Datasets:

ashishkgpian

/

astrorag_papers

like 0

1995PhRvD..51.5352F

Temperature and entropy of a quantum black hole and conformal anomaly

1995-01-01

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

[]

Attention is paid to the fact that the temperature of a classical black hole can be derived from the extremality condition of its free energy with respect to the variation of the mass of a hole. For a quantum Schwarzschild black hole evaporating massless particles the same condition is shown to result in the one-loop temperature T=(8πM)<SUP>-1</SUP>[1+σ(8πM<SUP>2</SUP>)<SUP>-1</SUP>] and entropy S=4πM<SUP>2</SUP>-σlnM expressed in terms of the effective mass M of a hole together with its radiation and the integral of the conformal anomaly σ that depends on the field species. Thus, in the given case quantum corrections to T and S turn out to be completely provided by the anomaly. When it is absent (σ=0), which happens in a number of supersymmetric models, the one-loop expressions of T and S preserve the classical form. On the other hand, if the anomaly is negative (σ&lt;0) an evaporating quantum hole seems to cease to heat up when its mass reaches the Planck scales.

[]

https://arxiv.org/pdf/hep-th/9412161.pdf

2006JHEP...02..024G

New connections between 4D and 5D black holes

2006-01-01

['-']

[]

A simple equality is proposed between the BPS partition function of a general 4D IIA Calabi-Yau black hole and that of a 5D spinning M-theory Calabi-Yau black hole. Combining with recent results then leads to a new relation between the 5D spinning BPS black hole partition function and the square of the N = 2 topological string partition function.

[]

https://arxiv.org/pdf/hep-th/0503217.pdf

2016PhRvD..94j4024B

Perturbed black holes in Einstein-dilaton-Gauss-Bonnet gravity: Stability, ringdown, and gravitational-wave emission

2016-01-01

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

[]

Gravitational waves emitted by distorted black holes—such as those arising from the coalescence of two neutron stars or black holes—carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant, and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here, we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations, (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that future ringdown detections with a large signal-to-noise ratio would improve current constraints on the coupling parameter of the theory.

[]

https://arxiv.org/pdf/1609.01286.pdf

1998ApJ...494L.181M

Dynamical Constraints on Alternatives to Supermassive Black Holes in Galactic Nuclei

1998-01-01

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

[]

The compelling dynamical evidence for massive dark objects in galactic nuclei does not uniquely imply massive black holes (BHs). To argue convincingly that these objects are BHs we must rule out alternatives to a BH, and the alternative to a point mass is a cluster of some sort of nonluminous objects, such as a cluster of brown dwarfs or stellar remnants. We use simple physical considerations to derive the maximum possible lifetime of a dark cluster that may consist of any plausible form of nonluminous gravitating objects--from brown dwarfs and very low mass objects of cosmic composition to white dwarfs, neutron stars, and black holes. The lower this limit relative to the galaxy age, the more implausible the cluster hypothesis is, thus arguing for a point mass. A cluster with a lifetime much shorter than 10 Gyr is unacceptable, since observing it at the present epoch would be highly improbable. Since the goal is to rule out a dark cluster by showing that its lifetime must be very short, we make the most generous assumptions possible under the observational constraints to allow for its survival. We find that the lifetime of such a hypothetical cluster must be much shorter than the galaxy age only in the cases of NGC 4258 and our Galaxy, thus strongly arguing for a point mass. In all other galaxies, the case of a massive BH, although compelling, is not yet watertight. We also note that there are two exotic alternatives to a massive BH that cannot be ruled out even in the cases of NGC 4258 and the Galaxy: clusters of elementary particles (e.g., bosons), and clusters of very low mass (&lt;~0.04 M<SUB>solar</SUB>) BHs. We point out, however, serious difficulties with these alternatives, and argue that they are highly implausible.

[]

https://arxiv.org/pdf/astro-ph/9710309.pdf

2006PhRvD..73j4002B

Binary black hole merger dynamics and waveforms

2006-01-01

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

[]

We study dynamics and radiation generation in the last few orbits and merger of a binary black hole system, applying recently developed techniques for simulations of moving black holes. Our analysis of the gravitational radiation waveforms and dynamical black hole trajectories produces a consistent picture for a set of simulations with black holes beginning on circular-orbit trajectories at a variety of initial separations. We find profound agreement at the level of 1% among the simulations for the last orbit, merger and ringdown. We are confident that this part of our waveform result accurately represents the predictions from Einstein’s General Relativity for the final burst of gravitational radiation resulting from the merger of an astrophysical system of equal-mass nonspinning black holes. The simulations result in a final black hole with spin parameter a/m=0.69. We also find good agreement at a level of roughly 10% for the radiation generated in the preceding few orbits.

[]

https://arxiv.org/pdf/gr-qc/0602026.pdf

2017MNRAS.464.2840A

Gravitational torque-driven black hole growth and feedback in cosmological simulations

2017-01-01

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

[]

We investigate black hole-host galaxy scaling relations in cosmological simulations with a self-consistent black hole growth and feedback model. Our sub-grid accretion model captures the key scalings governing angular momentum transport by gravitational torques from galactic scales down to parsec scales, while our kinetic feedback implementation enables the injection of outflows with properties chosen to match observed nuclear outflows (star formation-driven winds are not included to isolate the effects of black hole feedback). We show that `quasar mode' feedback can have a large impact on the thermal properties of the intergalactic medium and the growth of galaxies and massive black holes for kinetic feedback efficiencies as low as 0.1 per cent relative to the bolometric luminosity. None the less, our simulations indicate that the black hole-host scaling relations are only weakly dependent on the effects of black hole feedback on galactic scales, since black hole feedback suppresses the growth of galaxies and massive black holes by a similar amount. In contrast, the rate at which gravitational torques feed the central black hole relative to the host galaxy star formation rate governs the slope and normalization of the black hole-host correlations. Our results suggest that a common gas supply regulated by gravitational torques is the primary driver of the observed co-evolution of black holes and galaxies.

