Datasets:

ashishkgpian

/

astrorag_papers

like 0

2006PhLB..638..110Z

Charged particles' tunnelling from the Kerr Newman black hole

2006-01-01

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

[]

In this Letter, Parikh-Wilczek tunnelling framework, which treats Hawking radiation as a tunnelling process, is extended, and the emission rate of a charged particle tunnelling from the Kerr-Newman black hole is calculated. The emission spectrum takes the same functional form as that of uncharged particles and consists with an underlying unitary theory but deviates from the pure thermal spectrum. Moreover, our calculation indicates that the emission process is treated as a reversible process in the Parikh-Wilczek tunnelling framework, and the information conservation is a natural result of the first law of black hole thermodynamics.

[]

https://arxiv.org/pdf/gr-qc/0512153.pdf

2011PhRvD..84l4052P

Inspiral-merger-ringdown multipolar waveforms of nonspinning black-hole binaries using the effective-one-body formalism

2011-01-01

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

[]

We calibrate an effective-one-body (EOB) model to numerical-relativity simulations of mass ratios 1, 2, 3, 4, and 6, by maximizing phase and amplitude agreement of the leading (2, 2) mode and of the subleading modes (2, 1), (3, 3), (4, 4) and (5, 5). Aligning the calibrated EOB waveforms and the numerical waveforms at low frequency, the phase difference of the (2, 2) mode between model and numerical simulation remains below ∼0.1 rad throughout the evolution for all mass ratios considered. The fractional amplitude difference at peak amplitude of the (2, 2) mode is 2% and grows to 12% during the ringdown. Using the Advanced LIGO noise curve we study the effectualness and measurement accuracy of the EOB model, and stress the relevance of modeling the higher-order modes for parameter estimation. We find that the effectualness, measured by the mismatch between the EOB and numerical-relativity polarizations which include only the (2, 2) mode, is smaller than 0.2% for binaries with total mass 20-200M<SUB>⊙</SUB> and mass ratios 1, 2, 3, 4, and 6. When numerical-relativity polarizations contain the strongest seven modes, and stellar-mass black holes with masses less than 50M<SUB>⊙</SUB> are considered, the mismatch for mass ratio 6 (1) can be as high as 7% (0.2%) when only the EOB (2, 2) mode is included, and an upper bound of the mismatch is 0.5% (0.07%) when all the four subleading EOB modes calibrated in this paper are taken into account. For binaries with intermediate-mass black holes with masses greater than 50M<SUB>⊙</SUB> the mismatches are larger. We also determine for which signal-to-noise ratios the EOB model developed here can be used to measure binary parameters with systematic biases smaller than statistical errors due to detector noise.

[]

https://arxiv.org/pdf/1106.1021.pdf

2006PhRvD..74d4017I

Anomalies, Hawking radiations, and regularity in rotating black holes

2006-01-01

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

[]

This is an extended version of our previous letter [S. Iso, H. Umetsu, and F. Wilczek, Phys. Rev. Lett. 96, 151302 (2006).PRLTAO0031-900710.1103/PhysRevLett.96.151302]. In this paper we consider rotating black holes and show that the flux of Hawking radiation can be determined by anomaly cancellation conditions and regularity requirement at the horizon. By using a dimensional reduction technique, each partial wave of quantum fields in a d=4 rotating black hole background can be interpreted as a (1+1)-dimensional charged field with a charge proportional to the azimuthal angular momentum m. From this and the analysis [S. P. Robinson and F. Wilczek, Phys. Rev. Lett. 95, 011303 (2005)PRLTAO0031-900710.1103/PhysRevLett.95.011303, S. Iso, H. Umetsu, and F. Wilczek, Phys. Rev. Lett. 96, 151302 (2006).PRLTAO0031-900710.1103/PhysRevLett.96.151302] on Hawking radiation from charged black holes, we show that the total flux of Hawking radiation from rotating black holes can be universally determined in terms of the values of anomalies at the horizon by demanding gauge invariance and general coordinate covariance at the quantum level. We also clarify our choice of boundary conditions and show that our results are consistent with the effective action approach where regularity at the future horizon and vanishing of ingoing modes at r=∞ are imposed (i.e. Unruh vacuum).

[]

https://arxiv.org/pdf/hep-th/0606018.pdf

2019PhRvX...9d1060G

Black Hole Ringdown: The Importance of Overtones

2019-01-01

['-']

[]

It is possible to infer the mass and spin of the remnant black hole from binary black hole mergers by comparing the ringdown gravitational wave signal to results from studies of perturbed Kerr spacetimes. Typically, these studies are based on the fundamental quasinormal mode of the dominant ℓ=m =2 harmonic. By modeling the ringdown of accurate numerical relativity simulations, we find, in agreement with previous findings, that the fundamental mode alone is insufficient to recover the true underlying mass and spin, unless the analysis is started very late in the ringdown. Including higher overtones associated with this ℓ=m =2 harmonic resolves this issue and provides an unbiased estimate of the true remnant parameters. Further, including overtones allows for the modeling of the ringdown signal for all times beyond the peak strain amplitude, indicating that the linear quasinormal regime starts much sooner than previously expected. This result implies that the spacetime is well described as a linearly perturbed black hole with a fixed mass and spin as early as the peak. A model for the ringdown beginning at the peak strain amplitude can exploit the higher signal-to-noise ratio in detectors, reducing uncertainties in the extracted remnant quantities. These results should be taken into consideration when testing the no-hair theorem.

[]

https://arxiv.org/pdf/1903.08284.pdf

1997PhRvD..55.5871J

Primordial black hole formation during the QCD epoch

1997-01-01

['-', '-', '-', '-', 'black hole physics', '-', 'cosmology dark matter', '-', 'astrophysics', '-']

[]

We consider the formation of horizon-size primordial black holes (PBH's) from pre-existing density fluctuations during cosmic phase transitions. It is pointed out that the formation of PBH's should be particularly efficient during the QCD epoch due to a substantial reduction of pressure forces during adiabatic collapse, or equivalently, a significant decrease in the effective speed of sound during the color-confinement transition. Our considerations imply that for generic initial density perturbation spectra PBH mass functions are expected to exhibit a pronounced peak on the QCD-horizon mass scale ~1M<SUB>solar</SUB>. This mass scale is roughly coincident with the estimated masses for compact objects recently observed in our galactic halo by the MACHO Collaboration. Black holes formed during the QCD epoch may offer an attractive explanation for the origin of halo dark matter evading possibly problematic nucleosynthesis and luminosity bounds on baryonic halo dark matter.

[]

https://arxiv.org/pdf/astro-ph/9605152.pdf

2000MNRAS.313..193M

On the interpretation of the multicolour disc model for black hole candidates

2000-01-01

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

[]

We present a critical analysis of the usual interpretation of the multicolour disc model parameters for black hole candidates in terms of the inner radius and temperature of the accretion disc. Using a self-consistent model for the radiative transfer and the vertical temperature structure in a Shakura-Sunyaev disc, we simulate the observed disc spectra, taking into account Doppler blurring and gravitational redshift, and fit them with multicolour models. We show not only that such a model systematically underestimates the value of the inner-disc radius, but that when the accretion rate and/or the energy dissipated in the corona are allowed to change, the inner edge of the disc, as inferred from the multicolour model, appears to move even when it is in fact fixed at the innermost stable orbit.

[]

https://arxiv.org/pdf/astro-ph/9911457.pdf

2011PhRvL.106o1104K

Rotating Black Holes in Dilatonic Einstein-Gauss-Bonnet Theory

2011-01-01

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

[]

We construct generalizations of the Kerr black holes by including higher-curvature corrections in the form of the Gauss-Bonnet density coupled to the dilaton. We show that the domain of existence of these Einstein-Gauss-Bonnet-dilaton (EGBD) black holes is bounded by the Kerr black holes, the critical EGBD black holes, and the singular extremal EGBD solutions. The angular momentum of the EGBD black holes can exceed the Kerr bound. The EGBD black holes satisfy a generalized Smarr relation. We also compare their innermost stable circular orbits with those of the Kerr black holes and show the existence of differences which might be observable in astrophysical systems.

[]

https://arxiv.org/pdf/1101.2868.pdf

2008NJPh...10j3001C

Numerical observation of Hawking radiation from acoustic black holes in atomic Bose Einstein condensates

2008-01-01

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

[]

We report numerical evidence of Hawking emission of Bogoliubov phonons from a sonic horizon in a flowing one-dimensional atomic Bose-Einstein condensate. The presence of Hawking radiation is revealed from peculiar long-range patterns in the density-density correlation function of the gas. Quantitative agreement between our fully microscopic calculations and the prediction of analog models is obtained in the hydrodynamic limit. New features are predicted and the robustness of the Hawking signal against a finite temperature discussed.

[]

https://arxiv.org/pdf/0803.0507.pdf

2003MNRAS.343L..99F

Jet-dominated states: an alternative to advection across black hole event horizons in `quiescent' X-ray binaries

2003-01-01

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

[]

We demonstrate that at relatively low mass accretion rates, black hole candidate (BHC) X-ray binaries (XRBs) should enter `jet-dominated' states, in which the majority of the liberated accretion power is in the form of a (radiatively inefficient) jet and not dissipated as X-rays in the accretion flow. This result follows from the empirically established non-linear relation between radio and X-ray power from low/hard state BHC XRBs, which we assume also to hold for neutron star (NS) XRBs. Conservative estimates of the jet power indicate that all BHC XRBs in `quiescence' should be in this jet-dominated regime. In combination with an additional empirical result, namely that BHC XRBs are more `radio-loud' than NS XRBs, we find that in quiescence NS XRBs should be up to two orders of magnitude more luminous in X-rays than BHC XRBs, without requiring any significant advection of energy into a black hole. This ratio is as observed, and such observations should therefore no longer be considered as direct evidence for the existence of black hole event horizons. Furthermore, even if BHCs do contain black holes with event horizons, this work demonstrates that there is no requirement for the advection of significant amounts of accretion energy across the horizon.

[]

https://arxiv.org/pdf/astro-ph/0306614.pdf

2001ApJ...553L..47G

New Evidence for Black Hole Event Horizons from Chandra

2001-01-01

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

[]

Previously we claimed that black hole X-ray novae (BHXNs) in quiescence are much less luminous than equivalent neutron star X-ray novae (NSXNs). This claim was based on the quiescent detection of a single short-period BHXN (A0620-00, P<SUB>orb</SUB>=7.8 hr) and two longer period BHXNs (GRO J1655-40, P<SUB>orb</SUB>=62.9 hr; V404 Cygni, P<SUB>orb</SUB>=155.3 hr), along with sensitive upper limits. Here we announce the detection of two more short-period BHXNs (GRO J0422+32, P<SUB>orb</SUB>=5.1 hr; GS 2000+25, P<SUB>orb</SUB>=8.3 hr), an upper limit for a third that is improved by 2 orders of magnitude (4U 1543-47, P<SUB>orb</SUB>=27.0 hr), and a new, much lower quiescent measurement of GRO J1655-40. Taken together, these new Chandra Advanced CCD Imaging Spectrometer measurements confirm that the quiescent X-ray luminosities of BHXNs are significantly lower than those of NSXNs. We argue that this provides strong evidence for the existence of event horizons in BHXNs.

[]

https://arxiv.org/pdf/astro-ph/0012452.pdf

2012ApJ...753..125S

Comparing Single-epoch Virial Black Hole Mass Estimators for Luminous Quasars

2012-01-01

['black hole physics', 'galaxies active', 'galaxies quasars', '-']

[]

Single-epoch virial black hole (BH) mass estimators utilizing broad emission lines have been routinely applied to high-redshift quasars to estimate their BH masses. Depending on the redshift, different line estimators (Hα, Hβ, Mg II λ2798, C IV λ1549) are often used with optical/near-infrared spectroscopy. Here, we use a homogeneous sample of 60 intermediate-redshift (z ~ 1.5-2.2) Sloan Digital Sky Survey quasars with optical and near-infrared spectra covering C IV through Hα to investigate the consistency between different single-epoch virial BH mass estimators. We critically compare rest-frame UV line estimators (C IV λ1549, C III] λ1908, and Mg II λ2798) with optical estimators (Hβ and Hα) in terms of correlations between line widths and between continuum/line luminosities, for the high-luminosity regime (L <SUB>5100</SUB> &gt; 10<SUP>45.4</SUP> erg s<SUP>-1</SUP>) probed by our sample. The continuum luminosities of L <SUB>1350</SUB> and L <SUB>3000</SUB>, and the broad-line luminosities are well correlated with L <SUB>5100</SUB>, reflecting the homogeneity of quasar spectra in the rest-frame UV-optical, among which L <SUB>1350</SUB> and the line luminosities for C IV and C III] have the largest scatter in the correlation with L <SUB>5100</SUB>. We found that the Mg II FWHM correlates well with the FWHMs of the Balmer lines and that the Mg II line estimator can be calibrated to yield consistent virial mass estimates with those based on the Hβ/Hα estimators, thus extending earlier results on less luminous objects. The C IV FWHM is poorly correlated with the Balmer line FWHMs, and the scatter between the C IV and Hβ FWHMs consists of an irreducible part (~0.12 dex), and a part that correlates with the blueshift of the C IV centroid relative to that of Hβ, similar to earlier studies comparing C IV with Mg II. The C III] FWHM is found to correlate with the C IV FWHM, and hence is also poorly correlated with the Hβ FWHM. While the C IV and C III] lines can be calibrated to yield consistent virial mass estimates as Hβ on average, the scatter is substantially larger than Mg II, and the usage of C IV/C III] FWHM in the mass estimators does not improve the agreement with the Hβ estimator. We discuss controversial claims in the literature on the correlation between C IV and Hβ FWHMs, and suggest that the reported correlation is either a result based on small samples or only valid for low-luminosity objects.

[]

https://arxiv.org/pdf/1203.0601.pdf

2017IJMPD..2630021M

Observational evidence for intermediate-mass black holes

2017-01-01

['black hole physics', '-', 'galaxies nuclei', 'galaxies dwarf', 'galaxies photometry', 'galaxy globular clusters', 'astronomy x rays', 'astronomy radio', '-', 'gravitational waves', '-']

[]

Intermediate-mass black holes (IMBHs), with masses in the range 100-10<SUP>6</SUP>M⊙, are the link between stellar-mass BHs and supermassive BHs (SMBHs). They are thought to be the seeds from which SMBHs grow, which would explain the existence of quasars with BH masses of up to 10<SUP>10</SUP>M⊙ when the Universe was only 0.8 Gyr old. The detection and study of IMBHs has thus strong implications for understanding how SMBHs form and grow, which is ultimately linked to galaxy formation and growth, as well as for studies of the universality of BH accretion or the epoch of reionization. Proving the existence of seed BHs in the early Universe is not yet feasible with the current instrumentation; however, those seeds that did not grow into SMBHs can be found as IMBHs in the nearby Universe. In this review, I summarize the different scenarios proposed for the formation of IMBHs and gather all the observational evidence for the few hundreds of nearby IMBH candidates found in dwarf galaxies, globular clusters, and ultraluminous X-ray sources, as well as the possible discovery of a few seed BHs at high redshift. I discuss some of their properties, such as X-ray weakness and location in the BH mass scaling relations, and the possibility to discover IMBHs through high velocity clouds, tidal disruption events, gravitational waves, or accretion disks in active galactic nuclei. I finalize with the prospects for the detection of IMBHs with up-coming observatories.

[]

https://arxiv.org/pdf/1705.09667.pdf

2009MNRAS.394.2255S

Gravitational waves from resolvable massive black hole binary systems and observations with Pulsar Timing Arrays

2009-01-01

['black hole physics', 'gravitational waves', '-', 'cosmology theory', 'astrophysics', '-']

[]

Massive black holes are key components of the assembly and evolution of cosmic structures, and a number of surveys are currently on going or planned to probe the demographics of these objects and to gain insight into the relevant physical processes. Pulsar Timing Arrays (PTAs) currently provide the only means to observe gravitational radiation from massive black hole binary systems with masses &gt;~10<SUP>7</SUP>M<SUB>solar</SUB>. The whole cosmic population produces a stochastic background that could be detectable with upcoming PTAs. Sources sufficiently close and/or massive generate gravitational radiation that significantly exceeds the level of the background and could be individually resolved. We consider a wide range of massive black hole binary assembly scenarios, investigate the distribution of the main physical parameters of the sources, such as masses and redshift, and explore the consequences for PTAs observations. Depending on the specific massive black hole population model, we estimate that on average at least one resolvable source produces timing residuals in the range ~5-50ns. PTAs, and in particular the future Square Kilometre Array, can plausibly detect these unique systems, although the events are likely to be rare. These observations would naturally complement on the high-mass end of the massive black hole distribution function future surveys carried out by the Laser Interferometer Space Antenna.

