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2014arXiv1403.5695S

Addendum to Computational Complexity and Black Hole Horizons

2014-01-01

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

[]

In this addendum to [arXiv:1402.5674] two points are discussed. In the first additional evidence is provided for a dual connection between the geometric length of an Einstein-Rosen bridge and the computational complexity of the quantum state of the dual CFT's. The relation between growth of complexity and Page's ``Extreme Cosmic Censorship" principle is also remarked on. The second point involves a gedanken experiment in which Alice measures a complete set of commuting observables at her end of an Einstein-Rosen bridge is discussed. An apparent paradox is resolved by appealing to the properties of GHZ tripartite entanglement.

[]

https://arxiv.org/pdf/1403.5695.pdf

2010PhRvD..82b6006C

Boost invariant flow, black hole formation, and far-from-equilibrium dynamics in N=4 supersymmetric Yang-Mills theory

2010-01-01

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

[]

Using gauge/gravity duality, we study the creation and evolution of boost-invariant anisotropic, strongly-coupled N=4 supersymmetric Yang-Mills plasma. In the dual gravitational description, this corresponds to horizon formation in a geometry driven to be anisotropic by a time-dependent change in boundary conditions.

[]

https://arxiv.org/pdf/0906.4426.pdf

2011CQGra..28k4009M

Measuring the spins of accreting black holes

2011-01-01

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

[]

A typical galaxy is thought to contain tens of millions of stellar-mass black holes, the collapsed remnants of once massive stars, and a single nuclear supermassive black hole. Both classes of black holes accrete gas from their environments. The accreting gas forms a flattened orbiting structure known as an accretion disk. During the past several years, it has become possible to obtain measurements of the spins of the two classes of black holes by modeling the x-ray emission from their accretion disks. Two methods are employed, both of which depend upon identifying the inner radius of the accretion disk with the innermost stable circular orbit, whose radius depends only on the mass and spin of the black hole. In the Fe Kα method, which applies to both classes of black holes, one models the profile of the relativistically broadened iron line with a special focus on the gravitationally redshifted red wing of the line. In the continuum-fitting (CF) method, which has so far only been applied to stellar-mass black holes, one models the thermal x-ray continuum spectrum of the accretion disk. We discuss both methods, with a strong emphasis on the CF method and its application to stellar-mass black holes. Spin results for eight stellar-mass black holes are summarized. These data are used to argue that the high spins of at least some of these black holes are natal, and that the presence or absence of relativistic jets in accreting black holes is not entirely determined by the spin of the black hole.

[]

https://arxiv.org/pdf/1101.0811.pdf

2013Natur.494..449R

A rapidly spinning supermassive black hole at the centre of NGC 1365

2013-01-01

['-']

[]

Broad X-ray emission lines from neutral and partially ionized iron observed in active galaxies have been interpreted as fluorescence produced by the reflection of hard X-rays off the inner edge of an accretion disk. In this model, line broadening and distortion result from rapid rotation and relativistic effects near the black hole, the line shape being sensitive to its spin. Alternative models in which the distortions result from absorption by intervening structures provide an equally good description of the data, and there has been no general agreement on which is correct. Recent claims that the black hole (2 × 10<SUP>6</SUP> solar masses) at the centre of the galaxy NGC 1365 is rotating at close to its maximum possible speed rest on the assumption of relativistic reflection. Here we report X-ray observations of NGC 1365 that reveal the relativistic disk features through broadened Fe-line emission and an associated Compton scattering excess of 10-30 kiloelectronvolts. Using temporal and spectral analyses, we disentangle continuum changes due to time-variable absorption from reflection, which we find arises from a region within 2.5 gravitational radii of the rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out both statistically and on physical grounds.

[]

https://arxiv.org/pdf/1302.7002.pdf

2013PhRvD..88b3514B

Massive spin-2 fields on black hole spacetimes: Instability of the Schwarzschild and Kerr solutions and bounds on the graviton mass

2013-01-01

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

[]

Massive bosonic fields of arbitrary spin are predicted by general extensions of the standard model. It has been recently shown that there exists a family of bimetric theories of gravity—including massive gravity—which are free of Boulware-Deser ghosts at the nonlinear level. This opens up the possibility to describe consistently the dynamics of massive spin-2 particles in a gravitational field. Within this context, we develop the study of massive spin-2 fluctuations—including massive gravitons—around Schwarzschild and slowly rotating Kerr black holes. Our work has two important outcomes. First, we show that the Schwarzschild geometry is linearly unstable for small tensor masses, against a spherically symmetric mode. Second, we provide solid evidence that the Kerr geometry is also generically unstable, both against the spherical mode and against long-lived superradiant modes. In the absence of nonlinear effects, the observation of spinning black holes bounds the graviton mass μ to be μ≲5×10<SUP>-23</SUP>eV.

[]

https://arxiv.org/pdf/1304.6725.pdf

2019Sci...366..637T

A noninteracting low-mass black hole-giant star binary system

2019-01-01

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

[]

Black hole binary systems with companion stars are typically found via their x-ray emission, generated by interaction and accretion. Noninteracting binaries are expected to be plentiful in the Galaxy but must be observed using other methods. We combine radial velocity and photometric variability data to show that the bright, rapidly rotating giant star 2MASS J05215658+4359220 is in a binary system with a massive unseen companion. The system has an orbital period of ~83 days and near-zero eccentricity. The photometric variability period of the giant is consistent with the orbital period, indicating star spots and tidal synchronization. Constraints on the giant’s mass and radius imply that the unseen companion is 3.3-0.7+2.8 solar masses, indicating that it is a noninteracting low-mass black hole or an unexpectedly massive neutron star.

[]

https://arxiv.org/pdf/1806.02751.pdf

2017RvMP...89b5001B

Testing black hole candidates with electromagnetic radiation

2017-01-01

['-', '-']

[]

Astrophysical black hole candidates are thought to be the Kerr black holes of general relativity, but there is not yet direct observational evidence that the spacetime geometry around these objects is described by the Kerr solution. The study of the properties of the electromagnetic radiation emitted by gas or stars orbiting these objects can potentially test the Kerr black hole hypothesis. This paper reviews the state of the art of this research field, describing the possible approaches to test the Kerr metric with current and future observational facilities and discussing current constraints.

[]

https://arxiv.org/pdf/1509.03884.pdf

2018MNRAS.474.2959G

Merging black hole binaries: the effects of progenitor's metallicity, mass-loss rate and Eddington factor

2018-01-01

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

[]

The first four gravitational wave events detected by LIGO were all interpreted as merging black hole binaries (BHBs), opening a new perspective on the study of such systems. Here we use our new population-synthesis code MOBSE, an upgraded version of BSE, to investigate the demography of merging BHBs. MOBSE includes metallicity-dependent prescriptions for mass-loss of massive hot stars. It also accounts for the impact of the electron-scattering Eddington factor on mass-loss. We perform &gt;10<SUP>8</SUP> simulations of isolated massive binaries, with 12 different metallicities, to study the impact of mass-loss, core-collapse supernovae and common envelope on merging BHBs. Accounting for the dependence of stellar winds on the Eddington factor leads to the formation of black holes (BHs) with mass up to 65 M<SUB>⊙</SUB> at metallicity Z ∼ 0.0002. However, most BHs in merging BHBs have masses ≲ 40 M<SUB>⊙</SUB>. We find merging BHBs with mass ratios in the 0.1-1.0 range, even if mass ratios &gt;0.6 are more likely. We predict that systems like GW150914, GW170814 and GW170104 can form only from progenitors with metallicity Z ≤ 0.006, Z ≤ 0.008 and Z ≤ 0.012, respectively. Most merging BHBs have gone through a common envelope phase, but up to ∼17 per cent merging BHBs at low metallicity did not undergo any common envelope phase. We find a much higher number of mergers from metal-poor progenitors than from metal-rich ones: the number of BHB mergers per unit mass is ∼10<SUP>-4</SUP> M_{⊙}^{-1} at low metallicity (Z = 0.0002-0.002) and drops to ∼10<SUP>-7</SUP> M_{⊙}^{-1} at high metallicity (Z ∼ 0.02).

[]

https://arxiv.org/pdf/1711.03556.pdf

2006MNRAS.373L..90K

Growing supermassive black holes by chaotic accretion

2006-01-01

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

[]

We consider the problem of growing the largest supermassive black holes from stellar mass seeds at high redshift. Rapid growth without violating the Eddington limit requires that most mass is gained while the hole has a low spin and thus a low radiative accretion efficiency. If, as was formerly thought, the black hole spin aligns very rapidly with the accretion flow, even a randomly oriented sequence of accretion events would all spin up the hole and prevent rapid mass growth. However, using the recent result that the Bardeen-Petterson effect causes counteralignment of hole and disc spins under certain conditions, we show that holes can grow rapidly in mass if they acquire most of it in a sequence of randomly oriented accretion episodes whose angular momenta J<SUB>d</SUB> are no larger than the angular momentum of the hole, J<SUB>h</SUB>. Ultimately the hole has total angular momentum comparable with the last accretion episode. This points to a picture in which the accretion is chaotic on a lengthscale of order the disc size, that is, &lt;~0.1 pc.

[]

https://arxiv.org/pdf/astro-ph/0609598.pdf

2007PhRvD..75b7502H

Higher-dimensional black holes with a conformally invariant Maxwell source

2007-01-01

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

[]

We consider an action for an Abelian gauge field for which the density is given by a power of the Maxwell Lagrangian. In d spacetime dimensions this action is shown to enjoy conformal invariance if the power is chosen as d/4. We take advantage of this conformal invariance to derive black hole solutions electrically charged with a purely radial electric field. Since we are considering a power of the Maxwell density, the black hole solutions exist only for dimensions which are multiples of four. The expression for the electric field does not depend on the dimension and corresponds to the four-dimensional Reissner-Nordström field. Using the Hamiltonian action we identify the mass and the electric charge of these black hole solutions.

[]

https://arxiv.org/pdf/hep-th/0701058.pdf

1999MNRAS.303L..34F

The mass density in black holes inferred from the X-ray background

1999-01-01

['galaxies active', 'galaxies quasars', 'galaxies seyfert', 'astronomy infrared', 'astronomy x rays', 'astrophysics']

[]

The X-ray background (XRB) probably originates from the integrated X-ray emission of active galactic nuclei (AGN). Modelling of its flat spectrum implies considerable absorption in most AGN. Compton down-scattering means that sources in which the absorption is Compton-thick are unlikely to be major contributors to the background intensity, so the observed spectral intensity at about 30 keV is little affected by photoelectric absorption. Assuming that the intrinsic photon index of AGN is 2, we then use the 30-keV intensity of the XRB to infer the absorption-corrected energy density of the background. Soltan's argument then enables us to convert this to a mean local density in black holes, assuming an accretion efficiency of 0.1 and a mean AGN redshift of 2. The result is within a factor of 2 of that estimated by Haehnelt et al. from the optically determined black hole masses of Magorrian et al. We conclude that there is no strong need for any radiatively inefficient mode of accretion for building the masses of black holes. Furthermore, we show that the absorption model for the XRB implies that about 85 per cent of accretion power in the Universe is absorbed. This power probably emerges in the infrared bands where it can be several tens per cent of the recently inferred backgrounds there. The total power emitted by accretion is then about one fifth that of stars.

[]

https://arxiv.org/pdf/astro-ph/9901121.pdf

1999PhRvD..61b4014H

Charged and rotating AdS black holes and their CFT duals

1999-01-01

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

[]

Black hole solutions that are asymptotic to AdS<SUB>5</SUB>×S<SUP>5</SUP> or AdS<SUB>4</SUB>×S<SUP>7</SUP> can rotate in two different ways. If the internal sphere rotates, then one can obtain a Reissner-Nordström-AdS black hole. If the asymptotically AdS space rotates, then one can obtain a Kerr-AdS hole. One might expect superradiant scattering to be possible in either of these cases. Superradiant modes reflected off the potential barrier outside the hole would be reamplified at the horizon, and a classical instability would result. We point out that the existence of a Killing vector field timelike everywhere outside the horizon prevents this from occurring for black holes with negative action. Such black holes are also thermodynamically stable in the grand canonical ensemble. The CFT duals of these black holes correspond to a theory in an Einstein universe with a chemical potential and a theory in a rotating Einstein universe. We study these CFTs in the zero coupling limit. In the first case, Bose-Einstein condensation occurs on the boundary at a critical value of the chemical potential. However, the supergravity calculation demonstrates that this is not to be expected at strong coupling. In the second case, we investigate the limit in which the angular velocity of the Einstein universe approaches the speed of light at finite temperature. This is a new limit in which to compare the CFT at strong and weak coupling. We find that the free CFT partition function and supergravity action have the same type of divergence but the usual factor of 4/3 is modified at finite temperature.

[]

https://arxiv.org/pdf/hep-th/9908109.pdf

2023ApJ...953L..29L

A CEERS Discovery of an Accreting Supermassive Black Hole 570 Myr after the Big Bang: Identifying a Progenitor of Massive z &gt; 6 Quasars

2023-01-01

['-', 'black hole physics', '-', 'galaxies', 'astronomy infrared', 'techniques spectroscopic', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

We report the discovery of an accreting supermassive black hole at z = 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered as a Lyα-break galaxy by Hubble with a Lyα redshift from Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source with JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS and uncovered a plethora of emission lines. The Hβ line is best fit by a narrow plus a broad component, where the latter is measured at 2.5σ with an FWHM ~1200 km s<SUP>-1</SUP>. We conclude this originates in the broadline region of an active galactic nucleus (AGN). This is supported by the presence of weak high-ionization lines (N V, N IV], and C III]), as well as a spatial point-source component. The implied mass of the black hole (BH) is log (M <SUB>BH</SUB>/M <SUB>⊙</SUB>) = 6.95 ± 0.37, and we estimate that it is accreting at 1.2 ± 0.5 times the Eddington limit. The 1-8 μm photometric spectral energy distribution shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M<SUB>⊙</SUB> ~9.5) and highly star-forming (star formation rate, or SFR ~ 30 M<SUB>⊙</SUB> yr<SUP>-1</SUP>; log sSFR ~ - 7.9 yr<SUP>-1</SUP>). The line ratios show that the gas is metal-poor (Z/Z <SUB>⊙</SUB> ~ 0.1), dense (n <SUB> e </SUB> ~ 10<SUP>3</SUP> cm<SUP>-3</SUP>), and highly ionized (log U ~ - 2.1). We use this present highest-redshift AGN discovery to place constraints on BH seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from very massive BH seeds is required to form this object.

[]

https://arxiv.org/pdf/2303.08918.pdf

2009fbhg.book.....C

The Formation of Black Holes in General Relativity

2009-01-01

['-']

[]

The subject of this work is the formation of black holes in pure general relativity, by the focusing of incoming gravitational waves. The theorems established in this monograph constitute the first foray into the long time dynamics of general relativity in the large, that is, when the initial data are no longer confined to a suitably small neighborhood of Minkowskian data. The theorems are general, no symmetry conditions on the initial data being imposed.

[]

https://arxiv.org/pdf/0805.3880.pdf

1996PhRvL..77.4992G

Moduli, Scalar Charges, and the First Law of Black Hole Thermodynamics

1996-01-01

['-', '-']

[]

We show that under variation of moduli fields φ the first law of black hole thermodynamics becomes dM = κdA8π+ΩdJ+ψdq+χdp-Σdφ, where Σ are the scalar charges. Also the Arnowitt-Desner-Misner mass is extremized at fixed A, J, \(p,q\) when the moduli fields take the fixed value φ<SUB>fix</SUB>\(p,q\) which depend only on electric and magnetic charges. Thus the double-extreme black hole minimizes the mass for fixed conserved charges. We can now explain the fact that extreme black holes fix the moduli fields at the horizon φ = φ<SUB>fix</SUB>\(p,q\): φ<SUB>fix</SUB> is such that the scalar charges vanish: Σ\(φ<SUB>fix</SUB>,\(p,q\)\) = 0.