[]

https://arxiv.org/pdf/1603.08007.pdf

2012PhRvD..86j4006Y

Quasinormal-mode spectrum of Kerr black holes and its geometric interpretation

2012-01-01

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

[]

There is a well-known, intuitive geometric correspondence between high-frequency quasinormal modes of Schwarzschild black holes and null geodesics that reside on the light ring (often called spherical photon orbits): the real part of the mode’s frequency relates to the geodesic’s orbital frequency, and the imaginary part of the frequency corresponds to the Lyapunov exponent of the orbit. For slowly rotating black holes, the quasinormal mode’s real frequency is a linear combination of the orbit’s precessional and orbital frequencies, but the correspondence is otherwise unchanged. In this paper, we find a relationship between the quasinormal-mode frequencies of Kerr black holes of arbitrary (astrophysical) spins and general spherical photon orbits, which is analogous to the relationship for slowly rotating holes. To derive this result, we first use the Wentzel-Kramers-Brillouin approximation to compute accurate algebraic expressions for large-l quasinormal-mode frequencies. Comparing our Wentzel-Kramers-Brillouin calculation to the leading-order, geometric-optics approximation to scalar-wave propagation in the Kerr spacetime, we then draw a correspondence between the real parts of the parameters of a quasinormal mode and the conserved quantities of spherical photon orbits. At next-to-leading order in this comparison, we relate the imaginary parts of the quasinormal-mode parameters to coefficients that modify the amplitude of the scalar wave. With this correspondence, we find a geometric interpretation of two features of the quasinormal-mode spectrum of Kerr black holes: First, for Kerr holes rotating near the maximal rate, a large number of modes have nearly zero damping; we connect this characteristic to the fact that a large number of spherical photon orbits approach the horizon in this limit. Second, for black holes of any spins, the frequencies of specific sets of modes are degenerate; we find that this feature arises when the spherical photon orbits corresponding to these modes form closed (as opposed to ergodically winding) curves.

[]

https://arxiv.org/pdf/1207.4253.pdf

1998PhRvD..58h3510Y

Chaotic new inflation and formation of primordial black holes

1998-01-01

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

[]

It is shown that in a number of scalar potentials with an unstable local maximum at the origin chaotic inflation is followed by new inflation if model parameters are appropriately chosen. In this model density fluctuation can have a large-amplitude peak on the comoving Hubble scale at the onset of the slow-roll new inflation and can result in the formation of an appreciable amount of primordial black holes on astrophysically interesting mass scales.

[]

https://arxiv.org/pdf/astro-ph/9802357.pdf

2009ApJ...697.1861A

Strong Mass Segregation Around a Massive Black Hole

2009-01-01

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

[]

We show that the mass-segregation solution for the steady-state distribution of stars around a massive black hole (MBH) has two branches: the well known weak-segregation solution and a strong segregation solution, which is analyzed here for the first time. The nature of the solution depends on the heavy-to-light stellar mass ratio M<SUB>H</SUB> /M<SUB>L</SUB> and on the unbound population number ratio N<SUB>H</SUB> /N<SUB>L</SUB> , through the relaxational coupling parameter Δ = 4N<SUB>H</SUB>M <SUP>2</SUP> <SUB> H </SUB>/[N<SUB>L</SUB>M <SUP>2</SUP> <SUB> L </SUB>(3 + M<SUB>H</SUB> /M<SUB>L</SUB> )]. When the heavy stars are relatively common (Δ Gt 1), they scatter frequently on each other. This efficient self-coupling leads to weak mass segregation, where the stars form n∝ r^{-α_{M}} mass-dependent cusps near the MBH, with indices α<SUB> H </SUB> = 7/4 for the heavy stars and 3/2 &lt; α<SUB> L </SUB> &lt; 7/4 for the light stars (i.e. max(α<SUB> H </SUB> - α<SUB> L </SUB>) sime 1/4). However, when the heavy stars are relatively rare (Δ Lt 1), they scatter mostly on light stars, sink to the center by dynamical friction and settle into a much steeper cusp with 2 lsim α<SUB> H </SUB> lsim 11/4, while the light stars form a 3/2 &lt; α<SUB> L </SUB> &lt; 7/4 cusp, resulting in strong segregation (i.e., max(α<SUB> H </SUB> - α<SUB> L </SUB>) sime 1). We show that the present-day mass function of evolved stellar populations with a universal initial mass function (coeval or continuously star forming) separates into two distinct mass scales, ~1 M <SUB>sun</SUB> of main sequence and compact dwarfs, and ~10 M <SUB>sun</SUB> of stellar black holes (SBHs), and have Δ &lt; 0.1. We conclude that it is likely that many relaxed galactic nuclei are strongly segregated. We review indications of strong segregation in observations of the Galactic center and in results of numeric simulations, and briefly list possible implications of a very high central concentration of SBHs around an MBH.