[]

https://arxiv.org/pdf/0809.3412.pdf

1994PhRvD..49..975B

Dimensionally continued black holes

1994-01-01

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

[]

Static, spherically symmetric solutions of the field equations for a particular dimensional continuation of general relativity with a negative cosmological constant are studied. The action is, in odd dimensions, the Chern-Simons form for the anti-de Sitter group and, in even dimensions, the Euler density constructed with the Lorentz part of the anti-de Sitter curvature tensor. Both actions are special cases of the Lovelock action, and they reduce to the Hilbert action (with a negative cosmological constant) in the lower dimensional cases scrD=3 and scrD=4. Exact black hole solutions characterized by mass (M) and electric charge (Q) are found. In odd dimensions a negative cosmological constant is necessary to obtain a black hole, while in even dimensions both asymptotically flat and asymptotically anti-de Sitter black holes exist. The causal structure is analyzed and the Penrose diagrams are exhibited. The curvature tensor is singular at the origin for all dimensions greater than three. In dimensions of the form scrD=4k,4k-1, the number of horizons may be zero, one, or two, depending on the relative values of M and Q, while for a negative mass there is no horizon for any real value of Q. In the other cases, scrD=4k+1,4k+w, both naked and dressed singularities with a positive mass exist. As in three dimensions, in all odd dimensions anti-de Sitter space appears as a ``bound state'' of mass M=-1, separated from the continuous spectrum (M&gt;=0) by a gap of naked curvature singularities. In even dimensions anti-de Sitter space has zero mass. The analysis is Hamiltonian throughout, considerably simplifying the discussion of the boundary terms in the action and the thermodynamics. The Euclidean black hole has the topology scrR<SUP>2</SUP>×S<SUP>D-2</SUP>. Evaluation of the Euclidean action gives explicit expressions for all the relevant thermodynamical parameters of the system. The entropy, defined as a surface term in the action coming from the horizon, is shown to be a monotonically increasing function of the black-hole radius, different from the area for scrD&gt;4.

[]

https://arxiv.org/pdf/gr-qc/9307033.pdf

2010MNRAS.402.1516K

Black hole outflows

2010-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'galaxies formation', '-']

[]

I show that Eddington accretion episodes in active galactic nuclei (AGN) are likely to produce winds with velocities v ~ 0.1c and ionization parameters up to ξ ~ 10<SUP>4</SUP> (cgs), implying the presence of resonance lines of helium- and hydrogen-like iron. These properties are direct consequences of momentum and mass conservation, respectively, and agree with recent X-ray observations of fast outflows from AGN. Because the wind is significantly subluminal, it can persist long after the AGN is observed to have become sub-Eddington. The wind creates a strong cooling shock as it interacts with the interstellar medium of the host galaxy, and this cooling region may be observable in an inverse Compton continuum and lower excitation emission lines associated with lower velocities. The shell of matter swept up by the (`momentum-driven') shocked wind must propagate beyond the black hole's sphere of influence on a time-scale of &lt;~3 × 10<SUP>5</SUP>yr. Outside this radius, the shell stalls unless the black hole mass has reached the value M<SUB>σ</SUB> implied by the M-σ relation. If the wind shock did not cool, as suggested here, the resulting (`energy-driven') outflow would imply a far smaller supermassive black hole mass than actually observed. In galaxies with large bulges the black hole may grow somewhat beyond this value, suggesting that the observed M-σ relation may curve upwards at large M. Minor accretion events with small gas fractions can produce galaxy-wide outflows with velocities significantly exceeding σ, including fossil outflows in galaxies where there is little current AGN activity. Some rare cases may reveal the energy-driven outflows which sweep gas out of the galaxy and establish the black hole-bulge mass relation. However, these require the quasar to be at the Eddington luminosity.

[]

https://arxiv.org/pdf/0911.1639.pdf

2015PhRvD..91l4033X

P -V criticality in the extended phase space of black holes in massive gravity

2015-01-01

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

[]

We study the P -V criticality and phase transition in the extended phase space of charged anti-de Sitter black holes in canonical ensemble of ghost-free massive gravity, where the cosmological constant is viewed as a dynamical pressure of the black hole system. We give the generalized thermodynamic first law and the Smarr relation with massive gravity correction. We find that not only when the horizon topology is spherical but also in the Ricci flat or hyperbolic case, there appear the P -V criticality and phase transition up to the combination k +c<SUB>0</SUB><SUP>2</SUP>c<SUB>2</SUB>m<SUP>2</SUP> in the four-dimensional case, where k characterizes the horizon curvature and c<SUB>2</SUB>m<SUP>2</SUP> is the coefficient of the second term of massive potential associated with the graviton mass. The positivity of such combination indicate the van der Waals-like phase transition. When the spacetime dimension is larger then four, the Maxwell charge there seems unnecessary for the appearance of critical behavior, but a infinite repulsion effect needed, which can also be realized through negative valued c<SUB>3</SUB>m<SUP>2</SUP> or c<SUB>4</SUB>m<SUP>2</SUP> , which is third or fourth term of massive potential. When c<SUB>3</SUB>m<SUP>2</SUP> is positive, a Hawking-Page-like black hole to vacuum phase transition is shown in the five-dimensional chargeless case. For the van der Waals-like phase transition in four and five spacetime dimensions, we calculate the critical exponents near the critical point and find they are the same as those in the van der Waals liquid-gas system.

[]

https://arxiv.org/pdf/1506.03578.pdf

2004PhLB..595..484K

Born-Infeld black holes in the presence of a cosmological constant

2004-01-01

['-']

[]

We construct asymptotically anti-de Sitter (and de Sitter) black hole solutions of Einstein-Born-Infeld theory in arbitrary dimension. We critically analyse their geometries and discuss their thermodynamic properties.

[]

https://arxiv.org/pdf/hep-th/0406169.pdf

2007PhRvD..75d2003B

Using LISA extreme-mass-ratio inspiral sources to test off-Kerr deviations in the geometry of massive black holes

2007-01-01

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

[]

Inspirals of stellar-mass compact objects (COs) into ∼10<SUP>6</SUP>M<SUB>⊙</SUB> black holes are especially interesting sources of gravitational waves for the planned Laser Interferometer Space Antenna (LISA). The orbits of these extreme-mass-ratio inspirals (EMRIs) are highly relativistic, displaying extreme versions of both perihelion precession and Lense-Thirring precession of the orbital plane. We investigate the question of whether the emitted waveforms can be used to strongly constrain the geometry of the central massive object, and in essence check that it corresponds to a Kerr black hole (BH). For a Kerr BH, all multipole moments of the spacetime have a simple, unique relation to M and S, the BH mass, and spin; in particular, the spacetime’s mass quadrupole moment Q is given by Q=-S<SUP>2</SUP>/M. Here we treat Q as an additional parameter, independent of S and M, and ask how well observation can constrain its difference from the Kerr value. This was already estimated by Ryan, but for the simplified case of circular, equatorial orbits, and Ryan also neglected the signal modulations arising from the motion of the LISA satellites. We consider generic orbits and include the modulations due to the satellite motions. For this analysis, we use a family of approximate (basically post-Newtonian) waveforms, which represent the full parameter space of EMRI sources, and which exhibit the main qualitative features of true, general relativistic waveforms. We extend this parameter space to include (in an approximate manner) an arbitrary value of Q, and then construct the Fisher information matrix for the extended parameter space. By inverting the Fisher matrix, we estimate how accurately Q could be extracted from LISA observations of EMRIs. For 1 yr of coherent data from the inspiral of a 10M<SUB>⊙</SUB> black hole into rotating black holes of masses 10<SUP>5.5</SUP>M<SUB>⊙</SUB>, 10<SUP>6</SUP>M<SUB>⊙</SUB>, or 10<SUP>6.5</SUP>M<SUB>⊙</SUB>, we find Δ(Q/M<SUP>3</SUP>)∼10<SUP>-4</SUP>, 10<SUP>-3</SUP>, or 10<SUP>-2</SUP>, respectively (assuming total signal-to-noise ratio of 100, typical of the brightest detectable EMRIs). These results depend only weakly on the eccentricity of the inspiral orbit or the spin of the central object.

[]

https://arxiv.org/pdf/gr-qc/0612029.pdf

1996ApJ...464..664C

Grand Unification of Solutions of Accretion and Winds around Black Holes and Neutron Stars

1996-01-01

['accretion', 'accretion disks', 'black hole physics', 'hydrodynamics', 'shock waves', 'stars luminosity function;mass function', '-', 'astrophysics', '-']

[]

We provide the complete set of global solutions of viscous transonic flows (VTFs) around black holes and neutron stars. These solutions describe the optically thick and optically thin flows from the horizon of the black hole or from the neutron star's surface to the location where the flow joins with a Keplerian disk. We study the nature of the multiple sonic points as functions of advection, rotation, viscosity, heating, and cooling. Stable shock waves, which join two transonic solutions, are found to be present in a large region of the parameter space. We classify the solutions in terms of whether or not the flow can have a standing shock wave. We find no new topology of solutions other than what was observed in our previous studies of isothermal VTFs. We particularly stress the importance of the boundary conditions and argue that we have the most complete solution of accretion and winds around black holes and neutron stars.

[]

https://arxiv.org/pdf/astro-ph/9606145.pdf

2004PhRvD..70h4035M

Exact black hole solution with a minimally coupled scalar field

2004-01-01

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

[]

An exact four-dimensional black hole solution of gravity with a minimally coupled self-interacting scalar field is reported. The event horizon is a surface of negative constant curvature enclosing the curvature singularity at the origin, and the scalar field is regular everywhere outside the origin. This solution is an asymptotically locally anti-deSitter spacetime. The strong energy condition is satisfied on and outside the event horizon. The thermodynamical analysis shows the existence of a critical temperature, below which a black hole in vacuum undergoes a spontaneous dressing up with a nontrivial scalar field in a process reminiscent of ferromagnetism.

[]

https://arxiv.org/pdf/hep-th/0406111.pdf

2014JCAP...07..045Y

Calculating the mass fraction of primordial black holes

2014-01-01

['-', '-']

[]

We reinspect the calculation for the mass fraction of primordial black holes (PBHs) which are formed from primordial perturbations, finding that performing the calculation using the comoving curvature perturbation Script R<SUB>c</SUB> in the standard way vastly overestimates the number of PBHs, by many orders of magnitude. This is because PBHs form shortly after horizon entry, meaning modes significantly larger than the PBH are unobservable and should not affect whether a PBH forms or not—this important effect is not taken into account by smoothing the distribution in the standard fashion. We discuss alternative methods and argue that the density contrast, Δ, should be used instead as super-horizon modes are damped by a factor k<SUP>2</SUP>. We make a comparison between using a Press-Schechter approach and peaks theory, finding that the two are in close agreement in the region of interest. We also investigate the effect of varying the spectral index, and the running of the spectral index, on the abundance of primordial black holes.

[]

https://arxiv.org/pdf/1405.7023.pdf

2018PhRvD..98l3005R

Post-Newtonian dynamics in dense star clusters: Formation, masses, and merger rates of highly-eccentric black hole binaries

2018-01-01

['-']

[]

Using state-of-the-art dynamical simulations of globular clusters, including radiation reaction during black hole encounters and a cosmological model of star cluster formation, we create a realistic population of dynamically formed binary black hole mergers across cosmic space and time. We show that in the local universe, 10% of these binaries form as the result of gravitational-wave emission between unbound black holes during chaotic resonant encounters, with roughly half of those events having eccentricities detectable by current ground-based gravitational-wave detectors. The mergers that occur inside clusters typically have lower masses than binaries that were ejected from the cluster many Gyrs ago. Gravitational-wave captures from globular clusters contribute 1 - 2 Gpc<SUP>-3</SUP> yr<SUP>-1</SUP> to the binary merger rate in the local universe, increasing to ≳10 Gpc<SUP>-3</SUP> yr<SUP>-1</SUP> at z ∼3 . Finally, we discuss some of the technical difficulties associated with post-Newtonian scattering encounters, and how care must be taken when measuring the binary parameters during a dynamical capture.

[]

https://arxiv.org/pdf/1811.04926.pdf

2017Natur.549..488R

The close environments of accreting massive black holes are shaped by radiative feedback

2017-01-01

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

[]

The majority of the accreting supermassive black holes in the Universe are obscured by large columns of gas and dust. The location and evolution of this obscuring material have been the subject of intense research in the past decades, and are still debated. A decrease in the covering factor of the circumnuclear material with increasing accretion rates has been found by studies across the electromagnetic spectrum. The origin of this trend may be driven by the increase in the inner radius of the obscuring material with incident luminosity, which arises from the sublimation of dust; by the gravitational potential of the black hole; by radiative feedback; or by the interplay between outflows and inflows. However, the lack of a large, unbiased and complete sample of accreting black holes, with reliable information on gas column density, luminosity and mass, has left the main physical mechanism that regulates obscuration unclear. Here we report a systematic multi-wavelength survey of hard-X-ray-selected black holes that reveals that radiative feedback on dusty gas is the main physical mechanism that regulates the distribution of the circumnuclear material. Our results imply that the bulk of the obscuring dust and gas is located within a few to tens of parsecs of the accreting supermassive black hole (within the sphere of influence of the black hole), and that it can be swept away even at low radiative output rates. The main physical driver of the differences between obscured and unobscured accreting black holes is therefore their mass-normalized accretion rate.

[]

https://arxiv.org/pdf/1709.09651.pdf

2018PhRvD..98h4028C

Enriching the symphony of gravitational waves from binary black holes by tuning higher harmonics

2018-01-01

['-']

[]

For the first time, we construct an inspiral-merger-ringdown waveform model within the effective-one-body formalism for spinning, nonprecessing binary black holes that includes gravitational modes beyond the dominant (ℓ,|m |)=(2 ,2 ) mode, specifically (ℓ,|m |)=(2 ,1 ),(3 ,3 ),(4 ,4 ),(5 ,5 ). Our multipolar waveform model incorporates recent (resummed) post-Newtonian results for the inspiral and information from 157 numerical-relativity simulations, and 13 waveforms from black-hole perturbation theory for the (plunge-)merger and ringdown. We quantify the improvement in accuracy when including higher-order modes by computing the faithfulness of the waveform model against the numerical-relativity waveforms used to construct the model. We define the faithfulness as the match maximized over time, phase of arrival, gravitational-wave polarization and sky position of the waveform model, and averaged over binary orientation, gravitational-wave polarization and sky position of the numerical-relativity waveform. When the waveform model contains only the (2,2) mode, we find that the averaged faithfulness to numerical-relativity waveforms containing all modes with ℓ≤5 ranges from 90% to 99.9% for binaries with total mass 20 - 200 M<SUB>⊙</SUB> (using the Advanced LIGO's design noise curve). By contrast, when the (2,1), (3,3), (4,4), (5,5) modes are also included in the model, the faithfulness improves to 99% for all but four configurations in the numerical-relativity catalog, for which the faithfulness is greater than 98.5%. Starting from the complete inspiral-merger-ringdown model, we develop also a (stand-alone) waveform model for the merger-ringdown signal, calibrated to numerical-relativity waveforms, which can be used to measure multiple quasi-normal modes. The multipolar waveform model can be extended to include spin-precessional effects, and will be employed in upcoming observing runs of Advanced LIGO and Virgo.

[]

https://arxiv.org/pdf/1803.10701.pdf

2011ApJ...737...26N

Feedback from Central Black Holes in Elliptical Galaxies: Two-dimensional Models Compared to One-dimensional Models

2011-01-01

['galaxies active', 'galaxies elliptical lenticular;cd', 'cd', 'galaxies nuclei', 'galaxies quasars', '-']

[]

We extend the black hole (BH) feedback models of Ciotti, Ostriker, and Proga to two dimensions. In this paper, we focus on identifying the differences between the one-dimensional and two-dimensional hydrodynamical simulations. We examine a normal, isolated L <SUB>*</SUB> galaxy subject to the cooling flow instability of gas in the inner regions. Allowance is made for subsequent star formation, Type Ia and Type II supernovae, radiation pressure, and inflow to the central BH from mildly rotating galactic gas which is being replenished as a normal consequence of stellar evolution. The central BH accretes some of the infalling gas and expels a conical wind with mass, momentum, and energy flux derived from both observational and theoretical studies. The galaxy is assumed to have low specific angular momentum in analogy with the existing one-dimensional case in order to isolate the effect of dimensionality. The code then tracks the interaction of the outflowing radiation and winds with the galactic gas and their effects on regulating the accretion. After matching physical modeling to the extent possible between the one-dimensional and two-dimensional treatments, we find essentially similar results in terms of BH growth and duty cycle (fraction of the time above a given fraction of the Eddington luminosity). In the two-dimensional calculations, the cool shells forming at 0.1-1 kpc from the center are Rayleigh-Taylor unstable to fragmentation, leading to a somewhat higher accretion rate, less effective feedback, and a more irregular pattern of bursting compared with the one-dimensional case.