[]

https://arxiv.org/pdf/hep-th/9607108.pdf

2010MNRAS.403...61D

A global spectral study of black hole X-ray binaries

2010-01-01

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

[]

We report on a consistent and comprehensive spectral analysis of the X-ray emission of 25 black hole X-ray binaries. All publicly available observations of the black hole binaries in the RXTE archive were analysed. Three different types of model were fitted to investigate the spectral changes occurring during an outburst. For the population, as well as for each binary and each outburst from each binary, we construct two diagnostic diagrams. The hardness intensity/luminosity diagram (HID/HLD), the X-ray colour against the flux/luminosity of the binary, is most useful when studying a single binary. However, to compare different binary systems, the disc fraction luminosity diagram (DFLD) is more useful. The DFLD uses the luminosities of the disc and power-law components to calculate the ratio of the disc luminosity to the total luminosity, resulting in a more physical value, which is analogous to the X-ray colour calculated for X-ray binaries. The tracks of the outbursts populate the DFLD more evenly than the HLD. We discuss the limitations of both diagnostic diagrams for the study of the X-ray binary outbursts and clearly illustrate how the two diagrams map on to each other for real outburst data. The similarity of the X-ray colour and disc fraction behaviour over time during an outburst originally seen in GX 339-4 data is seen in other sources' outbursts. We extract the peak luminosities in a single outburst, as well as the luminosities at the transitions away from and returning to the power-law-dominated state for each outburst. The distribution of the luminosities at the transition from the power-law to the disc-dominated state peaks at around 0.3L<SUB>Edd</SUB>, the same as the peak of the distribution of the peak luminosities in an outburst. Using the disc fraction to calculate the transition luminosities shows that the distributions of the luminosities for the transitions away from and returning to the power-law-dominated state are both broad and appear to overlap. Using the change in disc fraction to calculate the date when a transition occurred is not drastically different from obtaining the dates from changes in the timing behaviour of the X-ray binary. In addition, we calculate the rate of motion of an X-ray binary through the DFLD during an outburst, a diagnostic which has the potential to be used as a comparison with populations of active galactic nuclei. The fastest rate of motion is on the egress and ingress from the power-law-dominated state. A further region of increased speed through the diagram occurs in the disc-dominated state on the return to the power-law-dominated state. Finally, we compare the measured X-ray luminosities with a small number of contemporaneous radio measurements. Overall, this is the most comprehensive and uniform global study of black hole X-ray binaries to date.

[]

https://arxiv.org/pdf/0912.0142.pdf

1995NuPhB.453..281K

Black hole entropy and entropy of entanglement

1995-01-01

['-', '-']

[]

We compare the one-loop corrections to the entropy of a black hole, from quantum fields of spin zero, one-half, and one, to the entropy of entanglement of the fields. For fields of spin zero and one-half the black hole entropy is identical to the entropy of entanglement. For spin one the two entropies differ by a contact interaction with the horizon which appears in the black hole entropy but not in the entropy of entanglement. The contact interaction can be expressed as a path integral over particle paths which begin and end on the horizon; it is the field theory limit of the interaction proposed by Susskind and Uglum, which couples a closed string to an open string stranded on the horizon.

[]

https://arxiv.org/pdf/hep-th/9503016.pdf

2009ApJ...701L.133A

Accretion onto the First Stellar-Mass Black Holes

2009-01-01

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

[]

The first stars, forming at redshifts z &gt; 15 in minihalos with M ~ 10<SUP>5-6</SUP> M <SUB>sun</SUB> may leave behind remnant black holes, which could conceivably have been the "seeds" for the supermassive black holes observed at z lsim 7. We study remnant black hole growth through accretion, including for the first time the radiation emitted due to accretion, with adaptive mesh refinement cosmological radiation-hydrodynamical simulations. The effects of photoionization and heating dramatically affect the large-scale inflow, resulting in negligible mass growth. We compare cases with accretion luminosity included and neglected to show that accretion radiation drastically changes the environment within 100 pc of the black hole, increasing gas temperatures by an order of magnitude. Gas densities are reduced and further star formation in the same minihalo is prevented for the 200 million years we followed. Without radiative feedback included most seed black holes do not gain mass as efficiently as has been hoped for in previous theories, implying that black hole remnants of population III stars in minihalos are not likely to be miniquasars. Most importantly, however, our calculations demonstrate that if these black holes are indeed accreting close to the Bondi-Hoyle rate with 10% radiative efficiency they have a dramatic local effect in regulating star formation in the first galaxies. This suggests a novel mechanism for massive black hole formation—stellar-mass black holes may have suppressed fragmentation and star formation after falling into halos with virial temperatures ~10<SUP>4</SUP> K, facilitating massive black hole formation at their centers.

[]

https://arxiv.org/pdf/0811.0820.pdf

2008MNRAS.385.1621K

The evolution of black hole mass and spin in active galactic nuclei

2008-01-01

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

[]

Observations show that the central black hole in galaxies has a mass M of only ~10<SUP>-3</SUP> of the stellar bulge mass. Thus, whatever process grows the black hole also promotes star formation with far higher efficiency. We interpret this in terms of the generic tendency of active galactic nucleus (AGN) accretion discs to become self-gravitating outside some small radius R<SUB>sg</SUB> ~ 0.01-0.1 pc from the black hole. We argue that mergers consist of sequences of such episodes, each limited by self-gravity to a mass ΔM<SUB>episode</SUB> ~ 10<SUP>-3</SUP> M, with angular momentum characteristic of the small part of the accretion flow which formed it. In this picture, a major merger with ΔM<SUB>merger</SUB> ~ M gives rise to a long series of low-mass accretion disc episodes, all chaotically oriented with respect to one another. Thus, the angular momentum vector oscillates randomly during the accretion process, on mass-scales ~ 10<SUP>3</SUP> times smaller than the total mass accreted in a major merger event. <P />We show that for essentially all AGN parameters, the disc produced by any accretion episode of this type has lower angular momentum than the hole, allowing stable co- and counter-alignment of the discs through the Lense-Thirring effect. A sequence of randomly oriented accretion episodes as envisaged above then produces accretion discs stably co- or counter-aligned with the black hole spin with almost equal frequency. Accretion from these discs very rapidly adjusts the hole's spin parameter to average values (the precise range depending slightly on the disc vertical viscosity coefficient α<SUB>2</SUB>) from any initial conditions, but with significant fluctuations (Δa ~ +/-0.2) about these. We conclude that (i) supermassive black holes (SMBH) should on average spin moderately, with the mean value decreasing slowly as the mass increases; (ii) SMBH coalescences leave little long-term effect on ; (iii) SMBH coalescence products in general have modest recoil velocities, so that there is little likelihood of their being ejected from the host galaxy; (iv) black holes can grow even from stellar masses to ~5 × 10<SUP>9</SUP>M<SUB>solar</SUB> at high redshift z ~ 6; and (v) jets produced in successive accretion episodes can have similar directions, but after several episodes the jet direction deviates significantly. Rare examples of massive holes with larger spin parameters could result from prograde coalescences with SMBHs of similar mass, and are most likely to be found in giant ellipticals. We compare these results with observation.

[]

https://arxiv.org/pdf/0801.1564.pdf

2005CQGra..22.3349A

Black hole evaporation: a paradigm

2005-01-01

['-', '-']

[]

A paradigm describing black hole evaporation in non-perturbative quantum gravity is developed by combining two sets of detailed results: (i) resolution of the Schwarzschild singularity using quantum geometry methods and (ii) time evolution of black holes in the trapping and dynamical horizon frameworks. Quantum geometry effects introduce a major modification in the traditional spacetime diagram of black hole evaporation, providing a possible mechanism for recovery of information that is classically lost in the process of black hole formation. The paradigm is developed directly in the Lorentzian regime and necessary conditions for its viability are discussed. If these conditions are met, much of the tension between expectations based on spacetime geometry and structure of quantum theory would be resolved.

[]

https://arxiv.org/pdf/gr-qc/0504029.pdf

2010CQGra..27k4103O

A new open-source code for spherically symmetric stellar collapse to neutron stars and black holes

2010-01-01

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

[]

We present the new open-source spherically symmetric general-relativistic (GR) hydrodynamics code GR1D. It is based on the Eulerian formulation of GR hydrodynamics (GRHD) put forth by Romero-Ibáñez-Gourgoulhon and employs radial-gauge, polar-slicing coordinates in which the 3+1 equations simplify substantially. We discretize the GRHD equations with a finite-volume scheme, employing piecewise-parabolic reconstruction and an approximate Riemann solver. GR1D is intended for the simulation of stellar collapse to neutron stars and black holes and will also serve as a testbed for modeling technology to be incorporated in multi-D GR codes. Its GRHD part is coupled to various finite-temperature microphysical equations of state in tabulated form that we make available with GR1D. An approximate deleptonization scheme for the collapse phase and a neutrino-leakage/heating scheme for the postbounce epoch are included and described. We also derive the equations for effective rotation in 1D and implement them in GR1D. We present an array of standard test calculations and also show how simple analytic equations of state in combination with presupernova models from stellar evolutionary calculations can be used to study qualitative aspects of black hole formation in failing rotating core-collapse supernovae. In addition, we present a simulation with microphysical equations of state and neutrino leakage/heating of a failing core-collapse supernova and black hole formation in a presupernova model of a 40 M<SUB>odot</SUB> zero-age main-sequence star. We find good agreement on the time of black hole formation (within 20%) and last stable protoneutron star mass (within 10%) with predictions from simulations with full Boltzmann neutrino radiation hydrodynamics.

[]

https://arxiv.org/pdf/0912.2393.pdf

1999PhLA..256..347H

Dynamic black-hole entropy

1999-01-01

['-']

[]

We consider two non-statistical definitions of the entropy of dynamic (non-stationary) black holes in a spherical symmetry. The first is analogous to the original Clausius definition of thermodynamic entropy: there is a first law containing an energy-supply term which equals surface gravity times a total differential. The second is Wald's Noether-charge method, adapted to dynamic black holes by using the Kodama flow. Both definitions give the same value for the Einstein gravity: one-quarter the area of the trapping horizon.

[]

https://arxiv.org/pdf/gr-qc/9810006.pdf

1995NuPhB.447..441C

Charged dilaton black holes with unusual asymptotics

1995-01-01

['-']

[]

We present a new class of black hole solutions in Einstein-Maxwell-dilaton gravity in n ⩾ 4 dimensions. These solutions have regular horizons and a singularity only at the origin. Their asymptotic behavior is neither asymptotically flat nor (anti-)de Sitter. Similar solutions exist for certain Liouville-type potentials for the dilaton.

[]

https://arxiv.org/pdf/gr-qc/9502042.pdf

2013ApJ...764..151G

The M <SUB>BH</SUB>-L <SUB>spheroid</SUB> Relation at High and Low Masses, the Quadratic Growth of Black Holes, and Intermediate-mass Black Hole Candidates

2013-01-01

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

[]

From a sample of 72 galaxies with reliable supermassive black hole masses M <SUB>bh</SUB>, we derive the M <SUB>bh</SUB>-(host spheroid luminosity, L) relation for (1) the subsample of 24 core-Sérsic galaxies with partially depleted cores, and (2) the remaining subsample of 48 Sérsic galaxies. Using K<SUB>s</SUB> -band Two Micron All Sky Survey data, we find the near-linear relation M <SUB>bh</SUB>vpropL <SUP>1.10 ± 0.20</SUP> <SUB>K<SUB>s</SUB> </SUB> for the core-Sérsic spheroids thought to be built in additive dry merger events, while we find the relation M <SUB>bh</SUB>vpropL <SUP>2.73 ± 0.55</SUP> <SUB>K<SUB>s</SUB> </SUB> for the Sérsic spheroids built from gas-rich processes. After converting literature B-band disk galaxy magnitudes into inclination- and dust-corrected bulge magnitudes, via a useful new equation presented herein, we obtain a similar result. Unlike with the M <SUB>bh</SUB>-(velocity dispersion) diagram, which is also updated here using the same galaxy sample, it remains unknown whether barred and non-barred Sérsic galaxies are offset from each other in the M <SUB>bh</SUB>-L diagram. While black hole feedback has typically been invoked to explain what was previously thought to be a nearly constant M <SUB>bh</SUB>/M <SUB>Spheroid</SUB> mass ratio of ~0.2%, we advocate that the near-linear M <SUB>bh</SUB>-L and M <SUB>bh</SUB>-M <SUB>Spheroid</SUB> relations observed at high masses may have instead arisen largely from the additive dry merging of galaxies. We argue that feedback results in a dramatically different scaling relation, such that black hole mass scales roughly quadratically with the spheroid mass in Sérsic galaxies. We therefore introduce a revised cold-gas "quasar" mode feeding equation for semi-analytical models to reflect what we dub the quadratic growth of black holes in Sérsic galaxies built amidst gas-rich processes. Finally, we use our new Sérsic M <SUB>bh</SUB>-L equations to predict the masses of candidate intermediate mass black holes in almost 50 low-luminosity spheroids containing active galactic nuclei, finding many masses between that of stellar mass black holes and supermassive black holes.

[]

https://arxiv.org/pdf/1211.3199.pdf

2012arXiv1208.4074D

Quantum Black Holes, Wall Crossing, and Mock Modular Forms

2012-01-01

['-', '-']

[]

We show that the meromorphic Jacobi form that counts the quarter-BPS states in N=4 string theories can be canonically decomposed as a sum of a mock Jacobi form and an Appell-Lerch sum. The quantum degeneracies of single-centered black holes are Fourier coefficients of this mock Jacobi form, while the Appell-Lerch sum captures the degeneracies of multi-centered black holes which decay upon wall-crossing. The completion of the mock Jacobi form restores the modular symmetries expected from $AdS_3/CFT_2$ holography but has a holomorphic anomaly reflecting the non-compactness of the microscopic CFT. For every positive integral value m of the magnetic charge invariant of the black hole, our analysis leads to a special mock Jacobi form of weight two and index m, which we characterize uniquely up to a Jacobi cusp form. This family of special forms and another closely related family of weight-one forms contain almost all the known mock modular forms including the mock theta functions of Ramanujan, the generating function of Hurwitz-Kronecker class numbers, the mock modular forms appearing in the Mathieu and Umbral moonshine, as well as an infinite number of new examples.

[]

https://arxiv.org/pdf/1208.4074.pdf

2010PhRvD..81l4045A

Null geodesics and shadow of a rotating black hole in extended Chern-Simons modified gravity

2010-01-01

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

[]

The Chern-Simons modification to general relativity in four dimensions consists of adding to the Einstein-Hilbert term a scalar field that couples to the first-class Pontryagin density. In this theory, which has attracted considerable attention recently, the Schwarzschild metric persists as an exact solution, and this is why this model resists several observational constraints. In contrast, the spinning black hole solution of the theory is not given by the Kerr metric but by a modification of it, so far only known for slow rotation and small coupling constant. In the present paper, we show that, in this approximation, the null geodesic equation can be integrated, and this allows us to investigate the shadow cast by a black hole. We discuss how, in addition to the angular momentum of the solution, the coupling to the Chern-Simons term deforms the shape of the shadow.

