of these galaxies and that the line-emitting gas is moving in the gravitational potential of that black hole. The time-delayed response of the emission lines to continuum variations is used to infer the size of the line-emitting region, which is then combined with measurements of the Doppler widths of the variable line components to estimate a virial mass. In the case of the best-studied galaxy, NGC 5548, various emission lines spanning an order of magnitude in distance from the central source show the expected V~r<SUP>-1/2</SUP> correlation between distance and line width and are thus consistent with a single value for the mass. Two other Seyfert galaxies, NGC 7469 and 3C 390.3, show a similar relationship. We compute the ratio of luminosity to mass for these three objects and the narrow-line Seyfert 1 galaxy NGC 4051 and find that the gravitational force on the line-emitting gas is much stronger than radiation pressure. These results strongly support the paradigm of gravitationally bound broad emission line region clouds.

[]

https://arxiv.org/pdf/astro-ph/0007147.pdf

2003ApJ...582..133D

Accretion onto the Supermassive Black Hole in M87

2003-01-01

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

[]

Chandra X-ray observations of the giant elliptical galaxy M87 resolve the thermal state of the hot interstellar medium into the accretion (Bondi) radius of its central 3×10<SUP>9</SUP>M<SUB>solar</SUB> black hole. We measure the X-ray gas temperature and density profiles and calculate the Bondi accretion rate, M<SUB>Bondi</SUB>~0.1M<SUB>solar</SUB> yr<SUP>-1</SUP>. The X-ray luminosity of the active nucleus of M87 observed with Chandra is L<SUB>X,0.5-7keV</SUB>~7×10<SUP>40</SUP> ergs s<SUP>-1</SUP>. This value is much less than the predicted nuclear luminosity, L<SUB>Bondi</SUB>~5×10<SUP>44</SUP> ergs s<SUP>-1</SUP>, for accretion at the Bondi rate with a canonical accretion radiative efficiency of 10%. If the black hole in M87 accretes at this rate it must do so at a much lower radiative efficiency than the canonical value. The multiwavelength spectrum of the nucleus is consistent with that predicted by an advection-dominated flow. However, as is likely, the X-ray nucleus is dominated by jet emission then the properties of flow must be modified, possibly by outflows. We show that the overall energetics of the system are just consistent with the predicted Bondi nuclear power. This suggests that either most of the accretion energy is released in the relativistic jet or the central engine of M87 undergoes on-off activity cycles. We show that, at present, the energy dumped into the ISM by the jet may reduce the accretion rate onto the black hole by a factor ~(v<SUB>j</SUB>/c<SUB>s</SUB>)<SUP>-2</SUP>, where v<SUB>j</SUB> is the jet velocity and c<SUB>s</SUB> the ISM sound speed, and that this is sufficient to account for the low nuclear luminosity.

[]

https://arxiv.org/pdf/astro-ph/0202238.pdf

2009ApJ...696.1798T

The Assembly of Supermassive Black Holes at High Redshifts

2009-01-01

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

[]

The supermassive black holes (SMBHs) massive enough (gsim few ×10<SUP>9</SUP> M <SUB>sun</SUB>) to power the bright redshift z ≈ 6 quasars observed in the Sloan Digital Sky Survey (SDSS) are thought to have assembled by mergers and/or gas accretion from less massive "seed" BHs. If the seeds are the ~10<SUP>2</SUP> M <SUB>sun</SUB> remnant BHs from the first generation of stars, they must be in place well before redshift z = 6, and must avoid being ejected from their parent protogalaxies by the large (several ×10<SUP>2</SUP> km s<SUP>-1</SUP>) kicks they suffer from gravitational-radiation-induced recoil during mergers with other BHs. We simulate the SMBH mass function at redshift z &gt; 6 using dark matter halo merger trees, coupled with a prescription for the halo occupation fraction, accretion histories, and radial recoil trajectories of the growing BHs. Our purpose is (1) to map out plausible scenarios for successful assembly of the z ≈ 6 quasar BHs by exploring a wide region of parameter space, and (2) to predict the rate of low-frequency gravitational wave events detectable by the Laser Interferometer Space Antenna (LISA) for each such scenario. Our main findings are as follows: (1) ~100 M <SUB>sun</SUB> seed BHs can grow into the SDSS quasar BHs without super-Eddington accretion, but only if they form in minihalos at z gsim 30 and subsequently accrete gsim60% of the time; (2) the scenarios with optimistic assumptions required to explain the SDSS quasar BHs overproduce the mass density in lower mass (few ×10<SUP>5</SUP> M <SUB>sun</SUB> lsim M <SUB>bh</SUB>lsim few × 10<SUP>7</SUP> M <SUB>sun</SUB>) BHs by a factor of 10<SUP>2</SUP>-10<SUP>3</SUP>, unless seeds stop forming, or accrete at a severely diminished rates or duty cycles (e.g., due to feedback), at z lsim 20-30. We also present several successful assembly models and their LISA detection rates, including a "maximal" model that gives the highest rate (~30 yr<SUP>-1</SUP> at z = 6) without overproducing the total SMBH density.