[]

https://arxiv.org/pdf/1007.3505.pdf

2003JHEP...09..025E

Instability of ultra-spinning black holes

2003-01-01

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

[]

It has long been known that, in higher-dimensional general relativity, there are black hole solutions with an arbitrarily large angular momentum for a fixed mass [1]. We examine the geometry of the event horizon of such ultra-spinning black holes and argue that these solutions become unstable at large enough rotation. Hence we find that higher-dimensional general relativity imposes an effective ``Kerr-bound'' on spinning black holes through a dynamical decay mechanism. Our results also give indications of the existence of new stationary black holes with ``rippled" horizons of spherical topology. We consider various scenarios for the possible decay of ultra-spinning black holes, and finally discuss the implications of our results for black holes in braneworld scenarios.

[]

https://arxiv.org/pdf/hep-th/0308056.pdf

2005ApJ...631..280B

HST STIS Spectroscopy of the Triple Nucleus of M31: Two Nested Disks in Keplerian Rotation around a Supermassive Black Hole

2005-01-01

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

[]

We present Hubble Space Telescope (HST) spectroscopy of the nucleus of M31 obtained with the Space Telescope Imaging Spectrograph (STIS). Spectra that include the Ca II infrared triplet (λ~=8500 Å) see only the red giant stars in the double brightness peaks P1 and P2. In contrast, spectra taken at λ~=3600-5100 Å are sensitive to the tiny blue nucleus embedded in P2, the lower surface brightness nucleus of the galaxy. P2 has a K-type spectrum, but we find that the blue nucleus has an A-type spectrum: it shows strong Balmer absorption lines. Hence, the blue nucleus is blue not because of AGN light but rather because it is dominated by hot stars. We show that the spectrum is well described by A0 giant stars, A0 dwarf stars, or a 200 Myr old, single-burst stellar population. White dwarfs, in contrast, cannot fit the blue nucleus spectrum. Given the small likelihood for stellar collisions, recent star formation appears to be the most plausible origin of the blue nucleus. In stellar population, size, and velocity dispersion, the blue nucleus is so different from P1 and P2 that we call it P3 and refer to the nucleus of M31 as triple. <P />Because P2 and P3 have very different spectra, we can make a clean decomposition of the red and blue stars and hence measure the light distribution and kinematics of each uncontaminated by the other. The line-of-sight velocity distributions of the red stars near P2 strengthen the support for Tremaine's eccentric disk model. Their wings indicate the presence of stars with velocities of up to 1000 km s<SUP>-1</SUP> on the anti-P1 side of P2. <P />The kinematics of P3 are consistent with a circular stellar disk in Keplerian rotation around a supermassive black hole. If the P3 disk is perfectly thin, then the inclination angle i~=55<SUP>deg</SUP> is identical within the errors to the inclination of the eccentric disk models for P1+P2 by Peiris &amp; Tremaine and by Salow &amp; Statler. Both disks rotate in the same sense and are almost coplanar. The observed velocity dispersion of P3 is largely caused by blurred rotation and has a maximum value of σ=1183+/-201 km s<SUP>-1</SUP>. This is much larger than the dispersion σ~=250 km s<SUP>-1</SUP> of the red stars along the same line of sight and is the largest integrated velocity dispersion observed in any galaxy. The rotation curve of P3 is symmetric around its center. It reaches an observed velocity of V=618+/-81 km s<SUP>-1</SUP> at radius 0.05"=0.19 pc, where the observed velocity dispersion is σ=674+/-95 km s<SUP>-1</SUP>. The corresponding circular rotation velocity at this radius is ~1700 km s<SUP>-1</SUP>. We therefore confirm earlier suggestions that the central dark object interpreted as a supermassive black hole is located in P3. <P />Thin-disk and Schwarzschild models with intrinsic axial ratios b/a&lt;~0.26 corresponding to inclinations between 55° and 58° match the P3 observations very well. Among these models, the best fit and the lowest black hole mass are obtained for a thin-disk model with M<SUB>•</SUB>=1.4×10<SUP>8</SUP> M<SUB>solar</SUB>. Allowing P3 to have some intrinsic thickness and considering possible systematic errors, the 1 σ confidence range becomes (1.1-2.3)×10<SUP>8</SUP> M<SUB>solar</SUB>. The black hole mass determined from P3 is independent of but consistent with Peiris &amp; Tremaine's mass estimate based on the eccentric disk model for P1+P2. It is ~2 times larger than the prediction by the correlation between M<SUB>•</SUB> and bulge velocity dispersion σ<SUB>bulge</SUB>. Taken together with other reliable black hole mass determinations in nearby galaxies, notably the Milky Way and M32, this strengthens the evidence that the M<SUB>•</SUB>-σ<SUB>bulge</SUB> relation has significant intrinsic scatter, at least at low black hole masses. <P />We show that any dark star cluster alternative to a black hole must have a half-mass radius &lt;~0.03"=0.11 pc in order to match the observations. Based on this, M31 becomes the third galaxy (after NGC 4258 and our Galaxy) in which clusters of brown dwarf stars or dead stars can be excluded on astrophysical grounds.

[]

https://arxiv.org/pdf/astro-ph/0509839.pdf

1997PhRvD..55..739T

Dilatonic black holes with a Gauss-Bonnet term

1997-01-01

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

[]

We discuss black holes in an effective theory derived from a superstring model, which includes a dilaton field, a gauge field, and the Gauss-Bonnet term. Assuming U(1) or SU(2) symmetry for the gauge field, we find four types of spherically symmetric solutions, i.e., a neutral, an electrically charged, a magnetically charged, and a ``colored'' black hole, and discuss their thermodynamical properties and fate via the Hawking evaporation process. For neutral and electrically charged black holes, we find a critical point and a singular end point. Below the mass corresponding to the critical point, no solution exists, while the curvature on the horizon diverges and a naked singularity appears at the singular point. A cusp structure in the mass-entropy diagram is found at the critical point and black holes on the branch between the critical and singular points become unstable. For magnetically charged and ``colored'' black holes, the solution becomes singular just at the end point with a finite mass. Because the black hole temperature is always finite even at the critical point or the singular point, we may conclude that the evaporation process will not be stopped even at the critical point or the singular point, and the black hole will move to a dynamical evaporation phase or a naked singularity will appear.

[]

https://arxiv.org/pdf/gr-qc/9606034.pdf

2007MNRAS.379..956D

Supermassive black hole binaries in gaseous and stellar circumnuclear discs: orbital dynamics and gas accretion

2007-01-01

['black hole physics', 'hydrodynamics', 'galaxies evolution', 'galaxies nuclei', 'galaxies starburst', 'astrophysics']

[]

The dynamics of two massive black holes in a rotationally supported nuclear disc of mass M<SUB>disc</SUB> = 10<SUP>8</SUP>M<SUB>solar</SUB> is explored using N-body/smoothed particle hydrodynamics simulations. Gas and star particles are copresent in the disc. Described by a Mestel profile, the disc has a vertical support provided by turbulence of the gas, and by stellar velocity dispersion. A primary black hole of mass 4 × 10<SUP>6</SUP>M<SUB>solar</SUB> is placed at the centre of the disc, while a secondary black hole is set initially on an eccentric corotating orbit in the disc plane. Its mass is in a 1:1, 1:4, and 1:10 ratio, relative to the primary. With this choice, we mimic the dynamics of black hole pairs released in the nuclear region at the end of a gas-rich galaxy merger. It is found that, under the action of dynamical friction, the two black holes form a close binary in ~10 Myr. The inspiral process is insensitive to the mass fraction in stars and gas present in the disc and is accompanied by the circularization of the orbit. We detail the gaseous mass profile bound to each black hole that can lead to the formation of two small Keplerian discs, weighing ~2per cent of the black hole mass, and of size ~0.01 pc. The mass of the tightly (loosely) bound particles increases (decreases) with time as the black holes spiral into closer and closer orbits. Double active galactic nucleus activity is expected to occur on an estimated time-scale of &lt;~10 Myr, comparable to the inspiral time-scale. The double nuclear point-like sources that may appear during dynamical evolution will have typical separations of &lt;~10 pc.

[]

https://arxiv.org/pdf/astro-ph/0612505.pdf

2017ApJ...840L..24F

Are LIGO's Black Holes Made from Smaller Black Holes?

2017-01-01

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

[]

One proposed formation channel for stellar mass black holes (BHs) is through hierarchical mergers of smaller BHs. Repeated mergers between comparable mass BHs leave an imprint on the spin of the resulting BH since the final BH spin is largely determined by the orbital angular momentum of the binary. We find that for stellar mass BHs forming hierarchically the distribution of spin magnitudes is universal, with a peak at a∼ 0.7 and little support below a∼ 0.5. We show that the spin distribution is robust against changes to the mass ratio of the merging binaries, the initial spin distribution of the first generation of BHs, and the number of merger generations. While we assume an isotropic distribution of initial spin directions, spins that are preferentially aligned or antialigned do not qualitatively change our results. We also consider a “cluster catastrophe” model for BH formation in which we allow for mergers of arbitrary mass ratios and show that this scenario predicts a unique spin distribution that is similar to the universal distribution derived for major majors. We explore the ability of spin measurements from ground-based gravitational-wave (GW) detectors to constrain hierarchical merger scenarios. We apply a hierarchical Bayesian mixture model to mock GW data and argue that the fraction of BHs that formed through hierarchical mergers will be constrained with { O }(100) LIGO binary black hole detections, while with { O }(10) detections we could falsify a model in which all component BHs form hierarchically.

[]

https://arxiv.org/pdf/1703.06869.pdf

2016MNRAS.462.3302E

BPASS predictions for binary black hole mergers

2016-01-01

['gravitational lensing', 'gravitational waves', 'stars binaries general', '-', '-', '-', '-']

[]

Using the Binary Population and Spectral Synthesis code, BPASS, we have calculated the rates, time-scales and mass distributions for binary black hole (BH) mergers as a function of metallicity. We consider these in the context of the recently reported first Laser Interferometer Gravitational-Wave Observatory (LIGO) event detection. We find that the event has a very low probability of arising from a stellar population with initial metallicity mass fraction above Z = 0.010 (Z ≳ 0.5 Z<SUB>⊙</SUB>). Binary BH merger events with the reported masses are most likely in populations below 0.008 (Z ≲ 0.4 Z<SUB>⊙</SUB>). Events of this kind can occur at all stellar population ages from 3 Myr up to the age of the Universe, but constitute only 0.1-0.4 per cent of binary BH mergers between metallicities of Z = 0.001 and 0.008. However at metallicity Z = 10<SUP>-4</SUP>, 26 per cent of binary BH mergers would be expected to have the reported masses. At this metallicity, the progenitor merger times can be close to ≈10 Gyr and rotationally mixed stars evolving through quasi-homogeneous evolution, due to mass transfer in a binary, dominate the rate. The masses inferred for the BHs in the binary progenitor of GW 150914 are amongst the most massive expected at anything but the lowest metallicities in our models. We discuss the implications of our analysis for the electromagnetic follow-up of future LIGO event detections.

[]

https://arxiv.org/pdf/1602.03790.pdf

2017PhRvD..95l3510I

Inflationary primordial black holes for the LIGO gravitational wave events and pulsar timing array experiments

2017-01-01

['-', '-']

[]

Primordial black holes (PBHs) are one of the candidates to explain the gravitational wave (GW) signals observed by the LIGO detectors. Among several phenomena in the early universe, cosmic inflation is a major example to generate PBHs from large primordial density perturbations. In this paper, we discuss the possibility to interpret the observed GW events as mergers of PBHs that are produced by cosmic inflation. The primordial curvature perturbation should be large enough to produce a sizable amount of PBHs, and thus we have several other probes to test this scenario. We point out that the current pulsar timing array (PTA) experiments already put severe constraints on GWs generated via the second-order effects, and that the observation of the cosmic microwave background puts severe restriction on its μ distortion. In particular, it is found that the scalar power spectrum should have a very sharp peak at k ∼1 0<SUP>6</SUP> Mpc<SUP>-1</SUP> to fulfill the required abundance of PBHs while evading constraints from the PTA experiments together with the μ distortion. We propose a mechanism that can realize such a sharp peak. In the future, simple inflation models that generate PBHs via almost Gaussian fluctuations could be probed/excluded.

[]

https://arxiv.org/pdf/1611.06130.pdf

2015PhRvD..91e2009K

Search for resonances and quantum black holes using dijet mass spectra in proton-proton collisions at √{s }=8 TeV

2015-01-01

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

[]

A search for resonances and quantum black holes is performed using the dijet mass spectra measured in proton-proton collisions at √{s }=8 TeV with the CMS detector at the LHC. The data set corresponds to an integrated luminosity of 19.7 fb<SUP>-1</SUP> . In a search for narrow resonances that couple to quark-quark, quark-gluon, or gluon-gluon pairs, model-independent upper limits, at 95% confidence level, are obtained on the production cross section of resonances, with masses above 1.2 TeV. When interpreted in the context of specific models the limits exclude string resonances with masses below 5.0 TeV; excited quarks below 3.5 TeV; scalar diquarks below 4.7 TeV; W<SUP>'</SUP> bosons below 1.9 TeV or between 2.0 and 2.2 TeV; Z<SUP>'</SUP> bosons below 1.7 TeV; and Randall-Sundrum gravitons below 1.6 TeV. A separate search is conducted for narrow resonances that decay to final states including b quarks. The first exclusion limit is set for excited b quarks, with a lower mass limit between 1.2 and 1.6 TeV depending on their decay properties. Searches are also carried out for wide resonances, assuming for the first time width-to-mass ratios up to 30%, and for quantum black holes with a range of model parameters. The wide resonance search excludes axigluons and colorons with mass below 3.6 TeV, and color-octet scalars with mass below 2.5 TeV. Lower bounds between 5.0 and 6.3 TeV are set on the masses of quantum black holes.

[]

https://arxiv.org/pdf/1501.04198.pdf

2003MNRAS.342.1169V

Galactic distribution of merging neutron stars and black holes - prospects for short gamma-ray burst progenitors and LIGO/VIRGO

2003-01-01

['black hole physics', 'gravitational waves', 'methods numerical', 'stars binaries close', '-', 'gamma rays', 'astrophysics']

[]

We have performed a detailed population synthesis on a large number (2 × 10<SUP>7</SUP>) of binary systems in order to investigate the properties of massive double degenerate binaries. We have included new important results in our input physics in order to obtain more reliable estimates of the merging time-scales and relative formation rates. These improvements include refined treatment of the binding energy in a common envelope, helium star evolution and reduced kicks imparted to new-born black holes. The discovery and observations of gamma-ray burst afterglows and the identification of host galaxies have allowed comparisons of theoretical distributions of merger sites with the observed distribution of afterglow positions relative to host galaxies. To help investigate the physical nature of short- and long-duration gamma-ray bursts, we compute the distances of merging neutron stars (NS) and/or black holes (BH) from the centres of their host galaxies, as predicted by their formation scenario combined with motion in galactic potentials. Furthermore, we estimate the formation rate and merging rate of these massive double degenerate binaries. The latter is very important for the prospects of detecting gravitational waves with LIGO/VIRGO. We find that the expected detection rate for LIGO II is ~850 yr<SUP>-1</SUP> for galactic field sources and that this rate is completely dominated by merging double black hole (BHBH) binaries. Even LIGO I may detect such an event (~0.25 yr<SUP>-1</SUP>). Our preferred model estimates the Galactic field double neutron star (NSNS) merger rate to be ~1.5 × 10<SUP>-6</SUP> yr<SUP>-1</SUP>. For BHBH systems this model predicts a merger rate of ~9.7 × 10<SUP>-6</SUP> yr<SUP>-1</SUP>. Our studies also reveal an accumulating numerous population of very wide-orbit BHBH systems which never merge (τ&gt;&gt;τ<SUB>Hubble</SUB>).

[]

https://arxiv.org/pdf/astro-ph/0303227.pdf

2009CQGra..26w5001M

Primordial black hole formation in the radiative era: investigation of the critical nature of the collapse

2009-01-01

['-', 'astrophysics']

[]

Following on after two previous papers discussing the formation of primordial black holes in the early universe, we present here results from an in-depth investigation of the extent to which primordial black hole formation in the radiative era can be considered as an example of the critical collapse phenomenon. We focus on initial supra-horizon-scale perturbations of a type which could have come from inflation, with only a growing component and no decaying component. In order to study perturbations with amplitudes extremely close to the supposed critical limit, we have modified our previous computer code with the introduction of an adaptive mesh refinement scheme. This has allowed us to follow black hole formation from perturbations whose amplitudes are up to eight orders of magnitude closer to the threshold than we could do before. We find that scaling-law behaviour continues down to the smallest black hole masses that we are able to follow and we see no evidence of shock production such as has been reported in some previous studies and which led there to a breaking of the scaling-law behaviour at small black hole masses. We attribute this difference to the different initial conditions used. In addition to the scaling law, we also present other features of the results which are characteristic of critical collapse in this context.