[]

https://arxiv.org/pdf/0808.3150.pdf

2006ApJ...645L.133H

The Effect of Mass Segregation on Gravitational Wave Sources near Massive Black Holes

2006-01-01

['black hole physics', 'galaxy center', 'gravitational waves', 'stars kinematics and dynamics', 'astrophysics', '-']

[]

Gravitational waves (GWs) from the inspiral of compact remnants (CRs) into massive black holes (MBHs) will be observable to cosmological distances. While a CR spirals in, two-body scattering by field stars may cause it to fall into the central MBH before reaching a short-period orbit that would give an observable signal. As a result, only CRs very near (~0.01 pc) the MBH can spiral in successfully. In a multimass stellar population, the heaviest objects sink to the center, where they are more likely to slowly spiral into the MBH without being swallowed prematurely. We study how mass segregation modifies the stellar distribution and the rate of GW events. We find that the inspiral rate per galaxy is 30 Gyr<SUP>-1</SUP> for white dwarfs, 6 Gyr<SUP>-1</SUP> for neutron stars, and 250 Gyr<SUP>-1</SUP> for 10 M<SUB>solar</SUB> stellar black holes (SBHs). The high rate for SBHs is due to their extremely steep density profile, n<SUB>BH</SUB>(r)~r<SUP>-2</SUP>. The GW detection rate will be dominated by SBHs.

[]

https://arxiv.org/pdf/astro-ph/0603324.pdf

2012PhRvD..86l4007F

Black-hole-neutron-star mergers: Disk mass predictions

2012-01-01

['-', '-', '-', 'methods numerical', 'relativity', 'gamma rays', 'gamma rays', '-', '-']

[]

Determining the final result of black-hole-neutron-star mergers, and, in particular, the amount of matter remaining outside the black hole at late times and its properties, has been one of the main motivations behind the numerical simulation of these systems. Black-hole-neutron-star binaries are among the most likely progenitors of short gamma-ray bursts—as long as massive (probably a few percents of a solar mass), hot accretion disks are formed around the black hole. Whether this actually happens strongly depends on the physical characteristics of the system, and, in particular, on the mass ratio, the spin of the black hole, and the radius of the neutron star. We present here a simple two-parameter model, fitted to existing numerical results, for the determination of the mass remaining outside the black hole a few milliseconds after a black-hole-neutron-star merger (i.e., the combined mass of the accretion disk, the tidal tail, and the potential ejecta). This model predicts the remnant mass within a few percents of the mass of the neutron star, at least for remnant masses up to 20% of the neutron star mass. Results across the range of parameters deemed to be the most likely astrophysically are presented here. We find that, for 10M<SUB>⊙</SUB> black holes, massive disks are only possible for large neutron stars (R<SUB>NS</SUB>≳12km), or quasiextremal black hole spins (a<SUB>BH</SUB>/M<SUB>BH</SUB>≳0.9). We also use our model to discuss how the equation of state of the neutron star affects the final remnant, and the strong influence that this can have on the rate of short gamma-ray bursts produced by black-hole-neutron-star mergers.

[]

https://arxiv.org/pdf/1207.6304.pdf

2018arXiv181012067C

Large AdS black holes from QFT

2018-01-01

['-']

[]

We study the index of $\mathcal{N}=4$ Yang-Mills theory on $S^3\times\mathbb{R}$ at large angular momenta. A generalized Cardy limit exhibits macroscopic entropy at large $N$. Our result is derived using free QFT analysis, and also a background field method on $S^3$. The index sets a lower bound on the entropy. It saturates the Bekenstein-Hawking entropy of known supersymmetric AdS$_5$ black holes, thus accounting for their microstates. We further analyze the so-called Macdonald index, exploring small black holes and possibly new black holes reminiscent of hairy black holes. Finally, we study aspects of large supersymmetric AdS$_7$ black holes, using background field method on $S^5$ and 't Hooft anomalies.

[]

https://arxiv.org/pdf/1810.12067.pdf

2016ApJ...821L..18P

Short Gamma-Ray Bursts from the Merger of Two Black Holes

2016-01-01

['accretion', 'accretion disks', 'gamma rays', 'gravitational waves', 'stars black holes', '-', '-']

[]

Short gamma-ray bursts (GRBs) are explosions of cosmic origins believed to be associated with the merger of two compact objects, either two neutron stars or a neutron star and a black hole (BH). The presence of at least one neutron star has long been thought to be an essential element of the model: its tidal disruption provides the needed baryonic material whose rapid accretion onto the post-merger BH powers the burst. The recent tentative detection by the Fermi satellite of a short GRB in association with the gravitational wave signal GW150914 produced by the merger of two BHs has challenged this standard paradigm. Here, we show that the evolution of two high-mass, low-metallicity stars with main-sequence rotational speeds a few tens of percent of the critical speed eventually undergoing a weak supernova explosion can produce a short GRB. The outer layers of the envelope of the last exploding star remain bound and circularize at large radii. With time, the disk cools and becomes neutral, suppressing the magnetorotational instability, and hence the viscosity. The disk remains “long-lived dead” until tidal torques and shocks during the pre-merger phase heat it up and re-ignite accretion, rapidly consuming the disk and powering the short GRB.