[]

https://arxiv.org/pdf/1005.0607.pdf

2002PhRvD..65l4027A

Black holes from cosmic rays: Probes of extra dimensions and new limits on TeV-scale gravity

2002-01-01

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

[]

If extra spacetime dimensions and low-scale gravity exist, black holes will be produced in observable collisions of elementary particles. For the next several years, ultrahigh-energy cosmic rays provide the most promising window on this phenomenon. In particular, cosmic neutrinos can produce black holes deep in the Earth's atmosphere, leading to quasihorizontal giant air showers. We determine the sensitivity of cosmic ray detectors to black hole production and compare the results to other probes of extra dimensions. With n&gt;=4 extra dimensions, current bounds on deeply penetrating showers from AGASA already provide the most stringent bound on low-scale gravity, requiring a fundamental Planck scale M<SUB>D</SUB>&gt;1.3-1.8 TeV. The Auger Observatory will probe M<SUB>D</SUB> as large as 4 TeV and may observe on the order of a hundred black holes in 5 years. We also consider the implications of angular momentum and possible exponentially suppressed parton cross sections; including these effects, large black hole rates are still possible. Finally, we demonstrate that even if only a few black hole events are observed, a standard model interpretation may be excluded by comparison with Earth-skimming neutrino rates.

[]

https://arxiv.org/pdf/hep-ph/0112247.pdf

2006Natur.441..953M

The magnetic nature of disk accretion onto black holes

2006-01-01

['astrophysics']

[]

Although disk accretion onto compact objects-white dwarfs, neutron stars and black holes-is central to much of high-energy astrophysics, the mechanisms that enable this process have remained observationally difficult to determine. Accretion disks must transfer angular momentum in order for matter to travel radially inward onto the compact object. Internal viscosity from magnetic processes and disk winds can both in principle transfer angular momentum, but hitherto we lacked evidence that either occurs. Here we report that an X-ray-absorbing wind discovered in an observation of the stellar-mass black hole binary GRO J1655 - 40 (ref. 6) must be powered by a magnetic process that can also drive accretion through the disk. Detailed spectral analysis and modelling of the wind shows that it can only be powered by pressure generated by magnetic viscosity internal to the disk or magnetocentrifugal forces. This result demonstrates that disk accretion onto black holes is a fundamentally magnetic process.

[]

https://arxiv.org/pdf/astro-ph/0605390.pdf

1997ApJ...478L..79N

Advection-dominated Accretion and Black Hole Event Horizons

1997-01-01

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

[]

The defining characteristic of a black hole is that it possesses an event horizon through which matter and energy can fall in but from which nothing escapes. Soft X-ray transients (SXTs), a class of X-ray binaries, appear to confirm this fundamental property of black holes. SXTs that are thought to contain accreting black holes display a large variation of luminosity between their bright and their faint states, while SXTs with accreting neutron stars have a smaller variation. This difference is predicted if the former stars have horizons, and the latter have normal surfaces.

[]

https://arxiv.org/pdf/astro-ph/9701139.pdf

1994PhRvD..49.1912B

Entropy bounds and black hole remnants

1994-01-01

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

[]

We rederive the universal bound on entropy with the help of black holes while allowing for Unruh-Wald buoyancy. We consider a box full of entropy lowered toward and then dropped into a Reissner-Nordström black hole in equilibrium with thermal radiation. We avoid the approximation that the buoyant pressure varies slowly across the box, and compute the buoyant force exactly. We find, in agreement with independent investigations, that the neutral point generically lies very near the horizon. A consequence is that in the generic case the Unruh-Wald entropy restriction is neither necessary nor sufficient for enforcement of the generalized second law. Another consequence is that generically the buoyancy makes only a negligible contribution to the energy bookkeeping, so that the original entropy bound is recovered if the generalized second law is assumed to hold. The number of particle species does not figure in the entropy bound, a point that has caused some perplexity. We demonstrate by explicit calculation that, for an arbitrarily large number of particle species, the bound is indeed satisfied by cavity thermal radiation in the thermodynamic regime, provided vacuum energies are included. We also show directly that thermal radiation in a cavity in D-dimensional space also respects the bound regardless of the value of D. As an application of the bound we show that it strongly restricts the information capacity of the posited black hole remnants, so that they cannot serve to resolve the information paradox.

[]

https://arxiv.org/pdf/gr-qc/9307035.pdf

2010GReGr..42.2269B

Gravitational lensing by black holes

2010-01-01

['gravitational lensing', 'black hole physics', 'galaxy center', '-', '-']

[]

We review the theoretical aspects of gravitational lensing by black holes, and discuss the perspectives for realistic observations. We will first treat lensing by spherically symmetric black holes, in which the formation of infinite sequences of higher order images emerges in the clearest way. We will then consider the effects of the spin of the black hole, with the formation of giant higher order caustics and multiple images. Finally, we will consider the perspectives for observations of black hole lensing, from the detection of secondary images of stellar sources and spots on the accretion disk to the interpretation of iron K-lines and direct imaging of the shadow of the black hole.

[]

https://arxiv.org/pdf/0911.2187.pdf

2000AJ....119.1157G

Axisymmetric, Three-Integral Models of Galaxies: A Massive Black Hole in NGC 3379

2000-01-01

['galaxies elliptical lenticular;cd', 'galaxies', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'astrophysics']

[]

We fit axisymmetric three-integral dynamical models to NGC 3379 using the line-of-sight velocity distribution obtained from Hubble Space Telescope FOS spectra of the galaxy center and ground-based long-slit spectroscopy along four position angles, with the light distribution constrained by WFPC2 and ground-based images. We have fitted models with inclinations from 29 deg (intrinsic galaxy type E5) to 90 deg (intrinsic E1) and black hole masses from 0 to 10<SUP>9</SUP> M<SUB>solar</SUB>. The best-fit black hole masses range from 6x10<SUP>7</SUP> to 2x10<SUP>8</SUP> M<SUB>solar</SUB>, depending on inclination. The preferred inclination is 90 deg (edge-on) however, the constraints on allowed inclination are not very strong, owing to our assumption of constant M/L<SUB>V</SUB>. The velocity ellipsoid of the best model is not consistent with either isotropy or a two-integral distribution function. Along the major axis, the velocity ellipsoid becomes tangential at the innermost bin, radial in the midrange radii, and tangential again at the outermost bins. The rotation rises quickly at small radii owing to the presence of the black hole. For the acceptable models, the radial-to-tangential [(σ<SUP>2</SUP><SUB>θ</SUB>+σ<SUP>2</SUP><SUB>φ</SUB>)/2] dispersion in the midrange radii ranges over 1.1&lt;σ<SUB>r</SUB>/σ<SUB>t</SUB>&lt;1.7, with the smaller black holes requiring larger radial anisotropy. Compared with these three-integral models, two-integral isotropic models overestimate the black hole mass since they cannot provide adequate radial motion. However, the models presented in this paper still contain restrictive assumptions-namely, assumptions of constant M/L<SUB>V</SUB> and spheroidal symmetry-requiring yet more models to study black hole properties in complete generality.

[]

https://arxiv.org/pdf/astro-ph/9912026.pdf

2009ApJ...700.1690G

The Black Hole Mass, Stellar Mass-to-Light Ratio, and Dark Halo in M87

2009-01-01

['galaxies elliptical lenticular;cd', 'cd', 'galaxies', 'galaxies kinematics and dynamics', '-']

[]

We model the dynamical structure of M87 (NGC4486) using high spatial resolution long-slit observations of stellar light in the central regions, two-dimensional stellar light kinematics out to half of the effective radius, and globular cluster velocities out to eight effective radii. We simultaneously fit for four parameters: black hole mass, dark halo core radius, dark halo circular velocity, and stellar mass-to-light (M/L) ratio. We find a black hole mass of 6.4(±0.5) × 10<SUP>9</SUP> M <SUB>sun</SUB> (the uncertainty is 68% confidence marginalized over the other parameters). The stellar M/L<SUB>V</SUB> = 6.3 ± 0.8. The best-fit dark halo core radius is 14 ± 2 kpc, assuming a cored logarithmic potential. The best-fit dark halo circular velocity is 715 ± 15 km s<SUP>-1</SUP>. Our black hole mass is over a factor of 2 larger than previous stellar dynamical measures, and our derived stellar M/L ratio is two times lower than previous dynamical measures. When we do not include a dark halo, we measure a black hole mass and stellar M/L ratio that is consistent with previous measures, implying that the major difference is in the model assumptions. The stellar M/L ratio from our models is very similar to that derived from stellar population models of M87. The reason for the difference in the black hole mass is because we allow the M/L ratio to change with radius. The dark halo is degenerate with the stellar M/L ratio, which is subsequently degenerate with the black hole mass. We argue that dynamical models of galaxies that do not include the contribution from a dark halo may produce a biased result for the black hole mass. This bias is especially large for a galaxy with a shallow light profile such as M87, and may not be as severe in galaxies with steeper light profiles unless they have a large stellar population change with radius.

[]

https://arxiv.org/pdf/0906.1492.pdf

2007PhRvD..76j4049B

Approaching faithful templates for nonspinning binary black holes using the effective-one-body approach

2007-01-01

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

[]

We present an accurate approximation of the full gravitational radiation waveforms generated in the merger of noneccentric systems of two nonspinning black holes. Utilizing information from recent numerical relativity simulations and the natural flexibility of the effective-one-body (EOB) model, we extend the latter so that it can successfully match the numerical relativity waveforms during the last stages of inspiral, merger, and ringdown. By “successfully” here, we mean with phase differences ≲8% of a gravitational-wave cycle accumulated by the end of the ringdown phase, maximizing only over time of arrival and initial phase. We obtain this result by simply adding a 4-post-Newtonian order correction in the EOB radial potential and determining the (constant) coefficient by imposing high-matching performances with numerical waveforms of mass ratios m<SUB>1</SUB>/m<SUB>2</SUB>=1, 3/2, 2 and 4, m<SUB>1</SUB> and m<SUB>2</SUB> being the individual black-hole masses. The final black-hole mass and spin predicted by the numerical simulations are used to determine the ringdown frequency and decay time of three quasinormal-mode damped sinusoids that are attached to the EOB inspiral-(plunge) waveform at the EOB light ring. The EOB waveforms might be tested and further improved in the future by comparison with extremely long and accurate inspiral numerical relativity waveforms. They may be already employed for coherent searches and parameter estimation of gravitational waves emitted by nonspinning coalescing binary black holes with ground-based laser-interferometer detectors.

[]

https://arxiv.org/pdf/0706.3732.pdf

2011MNRAS.415.1027H

An analytic model of angular momentum transport by gravitational torques: from galaxies to massive black holes

2011-01-01

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

[]

We present analytic calculations of angular momentum transport and gas inflow in galaxies, from scales of ∼ kpc to deep inside the potential of a central massive black hole (BH). We compare these analytic calculations to numerical simulations and use them to develop a sub-grid model of BH growth that can be incorporated into semi-analytic calculations or cosmological simulations. Motivated by both analytic calculations and simulations of gas inflow in galactic nuclei, we argue that the strongest torque on gas arises when non-axisymmetric perturbations to the stellar gravitational potential produce orbit crossings and shocks in the gas. This is true both at large radii ∼0.01-1 kpc, where bar-like stellar modes dominate the non-axisymmetric potential, and at smaller radii ≲10 pc, where a lopsided/eccentric stellar disc dominates. The traditional orbit-crossing criterion is not always adequate to predict the locations of, and inflow due to, shocks in gas+stellar discs with finite sound speeds. We derive a modified criterion that predicts the presence of shocks in stellar-dominated systems even absent formal orbit crossing. We then derive analytic expressions for the loss of angular momentum and the resulting gas inflow rates in the presence of such shocks. We test our analytic predictions using hydrodynamic simulations at a range of galactic scales, and show that they successfully predict the mass inflow rates and quasi-steady gas surface densities with a small scatter ≃0.3 dex. We use our analytic results to construct a new estimate of the BH accretion rate given galaxy properties at larger radii, for use in galaxy and cosmological simulations and semi-analytic models. While highly simplified, this accretion rate predictor captures the key scalings in the numerical simulations. By contrast, alternate estimates such as the local viscous accretion rate or the spherical Bondi rate fail systematically to reproduce the simulations and have significantly larger scatter.

[]

https://arxiv.org/pdf/1007.2647.pdf

2008ApJ...678..693M

The Effect of Radiation Pressure on Virial Black Hole Mass Estimates and the Case of Narrow-Line Seyfert 1 Galaxies

2008-01-01

['galaxies active', 'galaxies fundamental parameters', 'galaxies nuclei', 'galaxies seyfert', 'galaxies quasars', 'radiation', 'astrophysics']

[]

We consider the effect of radiation pressure from ionizing photons on black hole (BH) mass estimates based on the application of the virial theorem to broad emission lines in AGN spectra. BH masses based only on the virial product Δ V<SUP>2</SUP>R and neglecting the effect of radiation pressure can be severely underestimated, especially in objects close to the Eddington limit. We provide an empirical calibration of the correction for radiation pressure, and we show that it is consistent with a simple physical model in which BLR clouds are optically thick to ionizing radiation and have average column densities of N<SUB>H</SUB> ~ 10<SUP>23</SUP> cm <SUP>-2</SUP>. This value is remarkably similar to what is required in standard BLR photoionization models to explain observed spectra. With the inclusion of radiation pressure, the discrepancy between virial BH masses based on single-epoch spectra and on reverberation mapping data drops from 0.4 to 0.2 dex rms. The use of single-epoch observations as surrogates of reverberation mapping campaigns can thus provide more accurate BH masses than previously thought. Finally, we show that narrow-line Seyfert 1 (NLS1) galaxies have apparently low BH masses because they are radiating close to their Eddington limit. After the radiation pressure correction, NLS1 galaxies have BH masses similar to other broad-line AGNs and follow the same M<SUB>BH</SUB> - σ<SUB>e</SUB>/L<SUB>sph</SUB> relations as other active and normal galaxies. Radiation forces arising from ionizing photon momentum deposition constitute an important physical effect which must be taken into account when computing virial BH masses.

[]

https://arxiv.org/pdf/0802.2021.pdf

2011ApJ...727...20K

The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks

2011-01-01

['accretion', 'accretion disks', 'galaxies active', 'galaxies intergalactic medium', 'galaxies nuclei', 'galaxies seyfert', '-']

[]

Observations of H<SUB>2</SUB>O masers from circumnuclear disks in active galaxies for the Megamaser Cosmology Project (MCP) allow accurate measurement of the mass of supermassive black holes (BH) in these galaxies. We present the Very Long Baseline Interferometry images and kinematics of water maser emission in six active galaxies: NGC 1194, NGC 2273, NGC 2960 (Mrk 1419), NGC 4388, NGC 6264 and NGC 6323. We use the Keplerian rotation curves of these six megamaser galaxies, plus a seventh previously published, to determine accurate enclosed masses within the central ~0.3 pc of these galaxies, smaller than the radius of the sphere of influence of the central mass in all cases. We also set lower limits to the central mass densities of between 0.12 × 10<SUP>10</SUP> and 61 × 10<SUP>10</SUP> M <SUB>sun</SUB> pc<SUP>-3</SUP>. For six of the seven disks, the high central densities rule out clusters of stars or stellar remnants as the central objects, and this result further supports our assumption that the enclosed mass can be attributed predominantly to a supermassive BH. The seven BHs have masses ranging between 0.75 × 10<SUP>7</SUP> and 6.5 × 10<SUP>7</SUP> M <SUB>sun</SUB>, with the mass errors dominated by the uncertainty of the Hubble constant. We compare the megamaser BH mass determination with BH mass measured from the virial estimation method. The virial estimation BH mass in four galaxies is consistent with the megamaser BH mass, but the virial mass uncertainty is much greater. Circumnuclear megamaser disks allow the best mass determination of the central BH mass in external galaxies and significantly improve the observational basis at the low-mass end of the M-σ<SUB>sstarf</SUB> relation. The M-σ<SUB>sstarf</SUB> relation may not be a single, low-scatter power law as originally proposed. MCP observations continue and we expect to obtain more maser BH masses in the future.