[]

https://arxiv.org/pdf/0811.1452.pdf

2019PhRvL.123a1101C

Spontaneously Scalarized Kerr Black Holes in Extended Scalar-Tensor-Gauss-Bonnet Gravity

2019-01-01

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

[]

We construct asymptotically flat, spinning, regular on and outside an event horizon, scalarized black holes (SBHs) in extended scalar-tensor-Gauss-Bonnet models. They reduce to Kerr BHs when the scalar field vanishes. For an illustrative choice of nonminimal coupling, we scan the domain of existence. For each value of spin, SBHs exist in an interval between two critical masses, with the lowest one vanishing in the static limit. Non-uniqueness with Kerr BHs of equal global charges is observed; the SBHs are entropically favoured. This suggests that SBHs form dynamically from the spontaneous scalarization of Kerr BHs, which are prone to a scalar-triggered tachyonic instability, below the largest critical mass. Phenomenologically, the introduction of BH spin damps the maximal observable difference between comparable scalarized and vacuum BHs. In the static limit, (perturbatively stable) SBHs can store over 20% of the spacetime energy outside the event horizon; in comparison with Schwarzschild BHs, their geodesic frequency at the ISCO can differ by a factor of 2.5 and deviations in the shadow areal radius may top 40%. As the BH spin grows, low mass SBHs are excluded, and the maximal relative differences decrease, becoming of the order of a few percent for dimensionless spin j ≳0.5 . This reveals a spin selection effect: non-GR effects are only significant for low spin. We discuss if and how the recently measured shadow size of the M87 supermassive BH constrains the length scale of the Gauss-Bonnet coupling.

[]

https://arxiv.org/pdf/1904.09997.pdf

2019MNRAS.487.2947D

Merging black holes in young star clusters

2019-01-01

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

[]

Searching for distinctive signatures, which characterize different formation channels of binary black holes (BBHs), is a crucial step towards the interpretation of current and future gravitational wave detections. Here, we investigate the demography of merging BBHs in young star clusters (SCs), which are the nursery of massive stars. We performed 4 × 10<SUP>3</SUP>N-body simulations of SCs with metallicity Z = 0.002, initial binary fraction 0.4, and fractal initial conditions, to mimic the clumpiness of star-forming regions. Our simulations include a novel population-synthesis approach based on the code MOBSE. We find that SC dynamics does not affect the merger rate significantly, but leaves a strong fingerprint on the properties of merging BBHs. More than 50 per cent of merging BBHs in young SCs form by dynamical exchanges in the first few Myr. Dynamically formed merging BBHs are significantly heavier than merging BBHs in isolated binaries: merging BBHs with total mass up to ∼120 M<SUB>⊙</SUB> form in young SCs, while the maximum total mass of merging BBHs in isolated binaries with the same metallicity is only ∼70 M<SUB>⊙</SUB>. Merging BBHs born via dynamical exchanges tend to have smaller mass ratios than BBHs in isolated binaries. Furthermore, SC dynamics speeds up the merger: the delay time between star formation and coalescence is significantly shorter in young SCs. In our simulations, massive systems such as GW170729 form only via dynamical exchanges. Finally ∼2 per cent of merging BBHs in young SCs have mass in the pair-instability mass gap (∼60-120 M<SUB>⊙</SUB>). This represents a unique fingerprint of merging BBHs in SCs.

[]

https://arxiv.org/pdf/1901.00863.pdf

2006PhRvL..96o1302I

Hawking Radiation from Charged Black Holes via Gauge and Gravitational Anomalies

2006-01-01

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

[]

Extending the method of Robinson and Wolczek, we show that in order to avoid a breakdown of general covariance and gauge invariance at the quantum level the total flux of charge and energy in each outgoing partial wave of a charged quantum field in a Reissner-Nordström black hole background must be equal to that of a (1+1)-dimensional blackbody at the Hawking temperature with the appropriate chemical potential.

[]

https://arxiv.org/pdf/hep-th/0602146.pdf

1996PhRvD..54.6312B

Pair creation of black holes during inflation

1996-01-01

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

[]

Black holes came into existence together with the universe through the quantum process of pair creation in the inflationary era. We present the instantons responsible for this process and calculate the pair creation rate from the no boundary proposal for the wave function of the universe. We find that this proposal leads to physically sensible results, which fit in with other descriptions of pair creation, while the tunneling proposal makes unphysical predictions. We then describe how the pair-created black holes evolve during inflation. In the classical solution, they grow with the horizon scale during the slow roll down of the inflaton field; this is shown to correspond to the flux of field energy across the horizon according to the first law of black hole mechanics. When quantum effects are taken into account, however, it is found that most black holes evaporate before the end of inflation. Finally, we consider the pair creation of magnetically charged black holes, which cannot evaporate. In standard Einstein-Maxwell theory we find that their number in the presently observable universe is exponentially small. We speculate how this conclusion may change if dilatonic theories are applied.

[]

https://arxiv.org/pdf/gr-qc/9606052.pdf

2019Natur.569..688M

Observation of thermal Hawking radiation and its temperature in an analogue black hole

2019-01-01

['-', '-']

[]

The entropy of a black hole<SUP>1</SUP> and Hawking radiation<SUP>2</SUP> should have the same temperature given by the surface gravity, within a numerical factor of the order of unity. In addition, Hawking radiation should have a thermal spectrum, which creates an information paradox<SUP>3,4</SUP>. However, the thermality should be limited by greybody factors<SUP>5</SUP>, at the very least<SUP>6</SUP>. It has been proposed that the physics of Hawking radiation could be verified in an analogue system<SUP>7</SUP>, an idea that has been carefully studied and developed theoretically<SUP>8-18</SUP>. Classical white-hole analogues have been investigated experimentally<SUP>19-21</SUP>, and other analogue systems have been presented<SUP>22,23</SUP>. The theoretical works and our long-term study of this subject<SUP>15,24-27</SUP> enabled us to observe spontaneous Hawking radiation in an analogue black hole<SUP>28</SUP>. The observed correlation spectrum showed thermality at the lowest and highest energies, but the overall spectrum was not of the thermal form, and no temperature could be ascribed to it. Theoretical studies of our observation made predictions about the thermality and Hawking temperature<SUP>29-33</SUP>. Here we construct an analogue black hole with improvements compared with our previous setup, such as reduced magnetic field noise, enhanced mechanical and thermal stability and redesigned optics. We find that the correlation spectrum of Hawking radiation agrees well with a thermal spectrum, and its temperature is given by the surface gravity, confirming the predictions of Hawking's theory. The Hawking radiation observed is in the regime of linear dispersion, in analogy with a real black hole, and the radiation inside the black hole is composed of negative-energy partner modes only, as predicted.

[]

https://arxiv.org/pdf/1809.00913.pdf

2012MNRAS.427.3081T

Black hole growth to z = 2 - I. Improved virial methods for measuring M<SUB>BH</SUB> and L/L<SUB>Edd</SUB>

2012-01-01

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

[]

We analyse several large samples of active galactic nuclei (AGNs) in order to establish the best tools required to study the evolution of black hole mass (M<SUB>BH</SUB>) and normalized accretion rate (L/L<SUB>Edd</SUB>). The data include spectra from the Sloan Digital Sky Survey, 2dF QSO Redshift survey and 2dF SDSS LRG And QSO survey public surveys at z &lt; 2, and a compilation of smaller samples with 0 &lt; z &lt; 5. We critically evaluate the usage of the Mg II λ2798 and C IV λ1549 lines, and adjacent continuum bands, as estimators of M<SUB>BH</SUB> and L/L<SUB>Edd</SUB>, by focusing on sources where one of these lines is observed together with Hβ. We present a new, luminosity-dependent bolometric correction for the monochromatic luminosity at 3000 Å, L<SUB>3000</SUB>, which is lower by a factor of ∼1.75 than those used in previous studies. We also re-calibrate the use of L<SUB>3000</SUB> as an indicator for the size of the broad emission-line region (R<SUB>BLR</SUB>) and find that R BLR ∝L30000.62, in agreement with previous results. We find that FWHM ( Mg ii)≃ FWHM (Hβ) for all sources with FWHM ( Mg ii)≲6000 km s-1. Beyond this full width at half-maximum (FWHM), the Mg II line width seems to saturate. The spectral region of the Mg II line can thus be used to reproduce Hβ-based estimates of M<SUB>BH</SUB> and L/L<SUB>Edd</SUB>, with negligible systematic differences and a scatter of ∼0.3 dex. The width of the C IV line, on the other hand, shows no correlation with either that of the Hβ or the Mg II lines and we could not identify the reason for this discrepancy. The scatter of M<SUB>BH</SUB>(C IV), relative to M<SUB>BH</SUB>(Hβ), is of almost 0.5 dex. Moreover, 46 per cent of the sources have FWHM (C iv)≲ FWHM (Hβ), in contrast with the basic premise of the virial method, which predicts FWHM (C iv)/ FWHM (Hβ)≃&lt;msqrt&gt;3.7&lt;/msqrt&gt;, based on reverberation mapping experiments. This fundamental discrepancy cannot be corrected based on the continuum slope or any C IV-related observable. Thus, the C IV line cannot be used to obtain precise estimates of M<SUB>BH</SUB>. We conclude by presenting the observed evolution of M<SUB>BH</SUB> and L/L<SUB>Edd</SUB> with cosmic epoch. The steep rise of L/L<SUB>Edd</SUB> with redshift up to z ≃ 1 flattens towards the expected maximal value of L/L<SUB>Edd</SUB> ≃ 1, with lower M<SUB>BH</SUB> sources showing higher values of L/L<SUB>Edd</SUB> at all redshifts. These trends will be further analysed in a forthcoming paper.

[]

https://arxiv.org/pdf/1209.1096.pdf

2003MNRAS.344L..37R

A new simple model for high-frequency quasi-periodic oscillations in black hole candidates

2003-01-01

['accretion', 'accretion disks', 'relativity', 'stars oscillations', 'astronomy x rays', 'astrophysics', '-']

[]

Observations of X-ray emissions from binary systems have long since been considered important tools to test general relativity in strong-field regimes. The high-frequency quasi-periodic oscillations (HFQPOs) observed in binaries containing a black hole candidate, in particular, have been proposed as a means to measure more directly the properties of the black hole, such as its mass and spin. Numerous models have been suggested to explain the HFQPOs and the rich phenomenology accompanying them. Many of these models rest on a number of assumptions and are at times in conflict with the most recent observations. We here propose a new, simple model in which the HFQPOs result from basic p-mode oscillations of a small accretion torus orbiting close to the black hole. We show that within this model the key properties of the HFQPOs can be explained simply, given a single reasonable assumption. We also discuss observational tests that can refute the model.

[]

https://arxiv.org/pdf/astro-ph/0307487.pdf

1999PhRvD..59d4013C

Topological black holes in the dimensionally continued gravity

1999-01-01

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

[]

We investigate topological black holes in a special class of Lovelock gravity. In odd dimensions, the action is the Chern-Simons form for the anti-de Sitter group. In even dimensions, it is the Euler density constructed with the Lorentz part of the anti-de Sitter curvature tensor. The Lovelock coefficients are reduced to two independent parameters: the cosmological constant and gravitational constant. The event horizons of these topological black holes may have constant positive, zero, or negative curvature. Their thermodynamics is analyzed and electrically charged topological black holes are also considered. We emphasize the differences due to the different curvatures of event horizons.

[]

https://arxiv.org/pdf/gr-qc/9808067.pdf

1999CQGra..16....1G

Black holes of D = 5 supergravity

1999-01-01

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

[]

We discuss some general features of black holes of five-dimensional supergravity, such as the first law of black hole mechanics. We also discuss some special features of rotating supersymmetric black holes. In particular, we show that the horizon is a non-singular, and non-rotating, null hypersurface whose intersection with a Cauchy surface is a squashed 3-sphere. We find the Killing spinors of the near-horizon geometry and thereby determine the near-horizon isometry supergroup.

[]

https://arxiv.org/pdf/hep-th/9810204.pdf

2016MNRAS.460.2979V

The cosmic evolution of massive black holes in the Horizon-AGN simulation

2016-01-01

['methods numerical', 'galaxies active', 'galaxies evolution', '-', '-', '-']

[]

We analyse the demographics of black holes (BHs) in the large-volume cosmological hydrodynamical simulation Horizon-AGN. This simulation statistically models how much gas is accreted on to BHs, traces the energy deposited into their environment and, consequently, the back-reaction of the ambient medium on BH growth. The synthetic BHs reproduce a variety of observational constraints such as the redshift evolution of the BH mass density and the mass function. Strong self-regulation via AGN feedback, weak supernova feedback, and unresolved internal processes result in a tight BH-galaxy mass correlation. Starting at z ∼ 2, tidal stripping creates a small population of BHs over-massive with respect to the halo. The fraction of galaxies hosting a central BH or an AGN increases with stellar mass. The AGN fraction agrees better with multi-wavelength studies, than single-wavelength ones, unless obscuration is taken into account. The most massive haloes present BH multiplicity, with additional BHs gained by ongoing or past mergers. In some cases, both a central and an off-centre AGN shine concurrently, producing a dual AGN. This dual AGN population dwindles with decreasing redshift, as found in observations. Specific accretion rate and Eddington ratio distributions are in good agreement with observational estimates. The BH population is dominated in turn by fast, slow, and very slow accretors, with transitions occurring at z = 3 and z = 2, respectively.

[]

https://arxiv.org/pdf/1602.01941.pdf

2017JHEP...03..119C

Noether charge, black hole volume, and complexity

2017-01-01

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

[]

In this paper, we study the physical significance of the thermodynamic volumes of AdS black holes using the Noether charge formalism of Iyer and Wald. After applying this formalism to study the extended thermodynamics of a few examples, we discuss how the extended thermodynamics interacts with the recent complexity = action proposal of Brown et al. (CA-duality). We, in particular, discover that their proposal for the late time rate of change of complexity has a nice decomposition in terms of thermodynamic quantities reminiscent of the Smarr relation. This decomposition strongly suggests a geometric, and via CA-duality holographic, interpretation for the thermodynamic volume of an AdS black hole. We go on to discuss the role of thermodynamics in complexity = action for a number of black hole solutions, and then point out the possibility of an alternate proposal, which we dub "complexity = volume 2.0". In this alternate proposal the complexity would be thought of as the spacetime volume of the Wheeler-DeWitt patch. Finally, we provide evidence that, in certain cases, our proposal for complexity is consistent with the Lloyd bound whereas CA-duality is not.

[]

https://arxiv.org/pdf/1610.02038.pdf

2009PhRvD..79b4003S

High-accuracy waveforms for binary black hole inspiral, merger, and ringdown

2009-01-01

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

[]

The first spectral numerical simulations of 16 orbits, merger, and ringdown of an equal-mass nonspinning binary black hole system are presented. Gravitational waveforms from these simulations have accumulated numerical phase errors through ringdown of ≲0.1radian when measured from the beginning of the simulation, and ≲0.02radian when waveforms are time and phase shifted to agree at the peak amplitude. The waveform seen by an observer at infinity is determined from waveforms computed at finite radii by an extrapolation process accurate to ≲0.01radian in phase. The phase difference between this waveform at infinity and the waveform measured at a finite radius of r=100M is about half a radian. The ratio of final mass to initial mass is M<SUB>f</SUB>/M=0.95162±0.00002, and the final black hole spin is S<SUB>f</SUB>/M<SUB>f</SUB><SUP>2</SUP>=0.68646±0.00004.

[]

https://arxiv.org/pdf/0810.1767.pdf

2014MNRAS.441.3703Z

Dynamics of stellar black holes in young star clusters with different metallicities - II. Black hole-black hole binaries

2014-01-01

['black hole physics', 'gravitational waves', 'methods numerical', 'stars binaries general', '-', '-', '-', '-', '-', '-']

[]

In this paper, we study the formation and dynamical evolution of black hole-black hole (BH-BH) binaries in young star clusters (YSCs), by means of N-body simulations. The simulations include metallicity-dependent recipes for stellar evolution and stellar winds, and have been run for three different metallicities (Z = 0.01, 0.1 and 1 Z<SUB>⊙</SUB>). Following recent theoretical models of wind mass-loss and core-collapse supernovae, we assume that the mass of the stellar remnants depends on the metallicity of the progenitor stars. We find that BH-BH binaries form efficiently because of dynamical exchanges: in our simulations, we find about 10 times more BH-BH binaries than double neutron star binaries. The simulated BH-BH binaries form earlier in metal-poor YSCs, which host more massive black holes (BHs) than in metal-rich YSCs. The simulated BH-BH binaries have very large chirp masses (up to 80 M<SUB>⊙</SUB>), because the BH mass is assumed to depend on metallicity, and because BHs can grow in mass due to the merger with stars. The simulated BH-BH binaries span a wide range of orbital periods (10<SUP>-3</SUP>-10<SUP>7</SUP> yr), and only a small fraction of them (0.3 per cent) is expected to merge within a Hubble time. We discuss the estimated merger rate from our simulations and the implications for Advanced VIRGO and LIGO.