[]

https://arxiv.org/pdf/1602.05140.pdf

2012MNRAS.419..267P

Using the Fundamental Plane of black hole activity to distinguish X-ray processes from weakly accreting black holes

2012-01-01

['accretion', 'accretion disks', 'black hole physics', 'radiation', 'methods statistical', 'galaxies jets', 'astronomy x rays', '-', '-']

[]

The Fundamental Plane of black hole activity is a relation between X-ray luminosity, radio luminosity and black hole mass for hard-state Galactic black holes and their supermassive analogues. The Fundamental Plane suggests that, at low-accretion rates, the physical processes regulating the conversion of an accretion flow into radiative energy could be universal across the entire black hole mass scale. However, there is still a need to further refine the Fundamental Plane in order to better discern the radiative processes and their geometry very close to the black hole, in particular the source of hard X-rays. Further refinement is necessary because error bars on the best-fitting slopes of the Fundamental Plane are generally large, and also the inferred coefficients can be sensitive to the adopted sample of black holes. In this work, we regress the Fundamental Plane with a Bayesian technique. Our approach shows that sub-Eddington black holes emit X-ray emission that is predominantly optically thin synchrotron radiation from the jet, provided that their radio spectra are flat or inverted. X-ray emission dominated by very radiatively inefficient accretion flows is excluded at the &gt;3σ level. We also show that it is difficult to place Fanaroff-Riley type I (FR I) galaxies on to the Fundamental Plane because their X-ray jet emission is highly affected by synchrotron cooling. On the other hand, BL Lac objects (i.e. relativistically beamed sub-Eddington AGN) fit on to the Fundamental Plane. Including a uniform subset of high-energy peaked BL Lac objects from the Sloan Digital Sky Survey, we find sub-Eddington black holes with flat/inverted radio spectra follow log L<SUB>X</SUB>= (1.45 ± 0.04)log L<SUB>R</SUB>- (0.88 ± 0.06)log M<SUB>BH</SUB>- 6.07 ± 1.10, with σ<SUB>int</SUB>= 0.07 ± 0.05 dex. Finally, we discuss how the effects of synchrotron cooling of jet emission from the highest black hole masses can bias Fundamental Plane regressions, perhaps leading to incorrect inferences on X-ray radiation mechanisms.

[]

https://arxiv.org/pdf/1105.3211.pdf

2015MNRAS.452.1502D

Black hole evolution - I. Supernova-regulated black hole growth

2015-01-01

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

[]

The growth of a supermassive black hole (BH) is determined by how much gas the host galaxy is able to feed it, which in turn is controlled by the cosmic environment, through galaxy mergers and accretion of cosmic flows that time how galaxies obtain their gas, and also by internal processes in the galaxy, such as star formation and feedback from stars and the BH itself. In this paper, we study the growth of a 10<SUP>12</SUP> M<SUB>⊙</SUB> halo at z = 2, which is the progenitor of a group of galaxies at z = 0, and of its central BH by means of a high-resolution zoomed cosmological simulation, the Seth simulation. We study the evolution of the BH driven by the accretion of cold gas in the galaxy, and explore the efficiency of the feedback from supernovae (SNe). For a relatively inefficient energy input from SNe, the BH grows at the Eddington rate from early times, and reaches self-regulation once it is massive enough. We find that at early cosmic times z &gt; 3.5, efficient feedback from SNe forbids the formation of a settled disc as well as the accumulation of dense cold gas in the vicinity of the BH and starves the central compact object. As the galaxy and its halo accumulate mass, they become able to confine the nuclear inflows provided by major mergers and the BH grows at a sustained near-to-Eddington accretion rate. We argue that this mechanism should be ubiquitous amongst low-mass galaxies, corresponding to galaxies with a stellar mass below ≲ 10<SUP>9</SUP> M<SUB>⊙</SUB> in our simulations.

[]

https://arxiv.org/pdf/1504.00018.pdf

1995PhRvD..51..622C

Aspects of black hole quantum mechanics and thermodynamics in 2+1 dimensions

1995-01-01

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

[]

We discuss the quantum mechanics and thermodynamics of the (2+1)-dimensional black hole, using both minisuperspace methods and exact results from Chern-Simons theory. In particular, we evaluate the first quantum correction to the black hole entropy. We show that the dynamical variables of the black hole arise from the possibility of a deficit angle at the (Euclidean) horizon, and briefly speculate as to how they may provide a basis for a statistical picture of black hole thermodynamics.

[]

https://arxiv.org/pdf/gr-qc/9405070.pdf

2006PhRvD..73l4011V

How to move a black hole without excision: Gauge conditions for the numerical evolution of a moving puncture

2006-01-01

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

[]

Recent demonstrations of unexcised black holes traversing across computational grids represent a significant advance in numerical relativity. Stable and accurate simulations of multiple orbits, and their radiated waves, result. This capability is critically undergirded by a careful choice of gauge. Here we present analytic considerations which suggest certain gauge choices, and numerically demonstrate their efficacy in evolving a single moving puncture black hole.

[]

https://arxiv.org/pdf/gr-qc/0605030.pdf

1999PhR...316....1Y

Black holes and solitons in string theory

1999-01-01

['-', '-']

[]

We review various aspects of classical solutions in string theories. Emphasis is placed on their supersymmetry properties, their special roles in string dualities and microscopic interpretations. Topics include black hole solutions in string theories on tori and /N=2 supergravity theories; /p-branes; microscopic interpretation of black hole entropy. We also review aspects of dualities and BPS states.

[]

https://arxiv.org/pdf/hep-th/9710046.pdf

2002PhRvD..65h4040C

New black holes in the brane world?

2002-01-01

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

[]

It is known that the Einstein field equations in five dimensions admit more general spherically symmetric black holes on the brane than four-dimensional general relativity. We propose two families of analytic solutions (with g<SUB>tt</SUB>≠-g<SUP>-1</SUP><SUB>rr</SUB>), parametrized by the Arnowitt-Deser-Misner mass and the parametrized post-Newtonian parameter β, which reduce to Schwarzschild for β=1. Agreement with observations requires \|β-1\|~\|η\|&lt;&lt;1. The sign of η plays a key role in the global causal structure, separating metrics which behave like Schwarzschild (η&lt;0) from those similar to Reissner-Nordström spare-time (η&gt;0). In the latter case, we find a family of black hole space-times completely regular.