[]

https://arxiv.org/pdf/1008.2146.pdf

2019ApJ...881L...1F

Most Black Holes Are Born Very Slowly Rotating

2019-01-01

['-', '-', '-', '-', '-', 'sun evolution', 'mhd', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

The age of gravitational-wave astronomy has begun, and black hole (BH) mergers detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) are providing novel constraints on massive star evolution. A major uncertainty in stellar theory is the angular momentum (AM) transport within the star that determines its core rotation rate and the resulting BH’s spin. Internal rotation rates of low-mass stars measured from asteroseismology prove that AM transport is efficient, suggesting that massive stellar cores may rotate slower than prior expectations. We investigate AM transport via the magnetic Tayler instability, which can largely explain the rotation rates of low-mass stars and white dwarfs. Implementing an updated AM transport prescription into models of high-mass stars, we compute the spins of their BH remnants. We predict that BHs born from single stars rotate very slowly, with a ∼ 10<SUP>-2</SUP>, regardless of initial rotation rate, possibly explaining the low χ <SUB>eff</SUB> of most BH binaries detected by LIGO thus far. A limited set of binary models suggests slow rotation for many binary scenarios as well, although homogeneous evolution and tidal spin-up of post-common-envelope helium stars can create moderate or high BH spins. We make predictions for the values of χ <SUB>eff</SUB> in future LIGO events, and we discuss implications for engine-powered transients.

[]

https://arxiv.org/pdf/1907.03714.pdf

2008ApJ...678.1180B

The Influence of Magnetic Field Geometry on the Evolution of Black Hole Accretion Flows: Similar Disks, Drastically Different Jets

2008-01-01

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

[]

Because the magnetorotational instability is capable of exponentially amplifying weak pre-existing magnetic fields, it might be hoped that the character of the magnetic field in accretion disks would be independent of the nature of the seed field. However, the divergence-free nature of magnetic fields in highly conducting fluids ensures that their large-scale topology is preserved, no matter how greatly the field intensity is changed. By performing global two- and three-dimensional general relativistic magnetohydrodynamic disk simulations with several different topologies for the initial magnetic field, we explore the degree to which the character of the flows around black holes depends on the initial topology. We find that while the qualitative properties of the accretion flow are nearly independent of field topology, jet launching is very sensitive to it; a sense of vertical field consistent for at least an inner disk inflow time is essential to the support of strong jets.

[]

https://arxiv.org/pdf/0709.3833.pdf

2008MNRAS.391.1961D

Fluctuations in the high-redshift Lyman-Werner background: close halo pairs as the origin of supermassive black holes

2008-01-01

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

[]

The earliest generation of stars and black holes must have established an early `Lyman-Werner' background (LWB) at high redshift, prior to the epoch of reionization. Because of the long mean free path of photons with energies hν &lt; 13.6eV, the LWB was nearly uniform. However, some variation in the LWB is expected due to the discrete nature of the sources, and their highly clustered spatial distribution. In this paper, we compute the probability distribution function (PDF) of the LW flux that irradiates dark matter (DM) haloes collapsing at high redshift (z ~ 10). Our model accounts for (i) the clustering of DM haloes, (ii) Poisson fluctuations in the number of corresponding star-forming galaxies and (iii) scatter in the LW luminosity produced by haloes of a given mass (calibrated using local observations). We find that &gt;99 per cent of the DM haloes are illuminated by an LW flux within a factor of 2 of the global mean value. However, a small fraction, ~10<SUP>-8</SUP> to 10<SUP>-6</SUP>, of DM haloes with virial temperatures T<SUB>vir</SUB> &gt;~ 10<SUP>4</SUP> K have a close luminous neighbour within &lt;~10 kpc, and are exposed to an LW flux exceeding the global mean by a factor of &gt;20, or to J<SUB>21,LW</SUB> &gt; 10<SUP>3</SUP> (in units of 10<SUP>-21</SUP> erg s<SUP>-1</SUP> Hz<SUP>-1</SUP> sr<SUP>-1</SUP> cm<SUP>-2</SUP>). This large LW flux can photodissociate H<SUB>2</SUB> molecules in the gas collapsing due to atomic cooling in these haloes, and prevent its further cooling and fragmentation. Such close halo pairs therefore provide possible sites in which primordial gas clouds collapse directly into massive black holes (M<SUB>BH</SUB> ~ 10<SUP>4-6</SUP>M<SUB>solar</SUB>), and subsequently grow into supermassive (M<SUB>BH</SUB> &gt;~ 10<SUP>9</SUP>M<SUB>solar</SUB>) black holes by z ~ 6.

[]

https://arxiv.org/pdf/0810.0014.pdf

2003ApJ...596..860M

Long-Term Evolution of Massive Black Hole Binaries

2003-01-01

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

[]

The long-term evolution of massive black hole binaries at the centers of galaxies is studied in a variety of physical regimes, with the aim of resolving the ``final parsec problem,'' i.e., how black hole binaries manage to shrink to separations at which emission of gravity waves becomes efficient. A binary ejects stars by the gravitational slingshot and carves out a loss cone in the host galaxy. Continued decay of the binary requires a refilling of the loss cone. We show that the standard treatment of loss cone refilling, derived for collisionally relaxed systems like globular clusters, can substantially underestimate the refilling rates in galactic nuclei. We derive expressions for nonequilibrium loss cone dynamics and calculate timescales for the decay of massive black hole binaries following galaxy mergers, obtaining significantly higher decay rates than heretofore. Even in the absence of two-body relaxation, decay of binaries can persist as a result of repeated ejection of stars returning to the nucleus on eccentric orbits. We show that this recycling of stars leads to a gradual, approximately logarithmic dependence of the binary binding energy on time. We derive an expression for the loss cone refilling induced by the Brownian motion of a black hole binary. We also show that numerical N-body experiments are not well suited to probe these mechanisms over long times as a result of spurious relaxation.

[]

https://arxiv.org/pdf/astro-ph/0212459.pdf

2006PhRvD..74f6001B

Bubbling supertubes and foaming black holes

2006-01-01

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

[]

We construct smooth BPS three-charge geometries that resolve the zero-entropy singularity of the U(1)×U(1) invariant black ring. This singularity is resolved by a geometric transition that results in geometries without any branes sources or singularities but with nontrivial topology. These geometries are both ground states of the black ring, and nontrivial microstates of the D1-D5-P system. We also find the form of the geometries that result from the geometric transition of N zero-entropy black rings, and argue that, in general, such geometries give a very large number of smooth bound-state three-charge solutions, parametrized by 6N functions. The generic microstate solution is specified by a four-dimensional hyper-Kähler geometry of a certain signature, and contains a “foam” of nontrivial two-spheres. We conjecture that these geometries will account for a significant part of the entropy of the D1-D5-P black hole, and that Mathur’s conjecture might reduce to counting certain hyper-Kähler manifolds.

[]

https://arxiv.org/pdf/hep-th/0505166.pdf

2015ApJ...800....9M

The Dynamical Evolution of Stellar Black Holes in Globular Clusters

2015-01-01

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

[]

Our current understanding of the stellar initial mass function and massive star evolution suggests that young globular clusters (GCs) may have formed hundreds to thousands of stellar-mass black holes (BHs), the remnants of stars with initial masses from ~20-100 M <SUB>⊙</SUB>. Birth kicks from supernova explosions may eject some BHs from their birth clusters, but most should be retained. Using a Monte Carlo method we investigate the long-term dynamical evolution of GCs containing large numbers of stellar BHs. We describe numerical results for 42 models, covering a broad range of realistic initial conditions, including up to 1.6 × 10<SUP>6</SUP> stars. In almost all models we find that significant numbers of BHs (up to ~10<SUP>3</SUP>) are retained all the way to the present. This is in contrast to previous theoretical expectations that most BHs should be ejected dynamically within a few gigayears The main reason for this difference is that core collapse driven by BHs (through the Spitzer "mass segregation instability") is easily reverted through three-body processes, and involves only a small number of the most massive BHs, while lower-mass BHs remain well-mixed with ordinary stars far from the central cusp. Thus the rapid segregation of stellar BHs does not lead to a long-term physical separation of most BHs into a dynamically decoupled inner core, as often assumed previously. Combined with the recent detections of several BH X-ray binary candidates in Galactic GCs, our results suggest that stellar BHs could still be present in large numbers in many GCs today, and that they may play a significant role in shaping the long-term dynamical evolution and the present-day dynamical structure of many clusters.

[]

https://arxiv.org/pdf/1409.0866.pdf

2017JCAP...09..020K

Single field double inflation and primordial black holes

2017-01-01

['-', '-']

[]

Within the framework of scalar-tensor theories, we study the conditions that allow single field inflation dynamics on small cosmological scales to significantly differ from that of the large scales probed by the observations of cosmic microwave background. The resulting single field double inflation scenario is characterised by two consequent inflation eras, usually separated by a period where the slow-roll approximation fails. At large field values the dynamics of the inflaton is dominated by the interplay between its non-minimal coupling to gravity and the radiative corrections to the inflaton self-coupling. For small field values the potential is, instead, dominated by a polynomial that results in a hilltop inflation. Without relying on the slow-roll approximation, which is invalidated by the appearance of the intermediate stage, we propose a concrete model that matches the current measurements of inflationary observables and employs the freedom granted by the framework on small cosmological scales to give rise to a sizeable population of primordial black holes generated by large curvature fluctuations. We find that these features generally require a potential with a local minimum. We show that the associated primordial black hole mass function is only approximately lognormal.

[]

https://arxiv.org/pdf/1705.06225.pdf

2005CaJPh..83.1073B

Black-hole boundaries

2005-01-01

['-', 'dynamical systems', '-', 'relativity', '-', '-', 'gravitational collapse', 'thermodynamics', '-']

[]

Classical black holes and event horizons are highly nonlocal objects, defined in relation to the causal past of future null infinity. Alternative, quasilocal characterizations of black holes are often used in mathematical, quantum, and numerical relativity. These include apparent, Killing, trapping, isolated, dynamical, and slowly evolving horizons. All of these are closely associated with two-surfaces of zero outward null expansion. This paper reviews the traditional definition of black holes and provides an overview of some of the more recent work on alternative horizons.

[]

https://arxiv.org/pdf/gr-qc/0508107.pdf

2018ApJ...866...66M

Constraining Stellar-mass Black Hole Mergers in AGN Disks Detectable with LIGO

2018-01-01

['accretion', 'accretion disks', 'stars binaries close', 'black hole physics', 'galaxies active', 'gravitational waves', '-', '-', '-']

[]

Black hole (BH) mergers detectable with the Laser Interferometer Gravitational-wave Observatory (LIGO) can occur in active galactic nucleus (AGN) disks. Here we parameterize the merger rates, the mass spectrum, and the spin spectrum of BHs in AGN disks. The predicted merger rate spans ∼10<SUP>-3</SUP>-10<SUP>4</SUP> Gpc<SUP>-1</SUP> yr<SUP>-1</SUP>, so upper limits from LIGO (&lt;212 Gpc<SUP>-1</SUP> yr<SUP>-1</SUP>) already constrain it. The predicted mass spectrum has the form of a broken power law, consisting of a pre-existing BH power-law mass spectrum and a harder power-law mass spectrum resulting from mergers. The predicted spin spectrum is multipeaked with the evolution of retrograde spin BHs in the gas disk playing a key role. We outline the large uncertainties in each of these LIGO observables for this channel and we discuss ways in which they can be constrained in the future.

[]

https://arxiv.org/pdf/1702.07818.pdf

1996GReGr..28.1393A

Energy and Angular Momentum of Charged Rotating Black Holes

1996-01-01

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

[]

We show that the pseudotensors of Einstein, Tolman, Landau and Lifshitz, Papapetrou, and Weinberg essentially coincide for any Kerr-Schild metric if calculations are carried out in Kerr-Schild Cartesian coordinates. This generalizes a previous result by Gürses and Gürsey that dealt only with the pseudotensors of Einstein and Landau-Lifshitz. We compute exactly the energy and angular momentum distributions for the Kerr-Newman metric in Kerr-Schild Cartesian coordinates and compare the results with those obtained by using different definitions of quasilocal mass, which unlike pseudotensors do not agree for all Kerr-Schild metrics.

[]

https://arxiv.org/pdf/gr-qc/9501002.pdf

2006CQGra..23.5587M

Loop quantum black hole

2006-01-01

['-']

[]

We study the quantum properties of the Kantowski Sachs spacetime, using ideas from loop quantum gravity. This spacetime coincides with the Schwarzschild black hole solution inside the horizon. Recently it was shown that the classical black hole singularity is controlled by the quantum theory, using ADM variables. In this paper we have used Ashtekar-like variables, obtaining information both on quantum effects on the singularity and on the dynamics across the r = 0 singular point. Finally, we have found a regular spacetime inside the horizon and that the dynamics can be extended beyond the classical singularity.

[]

https://arxiv.org/pdf/gr-qc/0509078.pdf

2010MNRAS.402..371B

Stellar-mass black holes in star clusters: implications for gravitational wave radiation

2010-01-01

['black hole physics', 'gravitational waves', 'scattering', 'stars kinematics and dynamics', 'methods n body', 'galaxies star clusters', '-', '-', '-']

[]

We study the dynamics of stellar-mass black holes (BH) in star clusters with particular attention to the formation of BH-BH binaries, which are interesting as sources of gravitational waves (GW). In the present study, we examine the properties of these BH-BH binaries through direct N-body simulations of star clusters using the NBODY6 code on graphical processing unit platforms. We perform simulations for star clusters with &lt;=10<SUP>5</SUP> low-mass stars starting from Plummer models with an initial population of BHs, varying the cluster mass and BH-retention fraction. Additionally, we do several calculations of star clusters confined within a reflective boundary mimicking only the core of a massive star cluster which can be performed much faster than the corresponding full cluster integration. We find that stellar-mass BHs with masses ~10M<SUB>solar</SUB> segregate rapidly (~100 Myr time-scale) into the cluster core and form a dense subcluster of BHs within typically 0.2-0.5 pc radius. In such a subcluster, BH-BH binaries can be formed through three-body encounters, the rate of which can become substantial in dense enough BH cores. While most BH binaries are finally ejected from the cluster by recoils received during superelastic encounters with the single BHs, few of them harden sufficiently so that they can merge via GW emission within the cluster. We find that for clusters with N &gt;~ 5 × 10<SUP>4</SUP>, typically 1-2 BH-BH mergers occur per cluster within the first ~4 Gyr of cluster evolution. Also for each of these clusters, there are a few escaping BH binaries that can merge within a Hubble time, most of the merger times being within a few Gyr. These results indicate that intermediate-age massive clusters constitute the most important class of candidates for producing dynamical BH-BH mergers. Old globular clusters cannot contribute significantly to the present-day BH-BH merger rate since most of the mergers from them would have occurred much earlier. On the other hand, young massive clusters with ages less that 50 Myr are too young to produce significant number of BH-BH mergers. We finally discuss the detection rate of BH-BH inspirals by the `Laser Interferometer Gravitational-Wave Observatory' (LIGO) and `Advanced LIGO' GW detectors. Our results indicate that dynamical BH-BH binaries constitute the dominant channel for BH-BH merger detection.