[]

https://arxiv.org/pdf/1404.7147.pdf

1997PhRvD..56.4975M

Universal low-energy dynamics for rotating black holes

1997-01-01

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

[]

Fundamental string theory has been used to show that low-energy excitations of certain black holes are described by a two-dimensional conformal field theory. This picture has been found to be extremely robust. In this paper it is argued that many essential features of the low-energy effective theory can be inferred directly from a semiclassical analysis of the general Kerr-Newman solution of supersymmetric four-dimensional Einstein-Maxwell gravity, without using string theory. We consider the absorption and emission of scalars with orbital angular momentum, which provide a sensitive probe of the black hole. We find that the semiclassical emission rates-including super-radiant emission and greybody factors-for such scalars agree in striking detail with those computed in the effective conformal field theory, in both four and five dimensions. Also the value of the quantum mass gap to the lowest-lying excitation of a charge-Q black hole, E<SUB>gap</SUB>=1/8Q<SUP>3</SUP> in Planck units, can be derived without knowledge of fundamental string theory.

[]

https://arxiv.org/pdf/hep-th/9702015.pdf

1997ApJ...488..109R

Iron Fluorescence from within the Innermost Stable Orbit of Black Hole Accretion Disks

1997-01-01

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

[]

The fluorescent iron Kα line is a powerful observational probe of the inner regions of black hole accretion disks. Previous studies have assumed that only material outside the radius of marginal stability (r = 6m for a Schwarzschild hole) can contribute to the observed line emission. Here we show that fluorescence by material inside the radius of marginal stability, which is in the process of spiraling toward the event horizon, can have an observable influence on the iron line profile and equivalent width. For concreteness, we consider the case of a geometrically thin accretion disk, around a Schwarzschild black hole, in which fluorescence is excited by an X-ray source placed at some height above the disk and on the axis of the disk. Fully relativistic line profiles are presented for various source heights and efficiencies. It is found that the extra line flux generally emerges in the extreme red wing of the iron line, because of the large gravitational redshift experienced by photons from the region within the radius of marginal stability. <P />We apply our models to the variable iron line seen in the ASCA spectrum of the Seyfert nucleus MCG -6-30-15. It is found that the change in the line profile, equivalent width, and continuum normalization can be well explained as being due to a change in the height of the source above the disk. Thus, we can explain the iron line properties of MCG -6-30-15 within the context of an accretion disk around a nonrotating black hole. This contrasts with previous studies that, due to the absence of fluorescence from within the radius of marginal stability, have indicated that this object possesses a rapidly rotating (i.e., near-extremal Kerr) black hole. This is an important issue since it has a direct bearing on the spin paradigm for the radio-loud/radio-quiet dichotomy seen in accreting black hole systems. We discuss some future observational tests that could help distinguish slowly rotating black holes from rapidly rotating holes.

[]

https://arxiv.org/pdf/astro-ph/9705136.pdf

1998PhRvL..81.4553C

Black Holes and Superconformal Mechanics

1998-01-01

['-']

[]

The dynamics of a (super)particle near the horizon of an extreme Reissner-Nordström black hole is shown to be governed by an action that reduces to a (super)conformal mechanics model in the limit of large black hole mass.

[]

https://arxiv.org/pdf/hep-th/9804177.pdf

2010ApJ...721...26G

Precise Black Hole Masses from Megamaser Disks: Black Hole-Bulge Relations at Low Mass

2010-01-01

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

[]

The black hole (BH)-bulge correlations have greatly influenced the last decade of efforts to understand galaxy evolution. Current knowledge of these correlations is limited predominantly to high BH masses (M <SUB>BH</SUB>gsim10<SUP>8</SUP> M <SUB>sun</SUB>) that can be measured using direct stellar, gas, and maser kinematics. These objects, however, do not represent the demographics of more typical L &lt; L* galaxies. This study transcends prior limitations to probe BHs that are an order of magnitude lower in mass, using BH mass measurements derived from the dynamics of H<SUB>2</SUB>O megamasers in circumnuclear disks. The masers trace the Keplerian rotation of circumnuclear molecular disks starting at radii of a few tenths of a pc from the central BH. Modeling of the rotation curves, presented by Kuo et al., yields BH masses with exquisite precision. We present stellar velocity dispersion measurements for a sample of nine megamaser disk galaxies based on long-slit observations using the B&amp;C spectrograph on the Dupont telescope and the Dual Imaging Spectrograph on the 3.5 m telescope at Apache Point. We also perform bulge-to-disk decomposition of a subset of five of these galaxies with Sloan Digital Sky Survey imaging. The maser galaxies as a group fall below the M <SUB>BH</SUB>-σ<SUB>*</SUB> relation defined by elliptical galaxies. We show, now with very precise BH mass measurements, that the low-scatter power-law relation between M <SUB>BH</SUB> and σ<SUB>*</SUB> seen in elliptical galaxies is not universal. The elliptical galaxy M <SUB>BH</SUB>-σ<SUB>*</SUB> relation cannot be used to derive the BH mass function at low mass or the zero point for active BH masses. The processes (perhaps BH self-regulation or minor merging) that operate at higher mass have not effectively established an M <SUB>BH</SUB>-σ<SUB>*</SUB> relation in this low-mass regime.

[]

https://arxiv.org/pdf/1007.2851.pdf

2007JHEP...05..050E

Black saturn

2007-01-01

['-', '-']

[]

Using the inverse scattering method we construct an exact stationary asymptotically flat 4+1-dimensional vacuum solution describing ``black saturn'': a spherical black hole surrounded by a black ring. Angular momentum keeps the configuration in equilibrium. Black saturn reveals a number of interesting gravitational phenomena: (1) The balanced solution exhibits 2-fold continuous non-uniqueness for fixed mass and angular momentum; (2) Remarkably, the 4+1d Schwarzschild black hole is not unique, since the black ring and black hole of black saturn can counter-rotate to give zero total angular momentum at infinity, while maintaining balance; (3) The system cleanly demonstrates rotational frame-dragging when a black hole with vanishing Komar angular momentum is rotating as the black ring drags the surrounding spacetime. Possible generalizations include multiple rings of saturn as well as doubly spinning black saturn configurations.

[]

https://arxiv.org/pdf/hep-th/0701035.pdf

2010JCAP...04..023F

Primordial black holes as all dark matter

2010-01-01

['-', '-']

[]

We argue that a primordial black hole is a natural and unique candidate for all dark matter. We show that, in a smooth-hybrid new double inflation model, a right amount of the primordial black holes, with a sharply-defined mass, can be produced at the end of the smooth-hybrid regime, through preheating. We first consider masses &lt; 10<SUP>-7</SUP>M<SUB>odot</SUB> which are allowed by all the previous constraints. We next discuss much heavier mass 10<SUP>5</SUP>M<SUB>odot</SUB> hinted at by entropy, and galactic size evolution, arguments. Effects on the running of the scalar spectral index are computed.

[]

https://arxiv.org/pdf/1001.2308.pdf

2009JHEP...04..019H

CFT duals for extreme black holes

2009-01-01

['-']

[]

It is argued that the general four-dimensional extremal Kerr-Newman-AdS-dS black hole is holographically dual to a (chiral half of a) two-dimensional CFT, generalizing an argument given recently for the special case of extremal Kerr. Specifically, the asymptotic symmetries of the near-horizon region of the general extremal black hole are shown to be generated by a Virasoro algebra. Semiclassical formulae are derived for the central charge and temperature of the dual CFT as functions of the cosmological constant, Newton's constant and the black hole charges and spin. We then show, assuming the Cardy formula, that the microscopic entropy of the dual CFT precisely reproduces the macroscopic Bekenstein-Hawking area law. This CFT description becomes singular in the extreme Reissner-Nordstrom limit where the black hole has no spin. At this point a second dual CFT description is proposed in which the global part of the U(1) gauge symmetry is promoted to a Virasoro algebra. This second description is also found to reproduce the area law. Various further generalizations including higher dimensions are discussed.

[]

https://arxiv.org/pdf/0811.4393.pdf

1999ApJ...527L..39J

Black Hole-Neutron Star Mergers as Central Engines of Gamma-Ray Bursts

1999-01-01

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

[]

Hydrodynamic simulations of the merger of stellar mass black hole-neutron star binaries are compared with mergers of binary neutron stars. The simulations are Newtonian but take into account the emission and back-reaction of gravitational waves. The use of a physical nuclear equation of state allows us to include the effects of neutrino emission. For low neutron star-to-black hole mass ratios, the neutron star transfers mass to the black hole during a few cycles of orbital decay and subsequent widening before finally being disrupted, whereas for ratios near unity the neutron star is destroyed during its first approach. A gas mass between ~0.3 and ~0.7 M<SUB>solar</SUB> is left in an accretion torus around the black hole and radiates neutrinos at a luminosity of several times 10<SUP>53</SUP> ergs s<SUP>-1</SUP> during an estimated accretion timescale of about 0.1 s. The emitted neutrinos and antineutrinos annihilate into e<SUP>+/-</SUP> pairs with efficiencies of 1%-3% and rates of up to ~2×10<SUP>52</SUP> ergs s<SUP>-1</SUP>, thus depositing an energy E<SUB>νν¯</SUB>&lt;~10<SUP>51</SUP> ergs above the poles of the black hole in a region that contains less than 10<SUP>-5</SUP> M<SUB>solar</SUB> of baryonic matter. This could allow for relativistic expansion with Lorentz factors around 100 and is sufficient to explain apparent burst luminosities L<SUB>γ</SUB>~E<SUB>νν¯</SUB>/(f<SUB>Ω</SUB>t<SUB>γ</SUB>) up to several times 10<SUP>53</SUP> ergs s<SUP>-1</SUP> for burst durations t<SUB>γ</SUB>~0.1-1 s, if the γ emission is collimated in two moderately focused jets in a fraction f<SUB>Ω</SUB>=2δΩ/(4π)~(1/100)-(1/10) of the sky.

[]

https://arxiv.org/pdf/astro-ph/9908290.pdf

2019JHEP...10..062C

Microscopic origin of the Bekenstein-Hawking entropy of supersymmetric AdS<SUB>5</SUB> black holes

2019-01-01

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

[]

We present a holographic derivation of the entropy of supersymmetric asymp-totically AdS<SUB>5</SUB> black holes. We define a BPS limit of black hole thermodynamics by first focussing on a supersymmetric family of complexified solutions and then reaching extremality. We show that in this limit the black hole entropy is the Legendre transform of the on-shell gravitational action with respect to three chemical potentials subject toa constraint. This constraint follows from supersymmetry and regularity in the Euclidean bulk geometry. Further, we calculate, using localization, the exact partition function of the dual N = 1 SCFT on a twisted S<SUP>1</SUP> × S<SUP>3</SUP> with complexified chemical potentials obeying this constraint. This defines a generalization of the supersymmetric Casimir energy, whose Legendre transform at large N exactly reproduces the Bekenstein-Hawking entropy of the black hole.

[]

https://arxiv.org/pdf/1810.11442.pdf

2014Natur.513..398S

A supermassive black hole in an ultra-compact dwarf galaxy

2014-01-01

['-']

[]

Ultra-compact dwarf galaxies are among the densest stellar systems in the Universe. These systems have masses of up to 2 × 10<SUP>8</SUP> solar masses, but half-light radii of just 3-50 parsecs. Dynamical mass estimates show that many such dwarfs are more massive than expected from their luminosity. It remains unclear whether these high dynamical mass estimates arise because of the presence of supermassive black holes or result from a non-standard stellar initial mass function that causes the average stellar mass to be higher than expected. Here we report adaptive optics kinematic data of the ultra-compact dwarf galaxy M60-UCD1 that show a central velocity dispersion peak exceeding 100 kilometres per second and modest rotation. Dynamical modelling of these data reveals the presence of a supermassive black hole with a mass of 2.1 × 10<SUP>7</SUP> solar masses. This is 15 per cent of the object's total mass. The high black hole mass and mass fraction suggest that M60-UCD1 is the stripped nucleus of a galaxy. Our analysis also shows that M60-UCD1's stellar mass is consistent with its luminosity, implying a large population of previously unrecognized supermassive black holes in other ultra-compact dwarf galaxies.

[]

https://arxiv.org/pdf/1409.4769.pdf

2003ApJ...583L..95H

Dynamical Evidence for a Black Hole in GX 339-4

2003-01-01

['accretion', 'accretion disks', 'stars binaries close', '-', 'astronomy x rays', 'astrophysics']

[]

We present outburst spectroscopy of GX 339-4 that may reveal the motion of its elusive companion star. N III lines exhibit sharp emission components moving over ~300 km s<SUP>-1</SUP> in a single night. The most plausible interpretation of these components is that they are formed by irradiation of the companion star and the velocities indicate its orbital motion. We also detect motion of the wings of the He II 4686 Å line and changes in its morphology. No previously proposed period is consistent with periodic behavior of all of these measures. However, consistent and sensible solutions are obtained for periods around 1.7 days. For the best period, 1.7557 days, we estimate a mass function of 5.8+/-0.5 M<SUB>solar</SUB>. Even allowing for aliases, the 95% confidence lower limit on the mass function is 2.0 M<SUB>solar</SUB>. GX 339-4 can therefore be added to the list of dynamical black hole candidates. This is supported by the small motion in the wings of the He II line; if the compact object velocity is not larger than the observed motion, then the mass ratio is q&lt;~0.08, similar to other systems harboring black holes. Finally, we note that the sharp components are not always present but do seem to occur within a repeating phase range. This appears to migrate between our epochs of observation and may indicate shielding of the companion star by a variable accretion geometry such as a warp.

[]

https://arxiv.org/pdf/astro-ph/0301127.pdf

2016ApJ...831..134V

Unification of the fundamental plane and Super Massive Black Hole Masses

2016-01-01

['catalogs', 'galaxies bulges', 'galaxies fundamental parameters', 'galaxies kinematics and dynamics', 'gravitation', 'galaxies quasars', '-']

[]

According to the virial theorem, all gravitational systems in equilibrium sit on a plane in the three-dimensional parameter space defined by their mass, size, and second moment of the velocity tensor. While these quantities cannot be directly observed, there are suitable proxies: the luminosity L <SUB> k </SUB>, half-light radius R <SUB> e </SUB>, and dispersion {σ }<SUB>e</SUB>. These proxies indeed lie on a very tight fundamental plane (FP). How do the black holes (BHs) in the centers of galaxies relate to the FP? Their masses are known to exhibit no strong correlation with total galaxy mass, but they do correlate weakly with bulge mass (when present), and extremely well with the velocity dispersion through the {M}<SUB>\bullet </SUB>\propto {σ }<SUB>e</SUB><SUP>5.4</SUP> relation. These facts together imply that a tight plane must also exist defined by BH mass, total galaxy mass, and size. Here, I show that this is indeed the case using a heterogeneous set of 230 BHs. The sample includes BHs from zero to 10 billion solar masses and host galaxies ranging from low surface brightness dwarfs, through bulgeless disks, to brightest cluster galaxies. The resulting BH-size-luminosity relation {M}<SUB>\bullet </SUB>\propto {({L}<SUB>k</SUB>/{R}<SUB>e</SUB>)}<SUP>3.8</SUP> has the same amount of scatter as the M <SUB>•</SUB>-σ relation and is aligned with the galaxy FP, such that it is just a reprojection of {σ }<SUB>e</SUB>. The inferred BH-size-mass relation is {M}<SUB>\bullet </SUB>\propto {({M}<SUB>\star </SUB>/{R}<SUB>e</SUB>)}<SUP>2.9</SUP>. These relationships are universal and extend to galaxies without bulges. This implies that the BH is primarily correlated with its global velocity dispersion and not with the properties of the bulge. I show that the classical bulge-mass relation is a projection of the M <SUB>•</SUB>-σ relation. When the velocity dispersion cannot be measured (at high z or low dispersions), the BH-size-mass relation should be used as a proxy for BH mass in favor of just galaxy or bulge mass.

[]

https://arxiv.org/pdf/1606.01246.pdf

2002PhRvD..66d4002G

Zoom and whirl: Eccentric equatorial orbits around spinning black holes and their evolution under gravitational radiation reaction

2002-01-01

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

[]

We study eccentric equatorial orbits of a test-body around a Kerr black hole under the influence of gravitational radiation reaction. We have adopted a well established two-step approach: assuming that the particle is moving along a geodesic (justifiable as long as the orbital evolution is adiabatic) we calculate numerically the fluxes of energy and angular momentum radiated to infinity and to the black hole horizon, via the Teukolsky-Sasaki-Nakamura formalism. We can then infer the rate of change of orbital energy and angular momentum and thus the evolution of the orbit. The orbits are fully described by a semilatus rectum p and an eccentricity e. We find that while, during the inspiral, e decreases until shortly before the orbit reaches the separatrix of stable bound orbits [which is defined by p<SUB>s</SUB>(e)], in many astrophysically relevant cases the eccentricity will still be significant in the last stages of the inspiral. In addition, when a critical value p<SUB>crit</SUB>(e) is reached, the eccentricity begins to increase as a result of continued radiation induced inspiral. The two values p<SUB>s</SUB>, p<SUB>crit</SUB> (for given e) move closer to each other, in coordinate terms, as the black hole spin is increased, as they do also for fixed spin and increasing eccentricity. Of particular interest are moderate and high eccentricity orbits around rapidly spinning black holes, with p(e)~p<SUB>s</SUB>(e). We call these ``zoom-whirl'' orbits, because of their characteristic behavior involving several revolutions around the central body near periastron. Gravitational waveforms produced by such orbits are calculated and shown to have a very particular signature. Such signals may well prove of considerable astrophysical importance for the future Laser Interferometer Space Antenna detector.