[]

https://arxiv.org/pdf/gr-qc/0111072.pdf

2009PhRvD..80j4029A

Lifshitz black hole in three dimensions

2009-01-01

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

[]

We show that three-dimensional massive gravity admits Lifshitz metrics with generic values of the dynamical exponent z as exact solutions. At the point z=3, exact black hole solutions that are asymptotically Lifshitz arise. These spacetimes are three-dimensional analogues of those that were recently proposed as gravity duals for anisotropic scale invariant fixed points.

[]

https://arxiv.org/pdf/0909.1347.pdf

2009JHEP...09..034B

Weak field black hole formation in asymptotically AdS spacetimes

2009-01-01

['-']

[]

We use the AdS/CFT correspondence to study the thermalization of a strongly coupled conformal field theory that is forced out of its vacuum by a source that couples to a marginal operator. The source is taken to be of small amplitude and finite duration, but is otherwise an arbitrary function of time. When the field theory lives on R<SUP>d-1,1</SUP>, the source sets up a translationally invariant wave in the dual gravitational description. This wave propagates radially inwards in AdS<SUB>d+1</SUB> space and collapses to form a black brane. Outside its horizon the bulk spacetime for this collapse process may systematically be constructed in an expansion in the amplitude of the source function, and takes the Vaidya form at leading order in the source amplitude. This solution is dual to a remarkably rapid and intriguingly scale dependent thermalization process in the field theory. When the field theory lives on a sphere the resultant wave either slowly scatters into a thermal gas (dual to a glueball type phase in the boundary theory) or rapidly collapses into a black hole (dual to a plasma type phase in the field theory) depending on the time scale and amplitude of the source function. The transition between these two behaviors is sharp and can be tuned to the Choptuik scaling solution in R<SUP>d,1</SUP>.

[]

https://arxiv.org/pdf/0904.0464.pdf

2008ApJ...678..780G

Ejection of Supermassive Black Holes from Galaxy Cores

2008-01-01

['galaxies nuclei', 'stars kinematics and dynamics', 'astrophysics']

[]

Recent numerical relativity simulations have shown that the emission of gravitational waves during the merger of two supermassive black holes (SMBHs) delivers a kick to the final hole, with a magnitude as large as 4000 km s<SUP>-1</SUP>. We study the motion of SMBHs ejected from galaxy cores by such kicks and the effects on the stellar distribution using high-accuracy direct N-body simulations. Following the kick, the motion of the SMBH exhibits three distinct phases. (1) The SMBH oscillates with decreasing amplitude, losing energy via dynamical friction at each core passage. Chandrasekhar's theory accurately reproduces the motion of the SMBH if 2lesssim ln Λ lesssim 3 and if the changing core density is taken into account. (2) When the amplitude of the motion has fallen to roughly the core radius, the SMBH and core begin to exhibit oscillations about their common center of mass. These oscillations decay with a time constant that is at least 10 times longer than predicted by Chandrasekhar's formula. (3) Eventually, the SMBH reaches thermal equilibrium with the stars. The time for the SMBH's oscillations to damp to the Brownian level is as long as ~1 Gyr in the brightest galaxies. The longevity of the oscillations makes this mechanism competitive with others proposed to explain double or offset nuclei. Ejection of SMBHs also results in a lowered density of stars near the galaxy center; mass deficits as large as five times the SMBH mass can be produced. We compare the N-body density profiles with luminosity profiles of early-type galaxies in Virgo and show that even the largest observed cores can be reproduced by the kicks. Implications for displaced AGNs and helical radio structures are discussed.

[]

https://arxiv.org/pdf/0708.0771.pdf

2004A&A...426..587C

A study of the low-frequency quasi-periodic oscillations in the X-ray light curves of the black hole candidate <ASTROBJ>XTE J1859+226</ASTROBJ>

2004-01-01

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

[]

We present the results of an extensive timing analysis of the 1999 outburst of the soft X-ray transient and black hole candidate <ASTROBJ>XTE J1859+226</ASTROBJ> as observed with the Rossi X-Ray Timing Explorer. Three main different types of low frequency (1-9 Hz) quasi-periodic oscillations (QPOs) were observed and classified, strengthening the general picture that is emerging for the variability properties of black hole X-ray binaires. Rapid transitions between different power spectral shapes were observed and their link with the count rate was studied. Furthermore, we show that a frequency of ∼6 Hz seems to hold a particular place: one of the three QPO types we found was very stable when at this frequency, as it happens in Z sources as well. The coherence of its subharmonic peak was higher when the fundamental was close to 6 Hz, thus suggesting the presence of some resonance at this frequency.

[]

https://arxiv.org/pdf/astro-ph/0407262.pdf

2019JCAP...08..031M

Revisiting constraints on asteroid-mass primordial black holes as dark matter candidates

2019-01-01

['-']

[]