[]

https://arxiv.org/pdf/0910.3954.pdf

2007CQGra..24S.689A

A phenomenological template family for black-hole coalescence waveforms

2007-01-01

['-', 'astrophysics']

[]

Recent progress in numerical relativity has enabled us to model the non-perturbative merger phase of the binary black-hole coalescence problem. Based on these results, we propose a phenomenological family of waveforms which can model the inspiral, merger and ring-down stages of black-hole coalescence. We also construct a template bank using this family of waveforms and discuss its implementation in the search for signatures of gravitational waves produced by black-hole coalescences in the data of ground-based interferometers. This template bank might enable us to extend the present inspiral searches to higher-mass binary black-hole systems, i.e., systems with total mass greater than about 80 solar masses, thereby increasing the reach of the current generation of ground-based detectors.

[]

https://arxiv.org/pdf/0704.3764.pdf

2017Natur.548..426F

Distinguishing spin-aligned and isotropic black hole populations with gravitational waves

2017-01-01

['-', '-']

[]

The direct detection of gravitational waves from merging binary black holes opens up a window into the environments in which binary black holes form. One signature of such environments is the angular distribution of the black hole spins. Binary systems that formed through dynamical interactions between already-compact objects are expected to have isotropic spin orientations (that is, the spins of the black holes are randomly oriented with respect to the orbit of the binary system), whereas those that formed from pairs of stars born together are more likely to have spins that are preferentially aligned with the orbit. The best-measured combination of spin parameters for each of the four likely binary black hole detections GW150914, LVT151012, GW151226 and GW170104 is the ‘effective’ spin. Here we report that, if the magnitudes of the black hole spins are allowed to extend to high values, the effective spins for these systems indicate a 0.015 odds ratio against an aligned angular distribution compared to an isotropic one. When considering the effect of ten additional detections, this odds ratio decreases to 2.9 × 10<SUP>-7</SUP> against alignment. The existing preference for either an isotropic spin distribution or low spin magnitudes for the observed systems will be confirmed (or overturned) confidently in the near future.

[]

https://arxiv.org/pdf/1706.01385.pdf

2005MNRAS.363...49K

Aligning spinning black holes and accretion discs

2005-01-01

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

[]

We consider the alignment torque between a spinning black hole and an accretion disc whose angular momenta are misaligned. This situation must hold initially in almost all gas accretion events on to supermassive black holes, and may occur in binaries where the black hole receives a natal supernova kick. We show that the torque always acts to align the hole's spin with the total angular momentum without changing its magnitude. The torque acts dissipatively on the disc, reducing its angular momentum, and aligning it with the hole if and only if the angle θ between the angular momenta J<SUB>d</SUB> of the disc and J<SUB>h</SUB> of the hole satisfy the inequality cosθ &gt; -J<SUB>d</SUB>/2J<SUB>h</SUB>. If this condition fails, which requires both θ &gt; π/2 and J<SUB>d</SUB> &lt; 2J<SUB>h</SUB>, the disc counteraligns.

[]

https://arxiv.org/pdf/astro-ph/0507098.pdf

1995PhRvD..52.5865H

Duality between electric and magnetic black holes

1995-01-01

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

[]

A number of attempts have recently been made to extend the conjectured S duality of Yang-Mills theory to gravity. Central to these speculations has been the belief that electrically and magnetically charged black holes, the solitons of quantum gravity, have identical quantum properties. This is not obvious, because, although duality is a symmetry of the classical equations of motion, it changes the sign of the Maxwell action. Nevertheless, we show that the chemical potential and charge projection that one has to introduce for electric but not magnetic black holes exactly compensate for the difference in action in the semiclassical approximation. In particular, we show that the pair production of electric black holes is not a runaway process, as one might think if one just went by the action of the relevant instanton. We also comment on the definition of the entropy in cosmological situations, and show that we need to be more careful when defining the entropy than we are in an asymptotically flat case.

[]

https://arxiv.org/pdf/hep-th/9504019.pdf

1999PhRvD..59f4013H

Overcharging a black hole and cosmic censorship

1999-01-01

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

[]

We show that, contrary to a widespread belief, one can overcharge a near extremal Reissner-Nordström black hole by throwing in a charged particle, as long as the back reaction effects may be considered negligible. Furthermore, we find that we can make the particle's classical radius, mass, and charge, as well as the relative size of the back reaction terms arbitrarily small, by adjusting the parameters corresponding to the particle appropriately. This, however, is not sufficient to justify ignoring back reaction; a naive estimate indicates that cosmic censorship may be preserved. This suggests that the question of cosmic censorship is still not wholly resolved even in this simple scenario. We contrast this with attempting to overcharge a black hole with a charged imploding shell, where we find that cosmic censorship is upheld. We also briefly comment on a number of possible extensions.

[]

https://arxiv.org/pdf/gr-qc/9808043.pdf

2007PhRvD..76f6001H

Hall conductivity from dyonic black holes

2007-01-01

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

[]

A class of strongly interacting 2+1 dimensional conformal field theories in a transverse magnetic field can be studied using the AdS/CFT duality. We compute zero momentum hydrodynamic response functions of maximally supersymmetric 2+1 dimensional SU(N) Yang-Mills theory at the conformal fixed point, in the large N limit. With background magnetic field B and electric charge density ρ, the Hall conductivity is found to be ρ/B. The result, anticipated on kinematic grounds in field theory, is obtained from perturbations of a four-dimensional AdS black hole with both electric and magnetic charges.

[]

https://arxiv.org/pdf/0704.1160.pdf

2016CQGra..33o4001H

Kerr black holes with Proca hair

2016-01-01

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

[]

Bekenstein proved that in Einstein's gravity minimally coupled to one (or many) real, Abelian, Proca field, stationary black holes (BHs) cannot have Proca hair. Dropping Bekenstein's assumption that matter inherits spacetime symmetries, we show this model admits asymptotically flat, stationary, axi-symmetric, regular on and outside an event horizon BHs with Proca hair, for an even number of real (or an arbitrary number of complex) Proca fields. To establish it, we start by showing that a test, complex Proca field can form bound states, with real frequency, around Kerr BHs: stationary Proca clouds. These states exist at the threshold of superradiance. It was conjectured in [1, 2], that the existence of such clouds at the linear level implies the existence of a new family of BH solutions at the nonlinear level. We confirm this expectation and explicitly construct examples of such Kerr BHs with Proca hair (KBHsPH). For a single complex Proca field, these BHs form a countable number of families with three continuous parameters (ADM mass, ADM angular momentum and Noether charge). They branch off from the Kerr solutions that can support stationary Proca clouds and reduce to Proca stars [3] when the horizon size vanishes. We present the domain of existence of one family of KBHsPH, as well as its phase space in terms of ADM quantities. Some physical properties of the solutions are discussed; in particular, and in contrast with Kerr BHs with scalar hair, some spacetime regions can be counter-rotating with respect to the horizon. We further establish a no-Proca-hair theorem for static, spherically symmetric BHs but allowing the complex Proca field to have a harmonic time dependence, which shows BHs with Proca hair in this model require rotation and have no static limit. KBHsPH are also disconnected from Kerr-Newman BHs with a real, massless vector field.

[]

https://arxiv.org/pdf/1603.02687.pdf

2019PhRvD.100l3524M

Threshold for primordial black holes: Dependence on the shape of the cosmological perturbations

2019-01-01

['-', '-']

[]

Primordial black holes may have formed in the radiative era of the early Universe from the collapse of large enough amplitude perturbations of the metric. These correspond to non linear energy density perturbations characterized by an amplitude larger than a certain threshold, measured when the perturbations reenter the cosmological horizon. The process of primordial black hole formation is studied here within spherical symmetry, using the gradient expansion approximation in the long wavelength limit, where the pressure gradients are small, and the initial perturbations are functions only of a time-independent curvature profile. In this regime it is possible to understand how the threshold for primordial black hole formation depends on the shape of the initial energy density profile, clarifying the relation between local and averaged measures of the perturbation amplitude. Although there is no universal threshold for primordial black hole formation, the averaged mass excess of the perturbation depends on the amplitude of the energy density peak, and it is possible to formulate a well-defined criterion to establish when a cosmological perturbation is able to form a black hole in terms of one of these two key quantities. This gives understanding of how the abundance of primordial black holes depends on the shape of the inflationary power spectrum of cosmological perturbations.

[]

https://arxiv.org/pdf/1809.02127.pdf

2012ApJ...757...91B

Missing Black Holes Unveil the Supernova Explosion Mechanism

2012-01-01

['-', 'astronomy x rays', '-']

[]

It is firmly established that the stellar mass distribution is smooth, covering the range 0.1-100 M <SUB>⊙</SUB>. It is to be expected that the masses of the ensuing compact remnants correlate with the masses of their progenitor stars, and thus it is generally thought that the remnant masses should be smoothly distributed from the lightest white dwarfs to the heaviest black holes (BHs). However, this intuitive prediction is not borne out by observed data. In the rapidly growing population of remnants with observationally determined masses, a striking mass gap has emerged at the boundary between neutron stars (NSs) and BHs. The heaviest NSs reach a maximum of two solar masses, while the lightest BHs are at least five solar masses. Over a decade after the discovery, the gap has become a significant challenge to our understanding of compact object formation. We offer new insights into the physical processes that bifurcate the formation of remnants into lower-mass NSs and heavier BHs. Combining the results of stellar modeling with hydrodynamic simulations of supernovae, we both explain the existence of the gap and also put stringent constraints on the inner workings of the supernova explosion mechanism. In particular, we show that core-collapse supernovae are launched within 100-200 ms of the initial stellar collapse, implying that the explosions are driven by instabilities with a rapid (10-20 ms) growth time. Alternatively, if future observations fill in the gap, this will be an indication that these instabilities develop over a longer (&gt;200 ms) timescale.

[]

https://arxiv.org/pdf/1110.1635.pdf

2019PhRvL.123y1101L

Primordial Black Holes as a Dark Matter Candidate Are Severely Constrained by the Galactic Center 511 keV γ -Ray Line

2019-01-01

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

[]

We derive the strongest constraint on the fraction of dark matter that can be composed of low mass primordial black holes by using the observation of the Galactic Center 511 keV γ -ray line. Primordial black holes of masses ≲10<SUP>15</SUP> kg will evaporate to produce e<SUP>±</SUP> pairs. The positrons will lose energy in the Galactic Center, become nonrelativistic, then annihilate with the ambient electrons. We derive robust and conservative bounds by assuming that the rate of positron injection via primordial black hole evaporation is less than what is required to explain the SPI/INTEGRAL observation of the Galactic Center 511 keV γ -ray line. Depending on the primordial black hole mass function and other astrophysical uncertainties, these constraints are the most stringent in the literature and show that primordial black holes contribute to less than 1% of the dark matter density. Our technique also probes part of the mass range which was completely unconstrained by previous studies.

[]

https://arxiv.org/pdf/1906.09994.pdf

2017PhRvD..96c5019B

Black hole superradiance signatures of ultralight vectors

2017-01-01

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

[]

The process of superradiance can extract angular momentum and energy from astrophysical black holes (BHs) to populate gravitationally bound states with an exponentially large number of light bosons. We analytically calculate superradiant growth rates for vectors around rotating BHs in the regime where the vector Compton wavelength is much larger than the BH size. Spin-1 bound states have superradiance times as short as a second around stellar BHs, growing up to a thousand times faster than their spin-0 counterparts. The fast rates allow us to use measurements of rapidly spinning BHs in x-ray binaries to exclude a wide range of masses for weakly coupled spin-1 particles, 5 ×10<SUP>-14</SUP>-2 ×10<SUP>-11</SUP> eV ; lighter masses in the range 6 ×10<SUP>-20</SUP>-2 ×10<SUP>-17</SUP> eV start to be constrained by supermassive BH spin measurements at a lower level of confidence. We also explore routes to detection of new vector particles possible with the advent of gravitational wave (GW) astronomy. The LIGO-Virgo Collaboration could discover hints of a new light vector particle in statistical analyses of masses and spins of merging BHs. Vector annihilations source continuous monochromatic gravitational radiation which could be observed by current GW observatories. At design sensitivity, Advanced LIGO may measure up to thousands of annihilation signals from within the Milky Way, while hundreds of BHs born in binary mergers across the observable Universe may superradiate vector bound states and become new beacons of monochromatic gravitational waves.

[]

https://arxiv.org/pdf/1704.05081.pdf

1993PhRvL..71..328H

String theory formulation of the three-dimensional black hole

1993-01-01

['methods analytical', 'black hole physics', 'cosmology miscellaneous', 'string theory', '-', '-', '-', '-', '-', '-', '-', 'black hole physics', '-', '-']

[]

A black hole solution to three-dimensional general relativity with a negative cosmological constant has recently been found. We show that a slight modification of this solution yields an exact solution to string theory. This black hole is equivalent (under duality) to the previously discussed three-dimensional black string solution. Since the black string is asymptotically flat and the black hole is asymptotically anti-de Sitter, this suggests that strings are not affected by a negative cosmological constant in three dimensions.

[]

https://arxiv.org/pdf/hep-th/9302126.pdf

2005ApJ...634.1093G

An Intermediate-Mass Black Hole in the Globular Cluster G1: Improved Significance from New Keck and Hubble Space Telescope Observations

2005-01-01

['galaxies', 'galaxies star clusters', 'galaxy globular clusters', 'clusters globular', 'clusters globular', 'astrophysics']

[]

We present dynamical models for the massive globular cluster G1. The goal is to measure or place a significant upper limit on the mass of any central black hole. Whether or not globular clusters contain central massive black holes has important consequences for a variety of studies. We use new kinematic data obtained with Keck and new photometry from the Hubble Space Telescope (HST). The Keck spectra allow us to obtain kinematics out to large radii that are required to pin down the mass-to-light ratio of the dynamical model and the orbital structure. The HST observations give us a factor of 2 better spatial resolution for the surface brightness profile. By fitting nonparametric, spherical, isotropic models, we find a best-fit black hole mass of 1.7(+/-0.3)×10<SUP>4</SUP> M<SUB>solar</SUB>. Fully general axisymmetric orbit-based models give similar results, with a black hole mass of 1.8(+/-0.5)×10<SUP>4</SUP> M<SUB>solar</SUB>. The no-black-hole model has Δχ<SUP>2</SUP>=5 (marginalized over mass-to-light ratio), implying less than 3% significance. We have taken into account any change in the mass-to-light ratio in the center due to stellar remnants. These results are consistent with our previous estimate and inconsistent with the analysis of Baumgardt et al., who claim that G1 does not show evidence for a black hole. These new results make G1 the best example of a cluster that contains an intermediate-mass black hole. <P />Based on observations made with the Hubble Space Telescope, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

[]

https://arxiv.org/pdf/astro-ph/0508251.pdf

1998CQGra..15.3609C

What we don't know about BTZ black hole entropy

1998-01-01

['-', '-']

[]

With the recent discovery that many aspects of black hole thermodynamics can be effectively reduced to problems in three spacetime dimensions, it has become increasingly important to understand the `statistical mechanics' of the (2 + 1)-dimensional black hole of Bañados, Teitelboim, and Zanelli (BTZ). Several conformal field theoretic derivations of the BTZ entropy exist, but none is completely satisfactory, and many questions remain open: there is no consensus as to what fields provide the relevant degrees of freedom or where these excitations live. In this paper, I review some of the unresolved problems and suggest avenues for their solution.

[]

https://arxiv.org/pdf/hep-th/9806026.pdf

1999PhLB..454..187G

Black holes and Calogero models

1999-01-01

['-']

[]

We argue that the large n limit of the n-particle SU(1,12) superconformal Calogero model provides a microscopic description of the extreme Reissner-Nordström black hole in the near-horizon limit.