[]

https://arxiv.org/pdf/gr-qc/0203086.pdf

2002JHEP...08..043E

Quantum Black Holes as Holograms in AdS Braneworlds

2002-01-01

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

[]

We propose a new approach for using the AdS/CFT correspondence to study quantum black hole physics. The black holes on a brane in an AdS<SUB>D+1</SUB> braneworld that solve the classical bulk equations are interpreted as duals of quantum-corrected D-dimensional black holes, rather than classical ones, of a conformal field theory coupled to gravity. We check this explicitly in D = 3 and D = 4. In D = 3 we reinterpret the existing exact solutions on a flat membrane as states of the dual 2+1 CFT. We show that states with a sufficiently large mass really are 2+1 black holes where the quantum corrections dress the classical conical singularity with a horizon and censor it from the outside. On a negatively curved membrane, we reinterpret the classical bulk solutions as quantum-corrected BTZ black holes. In D = 4 we argue that the bulk solution for the brane black hole should include a radiation component in order to describe a quantum-corrected black hole in the 3+1 dual. Hawking radiation of the conformal field is then dual to classical gravitational bremsstrahlung in the AdS<SUB>5</SUB> bulk.

[]

https://arxiv.org/pdf/hep-th/0206155.pdf

2007Natur.445..183M

A black hole in a globular cluster

2007-01-01

['astrophysics']

[]

Globular star clusters contain thousands to millions of old stars packed within a region only tens of light years across. Their high stellar densities make it very probable that their member stars will interact or collide. There has accordingly been considerable debate about whether black holes should exist in these star clusters. Some theoretical work suggests that dynamical processes in the densest inner regions of globular clusters may lead to the formation of black holes of ~1,000 solar masses. Other numerical simulations instead predict that stellar interactions will eject most or all of the black holes that form in globular clusters. Here we report the X-ray signature of an accreting black hole in a globular cluster associated with the giant elliptical galaxy NGC 4472 (in the Virgo cluster). This object has an X-ray luminosity of about 4×10<SUP>39</SUP>ergs<SUP>-1</SUP>, which rules out any object other than a black hole in such an old stellar population. The X-ray luminosity varies by a factor of seven in a few hours, which excludes the possibility that the object is several neutron stars superposed.

[]

https://arxiv.org/pdf/astro-ph/0701310.pdf

2008PhRvD..78d4021R

Analysis of spin precession in binary black hole systems including quadrupole-monopole interaction

2008-01-01

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

[]

We analyze in detail the spin precession equations in binary black hole systems, when the tidal torque on a Kerr black hole due to quadrupole-monopole coupling is taken into account. We show that completing the precession equations with this term reveals the existence of a conserved quantity at 2PN order when averaging over orbital motion. This quantity allows one to solve the (orbit-averaged) precession equations exactly in the case of equal masses and arbitrary spins, neglecting radiation reaction. For unequal masses, an exact solution does not exist in closed form, but we are still able to derive accurate approximate analytic solutions. We also show how to incorporate radiation-reaction effects into our analytic solutions adiabatically, and compare the results to solutions obtained numerically. For various configurations of the binary, the relative difference in the accumulated orbital phase computed using our analytic solutions versus a full numerical solution varies from ∼0.3% to ∼1.8% over ∼80 140 orbital cycles accumulated while sweeping over the orbital frequency range ∼20 300Hz. This typically corresponds to a discrepancy of order ∼5 6 radians. While this may not be accurate enough for implementation in LIGO template banks, we still believe that our new solutions are potentially quite useful for comparing numerical relativity simulations of spinning binary black hole systems with post-Newtonian theory. They can also be used to gain more understanding of precession effects, with potential application to the gravitational recoil problem, and to provide semianalytical templates for spinning, precessing binaries.

[]

https://arxiv.org/pdf/0803.1820.pdf

2000hep.th....9126G

Instability of charged black holes in anti-de Sitter space

2000-01-01

['-']

[]

We exhibit a tachyonic mode in a linearized analysis of perturbations of large anti-de Sitter Reissner-Nordstrom black holes in four dimensions. In the large black hole limit, and up to a 0.7% discrepancy which is probably round-off error in the numerical analysis, the tachyon appears precisely when the black hole becomes thermodynamically unstable.

[]

https://arxiv.org/pdf/hep-th/0009126.pdf

2012MNRAS.425.2854A

Ubiquitous seeding of supermassive black holes by direct collapse

2012-01-01

['methods numerical', 'cosmology theory', 'cosmology early universe', '-']

[]

We study for the first time the environment of massive black hole (BH) seeds (∼10<SUP>4-5</SUP> M<SUB>⊙</SUB>) formed via the direct collapse of pristine gas clouds in massive haloes (≥10<SUP>7</SUP> M<SUB>⊙</SUB>) at z &gt; 6. Our model is based on the evolution of dark matter haloes within a cosmological N-body simulation, combined with prescriptions for the formation of BH along with both Population III (Pop III) and Population II (Pop II) stars. We calculate the spatially varying intensity of Lyman-Werner (LW) radiation from stars and identify the massive pristine haloes in which it is high enough to shut down molecular hydrogen cooling. In contrast to previous BH seeding models with a spatially constant LW background, we find that the intensity of LW radiation due to local sources, J<SUB>local</SUB>, can be up to ∼10<SUP>6</SUP> times the spatially averaged background in the simulated volume and exceeds the critical value, J<SUB>crit</SUB>, for the complete suppression of molecular cooling, in some cases by four orders of magnitude. Even after accounting for possible metal pollution in a halo from previous episodes of star formation, we find a steady rise in the formation rate of direct collapse BHs (DCBHs) with decreasing redshift from 10<SUP>-3</SUP> Mpc<SUP>-3</SUP> z<SUP>-1</SUP> at z = 12 to 10<SUP>-2</SUP> Mpc<SUP>-3</SUP> z<SUP>-1</SUP> at z = 6. The onset of Pop II star formation at z ≈ 16 simultaneously marks the onset of the epoch of DCBH formation, as the increased level of LW radiation from Pop II stars is able to elevate the local levels of the LW intensity to J<SUB>local</SUB> &gt; J<SUB>crit</SUB>, while Pop III stars fail to do so at any time. The number density of DCBHs is sensitive to the number of LW photons and can vary by over an order of magnitude at z = 7 after accounting for reionization feedback. Haloes hosting DCBHs are more clustered than similar massive counterparts that do not host DCBHs, especially at redshifts z ≳ 10. Also, the DCBHs that form at z &gt; 10 are found to reside in highly clustered regions, whereas the DCBHs formed around z ∼ 6 are more common. We also show that planned surveys with James Webb Space Telescope should be able to detect the supermassive stellar precursors of DCBHs.

[]

https://arxiv.org/pdf/1205.6464.pdf

1995hep.th....1071S

Les Houches Lectures on Black Holes

1995-01-01

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

[]

Contents: 1. Introduction 2. Causal Structure and Penrose Diagrams: Minkowski Space; 1+1 Dimensional Minkowski Space; Schwarzchild Black Holes; Gravitational Collapse and the Vaidya Spacetimes; Event Horizons, Apparent Horizons, and Trapped Surfaces 3. Black Holes in Two Dimensions: General Relativity in the $S$-Wave Sector; Classical Dilaton Gravity; Eternal Black Holes; Coupling to Conformal Matter; Hawking Radiation and the Trace Anomaly; The Quantum State; Including the Back-Reaction; The Large $N$ Approximation; Conformal Invariance and Generalizations of Dilaton Gravity; The Soluble $RST$ Model 4. The Information Puzzle in Four Dimensions: Can the Information Come Out Before the Endpoint?; Low-Energy Effective Descriptions of the Planckian Endpoint; Remnants?; Information Destruction?; The Superposition Principle; Energy Conservation The New Rules; Superselection Sectors, $\alpha$-parameters, and the Restoration of Unitarity 5. Conclusions and Outlook

[]

https://arxiv.org/pdf/hep-th/9501071.pdf

2001PhRvA..63b3611G

Sonic black holes in dilute Bose-Einstein condensates

2001-01-01

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

[]

The sonic analog of a gravitational black hole in dilute-gas Bose-Einstein condensates is investigated. It is shown that there exist both dynamically stable and unstable configurations which, in the hydrodynamic limit, exhibit behaviors completely analogous to that of gravitational black holes. The dynamical instabilities involve the creation of quasiparticle pairs in positive and negative energy states. We illustrate these features in two qualitatively different one-dimensional models, namely, a long, thin condensate with an outcoupler laser beam providing an ``atom sink,'' and a tight ring-shaped condensate. We also simulate the creation of a stable sonic black hole by solving the Gross-Pitaevskii equation numerically for a condensate subject to a trapping potential which is adiabatically deformed. A sonic black hole could, in this way, be created experimentally with state-of-the-art or planned technology.

[]

https://arxiv.org/pdf/gr-qc/0005131.pdf

2009PhRvD..80l4011D

Black holes in f(R) theories

2009-01-01

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

[]

In the context of f(R) theories of gravity, we address the problem of finding static and spherically symmetric black hole solutions. Several aspects of constant curvature solutions with and without electric charge are discussed. We also study the general case (without imposing constant curvature). Following a perturbative approach around the Einstein-Hilbert action, it is found that only solutions of the Schwarzschild-(anti) de Sitter type are present up to second order in perturbations. Explicit expressions for the effective cosmological constant are obtained in terms of the f(R) function. Finally, we have considered the thermodynamics of black holes in anti-de Sitter space-time and found that this kind of solution can only exist provided the theory satisfies R<SUB>0</SUB>+f(R<SUB>0</SUB>)&lt;0. Interestingly, this expression is related to the condition which guarantees the positivity of the effective Newton’s constant in this type of theories. In addition, it also ensures that the thermodynamical properties in f(R) gravities are qualitatively similar to those of standard general relativity.

[]

https://arxiv.org/pdf/0907.3872.pdf

2012ApJ...753L..30M

The Hidden "AGN Main Sequence": Evidence for a Universal Black Hole Accretion to Star Formation Rate Ratio since z ~ 2 Producing an M <SUB>BH</SUB>-M <SUB>*</SUB> Relation

2012-01-01

['galaxies active', 'galaxies evolution', 'galaxies star clusters', 'astronomy x rays', '-']

[]

Using X-ray stacking analyses we estimate the average amounts of supermassive black hole (SMBH) growth taking place in star-forming galaxies at z ~ 1 and z ~ 2 as a function of galaxy stellar mass (M <SUB>*</SUB>). We find that the average SMBH growth rate follows remarkably similar trends with M <SUB>*</SUB> and redshift as the average star formation rates (SFRs) of their host galaxies (i.e., \dot{M}_BH vprop M <SUB>*</SUB> <SUP>0.86 ± 0.39</SUP> for the z ~ 1 sample and \dot{M}_BH vprop M <SUB>*</SUB> <SUP>1.05 ± 0.36</SUP> for the z ~ 2 sample). It follows that the ratio of SMBH growth rate to SFR is (1) flat with respect to M <SUB>*</SUB>, (2) not evolving with redshift, and (3) close to the ratio required to maintain/establish an SMBH to stellar mass ratio of ≈10<SUP>-3</SUP> as also inferred from today's M <SUB>BH</SUB>-M <SUB>Bulge</SUB> relationship. We interpret this as evidence that SMBHs have, on average, grown in step with their host galaxies since at least z ~ 2, irrespective of host galaxy mass and active galactic nucleus triggering mechanism. As such, we suggest that the same secular processes that drive the bulk of star formation are also responsible for the majority of SMBH growth. From this, we speculate that it is the availability of gas reservoirs that regulate both cosmological SMBH growth and star formation.

[]

https://arxiv.org/pdf/1204.2824.pdf

1998PhRvD..57.4566F

Measuring gravitational waves from binary black hole coalescences. II. The waves' information and its extraction, with and without templates

1998-01-01

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

[]

We discuss the extraction of information from detected binary black hole (BBH) coalescence gravitational waves by the ground-based interferometers LIGO and VIRGO, and by the space-based interferometer LISA. We focus on the merger phase that occurs after the gradual inspiral and before the ringdown. Our results are (i) if numerical relativity simulations have not produced template merger waveforms before BBH events are detected, one can study the merger waves using simple band-pass filters. For BBHs smaller than about 40M<SUB>solar</SUB> detected via their inspiral waves, the band-pass filtering signal-to-noise ratio indicates that the merger waves should typically be just barely visible in the noise for initial and advanced LIGO interferometers. (ii) We derive an optimized maximum-likelihood method for extracting a best-fit merger waveform from the noisy detector output; one ``perpendicularly projects'' this output onto a function space (specified using wavelets) that incorporates our (possibly sketchy) prior knowledge of the waveforms. An extension of the method allows one to extract the BBH's two independent waveforms from outputs of several interferometers. (iii) We propose a computational strategy for numerical relativists to pursue, if they successfully produce computer codes for generating merger waveforms, but if running the codes is too expensive to permit an extensive survey of the merger parameter space. In this case, for LIGO-VIRGO data analysis purposes, it would be advantageous to do a coarse survey of the parameter space aimed at exploring several qualitative issues and at determining the ranges of the several key parameters which we describe. (iv) A complete set of templates could be used to test the nonlinear dynamics of general relativity and to measure some of the binary's parameters via matched filtering. We estimate the number of bits of information obtainable from the merger waves (about 10-60 for LIGO-VIRGO, up to 200 for LISA), estimate the information loss due to template numerical errors or sparseness in the template grid, and infer approximate requirements on template accuracy and spacing.

[]

https://arxiv.org/pdf/gr-qc/9710129.pdf

2020JCAP...07..053K

Rotating black holes in 4D Einstein-Gauss-Bonnet gravity and its shadow

2020-01-01

['-']

[]

Recently there has been a surge of interest in regularizing, a D → 4 limit of, the Einstein-Gauss-Bonnet (EGB) gravity, and the resulting regularized 4D EGB gravity has nontrivial dynamics. The theory admits spherically symmetric black holes generalizing the Schwarzschild black holes. We consider the rotating black hole in regularized 4D EGB gravity and discuss their horizon properties and shadow cast. The effects of the GB coupling parameter on the shape and size of shadows are investigated in the context of recent M87* observations from the EHT . Interestingly, for a given spin parameter, the apparent size of the shadow decreases and gets more distorted due to the GB coupling parameter. We find that within the finite parameter space, e.g. for a=0.1M, α&lt;= 0.00394M<SUP>2</SUP>, and within the current observational uncertainties, the rotating black holes of the 4D EGB gravity are consistent with the inferred features of M87* black hole shadow.

[]

https://arxiv.org/pdf/2003.08927.pdf

2018NatAs...2..585M

The current ability to test theories of gravity with black hole shadows

2018-01-01

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

[]

Our Galactic Centre, Sagittarius A*, is believed to harbour a supermassive black hole, as suggested by observations tracking individual orbiting stars<SUP>1,2</SUP>. Upcoming submillimetre very-long baseline interferometry images of Sagittarius A* carried out by the Event Horizon Telescope collaboration (EHTC)<SUP>3,4</SUP> are expected to provide critical evidence for the existence of this supermassive black hole<SUP>5,6</SUP>. We assess our present ability to use EHTC images to determine whether they correspond to a Kerr black hole as predicted by Einstein's theory of general relativity or to a black hole in alternative theories of gravity. To this end, we perform general-relativistic magnetohydrodynamical simulations and use general-relativistic radiative-transfer calculations to generate synthetic shadow images of a magnetized accretion flow onto a Kerr black hole. In addition, we perform these simulations and calculations for a dilaton black hole, which we take as a representative solution of an alternative theory of gravity. Adopting the very-long baseline interferometry configuration from the 2017 EHTC campaign, we find that it could be extremely difficult to distinguish between black holes from different theories of gravity, thus highlighting that great caution is needed when interpreting black hole images as tests of general relativity.