As the only dark matter candidate that does not invoke a new particle that survives to the present day, primordial black holes (PBHs) have drawn increasing attention recently. Up to now, various observations have strongly constrained most of the mass range for PBHs, leaving only small windows where PBHs could make up a substantial fraction of the dark matter. Here we revisit the PBH constraints for the asteroid-mass window, i.e., the mass range 3.5× 10<SUP>-17</SUP>M<SUB>solar</SUB> &lt; m<SUB>PBH</SUB> &lt; 4× 10<SUP>-12</SUP>M<SUB>solar</SUB>. We revisit 3 categories of constraints. (1) For optical microlensing, we analyze the finite source size and diffractive effects and discuss the scaling relations between the event rate, m<SUB>PBH</SUB> and the event duration. We argue that it will be difficult to push the existing optical microlensing constraints to much lower m<SUB>PBH</SUB>. (2) For dynamical capture of PBHs in stars, we derive a general result on the capture rate based on phase space arguments. We argue that survival of stars does not constrain PBHs, but that disruption of stars by captured PBHs should occur and that the asteroid-mass PBH hypothesis could be constrained if we can work out the observational signature of this process. (3) For destruction of white dwarfs by PBHs that pass through the white dwarf without getting gravitationally captured, but which produce a shock that ignites carbon fusion, we perform a 1+1D hydrodynamic simulation to explore the post-shock temperature and relevant timescales, and again we find this constraint to be ineffective. In summary, we find that the asteroid-mass window, which was previously constrained due to femtolensing, WD survival, optical microlensing, and neutron star capture is no longer constrained. Hence, the asteroid-mass window remains open for PBHs to account for all the dark matter.

[]

https://arxiv.org/pdf/1906.05950.pdf

2015NatCo...6.6647D

Transport properties of pristine few-layer black phosphorus by van der Waals passivation in an inert atmosphere

2015-01-01

['-', '-']

[]

Ultrathin black phosphorus is a two-dimensional semiconductor with a sizeable band gap. Its excellent electronic properties make it attractive for applications in transistor, logic and optoelectronic devices. However, it is also the first widely investigated two-dimensional material to undergo degradation upon exposure to ambient air. Therefore a passivation method is required to study the intrinsic material properties, understand how oxidation affects the physical properties and enable applications of phosphorene. Here we demonstrate that atomically thin graphene and hexagonal boron nitride can be used for passivation of ultrathin black phosphorus. We report that few-layer pristine black phosphorus channels passivated in an inert gas environment, without any prior exposure to air, exhibit greatly improved n-type charge transport resulting in symmetric electron and hole transconductance characteristics.

[]

https://arxiv.org/pdf/1412.1274.pdf

2017PhRvD..95d3511N

Stochastic gravitational waves associated with the formation of primordial black holes

2017-01-01

['-', '-']

[]

Primordial black hole (PBH) mergers have been proposed as an explanation for the gravitational wave events detected by the LIGO collaboration. Such PBHs may be formed in the early Universe as a result of the collapse of extremely rare high-sigma peaks of primordial fluctuations on small scales, as long as the amplitude of primordial perturbations on small scales is enhanced significantly relative to the amplitude of perturbations observed on large scales. One consequence of these small-scale perturbations is generation of stochastic gravitational waves that arise at second order in scalar perturbations, mostly before the formation of the PBHs. These induced gravitational waves have been shown, assuming Gaussian initial conditions, to be comparable to the current limits from the European Pulsar Timing Array, severely restricting this scenario. We show, however, that models with enhanced fluctuation amplitudes typically involve non-Gaussian initial conditions. With such initial conditions, the current limits from pulsar timing can be evaded. The amplitude of the induced gravitational-wave background can be larger or smaller than the stochastic gravitational-wave background from supermassive black hole binaries.

[]

https://arxiv.org/pdf/1612.06264.pdf

2016PhRvL.117j1102B

Spectroscopy of Kerr Black Holes with Earth- and Space-Based Interferometers

2016-01-01

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

[]

We estimate the potential of present and future interferometric gravitational-wave detectors to test the Kerr nature of black holes through "gravitational spectroscopy," i.e., the measurement of multiple quasinormal mode frequencies from the remnant of a black hole merger. Using population synthesis models of the formation and evolution of stellar-mass black hole binaries, we find that Voyager-class interferometers will be necessary to perform these tests. Gravitational spectroscopy in the local Universe may become routine with the Einstein Telescope, but a 40-km facility like Cosmic Explorer is necessary to go beyond z ∼3 . In contrast, detectors like eLISA (evolved Laser Interferometer Space Antenna) should carry out a few—or even hundreds—of these tests every year, depending on uncertainties in massive black hole formation models. Many space-based spectroscopical measurements will occur at high redshift, testing the strong gravity dynamics of Kerr black holes in domains where cosmological corrections to general relativity (if they occur in nature) must be significant.

[]

https://arxiv.org/pdf/1605.09286.pdf

2020PhRvD.101l3514L

I N T E G R A L constraints on primordial black holes and particle dark matter

2020-01-01

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

[]

The International Gamma-Ray Astrophysics Laboratory (I N T E G R A L ) satellite has yielded unprecedented measurements of the soft gamma-ray spectrum of our Galaxy. Here we use those measurements to set constraints on dark matter (DM) that decays or annihilates into photons with energies E ≈0.02 - 2 MeV . First, we revisit the constraints on particle DM that decays or annihilates to photon pairs. In particular, for decaying DM, we find that previous limits were overstated by roughly an order of magnitude. Our new, conservative analysis finds that the DM lifetime must satisfy τ ≳5 ×10<SUP>26</SUP> s ×(m<SUB>χ</SUB>/MeV )<SUP>-1</SUP> for DM masses m<SUB>χ</SUB>=0.054 - 3.6 MeV . For MeV-scale DM that annihilates into photons I N T E G R A L sets the strongest constraints to date. Second, we target ultralight primordial black holes (PBHs) through their Hawking radiation. This makes them appear as decaying DM with a photon spectrum peaking at E ≈5.77 /(8 π G M<SUB>PBH</SUB>), for a PBH of mass M<SUB>PBH</SUB>. We use the I N T E G R A L data to demonstrate that, at 95% C.L., PBHs with masses less than 1.2 ×10<SUP>17</SUP> g cannot comprise all of the DM, setting the tightest bound to date on ultralight PBHs.