[]

https://arxiv.org/pdf/0807.4702.pdf

2010PhRvL.105x0401L

Realization of a Sonic Black Hole Analog in a Bose-Einstein Condensate

2010-01-01

['-', '-', 'dynamical systems', '-', '-', '-', '-']

[]

We have created an analog of a black hole in a Bose-Einstein condensate. In this sonic black hole, sound waves, rather than light waves, cannot escape the event horizon. A steplike potential accelerates the flow of the condensate to velocities which cross and exceed the speed of sound by an order of magnitude. The Landau critical velocity is therefore surpassed. The point where the flow velocity equals the speed of sound is the sonic event horizon. The effective gravity is determined from the profiles of the velocity and speed of sound. A simulation finds negative energy excitations, by means of Bragg spectroscopy.

[]

https://arxiv.org/pdf/0906.1337.pdf

2008PhRvD..77d5027D

Black hole bound on the number of species and quantum gravity at CERN LHC

2008-01-01

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

[]

In theories with a large number N of particle species, black hole physics imposes an upper bound on the mass of the species equal to M<SUB>Planck</SUB>/N. This bound suggests a novel solution to the hierarchy problem in which there are N≈10<SUP>32</SUP> gravitationally coupled species, for example 10<SUP>32</SUP> copies of the standard model. The black hole bound forces them to be at the weak scale, hence providing a stable hierarchy. We present various arguments, that in such theories the effective gravitational cutoff is reduced to Λ<SUB>G</SUB>≈M<SUB>Planck</SUB>/N and a new description is needed around this scale. In particular, black holes smaller than Λ<SUB>G</SUB><SUP>-1</SUP> are already no longer semiclassical. The nature of the completion is model dependent. One natural possibility is that Λ<SUB>G</SUB> is the quantum gravity scale. We provide evidence that within this type of scenarios, contrary to the standard intuition, micro-black-holes have a (slowly fading) memory of the species of origin. Consequently, the black holes produced at LHC will predominantly decay into the standard model particles, and negligibly into the other species.

[]

https://arxiv.org/pdf/0710.4344.pdf

1997CQGra..14L.109M

LETTER TO THE EDITOR: Pair production of topological anti-de Sitter black holes

1997-01-01

['-']

[]

The pair creation of black holes with event horizons of non-trivial topology is described. The spacetimes are all limiting cases of the cosmological C-metric. They are generalizations of the (2 + 1)-dimensional black hole and have asymptotically anti-de Sitter behaviour. Domain wall instantons can mediate their pair creation for a wide range of mass and charge.

[]

https://arxiv.org/pdf/gr-qc/9607071.pdf

2009MNRAS.397..135K

Feast and Famine: regulation of black hole growth in low-redshift galaxies

2009-01-01

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

[]

We analyse the observed distribution of Eddington ratios (L/L<SUB>Edd</SUB>) as a function of supermassive black hole mass for a large sample of nearby galaxies drawn from the Sloan Digital Sky Survey. We demonstrate that there are two distinct regimes of black hole growth in nearby galaxies. The first is associated with galaxies with significant star formation [M<SUB>*</SUB>/starformationrate (SFR) ~ a Hubble time] in their central kiloparsec regions, and is characterized by a broad lognormal distribution of accretion rates peaked at a few per cent of the Eddington limit. In this regime, the Eddington ratio distribution is independent of the mass of the black hole and shows little dependence on the central stellar population of the galaxy. The second regime is associated with galaxies with old central stellar populations (M<SUB>*</SUB>/SFR &gt;&gt; a Hubble time), and is characterized by a power-law distribution function of Eddington ratios. In this regime, the time-averaged mass accretion rate on to black holes is proportional to the mass of stars in the galaxy bulge, with a constant of proportionality that depends on the mean stellar age of the stars. This result is once again independent of black hole mass. We show that both the slope of the power law and the decrease in the accretion rate on to black holes in old galaxies are consistent with population synthesis model predictions of the decline in stellar mass loss rates as a function of mean stellar age. Our results lead to a very simple picture of black hole growth in the local Universe. If the supply of cold gas in a galaxy bulge is plentiful, the black hole regulates its own growth at a rate that does not further depend on the properties of the interstellar medium. Once the gas runs out, black hole growth is regulated by the rate at which evolved stars lose their mass.

[]

https://arxiv.org/pdf/0812.1224.pdf