[]

https://arxiv.org/pdf/hep-th/9812034.pdf

1999NuPhB.554..237D

Anti-de Sitter black holes in gauged N = 8 supergravity

1999-01-01

['-']

[]

We present new anti-de Sitter black hole solutions of gauged N = 8, SO(8) supergravity, which is the massless sector of the AdS <SUB>4</SUB> × S<SUP>70</SUP> vacuum of M-theory. By focusing on the U(1) <SUP>4</SUP> Cartan subgroup, we find non-extremal 1, 2, 3 and 4 charge solutions. In the extremal limit, they may preserve up to {1}/{2}, {1}/{4}, {1}/{8}and{1}/{8} of the supersymmetry, respectively. In the limit of vanishing SO(8) coupling constant, the solutions reduce to the familiar black holes of the M<SUB>4</SUB> × T<SUP>7</SUP> vacuum, but have very different interpretation since there are no winding states on S<SUP>7</SUP> and no U-duality. In contrast to the T<SUP>7</SUP> compactification, moreover, we find no static multi-center solutions. Also in contrast, the S<SUP>7</SUP> fields appear "already dualized" so that the 4 charges may be all electric or all magnetic rather than 2 electric and 2 magnetic. Curiously, however, the magnetic solutions preserve no supersymmetries. We conjecture that a subset of the extreme electric black holes preserving {1}/{2} the supersymmetry may be identified with the S<SUP>7</SUP> Kaluza-Klein spectrum, with the non-abelian SO(8) quantum numbers provided by the fermionic zero-modes.

[]

https://arxiv.org/pdf/hep-th/9901149.pdf

2006ApJ...642L..21B

Efficient Merger of Binary Supermassive Black Holes in Nonaxisymmetric Galaxies

2006-01-01

['black hole physics', 'galaxies evolution', 'galaxies interactions', 'astrophysics', '-']

[]

Binary supermassive black holes (SBHs) form naturally in galaxy mergers, but their long-term evolution is uncertain. In spherical galaxies, N-body simulations show that binary evolution stalls at separations much too large for significant emission of gravitational waves (the ``final-parsec problem''). Here we follow the long-term evolution of a massive binary in more realistic, triaxial and rotating galaxy models with particle numbers as high as 10<SUP>6</SUP>. We find that the binary does not stall. The binary hardening rates that we observe are sufficient to allow complete coalescence of binary SBHs in 10 Gyr or less, even in the absence of collisional loss-cone refilling or gasdynamical torques, thus providing a potential solution to the final-parsec problem.

[]

https://arxiv.org/pdf/astro-ph/0601698.pdf

1998ApJ...493..613V

Improved Evidence for a Black Hole in M32 from HST/FOS Spectra. II. Axisymmetric Dynamical Models

1998-01-01

['black hole physics', 'galaxies elliptical lenticular;cd', 'cd', 'galaxies', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'galaxies structure', 'black hole physics', 'galaxies elliptical lenticular;cd', 'cd', 'galaxies', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'galaxies structure', 'astrophysics']

[]

Axisymmetric dynamical models are constructed for the E3 galaxy M32 to interpret high spatial resolution stellar kinematical data obtained with the Hubble Space Telescope (HST). Models are studied with two-integral, f(E, L<SUB>z</SUB>), phase-space distribution functions and with fully general three-integral distribution functions. The latter are built using an extension of Schwarzschild's approach: individual orbits in the axisymmetric potential are calculated numerically, and populated using nonnegative least-squares fitting so as to reproduce all available kinematical data, including line-of-sight velocity profile shapes. The details of this method are described in companion papers by Rix et al. and Cretton et al. <P />Models are constructed for inclinations i = 90° (edge on) and i = 55°. No model without a nuclear dark object can fit the combined ground-based and HST data, independent of the dynamical structure of M32. Models with a nuclear dark object of mass M<SUB>•</SUB> = 3.4 × 10<SUP>6</SUP> M<SUB>⊙</SUB> (with 1 σ and 3 σ error bars of 0.7 × 10<SUP>6</SUP> M<SUB>⊙</SUB> and 1.6 × 10<SUP>6</SUP> M<SUB>⊙</SUB>, respectively) do provide an excellent fit. The inclined models provide the best fit, but the inferred M<SUB>•</SUB> does not depend sensitively on the assumed inclination. The models that best fit the data are not two-integral models, but like two-integral models they are azimuthally anisotropic. Two-integral models therefore provide useful low-order approximations to the dynamical structure of M32. We use them to show that an extended dark object can fit the data only if its half-mass radius is r<SUB>h</SUB> &lt;~ 0.08" (=0.26 pc), implying a central dark matter density exceeding 1 × 10<SUP>8</SUP> M<SUB>⊙</SUB> pc<SUP>-3</SUP>. <P />The inferred M<SUB>•</SUB> is consistent with that suggested previously by ground-based kinematical data. However, radially anisotropic axisymmetric constant mass-to-light ratio models are now ruled out for the first time, and the limit on the dark matter density implied by the HST data is now stringent enough to rule out most plausible alternatives to a massive black hole. <P />The dynamically inferred M<SUB>•</SUB> is identical to that suggested by existing models for HST photometry of M32 that assume adiabatic growth (over a timescale exceeding 10<SUP>6</SUP> yr) of a black hole into a preexisting core. The low activity of the nucleus of M32 implies either that only a very small fraction of the gas that is shed by evolving stars is accreted onto the black hole or, alternatively, that accretion proceeds at very low efficiency, e.g., in an advection-dominated mode. <P />Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

[]

https://arxiv.org/pdf/astro-ph/9705081.pdf

2004PhLB..582..237C

A note on thermodynamics of black holes in Lovelock gravity

2004-01-01

['-', '-']

[]

The Lovelock gravity consists of the dimensionally extended Euler densities. The geometry and horizon structure of black hole solutions could be quite complicated in this gravity, however, we find that some thermodynamic quantities of the black holes like the mass, Hawking temperature and entropy, have simple forms expressed in terms of horizon radius. The case with black hole horizon being a Ricci flat hypersurface is particularly simple. In that case the black holes are always thermodynamically stable with a positive heat capacity and their entropy still obeys the area formula, which is no longer valid for black holes with positive or negative constant curvature horizon hypersurface. In addition, for black holes in the gravity theory of Ricci scalar plus a 2n-dimensional Euler density with a positive coefficient, thermodynamically stable small black holes always exist in D=2n+1 dimensions, which are absent in the case without the Euler density term, while the thermodynamic properties of the black hole solutions with the Euler density term are qualitatively similar to those of black holes without the Euler density term as D&gt;2n+1.

[]

https://arxiv.org/pdf/hep-th/0311240.pdf

2013MNRAS.431.2441D

Discovery of a relation between black hole mass and soft X-ray time lags in active galactic nuclei

2013-01-01

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

[]

We carried out a systematic analysis of time lags between X-ray energy bands in a large sample (32 sources) of unabsorbed, radio quiet active galactic nuclei (AGN), observed by XMM-Newton. The analysis of X-ray lags (up to the highest/shortest frequencies/time-scales), is performed in the Fourier-frequency domain, between energy bands where the soft excess (soft band) and the primary power law (hard band) dominate the emission. We report a total of 15 out of 32 sources displaying a high-frequency soft lag in their light curves. All 15 are at a significance level exceeding 97 per cent and 11 are at a level exceeding 99 per cent. Of these soft lags, seven have not been previously reported in the literature, thus this work significantly increases the number of known sources with a soft/negative lag. The characteristic time-scales of the soft/negative lag are relatively short (with typical frequencies and amplitudes of ν ∼ 0.07-4 × 10<SUP>-3</SUP> Hz and τ ∼ 10-600 s, respectively), and show a highly significant (≳4σ) correlation with the black hole mass. The measured correlations indicate that soft lags are systematically shifted to lower frequencies and higher absolute amplitudes as the mass of the source increases. To first approximation, all the sources in the sample are consistent with having similar mass-scaled lag properties. These results strongly suggest the existence of a mass-scaling law for the soft/negative lag, that holds for AGN spanning a large range of masses (about 2.5 orders of magnitude), thus supporting the idea that soft lags originate in the innermost regions of AGN and are powerful tools for testing their physics and geometry.

[]

https://arxiv.org/pdf/1201.0196.pdf

2006ApJ...653..525M

A Long, Hard Look at the Low/Hard State in Accreting Black Holes

2006-01-01

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

[]

We present the first results of coordinated multiwavelength observations of the Galactic black hole GX 339-4 in a canonical low/hard state, obtained during its 2004 outburst. XMM-Newton observed the source for two revolutions, or approximately 280 ks; RXTE monitored the source throughout this long stare. The resulting data offer the best view yet obtained of the inner accretion flow geometry in the low/hard state, which is thought to be analogous to the geometry in low-luminosity active galactic nuclei. The XMM-Newton spectra clearly reveal the presence of a cool accretion disk component and a relativistic Fe K emission line. The results of fits made to both components strongly suggest that a standard thin disk remains at or near to the innermost stable circular orbit, at least in bright phases of the low/hard state. These findings indicate that potential links between the inner disk radius and the onset of a steady compact jet, and the paradigm of a radially recessed disk in the low/hard state, do not hold universally. The results of our observations can best be explained if a standard thin accretion disk fuels a corona that is closely related to, or consistent with, the base of a compact jet. In a brief examination of archival data, we show that Cygnus X-1 supports this picture of the low/hard state. We discuss our results within the context of disk-jet connections and prevailing models for accretion onto black holes.

[]

https://arxiv.org/pdf/astro-ph/0602633.pdf

2021PhRvL.126d1303D

NANOGrav Data Hints at Primordial Black Holes as Dark Matter

2021-01-01

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

[]

The NANOGrav Collaboration has recently published strong evidence for a stochastic common-spectrum process that may be interpreted as a stochastic gravitational wave background. We show that such a signal can be explained by second-order gravitational waves produced during the formation of primordial black holes from the collapse of sizeable scalar perturbations generated during inflation. This possibility has two predictions: (i) the primordial black holes may comprise the totality of the dark matter with the dominant contribution to their mass function falling in the range (10<SUP>-15</SUP>÷10<SUP>-11</SUP>)M<SUB>⊙</SUB> and (ii) the gravitational wave stochastic background will be seen as well by the Laser Interferometer Space Antenna experiment.

[]

https://arxiv.org/pdf/2009.08268.pdf

2017ApJ...836...39S

Lidov-Kozai Cycles with Gravitational Radiation: Merging Black Holes in Isolated Triple Systems

2017-01-01

['stars binaries general', 'black hole physics', 'gravitational waves', 'stars black holes', 'stars kinematics and dynamics', '-']

[]

We show that a black-hole binary with an external companion can undergo Lidov-Kozai cycles that cause a close pericenter passage, leading to a rapid merger due to gravitational-wave emission. This scenario occurs most often for systems in which the companion has a mass comparable to the reduced mass of the binary and the companion orbit has a semimajor axis within a factor of ∼10 of the binary semimajor axis. Using a simple population-synthesis model and three-body simulations, we estimate the rate of mergers in triple black-hole systems in the field to be about six per Gpc<SUP>3</SUP> per year in the absence of natal kicks during black-hole formation. This value is within the low end of the 90% credible interval for the total black hole-black hole merger rate inferred from the current LIGO results. There are many uncertainties in these calculations, the largest of which is the unknown distribution of natal kicks. Even modest natal kicks of 40 km s<SUP>-1</SUP> will reduce the merger rate by a factor of 40. A few percent of these systems will have eccentricity greater than 0.999 when they first enter the frequency band detectable by aLIGO (above 10 Hz).

[]

https://arxiv.org/pdf/1608.07642.pdf

2016ApJ...818...47S

The SINFONI Black Hole Survey: The Black Hole Fundamental Plane Revisited and the Paths of (Co)evolution of Supermassive Black Holes and Bulges

2016-01-01

['galaxies bulges', 'galaxies elliptical lenticular;cd', 'cd', 'galaxies fundamental parameters', 'galaxies spiral', 'galaxies quasars', '-']

[]

We investigate the correlations between the black hole (BH) mass M<SUB>BH</SUB>, the velocity dispersion σ, the bulge mass M<SUB>Bu</SUB>, the bulge average spherical density {ρ }<SUB>{{h</SUB>}}, and its spherical half-mass radius r<SUB>h</SUB>, constructing a database of 97 galaxies (31 core ellipticals, 17 power-law ellipticals, 30 classical bulges, and 19 pseudobulges) by joining 72 galaxies from the literature to 25 galaxies observed during our recent SINFONI BH survey. For the first time we discuss the full error covariance matrix. We analyze the well-known M<SUB>BH</SUB>-σ and M<SUB>BH</SUB>-M<SUB>Bu</SUB> relations and establish the existence of statistically significant correlations between M<SUB>Bu</SUB> and r<SUB>h</SUB> and anticorrelations between M<SUB>Bu</SUB> and {ρ }<SUB>{{h</SUB>}}. We establish five significant bivariate correlations (M<SUB>BH</SUB>-σ-ρ<SUB>h</SUB>, M<SUB>BH</SUB>-σ-r<SUB>h</SUB>, M<SUB>BH</SUB>-M<SUB>Bu</SUB>-σ, M<SUB>BH</SUB>-M<SUB>Bu</SUB>-ρ<SUB>h</SUB>, M<SUB>BH</SUB>-M<SUB>Bu</SUB>-r<SUB>h</SUB>) that predict M<SUB>BH</SUB> of 77 core and power-law ellipticals and classical bulges with measured and intrinsic scatter as small as ≈ 0.36 dex and ≈ 0.33 dex, respectively, or 0.26 dex when the subsample of 45 galaxies defined by Kormendy &amp; Ho is considered. In contrast, pseudobulges have systematically lower M<SUB>BH</SUB> but approach the predictions of all of the above relations at spherical densities {ρ }<SUB>{{h</SUB>}}≥slant {10}<SUP>10</SUP> {M}<SUB>⊙ </SUB> {{kpc}}<SUP>-3</SUP> or scale lengths {r}<SUB>{{h</SUB>}}≤slant 1 {{kpc}}. These findings fit in a scenario of coevolution of BH and classical-bulge masses, where core ellipticals are the product of dry mergers of power-law bulges and power-law ellipticals and bulges the result of (early) gas-rich mergers and of disk galaxies. In contrast, the (secular) growth of BHs is decoupled from the growth of their pseudobulge hosts, except when (gas) densities are high enough to trigger the feedback mechanism responsible for the existence of the correlations between M<SUB>BH</SUB> and galaxy structural parameters.

[]

https://arxiv.org/pdf/1601.00974.pdf

2017PhRvD..96h3524P

CMB bounds on disk-accreting massive primordial black holes

2017-01-01

['-']

[]

Stellar-mass primordial black holes (PBH) have been recently reconsidered as a dark matter (DM) candidate after the aLIGO discovery of several binary black hole (BH) mergers with masses of tens of M<SUB>⊙</SUB> . Matter accretion on such massive objects leads to the emission of high-energy photons, capable of altering the ionization and thermal history of the universe. This, in turn, affects the statistical properties of the cosmic microwave background (CMB) anisotropies. Previous analyses have assumed spherical accretion. We argue that this approximation likely breaks down and that an accretion disk should form in the dark ages. Using the most up-to-date tools to compute the energy deposition in the medium, we derive constraints on the fraction of DM in PBH. Provided that disks form early on, even under conservative assumptions for accretion, these constraints exclude a monochromatic distribution of PBH with masses above ∼2 M<SUB>⊙</SUB> as the dominant form of DM. The bound on the median PBH mass gets more stringent if a broad, log-normal mass function is considered. A deepened understanding of nonlinear clustering properties and BH accretion disk physics would permit an improved treatment and possibly lead to more stringent constraints.