[]

https://arxiv.org/pdf/1804.05812.pdf

2014PhRvD..89d4002Z

Critical behavior of Born-Infeld AdS black holes in the extended phase space thermodynamics

2014-01-01

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

[]

We study the thermodynamics of D-dimensional Born-Infeld AdS black holes in the extended phase space. We find that the usual small-large black hole phase transition, which exhibits analogy with the Van de Waals liquid-gas system, holds in all dimensions greater than three. However, different from the four-dimensional case, in the system of higher dimensional Born-Infeld AdS black holes there is no reentrant phase transition. For the three-dimensional Born-Infeld AS black hole, there does not exist critical phenomena.

[]

https://arxiv.org/pdf/1311.7299.pdf

2007AJ....134.1150J

Gemini Near-Infrared Spectroscopy of Luminous z ~ 6 Quasars: Chemical Abundances, Black Hole Masses, and Mg II Absorption

2007-01-01

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

[]

We present Gemini near-infrared spectroscopic observations of six luminous quasars at z = 5.8 to ~6.3. Five of them were observed using Gemini South GNIRS, which provides a simultaneous wavelength coverage of 0.9-2.5 μm in cross-dispersion mode. The other source was observed in the K band with Gemini North NIRI. We calculate line strengths for all detected emission lines and use their ratios to estimate gas metallicity in the broad-line regions of the quasars. The metallicity is found to be supersolar, with a typical value of ~4 Z<SUB>odot</SUB>, and a comparison with low-redshift observations shows no strong evolution in metallicity up to z ~ 6. The Fe II/Mg II ratio of the quasars is 4.9 ± 1.4, consistent with low-redshift measurements. We estimate central black hole masses of 10<SUP>9</SUP>-10<SUP>10</SUP> M<SUB>odot</SUB> and Eddington luminosity ratios of order unity. We identify two Mg II λλ2796, 2803 absorbers with rest equivalent width W &gt; 1 Å at 2.2 &lt; z &lt; 3 and three Mg II absorbers with W &gt; 1.5 Å at z &gt; 3 in the spectra, with the two most distant absorbers at z = 4.8668 and 4.8823, respectively. The redshift number densities (dN/dz) of Mg II absorbers with W &gt; 1.5 Å are consistent with no cosmic evolution up to z &gt; 4. <P />Based on observations obtained at the Gemini Observatory (acquired through the Gemini Science Archive), which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina).

[]

https://arxiv.org/pdf/0707.1663.pdf

2009PhRvD..79h4031P

Are black holes in alternative theories serious astrophysical candidates? The case for Einstein-dilaton-Gauss-Bonnet black holes

2009-01-01

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

[]

It is generally accepted that Einstein’s theory will get some as yet unknown corrections, possibly large in the strong-field regime. An ideal place to look for these modifications is in the vicinities of compact objects such as black holes. Here, we study dilatonic black holes, which arise in the framework of Gauss-Bonnet couplings and one-loop corrected four-dimensional effective theory of heterotic superstrings at low energies. These are interesting objects as a prototype for alternative, yet well-behaved gravity theories: they evade the “no-hair” theorem of general relativity but were proven to be stable against radial perturbations. We investigate the viability of these black holes as astrophysical objects and try to provide some means to distinguish them from black holes in general relativity. We start by extending previous works and establishing the stability of these black holes against axial perturbations. We then look for solutions of the field equations describing slowly rotating black holes and study geodesic motion around this geometry. Depending on the values of mass, dilaton charge, and angular momentum of the solution, one can have differences in the innermost-stable-circular-orbit location and orbital frequency, relative to black holes in general relativity. In the most favorable cases, the difference amounts to a few percent. Given the current state-of-the-art, we discuss the difficulty of distinguishing the correct theory of gravity from electromagnetic observations or even with gravitational-wave detectors.

[]

https://arxiv.org/pdf/0902.1569.pdf

2002ApJ...576..894M

Four-Body Effects in Globular Cluster Black Hole Coalescence

2002-01-01

['black hole physics', 'galaxy globular clusters', 'gravitational waves', 'stars kinematics and dynamics', 'astrophysics']

[]

In the high-density cores of globular clusters, multibody interactions are expected to be common, with the result that black holes in binaries are hardened by interactions. It was shown by Sigurdsson and Hernquist, Kulkarni, Hut, and McMillan, and others in 1993 that 10 M<SUB>solar</SUB> black holes interacting exclusively by three-body encounters do not merge in the clusters themselves, because recoil kicks the binaries out of the clusters before the binaries are tight enough to merge. Here we consider a new mechanism, involving four-body encounters. Numerical simulations by a number of authors suggest that roughly 20%-50% of binary-binary encounters will eject one star but leave behind a stable hierarchical triple. If the orbital plane of the inner binary is strongly tilted with respect to the orbital plane of the outer object, a secular Kozai resonance, first investigated in the context of asteroids in the solar system, can increase the eccentricity of the inner body significantly. We show that in a substantial fraction of cases, the eccentricity is driven to a high enough value that the inner binary will merge by gravitational radiation, without a strong accompanying kick. Thus, the merged object remains in the cluster; depending on the binary fraction of black holes and the inclination distribution of newly formed hierarchical triples, this mechanism may allow massive black holes to accumulate through successive mergers in the cores of globular clusters. It may also increase the likelihood that stellar-mass black holes in globular clusters will be detectable by their gravitational radiation.

[]

https://arxiv.org/pdf/astro-ph/0202298.pdf

2012PhRvD..86j4026H

Stationary scalar clouds around rotating black holes

2012-01-01

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

[]

Motivated by novel results in the theory of wave dynamics in black-hole spacetimes, we analyze the dynamics of a massive scalar field surrounding a rapidly rotating Kerr black hole. In particular, we report on the existence of stationary (infinitely long-lived) regular field configurations in the background of maximally rotating black holes. The effective height of these scalar “clouds” above the central black hole is determined analytically. Our results support the possible existence of stationary scalar field dark matter distributions surrounding rapidly rotating black holes.

[]

https://arxiv.org/pdf/1211.3202.pdf

2020ApJ...903L...5R

GW190521: Orbital Eccentricity and Signatures of Dynamical Formation in a Binary Black Hole Merger Signal

2020-01-01

['black hole physics', '-', '-', '-', 'celestial mechanics', '-', 'gravitational waves', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

Pair-instability supernovae are thought to restrict the formation of black holes in the mass range $\sim 50\mbox{--}135\,{M}_{\odot }$ . However, black holes with masses within this "high mass gap" are expected to form as the remnants of binary black hole mergers. These remnants can merge again dynamically in densely populated environments such as globular clusters. The hypothesis that the binary black hole merger GW190521 formed dynamically is supported by its high mass. Orbital eccentricity can also be a signature of dynamical formation, since a binary that merges quickly after becoming bound may not circularize before merger. In this work, we measure the orbital eccentricity of GW190521. We find that the data prefer a signal with eccentricity $e\geqslant 0.1$ at 10 Hz to a nonprecessing, quasi-circular signal, with a log Bayes factor $\mathrm{ln}{ \mathcal B }=5.0$ . When compared to precessing, quasi-circular analyses, the data prefer a nonprecessing, $e\geqslant 0.1$ signal, with log Bayes factors $\mathrm{ln}{ \mathcal B }\approx 2$ . Using injection studies, we find that a nonspinning, moderately eccentric (e = 0.13) GW190521-like binary can be mistaken for a quasi-circular, precessing binary. Conversely, a quasi-circular binary with spin-induced precession may be mistaken for an eccentric binary. We therefore cannot confidently determine whether GW190521 was precessing or eccentric. Nevertheless, since both of these properties support the dynamical formation hypothesis, our findings support the hypothesis that GW190521 formed dynamically.

[]

https://arxiv.org/pdf/2009.04771.pdf

2017PhRvD..95d3001A

Black hole mergers and the QCD axion at Advanced LIGO

2017-01-01

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

[]

In the next few years, Advanced LIGO (aLIGO) may see gravitational waves (GWs) from thousands of black hole (BH) mergers. This marks the beginning of a new precision tool for physics. Here we show how to search for new physics beyond the standard model using this tool, in particular the QCD axion in the mass range μ<SUB>a</SUB>∼10<SUP>-14</SUP> to 10<SUP>-10</SUP> eV . Axions (or any bosons) in this mass range cause rapidly rotating BHs to shed their spin into a large cloud of axions in atomic Bohr orbits around the BH, through the effect of superradiance (SR). This results in a gap in the mass vs spin distribution of BHs when the BH size is comparable to the axion's Compton wavelength. By measuring the spin and mass of the merging objects observed at LIGO, we could verify the presence and shape of the gap in the BH distribution produced by the axion. The axion cloud can also be discovered through the GWs it radiates via axion annihilations or level transitions. A blind monochromatic GW search may reveal up to 1 0<SUP>5</SUP> BHs radiating through axion annihilations, at distinct frequencies within ∼3 % of 2 μ<SUB>a</SUB> . Axion transitions probe heavier axions and may be observable in future GW observatories. The merger events are perfect candidates for a targeted GW search. If the final BH has high spin, a SR cloud may grow and emit monochromatic GWs from axion annihilations. We may observe the SR evolution in real time.

[]

https://arxiv.org/pdf/1604.03958.pdf

2020EPJC...80.1049K

Quasinormal modes, stability and shadows of a black hole in the 4D Einstein–Gauss–Bonnet gravity

2020-01-01

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

[]

Recently a D-dimensional regularization approach leading to the non-trivial <inline-formula id="IEq1"><mml:math><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mn>3</mml:mn><mml:mo>+</mml:mo><mml:mn>1</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math></inline-formula>-dimensional Einstein–Gauss–Bonnet (EGB) effective description of gravity was formulated which was claimed to bypass the Lovelock's theorem and avoid Ostrogradsky instability. Later it was shown that the regularization is possible only for some broad, but limited, class of metrics and Aoki et al. (arXiv:2005.03859) formulated a well-defined four-dimensional EGB theory, which breaks the Lorentz invariance in a theoretically consistent and observationally viable way. The black-hole solution of the first naive approach proved out to be also the exact solution of the well-defined theory. Here we calculate quasinormal modes of scalar, electromagnetic and gravitational perturbations and find the radius of shadow for spherically symmetric and asymptotically flat black holes with Gauss–Bonnet corrections. We show that the black hole is gravitationally stable when (<inline-formula id="IEq2"><mml:math><mml:mrow><mml:mo>-</mml:mo><mml:mn>16</mml:mn><mml:msup><mml:mi>M</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:mo>&lt;</mml:mo><mml:mi>α</mml:mi><mml:mo>⪅</mml:mo><mml:mn>0.6</mml:mn><mml:msup><mml:mi>M</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math></inline-formula>). The instability in the outer range is the eikonal one and it develops at high multipole numbers. The radius of the shadow <inline-formula id="IEq3"><mml:math><mml:msub><mml:mi>R</mml:mi><mml:mrow><mml:mi mathvariant="italic">Sh</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> obeys the linear law with a remarkable accuracy.

[]

https://arxiv.org/pdf/2003.01188.pdf

2002NuPhB.622..141K

A matrix model for the two-dimensional black hole

2002-01-01

['-']

[]

We construct and study a matrix model that describes two-dimensional string theory in the Euclidean black hole background. A conjecture of V. Fateev, A. Zamolodchikov and Al. Zamolodchikov, relating the black hole background to condensation of vortices (winding modes around Euclidean time) plays an important role in the construction. We use the matrix model to study quantum corrections to the thermodynamics of two-dimensional black holes.

[]

https://arxiv.org/pdf/hep-th/0101011.pdf

2009ApJ...690..802J

Equal- and Unequal-Mass Mergers of Disk and Elliptical Galaxies with Black Holes

2009-01-01

['galaxies active', 'galaxies evolution', 'galaxies formation', 'galaxies interactions', 'methods numerical', 'astrophysics']

[]

We present binary galaxy merger simulations with varying mass ratios and different progenitor morphologies. The simulations include mergers of gas-rich disks (Sp-Sp), of early-type galaxies and disks (E-Sp, mixed mergers), and mergers of early-type galaxies (E-E, dry mergers). We follow the dynamics of gas, stars, and dark matter, and include radiative cooling, star formation and black hole (BH) accretion, and the associated feedback processes as in Springel et al. We study the mass assembly of the BHs and discuss technical issues of the implemented model in detail. For Sp-Sp mergers, the peak star formation rate and BH accretion rate decrease and the growth timescales of the central BHs and newly formed stars increase with higher progenitor mass ratios. The peak BH accretion rate typically occurs shortly after the time of BH merging for low progenitor mass ratios (e.g., 3:1 and lower), whereas for higher progenitor mass ratios there is no clear correlation between the peak BH accretion rate and the BH merging time. The termination of star formation by BH feedback in disk mergers is significantly less important for higher progenitor mass ratios (e.g., 3:1 and higher). In addition, the inclusion of BH feedback efficiently suppresses star formation in dry E-E mergers and mixed E-Sp mergers. All merger remnants, independent of their progenitors, follow the observed relations between the central BH mass and the stellar velocity dispersion (M <SUB>BH</SUB> - σ), the bulge mass (M <SUB>BH</SUB> - M <SUB>*</SUB>), and the bulge binding energy (M <SUB>BH</SUB> - M <SUB>*</SUB>σ<SUP>2</SUP>), with the dominant source of scatter arising from variations in the initial gas mass fraction. The normalizations for all relations and the simulated slope of the M <SUB>BH</SUB> - σ and M <SUB>BH</SUB> - M <SUB>*</SUB>σ<SUP>2</SUP> relations are in good agreement with the observations, whereas the simulated slope of the M <SUB>BH</SUB> - M <SUB>*</SUB> relation is slightly steeper compared to the observations. This indicates that the simple BH feedback model self-regulates the mass growth of the BHs in accordance with the observed relations for a very wide range of merger progenitors.

[]

https://arxiv.org/pdf/0802.0210.pdf

2001sbg..conf..353P

TASI Lectures on Black Holes in String Theory

2001-01-01

['-', '-']

[]

This is a write-up of introductory lectures on black holes in string theory given at TASI-99. Topics discussed include: black holes, thermodynamics and the Bekenstein-Hawking entropy, the information problem; supergravity actions, conserved quantum numbers, supersymmetry and BPS states, units, duality and dimensional reduction, solution-generating; extremal M-branes and D-branes, smearing, probe actions, nonextremal branes, the Gregory-Laflamme instability; breakdown of supergravity and the Correspondence Principle, limits in parameter space, singularities; making black holes with branes, intersection-ology, the harmonic function rule, explicit d = 5, 4 examples; string computations of extremal black hole entropy in d = 5, 4, rotation, fractionation; non-extremality and entropy, the link to BTZ black holes, Hawking radiation and absorption cross-sections in the string/brane and supergravity pictures.

[]

https://arxiv.org/pdf/hep-th/0008241.pdf

2010ApJ...717..708C

Feedback from Central Black Holes in Elliptical Galaxies. III. Models with Both Radiative and Mechanical Feedback

2010-01-01

['accretion', 'accretion disks', 'black hole physics', 'galaxies active', 'galaxies nuclei', 'galaxies starburst', 'galaxies quasars', '-', '-']

[]

We find, from high-resolution hydro simulations, that winds from active galactic nuclei effectively heat the inner parts (≈100 pc) of elliptical galaxies, reducing infall to the central black hole; and radiative (photoionization and X-ray) heating reduces cooling flows at the kpc scale. Including both types of feedback with (peak) efficiencies of 3 × 10<SUP>-4</SUP> &lt;~ epsilon<SUB>w</SUB> &lt;~ 10<SUP>-3</SUP> and of epsilon<SUB>EM</SUB> ~= 10<SUP>-1.3</SUP> respectively, produces systems having duty cycles, central black hole masses, X-ray luminosities, optical light profiles, and E+A spectra in accord with the broad suite of modern observations of massive elliptical systems. Our main conclusion is that mechanical feedback (including energy, momentum, and mass) is necessary but the efficiency, based on several independent arguments, must be a factor of 10 lower than is commonly assumed. Bursts are frequent at z &gt; 1 and decline in frequency toward the present epoch as energy and metal-rich gas are expelled from the galaxies into the surrounding medium. For a representative galaxy of final stellar mass sime3 × 10<SUP>11</SUP> M <SUB>sun</SUB>, roughly 3 × 10<SUP>10</SUP> M <SUB>sun</SUB> of recycled gas has been added to the interstellar medium (ISM) since z ~= 2 and, of that, roughly 63% has been expelled from the galaxy, 19% has been converted into new metal-rich stars in the central few hundred parsecs, and 2% has been added to the central supermassive black hole (SMBH), with the remaining 16% in the form of hot X-ray emitting ISM. The bursts occupy a total time of sime170 Myr, which is roughly 1.4% of the available time. Of this time, the central supermassive black hole would be seen as a UV or optical source for sime45% and sime71% of the time, respectively. Restricting to the last 8.5 Gyr, the bursts occupy sime44 Myr, corresponding to a fiducial duty cycle of sime5 × 10<SUP>-3</SUP>.