[]

https://arxiv.org/pdf/2004.00627.pdf

2011Sci...332..438L

Polarized Gamma-Ray Emission from the Galactic Black Hole Cygnus X-1

2011-01-01

['-', '-']

[]

Because of their inherently high flux allowing the detection of clear signals, black hole x-ray binaries are interesting candidates for polarization studies, even if no polarization signals have been observed from them before. Such measurements would provide further detailed insight into these sources’ emission mechanisms. We measured the polarization of the gamma-ray emission from the black hole binary system Cygnus X-1 with the International Gamma-Ray Astrophysics Laboratory Imager on Board the Integral Satellite (INTEGRAL/IBIS) telescope. Spectral modeling of the data reveals two emission mechanisms: The 250- to 400-keV (kilo-electron volt) data are consistent with emission dominated by Compton scattering on thermal electrons and are weakly polarized. The second spectral component seen in the 400-keV to 2-MeV band is by contrast strongly polarized, revealing that the MeV emission is probably related to the jet first detected in the radio band.

[]

https://arxiv.org/pdf/1104.4282.pdf

2009ApJ...707.1334W

Estimating Black Hole Masses in Active Galactic Nuclei Using the Mg II λ2800 Emission Line

2009-01-01

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

[]

We investigate the relationship between the linewidths of broad Mg II λ2800 and Hβ in active galactic nuclei (AGNs) to refine them as tools to estimate black hole (BH) masses. We perform a detailed spectral analysis of a large sample of AGNs at intermediate redshifts selected from the Sloan Digital Sky Survey, along with a smaller sample of archival ultraviolet spectra for nearby sources monitored with reverberation mapping (RM). Careful attention is devoted to accurate spectral decomposition, especially in the treatment of narrow-line blending and Fe II contamination. We show that, contrary to popular belief, the velocity width of Mg II tends to be smaller than that of Hβ, suggesting that the two species are not cospatial in the broad-line region. Using these findings and recently updated BH mass measurements from RM, we present a new calibration of the empirical prescriptions for estimating virial BH masses for AGNs using the broad Mg II and Hβ lines. We show that the BH masses derived from our new formalisms show subtle but important differences compared to some of the mass estimators currently used in the literature.

[]

https://arxiv.org/pdf/0910.2848.pdf

2009Natur.458...53B

A candidate sub-parsec supermassive binary black hole system

2009-01-01

['-']

[]

The role of mergers in producing galaxies, together with the finding that most large galaxies harbour black holes in their nuclei, implies that binary supermassive black hole systems should be common. Here we report that the quasar SDSS J153636.22+044127.0 is a plausible example of such a system. This quasar shows two broad-line emission systems, separated in velocity by 3,500kms<SUP>-1</SUP>. A third system of unresolved absorption lines has an intermediate velocity. These characteristics are unique among known quasars. We interpret this object as a binary system of two black holes, having masses of 10<SUP>7.3</SUP> and 10<SUP>8.9</SUP> solar masses separated by ~0.1parsec with an orbital period of ~100years.

[]

https://arxiv.org/pdf/0901.3779.pdf

1996MPLA...11..689T

Extreme Dyonic Black Holes in String Theory

1996-01-01

['-', '-']

[]

Supersymmetric extreme dyonic black holes of toroidally compactified heterotic or type-II string theory can be viewed as lower-dimensional images of solitonic strings wound around a compact dimension. We consider conformal sigma models which describe string configurations corresponding to various extreme dyonic black holes in four and five dimensions. These conformal models have regular short-distance region equivalent to a WZW theory with level proportional to magnetic charges. Arguments are presented suggesting a universal relation between the black hole entropy (area) and the statistical entropy of BPS-saturated oscillation states of solitonic string.

[]

https://arxiv.org/pdf/hep-th/9601177.pdf

2013PhRvD..87l4026D

Superradiant instabilities of rotating black holes in the time domain

2013-01-01

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

[]

Bosonic fields on rotating black hole spacetimes are subject to amplification by superradiance, which induces exponentially-growing instabilities (the “black hole bomb”) in two scenarios: if the black hole is enclosed by a mirror, or if the bosonic field has rest mass. Here we present a time-domain study of the scalar field on Kerr spacetime which probes ultra-long timescales up to t≲5×10<SUP>6</SUP>M, to reveal the growth of the instability. We describe a highly-efficient method for evolving the field, based on a spectral decomposition into a coupled set of 1+1D equations, and an absorbing boundary condition inspired by the “perfectly-matched layers” paradigm. First, we examine the mirror case to study how the instability timescale and mode structure depend on mirror radius. Next, we examine the massive-field, whose rich spectrum (revealed through Fourier analysis) generates “beating” effects which disguise the instability. We show that the instability is clearly revealed by tracking the stress-energy of the field in the exterior spacetime. We calculate the growth rate for a range of mass couplings, by applying a frequency-filter to isolate individual modal contributions to the time-domain signal. Our results are in accord with previous frequency-domain studies which put the maximum growth rate at τ<SUP>-1</SUP>≈1.72×10<SUP>-7</SUP>(GM/c<SUP>3</SUP>)<SUP>-1</SUP> for the massive scalar field on Kerr spacetime.