[]

https://arxiv.org/pdf/1707.04206.pdf

2002AJ....124.3270G

Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15. II. Kinematic Analysis and Dynamical Modeling

2002-01-01

['galaxy globular clusters', 'stars kinematics and dynamics', 'astrophysics']

[]

We have used the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) to obtain high spatial resolution spectroscopy of the central region of the dense globular cluster M15. The observational strategy and data reduction were described in Paper I of this series. Here we analyze the extracted spectra with a cross-correlation technique to determine the line-of-sight velocities of individual stars. Our final STIS velocity sample contains 64 stars, two-thirds of which have their velocity measured for the first time. The new data set triples the number of stars with measured velocities in the central projected R&lt;=1" of M15 and doubles the number in the central R&lt;=2". We combine our data with existing ground-based data to obtain nonparametric estimates of the radial profiles of the projected rotation velocity, velocity dispersion, and rms velocity σ<SUB>rms</SUB>. The results differ from earlier work in the central few arcseconds in that we find that σ<SUB>rms</SUB> rises to ~14 km s<SUP>-1</SUP>, somewhat higher than the values of 10-12 km s<SUP>-1</SUP> inferred previously from ground-based data. To interpret the results we construct dynamical models based on the Jeans equation for a spherical system. If the velocity distribution is isotropic, then M15 must have a central concentration of nonluminous material. If this is due to a single black hole, then a fit to the full velocity information as function of radius implies that its mass is M<SUB>BH</SUB>=(3.9+/-2.2)×10<SUP>3</SUP> M<SUB>solar</SUB>. The existence of intermediate-mass black holes in globular clusters is consistent with several scenarios for globular cluster evolution proposed in the literature. The inferred mass for M15 is consistent with the extrapolation of the relation between M<SUB>BH</SUB> and σ<SUB>rms</SUB> that has been established for galaxies. Therefore, these results may have important implications for our understanding of the evolution of globular clusters, the growth of black holes, the connection between globular cluster and galaxy formation, and the nature of the recently discovered ``ultraluminous'' X-ray sources in nearby galaxies. Instead of a single intermediate-mass black hole, M15 could have a central concentration of dark remnants (e.g., neutron stars) due to mass segregation. However, we argue that the best-fitting Fokker-Planck models that have previously been constructed for M15 do not predict a central mass concentration that is sufficient to explain the observed kinematics. To fit the M15 data without any central dark mass concentration one must assume that the velocity distribution is significantly radially anisotropic near the center, which contradicts predictions from both Fokker-Planck and N-body calculations. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposal No. 8262.

[]

https://arxiv.org/pdf/astro-ph/0209315.pdf

2007CQGra..24.4191C

How to tell a gravastar from a black hole

2007-01-01

['-', 'astrophysics']

[]

Gravastars have been recently proposed as potential alternatives to explain the astrophysical phenomenology traditionally associated with black holes, raising the question of whether the two objects can be distinguished at all. Leaving aside the debate about the processes that would lead to the formation of a gravastar and the astronomical evidence in their support, here we address two basic questions: is a gravastar stable against generic perturbations? If it is stable, can an observer distinguish it from a black hole of the same mass? To answer these questions we construct a general class of gravastars and determine the conditions they must satisfy in order to exist as equilibrium solutions of the Einstein equations. For such models we perform a systematic stability analysis against axial perturbations, computing the real and imaginary parts of the eigenfrequencies. Overall, we find that gravastars are stable to axial perturbations, but also that their quasi-normal modes differ from those of a black hole of the same mass and thus can be used to discern, beyond dispute, a gravastar from a black hole.

[]

https://arxiv.org/pdf/0706.1513.pdf

2011Natur.469..374K

Supermassive black holes do not correlate with galaxy disks or pseudobulges

2011-01-01

['-', '-']

[]

The masses of supermassive black holes are known to correlate with the properties of the bulge components of their host galaxies. In contrast, they seem not to correlate with galaxy disks. Disk-grown `pseudobulges' are intermediate in properties between bulges and disks; it has been unclear whether they do or do not correlate with black holes in the same way that bulges do. At stake in this issue are conclusions about which parts of galaxies coevolve with black holes, possibly by being regulated by energy feedback from black holes. Here we report pseudobulge classifications for galaxies with dynamically detected black holes and combine them with recent measurements of velocity dispersions in the biggest bulgeless galaxies. These data confirm that black holes do not correlate with disks and show that they correlate little or not at all with pseudobulges. We suggest that there are two different modes of black-hole feeding. Black holes in bulges grow rapidly to high masses when mergers drive gas infall that feeds quasar-like events. In contrast, small black holes in bulgeless galaxies and in galaxies with pseudobulges grow as low-level Seyfert galaxies. Growth of the former is driven by global processes, so the biggest black holes coevolve with bulges, but growth of the latter is driven locally and stochastically, and they do not coevolve with disks and pseudobulges.

[]

https://arxiv.org/pdf/1101.3781.pdf

2017NatAs...1E.165H

Impact of supermassive black hole growth on star formation

2017-01-01

['-', '-']

[]

Supermassive black holes are found at the centres of massive galaxies. During the growth of these black holes they light up to become visible as active galactic nuclei (AGNs) and release extraordinary amounts of energy across the electromagnetic spectrum. This energy is widely believed to regulate the rate of star formation in the black holes' host galaxies via so-called AGN feedback. However, the details of how and when this occurs remain uncertain from both an observational and theoretical perspective. I review some of the theoretical motivation and observational results and discuss possible observational signatures of the impact of supermassive black hole growth on star formation.

[]

https://arxiv.org/pdf/1703.06889.pdf

2005ApJ...621..372D

Relativistic Accretion Disk Models of High-State Black Hole X-Ray Binary Spectra

2005-01-01

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

[]

We present calculations of non-LTE, relativistic accretion disk models applicable to the high/soft state of black hole X-ray binaries. We include the effects of thermal Comptonization and bound-free and free-free opacities of all abundant ion species. Taking into account the relativistic propagation of photons from the local disk surface to an observer at infinity, we present spectra calculated for a variety of accretion rates, black hole spin parameters, disk inclinations, and stress prescriptions. We also consider nonzero inner torques on the disk and explore different vertical dissipation profiles, including some that are motivated by recent radiation magnetohydrodynamic (MHD) simulations of magnetorotational turbulence. Bound-free metal opacity generally produces significantly less spectral hardening than previous models that only considered Compton scattering and free-free opacity. We find that the resulting effective photosphere usually lies at a small fraction of the total column depth, producing spectra that are remarkably independent of the stress prescription and vertical structure assumptions. We provide detailed comparisons between our models and the widely used multicolor disk model. Frequency-dependent discrepancies exist that may affect the parameters of other spectral components when this simpler disk model is used to fit modern X-ray data. For a given source, our models predict that the luminosity in the high/soft state should approximately scale with the fourth power of the empirically inferred maximum temperature, but with a slight hardening at high luminosities. This is in good agreement with observations.

[]

https://arxiv.org/pdf/astro-ph/0408590.pdf

2001AJ....122.2469G

M33: A Galaxy with No Supermassive Black Hole

2001-01-01

['galaxies general', 'galaxies nuclei', 'astrophysics']

[]

Galaxies that contain bulges appear to contain central black holes whose masses correlate with the velocity dispersion of the bulge. We show that no corresponding relationship applies in the pure disk galaxy M33. Three-integral dynamical models fit Hubble Space Telescope WFPC2 photometry and Space Telescope Imaging Spectrograph spectroscopy best if the central black hole mass is zero. The upper limit is 1500 M<SUB>solar</SUB>. This is significantly below the mass expected from the velocity dispersion of the nucleus and far below any mass predicted from the disk kinematics. Our results suggest that supermassive black holes are associated only with galaxy bulges and not with their disks. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at 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/astro-ph/0107135.pdf

2019JCAP...02..042S

Black-bounce to traversable wormhole

2019-01-01

['-']

[]

So-called "regular black holes" are a topic currently of considerable interest in the general relativity and astrophysics communities. Herein we investigate a particularly interesting regular black hole spacetime described by the line element <P />This spacetime neatly interpolates between the standard Schwarzschild black hole and the Morris-Thorne traversable wormhole; at intermediate stages passing through a black-bounce (into a future incarnation of the universe), an extremal null-bounce (into a future incarnation of the universe), and a traversable wormhole. As long as the parameter a is non-zero the geometry is everywhere regular, so one has a somewhat unusual form of "regular black hole", where the "origin" r=0 can be either spacelike, null, or timelike. Thus this spacetime generalizes and broadens the class of "regular black holes" beyond those usually considered.

[]

https://arxiv.org/pdf/1812.07114.pdf

2000PhRvD..62d3523G

Brane-world creation and black holes

2000-01-01

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

[]

An inflating brane world can be created from ``nothing'' together with its anti-de Sitter (AdS) bulk. The resulting space-time has compact spatial sections bounded by the brane. During inflation, the continuum of KK modes is separated from the massless zero mode by the gap m=(3/2)H, where H is the Hubble rate. We consider the analogue of the Nariai solution and argue that it describes the pair production of ``black cigars'' attached to the inflating brane. In the case when the size of the instantons is much larger than the AdS radius, the 5-dimensional action agrees with the 4-dimensional one. Hence, the 5D and 4D gravitational entropies are the same in this limit. We also consider thermal instantons with an AdS black hole in the bulk. These may be interpreted as describing the creation of a hot universe from nothing or the production of AdS black holes in the vicinity of a pre-existing inflating brane world. The Lorentzian evolution of the brane world after creation is briefly discussed. An additional ``integration constant'' in the Friedmann equation-accompanying a term which dilutes like radiation-describes the tidal force in the fifth direction and arises from the mass of a spherical object inside the bulk. In general, this could be a 5-dimensional black hole or a ``parallel'' brane world of negative tension concentrical with our brane-world. In the case of thermal solutions, and in the spirit of the AdS/CFT correspondence, one may attribute the additional term to thermal radiation in the boundary theory. Then, for temperatures well below the AdS scale, the entropy of this radiation agrees with the entropy of the black hole in the AdS bulk.

[]

https://arxiv.org/pdf/hep-th/9912118.pdf

2012PhRvL.109m1102P

Black-Hole Bombs and Photon-Mass Bounds

2012-01-01

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

[]

Generic extensions of the standard model predict the existence of ultralight bosonic degrees of freedom. Several ongoing experiments are aimed at detecting these particles or constraining their mass range. Here we show that massive vector fields around rotating black holes can give rise to a strong superradiant instability, which extracts angular momentum from the hole. The observation of supermassive spinning black holes imposes limits on this mechanism. We show that current supermassive black-hole spin estimates provide the tightest upper limits on the mass of the photon (m<SUB>v</SUB>≲4×10<SUP>-20</SUP>eV according to our most conservative estimate), and that spin measurements for the largest known supermassive black holes could further lower this bound to m<SUB>v</SUB>≲10<SUP>-22</SUP>eV. Our analysis relies on a novel framework to study perturbations of rotating Kerr black holes in the slow-rotation regime, that we developed up to second order in rotation, and that can be extended to other spacetime metrics and other theories.

[]

https://arxiv.org/pdf/1209.0465.pdf

2019ApJ...876L...7S

First Measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary-Black-hole Merger GW170814

2019-01-01

['catalogs', 'cosmology observations', 'gravitational waves', 'surveys', '-']

[]

We present a multi-messenger measurement of the Hubble constant H <SUB>0</SUB> using the binary-black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in {H}<SUB>0</SUB>={75}<SUB>-32</SUB><SUP>+40</SUP> {km} {{{s}}}<SUP>-1</SUP> {Mpc}}<SUP>-1</SUP>, which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>, we find {H}<SUB>0</SUB>={78}<SUB>-24</SUB><SUP>+96</SUP> {km} {{{s}}}<SUP>-1</SUP> {Mpc}}<SUP>-1</SUP> (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H <SUB>0</SUB>.

[]

https://arxiv.org/pdf/1901.01540.pdf

2011MNRAS.414..677C

Radiatively efficient accreting black holes in the hard state: the case study of H1743-322

2011-01-01

['accretion', 'accretion disks', 'ism jets and outflows', 'astronomy radio', 'astronomy x rays', 'astronomy x rays', '-']

[]

In recent years, much effort has been devoted to unravelling the connection between the accretion flow and the jets in accreting compact objects. In the present work, we report new constraints on these issues, through the long-term study of the radio and X-ray behaviour of the black hole candidate H1743-322. This source is known to be one of the 'outliers' of the universal radio/X-ray correlation, i.e. a group of accreting stellar-mass black holes displaying fainter radio emission for a given X-ray luminosity than expected from the correlation. Our study shows that the radio and X-ray emission of H1743-322 are strongly correlated at high luminosity in the hard spectral state. However, this correlation is unusually steep for a black hole X-ray binary: b∼ 1.4 (with L<SUB>radio</SUB>∝L<SUP>b</SUP><SUB>X</SUB>). Below a critical luminosity, the correlation becomes shallower until it rejoins the standard correlation with b∼ 0.6. Based on these results, we first show that the steep correlation can be explained if the inner accretion flow is radiatively efficient during the hard state, in contrast to what is usually assumed for black hole X-ray binaries in this spectral state. The transition between the steep and the standard correlation would therefore reflect a change from a radiatively efficient to a radiatively inefficient accretion flow. Finally, we investigate the possibility that the discrepancy between 'outliers' and 'standard' black holes arises from the outflow properties rather than from the accretion flow.

[]

https://arxiv.org/pdf/1101.5159.pdf

2018MNRAS.478.3756C

Primordial black holes as generators of cosmic structures

2018-01-01

['gravitational waves', '-', 'galaxies formation', 'galaxies quasars', 'cosmology dark matter', 'cosmology early universe', '-']

[]

Primordial black holes (PBHs) could provide the dark matter in various mass windows below 10<SUP>2</SUP> M<SUB>⊙</SUB> and those of 30 M<SUB>⊙</SUB> might explain the LIGO events. PBHs much larger than this might have important consequences even if they provide only a small fraction of the dark matter. In particular, they could generate cosmological structure either individually through the `seed' effect or collectively through the `Poisson' effect, thereby alleviating some problems associated with the standard cold dark matter scenario. If the PBHs all have a similar mass and make a small contribution to the dark matter, then the seed effect dominates on small scales, in which case PBHs could generate the supermassive black holes in galactic nuclei or even galaxies themselves. If they have a similar mass and provide the dark matter, the Poisson effect dominates on all scales and the first bound clouds would form earlier than in the usual scenario, with interesting observational consequences. If the PBHs have an extended mass spectrum, which is more likely, they could fulfill all three roles - providing the dark matter, binding the first bound clouds, and generating galaxies. In this case, the galactic mass function naturally has the observed form, with the galaxy mass being simply related to the black hole mass. The stochastic gravitational wave background from the PBHs in this scenario would extend continuously from the LIGO frequency to the LISA frequency, offering a potential goal for future surveys.

[]

https://arxiv.org/pdf/1801.00672.pdf

2017PhRvL.119d1101E

Superradiant Instability and Backreaction of Massive Vector Fields around Kerr Black Holes

2017-01-01

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

[]

We study the growth and saturation of the superradiant instability of a complex, massive vector (Proca) field as it extracts energy and angular momentum from a spinning black hole, using numerical solutions of the full Einstein-Proca equations. We concentrate on a rapidly spinning black hole (a =0.99 ) and the dominant m =1 azimuthal mode of the Proca field, with real and imaginary components of the field chosen to yield an axisymmetric stress-energy tensor and, hence, spacetime. We find that in excess of 9% of the black hole's mass can be transferred into the field. In all cases studied, the superradiant instability smoothly saturates when the black hole's horizon frequency decreases to match the frequency of the Proca cloud that spontaneously forms around the black hole.