[]

https://arxiv.org/pdf/1003.0578.pdf

2006CQGra..23.2585A

Black-hole thermodynamics with modified dispersion relations and generalized uncertainty principles

2006-01-01

['-']

[]

In several approaches to the quantum-gravity problem evidence has emerged of the validity of a 'GUP' (a generalized position-momentum uncertainty principle) and/or a 'MDR' (a modification of the energy-momentum dispersion relation), but very little is known about the implications of GUPs and MDRs for black-hole thermodynamics, another key topic for quantum-gravity research. We investigate an apparent link, already suggested in an earlier exploratory study involving two of us, between the possibility of a GUP and/or an MDR and the possibility of a log term in the area-entropy black-hole formula. We then obtain, from that same perspective, a modified relation between the mass of a black hole and its temperature, and we examine the validity of the 'generalized second law of black-hole thermodynamics' in theories with a GUP and/or an MDR. After an analysis of GUP- and MDR-modifications of the black-body radiation spectrum, we conclude the study with a description of the black-hole evaporation process.

[]

https://arxiv.org/pdf/gr-qc/0506110.pdf

2013JCAP...11..063W

Observing the shadow of Einstein-Maxwell-Dilaton-Axion black hole

2013-01-01

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

[]

In this paper, the shadows cast by Einstein-Maxwell-Dilaton-Axion black hole and naked singularity are studied. The shadow of a rotating black hole is found to be a dark zone covered by a deformed circle. For a fixed value of the spin a, the size of the shadow decreases with the dilaton parameter b. The distortion of the shadow monotonically increases with b and takes its maximal when the black hole approaches to the extremal case. Due to the optical properties, the area of the black hole shadow is supposed to equal to the high-energy absorption cross section. Based on this assumption, the energy emission rate is investigated. For a naked singularity, the shadow has a dark arc and a dark spot or straight, and the corresponding observables are obtained. These results show that there is a significant effect of the spin a and dilaton parameter b on these shadows. Moreover, we examine the observables of the shadow cast by the supermassive black hole at the center of the Milky Way, which is very useful for us to probe the nature of the black hole through the astronomical observations in the near future.

[]

https://arxiv.org/pdf/1311.4251.pdf

1995PhRvD..52.2245D

Black hole entropy without brick walls

1995-01-01

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

[]

We present evidence which confirms a suggestion by Susskind and Uglum regarding black hole entropy. Using a Pauli-Villars regulator, we find that 't Hooft's approach to evaluating black hole entropy through a statistical-mechanical counting of states for a scalar field propagating outside the event horizon yields precisely the one-loop renormalization of the standard Bekenstein-Hawking formula S=scrA/(4G). Our calculation also yields a constant contribution to the black hole entropy, a contribution associated with the one-loop renormalization of higher curvature terms in the gravitational action.

[]

https://arxiv.org/pdf/gr-qc/9503003.pdf

1997PhRvD..56.4994C

General rotating black holes in string theory: Greybody factors and event horizons

1997-01-01

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

[]

We derive the wave equation for a minimally coupled scalar field in the background of a general rotating five-dimensional black hole. It is written in a form that involves two types of thermodynamic variables, defined at the inner and outer event horizon, respectively. We model the microscopic structure as an effective string theory, with the thermodynamic properties of the left- and right-moving excitations related to those of the horizons. Previously known solutions to the wave equation are generalized to the rotating case, and their regime of validity is sharpened. We calculate the greybody factors and interpret the resulting Hawking emission spectrum microscopically in several limits. We find a U-duality-invariant expression for the effective string length that does not assume a hierarchy between the charges. It accounts for the universal low-energy absorption cross section in the general nonextremal case.

[]

https://arxiv.org/pdf/hep-th/9705192.pdf

2006JHEP...03..052S

Hydrodynamics of R-charged black holes

2006-01-01

['-']

[]

We consider hydrodynamics of Script N = 4 supersymmetric SU(N<SUB>c</SUB>) Yang-Mills plasma at a nonzero density of R-charge. In the regime of large N<SUB>c</SUB> and large 't Hooft coupling the gravity dual description involves an asymptotically Anti- de Sitter five-dimensional charged black hole solution of Behrnd, Cvetic and Sabra. We compute the shear viscosity as a function of chemical potentials conjugated to the three U(1)⊂SO(6)<SUB>R</SUB> charges. The ratio of the shear viscosity to entropy density is independent of the chemical potentials and is equal to 1/4π. For a single charge black hole we also compute the thermal conductivity, and investigate the critical behavior of the transport coefficients near the boundary of thermodynamic stability.

[]

https://arxiv.org/pdf/hep-th/0601157.pdf

2014PhRvD..89h6010P

State-dependent bulk-boundary maps and black hole complementarity

2014-01-01

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

[]

We provide a simple and explicit construction of local bulk operators that describe the interior of a black hole in the AdS/CFT correspondence. The existence of these operators is predicated on the assumption that the mapping of CFT operators to local bulk operators depends on the state of the CFT. We show that our construction leads to an exactly local effective field theory in the bulk. Barring the fact that their charge and energy can be measured at infinity, we show that the commutator of local operators inside and outside the black hole vanishes exactly, when evaluated within correlation functions of the CFT. Our construction leads to a natural resolution of the strong subadditivity paradox of Mathur and Almheiri et al. Furthermore, we show how, using these operators, it is possible to reconcile small corrections to effective field theory correlators with the unitarity of black hole evaporation. We address and resolve all other arguments, advanced in A. Almheiri et al. J. High Energy Phys. 09 (2013) 018 and D. Marolf and J. Polchinski, Phys. Rev. Lett. 111, 171301 (2013), in favor of structure at the black hole horizon. We extend our construction to states that are near equilibrium, and thereby also address the "frozen vacuum" objections of R. Bousso, Phys. Rev. Lett. 112, 041102 (2014). Finally, we explore an intriguing link between our construction of interior operators and Tomita-Takesaki theory.

[]

https://arxiv.org/pdf/1310.6335.pdf

2013PhRvL.111q1301M

Gauge-Gravity Duality and the Black Hole Interior

2013-01-01

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

[]

We present a further argument that typical black holes with field theory duals have firewalls at the horizon. This argument makes no reference to entanglement between the black hole and any distant system, and so is not evaded by identifying degrees of freedom inside the black hole with those outside. We also address the Einstein-Rosen=Einstein-Podolsky-Rosen conjecture of Maldacena and Susskind, arguing that the correlations in generic highly entangled states cannot be geometrized as a smooth wormhole.

[]

https://arxiv.org/pdf/1307.4706.pdf

2017PhRvD..96b4011M

Quasinormal modes of black holes: The improved semianalytic approach

2017-01-01

['-']

[]

We extend the semianalytic technique of Iyer and Will for computing the complex quasinormal frequencies of black holes, ω , by constructing the Padé approximants of the (formal) series for ω<SUP>2</SUP>. It is shown that for the (so-far best documented) quasinormal frequencies of the Schwarzschild and Reissner-Nordström black holes the Padé transforms P<SUB>6</SUB><SUP>6</SUP> and P<SUB>7</SUB><SUP>6</SUP> are, within the domain of applicability, always in excellent agreement with the numerical results. We argue that the method may serve as a black box with the "potential" Q (x ) as an input and the accurate quasinormal modes as the output. The generalizations and modifications of the method are briefly discussed as well as the preliminary results for other classes of black holes.

[]

https://arxiv.org/pdf/1704.00361.pdf

2017PhRvD..96d3504I

Inflationary primordial black holes as all dark matter

2017-01-01

['-', '-']

[]

Following a new microlensing constraint on primordial black holes (PBHs) with ∼1 0<SUP>20</SUP>- 1 0<SUP>28</SUP> g [H. Niikura et al., arXiv:1701.02151.], we revisit the idea of PBH as all dark matter (DM). We have shown that the updated observational constraints suggest the viable mass function for PBHs as all DM to have a peak at ≃1 0<SUP>20</SUP> g with a small width σ ≲0.1 , by imposing observational constraints on an extended mass function in a proper way. We have also provided an inflation model that successfully generates PBHs as all DM fulfilling this requirement.

[]

https://arxiv.org/pdf/1701.02544.pdf

2016PhRvD..94j4056F

Notes on nonsingular models of black holes

2016-01-01

['-', '-']

[]

We discuss static spherically symmetric metrics which represent nonsingular black holes in four- and higher-dimensional spacetime. We impose a set of restrictions, such as a regularity of the metric at the center r =0 and Schwarzschild asymptotic behavior at large r . We assume that the metric besides mass M contains an additional parameter ℓ, which determines the scale where modification of the solution of the Einstein equations becomes significant. We require that the modified metric obeys the limiting curvature condition; that is, its curvature is uniformly restricted by the value ∼ℓ-<SUP>2</SUP>. We also make a "more technical" assumption that the metric coefficients are rational functions of r . In particular, the invariant (∇r )<SUP>2</SUP> has the form P<SUB>n</SUB>(r )/P<SUB>∼n</SUB>(r ), where P<SUB>n</SUB> and P<SUB>∼n</SUB> are polynomials of the order of n . We discuss first the case of four dimensions. We show that when n ≤2 such a metric cannot describe a nonsingular black hole. For n =3 we find a suitable metric, which besides M and ℓ contains a dimensionless numerical parameter. When this parameter vanishes, the obtained metric coincides with Hayward's one. The characteristic property of such spacetimes is -ξ<SUP>2</SUP>=(∇r )<SUP>2</SUP>, where ξ<SUP>2</SUP> is a timelike at infinity Killing vector. We describe a possible generalization of a nonsingular black-hole metric to the case when this equality is violated. We also obtain a metric for a charged nonsingular black hole obeying similar restrictions as the neutral one and construct higher dimensional models of neutral and charged black holes.

[]

https://arxiv.org/pdf/1609.01758.pdf

2021PhRvD.103j4047K

Constraints on black-hole charges with the 2017 EHT observations of M87*

2021-01-01

['-']

[]

Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87* shadow size to infer constraints on the physical charges of a large variety of nonrotating or rotating black holes. For example, we show that the quality of the measurements is already sufficient to rule out that M87* is a highly charged dilaton black hole. Similarly, when considering black holes with two physical and independent charges, we are able to exclude considerable regions of the space of parameters for the doubly-charged dilaton and the Sen black holes.

[]

https://arxiv.org/pdf/2105.09343.pdf

2002ApJ...568..845O

Dynamical Evidence for a Black Hole in the Microquasar XTE J1550-564

2002-01-01

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

[]

Optical spectroscopic observations of the companion star (type G8 IV to K4 III) in the microquasar system XTE J1550-564 reveal a radial velocity curve with a best-fitting spectroscopic period of P<SUB>sp</SUB>=1.552+/-0.010 days and a semiamplitude of K<SUB>2</SUB>=349+/-12 km s<SUP>-1</SUP>. The optical mass function is f(M)=6.86+/-0.71M<SUB>solar</SUB> (1 σ). We tentatively measure the rotational velocity of the companion star to be V<SUB>rot</SUB>sini=90+/-10 km s<SUP>-1</SUP>, which when taken at face value implies a mass ratio of Q≡M<SUB>1</SUB>/M<SUB>2</SUB>=6.6<SUP>+2.5</SUP><SUB>-1.6</SUB> (1 σ), using the above value of K<SUB>2</SUB>. We derive constraints on the binary parameters from simultaneous modeling of the ellipsoidal light and radial velocity curves. We find 1 σ ranges for the photometric period (1.5430days&lt;=P<SUB>ph</SUB>&lt;=1.5440days), K-velocity (350.2&lt;=K<SUB>2</SUB>&lt;=368.6 km s<SUP>-1</SUP>), inclination (67.0d&lt;=i&lt;=77.4d), mass ratio (Q&gt;=12.0), and orbital separation (11.55R<SUB>solar</SUB>&lt;=a&lt;=12.50R<SUB>solar</SUB>). Given these geometrical constraints, we find that the most likely value of the mass of the compact object is 9.41 M<SUB>solar</SUB> with a 1 σ range of 8.36M<SUB>solar</SUB>&lt;=M<SUB>1</SUB>&lt;=10.76M<SUB>solar</SUB>. If we apply our tentative value of V<SUB>rot</SUB>sini=90+/-10 km s<SUP>-1</SUP> as an additional constraint in the ellipsoidal modeling, we find 1 σ ranges of 1.5432days&lt;=P<SUB>ph</SUB>&lt;=1.5441days for the photometric period, 352.2&lt;=K<SUB>2</SUB>&lt;=370.1 km s<SUP>-1</SUP> for the K-velocity, 70.8d&lt;=i&lt;=75.4d for the inclination, 6.7&lt;=Q&lt;=11.0 for the mass ratio, and 12.35R<SUB>solar</SUB>&lt;=a&lt;=13.22R<SUB>solar</SUB> for the orbital separation. These geometrical constraints imply the most likely value of the mass of the compact object of 10.56 M<SUB>solar</SUB> with a 1 σ range of 9.68M<SUB>solar</SUB>&lt;=M<SUB>1</SUB>&lt;=11.58M<SUB>solar</SUB>. In either case the mass of the compact object is well above the maximum mass of a stable neutron star, and we therefore conclude that XTE J1550-564 contains a black hole. Based on observations collected at the European Southern Observatory, Chile (program 67.D-0229), at the Magellan Walter Baade Telescope at the Las Campanas Observatory, Chile, and the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

[]

https://arxiv.org/pdf/astro-ph/0112101.pdf

2006JHEP...06..007B

Supergravity microstates for BPS black holes and black rings

2006-01-01

['-']

[]

We demonstrate a solution generating technique, modulo some constraints, for a large class of smooth supergravity solutions with the same asymptotic charges as a five dimensional 3-charge BPS black hole or black ring, dual to a D1/D5/P system. These solutions are characterized by a harmonic function with both positive and negative poles, which induces a geometric transition whereby singular sources have disappeared and all of the net charge at infinity is sourced by fluxes through two-cycles joining the poles of the harmonic function.

[]

https://arxiv.org/pdf/hep-th/0505167.pdf

2013MNRAS.428.2500C

The `universal' radio/X-ray flux correlation: the case study of the black hole GX 339-4

2013-01-01

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

[]

The existing radio and X-ray flux correlation for Galactic black holes in the hard and quiescent states relies on a sample which is mostly dominated by two sources (GX 339-4 and V404 Cyg) observed in a single outburst. In this paper, we report on a series of radio and X-ray observations of the recurrent black hole GX 339-4 with the Australia Telescope Compact Array, the Rossi X-ray Timing Explorer and the Swift satellites. With our new long-term campaign, we now have a total of 88 quasi-simultaneous radio and X-ray observations of GX 339-4 during its hard state, covering a total of seven outbursts over a 15-yr period. Our new measurements represent the largest sample for a stellar mass black hole, without any bias from distance uncertainties, over the largest flux variations and down to a level that could be close to quiescence, making GX 339-4 the reference source for comparison with other accreting sources (black holes, neutrons stars, white dwarfs and active galactic nuclei). Our results demonstrate a very strong and stable coupling between radio and X-ray emission, despite several outbursts of different nature and separated by a period of quiescence. The radio and X-ray luminosity correlation of the form L<SUB>X</SUB>∝L<SUP>0.62 ± 0.01</SUP><SUB>Rad</SUB> confirms the non-linear coupling between the jet and the inner accretion flow powers and better defines the standard correlation track in the radio-X-ray diagram for stellar mass black holes. We further note epochs of deviations from the fit that significantly exceed the measurement uncertainties, especially during the time of formation and destruction of the self-absorbed compact jets. The jet luminosity could appear brighter (up to a factor of 2) during the decay compared to the rise for a given X-ray luminosity, possibly related to the compact jets. We furthermore connect the radio/X-ray measurements to the near-infrared/X-ray empirical correlation in GX 339-4, further demonstrating a coupled correlation between these three frequency ranges. The level of radio emission would then be tied to the near-infrared emission, possibly by the evolution of the broad-band properties of the jets. We further incorporated our new data of GX 339-4 in a more global study of black hole candidates strongly supporting a scale invariance in the jet-accretion coupling of accreting black holes, and confirms the existence of two populations of sources in the radio/X-ray diagram.

[]

https://arxiv.org/pdf/1211.1600.pdf

2019PhLB..795....1K

Shadow of a black hole surrounded by dark matter

2019-01-01

['-']

[]

We consider a simple spherical model consisting of a Schwarzschild black hole of mass M and a dark matter of mass ΔM around it. The general formula for the radius of black-hole shadow has been derived in this case. It is shown that the change of the shadow is not negligible, once the effective radius of the dark matter halo is of order ∼√{ 3 MΔM }. For this to happen, for example, for the galactic black hole, the dark matter must be concentrated near the black hole. For small deviations from the Schwarzschild limit, the dominant contribution into the size of a shadow is due to the dark matter under the photon sphere, but at larger deviations, the matter outside the photon sphere cannot be ignored.

[]

https://arxiv.org/pdf/1905.00064.pdf