[]

https://arxiv.org/pdf/1704.04791.pdf

2024Natur.627...59M

A small and vigorous black hole in the early Universe

2024-01-01

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

[]

Several theories have been proposed to describe the formation of black hole seeds in the early Universe and to explain the emergence of very massive black holes observed in the first thousand million years after the Big Bang<SUP>1-3</SUP>. Models consider different seeding and accretion scenarios<SUP>4-7</SUP>, which require the detection and characterization of black holes in the first few hundred million years after the Big Bang to be validated. Here we present an extensive analysis of the JWST-NIRSpec spectrum of GN-z11, an exceptionally luminous galaxy at z = 10.6, revealing the detection of the [NeIV]λ2423 and CII*λ1335 transitions (typical of active galactic nuclei), as well as semi-forbidden nebular lines tracing gas densities higher than 10<SUP>9</SUP> cm<SUP>−3</SUP>, typical of the broad line region of active galactic nuclei. These spectral features indicate that GN-z11 hosts an accreting black hole. The spectrum also reveals a deep and blueshifted CIVλ1549 absorption trough, tracing an outflow with velocity 800−1,000 km s<SUP>−1</SUP>, probably driven by the active galactic nucleus. Assuming local virial relations, we derive a black hole mass of log (M<SUB>BH</SUB>/M<SUB>⊙</SUB> ) =6.2 ±0.3 , accreting at about five times the Eddington rate. These properties are consistent with both heavy seeds scenarios and scenarios considering intermediate and light seeds experiencing episodic super-Eddington phases. Our finding explains the high luminosity of GN-z11 and can also provide an explanation for its exceptionally high nitrogen abundance.

[]

https://arxiv.org/pdf/2305.12492.pdf

2010JHEP...08..067M

Black holes in quasi-topological gravity

2010-01-01

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

[]

We construct a new gravitational action which includes cubic curvature interactions and which provides a useful toy model for the holographic study of a three parameter family of four- and higher-dimensional CFT’s. We also investigate the black hole solutions of this new gravity theory. Further we examine the equations of motion of quasi-topological gravity. While the full equations in a general background are fourth-order in derivatives, we show that the linearized equations describing gravitons propagating in the AdS vacua match precisely the second-order equations of Einstein gravity.

[]

https://arxiv.org/pdf/1003.5357.pdf

2004ApJ...607...90B

POX 52: A Dwarf Seyfert 1 Galaxy with an Intermediate-Mass Black Hole

2004-01-01

['galaxies active', 'galaxies dwarf', 'galaxies', 'galaxies kinematics and dynamics', 'galaxies nuclei', 'galaxies seyfert', 'astrophysics']

[]

We describe new optical images and spectra of POX 52, a dwarf galaxy with an active nucleus that was originally detected in the POX objective-prism survey. While POX 52 was originally thought to be a Seyfert 2 galaxy, the new data reveal an emission-line spectrum very similar to that of the dwarf Seyfert 1 galaxy NGC 4395, with broad components to the permitted line profiles, and we classify POX 52 as a Seyfert 1 galaxy. The host galaxy appears to be a dwarf elliptical, and its brightness profile is best fit by a Sérsic model with an index of 3.6+/-0.2 and a total magnitude of M<SUB>V</SUB>=-17.6. Applying mass-luminosity-line width scaling relations to estimate the black hole mass from the broad Hβ line width and nonstellar continuum luminosity, we find M<SUB>BH</SUB>~1.6×10<SUP>5</SUP>M<SUB>solar</SUB>. The stellar velocity dispersion in the host galaxy, measured from the Ca II λ8498, 8542 lines, is 36+/-5 km s<SUP>-1</SUP>, also suggestive of a black hole mass of order 10<SUP>5</SUP>M<SUB>solar</SUB>. Further searches for active nuclei in dwarf galaxies can provide unique constraints on the demographics of black holes in the mass range below 10<SUP>6</SUP>M<SUB>solar</SUB>.

[]

https://arxiv.org/pdf/astro-ph/0402110.pdf

2008PhRvD..77l4035B

Noncommutative black hole thermodynamics

2008-01-01

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

[]

We give a general derivation, for any static spherically symmetric metric, of the relation T<SUB>h</SUB>=(K)/(2π) connecting the black hole temperature (T<SUB>h</SUB>) with the surface gravity (K), following the tunneling interpretation of Hawking radiation. This derivation is valid even beyond the semi-classical regime, i.e. when quantum effects are not negligible. The formalism is then applied to a spherically symmetric, stationary noncommutative Schwarzschild space-time. The effects of backreaction are also included. For such a black hole the Hawking temperature is computed in a closed form. A graphical analysis reveals interesting features regarding the variation of the Hawking temperature (including corrections due to noncommutativity and backreaction) with the small radius of the black hole. The entropy and tunneling rate valid for the leading order in the noncommutative parameter are calculated. We also show that the noncommutative Bekenstein-Hawking area law has the same functional form as the usual one.

[]

https://arxiv.org/pdf/0801.3583.pdf

2013PhRvD..87j4017D

Thermodynamic volumes and isoperimetric inequalities for de Sitter black holes

2013-01-01

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

[]

We consider the thermodynamics of rotating and charged asymptotically de Sitter (dS) black holes. Using Hamiltonian perturbation-theory techniques, we derive three different first-law relations including variations in the cosmological constant, and associated Smarr formulas that are satisfied by such spacetimes. Each first law introduces a different thermodynamic volume conjugate to the cosmological constant. We examine the relation between these thermodynamic volumes and associated geometric volumes in a number of examples, including Kerr-dS black holes in all dimensions and Kerr-Newman-dS black holes in D=4. We also show that the Chong-Cvetic-Lu-Pope solution of D=5 minimal supergravity—analytically continued to positive cosmological constant—describes black hole solutions of the Einstein-Chern-Simons theory and include such charged asymptotically de Sitter black holes in our analysis. In all these examples we find that the particular thermodynamic volume associated with the region between the black hole and cosmological horizons is equal to the naive geometric volume. Isoperimetric inequalities, which hold in the examples considered, are formulated for the different thermodynamic volumes and conjectured to remain valid for all asymptotically de Sitter black holes. In particular, in all examples considered, we find that for a fixed volume of the observable universe, the entropy is increased by adding black holes. We conjecture that this is true in general.

[]

https://arxiv.org/pdf/1301.5926.pdf

2015PhRvD..92j4031P

Influence of a plasma on the shadow of a spherically symmetric black hole

2015-01-01

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

[]

We analytically calculate the influence of a plasma on the shadow of a black hole (or of another compact object). We restrict to spherically symmetric and static situations, where the shadow is circular. The plasma is assumed to be nonmagnetized and pressureless. We derive the general formulas for a spherically symmetric plasma density on an unspecified spherically symmetric and static spacetime. Our main result is an analytical formula for the angular size of the shadow. As a plasma is a dispersive medium, the radius of the shadow depends on the photon frequency. The effect of the plasma is significant only in the radio regime. The formalism applies not only to black holes but also, e.g., to wormholes. As examples for the underlying spacetime model, we consider the Schwarzschild spacetime and the Ellis wormhole. In particular, we treat the case that the plasma is in radial free fall from infinity onto a Schwarzschild black hole. We find that for an observer far away from a Schwarzschild black hole, the plasma has a decreasing effect on the size of the shadow. The perspectives of actually observing the influence of a plasma on the shadows of supermassive black holes are discussed.

[]

https://arxiv.org/pdf/1507.04217.pdf

2004PhRvD..70l4034C

Born-Infeld black holes in (A)dS spaces

2004-01-01

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

[]

We study some exact solutions in a D(≥4)-dimensional Einstein-Born-Infeld theory with a cosmological constant. These solutions are asymptotically de Sitter or anti-de Sitter, depending on the sign of the cosmological constant. Black hole horizon and cosmological horizon in these spacetimes can be a positive, zero or negative constant curvature hypersurface. We discuss the thermodynamics associated with black hole horizon and cosmological horizon. In particular we find that for the Born-Infeld black holes with Ricci flat or hyperbolic horizon in AdS space, they are always thermodynamically stable, and that for the case with a positive constant curvature, there is a critical value for the Born-Infeld parameter, above which the black hole is also always thermodynamically stable, and below which a unstable black hole phase appears. In addition, we show that although the Born-Infeld electrodynamics is nonlinear, both black hole horizon entropy and cosmological horizon entropy can be expressed in terms of the Cardy-Verlinde formula. We also find a factorized solution in the Einstein-Born-Infeld theory, which is a direct product of two constant curvature spaces: one is a two-dimensional de Sitter or anti-de Sitter space, the other is a (D-2)-dimensional positive, zero or negative constant curvature space.

[]

https://arxiv.org/pdf/hep-th/0410158.pdf

2012PhRvD..86h4048R

Black holes with nonminimal derivative coupling

2012-01-01

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

[]

We study the gravitational field equations in the presence of a coupling between the derivative of a massless scalar field and the Einstein tensor. This configuration is motivated by Galileon gravity as it preserves shift invariance in the scalar sector. We analytically obtain solutions with static and spherically symmetric geometry, which also include black holes with a single regular horizon. We examine the thermodynamical properties of these solutions, and we reveal the nonperturbative nature of the coupling constant. We also find a phase transition, similar to the one described by Hawking and Page, which occurs at a critical temperature determined by both the black hole mass and by the strength of the coupling.

[]

https://arxiv.org/pdf/1208.0103.pdf

2016PhRvL.116i1101D

Supertranslations and Superrotations at the Black Hole Horizon

2016-01-01

['-', '-']

[]

We show that the asymptotic symmetries close to nonextremal black hole horizons are generated by an extension of supertranslations. This group is generated by a semidirect sum of Virasoro and Abelian currents. The charges associated with the asymptotic Killing symmetries satisfy the same algebra. When considering the special case of a stationary black hole, the zero mode charges correspond to the angular momentum and the entropy at the horizon.

[]

https://arxiv.org/pdf/1511.08687.pdf

2020EPJC...80..588G

Innermost stable circular orbit and shadow of the 4D Einstein–Gauss–Bonnet black hole

2020-01-01

['-']

[]

Recently, a novel 4D Einstein–Gauss–Bonnet gravity was formulated by Glavan and Lin (Phys Rev Lett 124(8):081301, 2020). Although whether the theory is well defined is currently debatable, the spherically symmetric black hole solution is still meaningful and worthy of study. In this paper, we study the geodesic motions in the spacetime of the spherically symmetric black hole solution. First of all, we find that a negative GB coupling constant is allowable, as in which case the singular behavior of the black hole can be hidden inside the event horizon. Then we calculate the innermost stable circular orbits for massive particles, which turn out to be monotonic decreasing functions of the GB coupling constant. Furthermore, we study the unstable photon sphere and shadow of the black hole. It is interesting to find that the proposed universal bounds on black hole size in Lu and Lyu (Phys Rev D 101(4):044059, 2020) recently can be broken when the GB coupling constant takes a negative value.

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https://arxiv.org/pdf/2003.02523.pdf

2016MNRAS.459.3432M

Massive black hole binaries from runaway collisions: the impact of metallicity

2016-01-01

['gravitational waves', 'methods numerical', 'stars black holes', 'stars kinematics and dynamics', 'stars luminosity function;mass function', '-', '-', '-', '-']

[]

The runaway collision scenario is one of the most promising mechanisms to explain the formation of intermediate-mass black holes (IMBHs) in young dense star clusters. On the other hand, the massive stars that participate in the runaway collisions lose mass by stellar winds. In this paper, we discuss new N-body simulations of massive (6.5 × 10<SUP>4</SUP> M<SUB>⊙</SUB>) star clusters, in which we added upgraded recipes for stellar winds and supernova explosion at different metallicity. We follow the evolution of the principal collision product (PCP), through dynamics and stellar evolution, till it forms a stellar remnant. At solar metallicity, the mass of the final merger product spans from few solar masses up to ∼30 M<SUB>⊙</SUB>. At low metallicity (0.01-0.1 Z<SUB>⊙</SUB>) the maximum remnant mass is ∼250 M<SUB>⊙</SUB>, in the range of IMBHs. A large fraction (∼0.6) of the PCPs are not ejected from the parent star cluster and acquire stellar or black hole (BH) companions. Most of the long-lived binaries hosting a PCP are BH-BH binaries. We discuss the importance of this result for gravitational wave detection.

[]

https://arxiv.org/pdf/1604.03559.pdf

2011Natur.470...66R

An actively accreting massive black hole in the dwarf starburst galaxy Henize2-10

2011-01-01

['-', '-']

[]

Supermassive black holes are now thought to lie at the heart of every giant galaxy with a spheroidal component, including our own Milky Way. The birth and growth of the first `seed' black holes in the earlier Universe, however, is observationally unconstrained and we are only beginning to piece together a scenario for their subsequent evolution. Here we report that the nearby dwarf starburst galaxy Henize2-10 (refs 5 and 6) contains a compact radio source at the dynamical centre of the galaxy that is spatially coincident with a hard X-ray source. From these observations, we conclude that Henize2-10 harbours an actively accreting central black hole with a mass of approximately one million solar masses. This nearby dwarf galaxy, simultaneously hosting a massive black hole and an extreme burst of star formation, is analogous in many ways to galaxies in the infant Universe during the early stages of black-hole growth and galaxy mass assembly. Our results confirm that nearby star-forming dwarf galaxies can indeed form massive black holes, and that by implication so can their primordial counterparts. Moreover, the lack of a substantial spheroidal component in Henize2-10 indicates that supermassive black-hole growth may precede the build-up of galaxy spheroids.

[]

https://arxiv.org/pdf/1101.1309.pdf

2008ApJ...686..801O

Can Supermassive Black Holes Form in Metal-enriched High-Redshift Protogalaxies?

2008-01-01

['cosmology theory', 'galaxies formation', 'stars fundamental parameters', 'astrophysics']

[]

Primordial gas in protogalactic DM halos with virial temperatures T<SUB>vir</SUB>gtrsim 10<SUP>4</SUP> K begins to cool and condense via atomic hydrogen. Provided that this gas is irradiated by a strong UV flux and remains free of H<SUB>2</SUB> and other molecules, it has been proposed that the halo with T<SUB>vir</SUB> ~ 10<SUP>4</SUP> K may avoid fragmentation and lead to the rapid formation of an SMBH as massive as M ≈ 10<SUP>5</SUP>-10<SUP>6</SUP> M<SUB>⊙</SUB>. This "head start" would help explain the presence of SMBHs with inferred masses of several times 10<SUP>9</SUP> M<SUB>⊙</SUB>, powering the bright quasars discovered in the SDSS at redshift zgtrsim 6. However, high-redshift DM halos with T<SUB>vir</SUB> ~ 10<SUP>4</SUP> K are likely already enriched with at least trace amounts of metals and dust produced by prior star formation in their progenitors. Here we study the thermal and chemical evolution of low-metallicity gas exposed to extremely strong UV radiation fields. Our results, obtained in one-zone models, suggest that gas fragmentation is inevitable above a critical metallicity, whose value is between Z<SUB>cr</SUB> ≈ 3 × 10<SUP>-4</SUP> Z<SUB>⊙</SUB> (in the absence of dust) and as low as Z<SUB>cr</SUB> ≈ 5 × 10<SUP>-6</SUP> Z<SUB>⊙</SUB> (with a dust-to-gas mass ratio of about 0.01Z/Z<SUB>⊙</SUB>). We propose that when the metallicity exceeds these critical values, dense clusters of low-mass stars may form at the halo nucleus. Relatively massive stars in such a cluster can then rapidly coalesce into a single more massive object, which may produce an intermediate-mass BH remnant with a mass up to Mlesssim 10<SUP>2</SUP>-10<SUP>3</SUP> M<SUB>⊙</SUB>.

[]

https://arxiv.org/pdf/0804.3141.pdf