[]

https://arxiv.org/pdf/1212.1477.pdf

2020PhRvR...2b3204S

Cosmic microwave background bounds on primordial black holes including dark matter halo accretion

2020-01-01

['-', '-']

[]

Even if massive (10 M<SUB>⊙</SUB>≲M ≲10<SUP>4</SUP>M<SUB>⊙</SUB> ) primordial black holes (PBHs) can only account for a small fraction of the dark matter (DM) in the universe, they may still be responsible for a sizable fraction of the coalescence events measured by LIGO/Virgo, and/or act as progenitors of the supermassive black holes (SMBHs) observed already at high redshift (z ≳6 ). In the presence of a dominant, non-PBH DM component, the bounds set by CMB via an altered ionization history are modified. We revisit the cosmological accretion of a DM halo around PBHs via toy models and dedicated numerical simulations, deriving updated CMB bounds which also take into account the last Planck data release. We prove that these constraints dominate over other constraints available in the literature at masses M ≳20 -50 M<SUB>⊙</SUB> (depending on uncertainty in accretion physics), reaching the level f<SUB>PBH</SUB>&lt;3 ×10<SUP>-9</SUP> around M ∼10<SUP>4</SUP>M<SUB>⊙</SUB> . These tight bounds are nonetheless consistent with the hypothesis of a primordial origin of the SMBH massive seeds.

[]

https://arxiv.org/pdf/2002.10771.pdf

2017PhRvD..95b1501H

Van der Waals like behavior of topological AdS black holes in massive gravity

2017-01-01

['-', '-']

[]

Motivated by recent developments in black hole thermodynamics, we investigate van der Waals phase transitions of charged black holes in massive gravity. We find that massive gravity theories can exhibit strikingly different thermodynamic behavior compared to that of Einstein gravity, and that the mass of the graviton can generate a range of new phase transitions for topological black holes that are otherwise forbidden.

[]

https://arxiv.org/pdf/1702.00432.pdf

1992NuPhB.378..175C

Quantum hair on black holes

1992-01-01

['-']

[]

A black hole may carry quantum numbers that are not associated with massless gauge fields, contrary to the spirit of the ``no-hair'' theorems. We describe in detail two different types of black-hole hair that decay exponentially at long range. The first type is associated with discrete gauge charge and the screening is due to the Higgs mechanism. The second type is associated with color magnetic charge, and the screening is due to color confinement. In both cases, we perform semiclassical calculations of the effect of the hair on local observables outside the horizon, and on black-hole thermodynamics. These effects are generated by virtual cosmic strings, or virtual electric flux tubes, that sweep around the event horizon. The effects of discrete gauge charge are nonperturbative in h, but the effects of color magnetic charge become h-independent in a suitable limit. We present an alternative treatment of discrete gauge charge using dual variables, and examine the possibility of black-hole hair associated with discrete global symmetry. We draw the distinction between primary hair, which endows a black hole with new quantum numbers, and secondary hair, which does not, and we point out some varieties of secondary hair that occur in the standard model of particle physics. <P />Reserch supported in part by DOE grant DE-FG02-90ER40542.

[]

https://arxiv.org/pdf/hep-th/9201059.pdf

2009PhRvD..79h1503D

Improved analytical description of inspiralling and coalescing black-hole binaries

2009-01-01

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

[]

We present an analytical formalism, within the effective-one-body framework, which predicts gravitational-wave signals from inspiralling and coalescing black-hole binaries that agree, within numerical errors, with the results of the currently most accurate numerical-relativity simulations for several different mass ratios. In the equal-mass case, the gravitational-wave energy flux predicted by our formalism agrees, within numerical errors, with the most accurate numerical-relativity energy flux. We think that our formalism opens a realistic possibility of constructing a sufficiently accurate, large bank of gravitational-wave templates, as needed both for detection and data analysis of (nonspinning) coalescing binary black holes.

[]

https://arxiv.org/pdf/0902.0136.pdf

2008PhLB..665..106C

Hawking radiation of Dirac particles via tunnelling from rotating black holes in de Sitter spaces

2008-01-01

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

[]

Hawking radiation from black hole horizon can be viewed as a quantum tunnelling process, and recent research shows fermions via tunnelling from black holes can correctly recover Hawking temperature. In this letter, considering the tunnelling particles with spin 1/2 (namely, Dirac particles), we further improve Kerner and Mann's fermions tunnelling method to study Hawking radiation via tunnelling from rotating black holes in de Sitter spaces, specifically including that from Kerr-de Sitter black hole and Kerr-Newman-de Sitter black hole. As a result, Hawking temperatures at the event horizon (EH) and the cosmological horizon (CH) are well described via Dirac particles' tunnelling.

[]

https://arxiv.org/pdf/0804.0131.pdf

2008PhRvD..77d3512M

Precision of Hubble constant derived using black hole binary absolute distances and statistical redshift information

2008-01-01

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

[]

Measured gravitational waveforms from black hole binary inspiral events directly determine absolute luminosity distances. To use these data for cosmology, it is necessary to independently obtain redshifts for the events, which may be difficult for those without electromagnetic counterparts. Here it is demonstrated that certainly in principle, and possibly in practice, clustering of galaxies allows extraction of the redshift information from a sample statistically for the purpose of estimating mean cosmological parameters, without identification of host galaxies for individual events. We extract mock galaxy samples from the 6th data release of the Sloan Digital Sky Survey resembling those that would be associated with inspiral events of stellar mass black holes falling into massive black holes at redshift z≈0.1 to 0.5. A simple statistical procedure is described to estimate a likelihood function for the Hubble constant H<SUB>0</SUB>: each galaxy in a LISA error volume contributes linearly to the log likelihood for the source redshift, and the log likelihood for each source contributes linearly to that of H<SUB>0</SUB>. This procedure is shown to provide an accurate and unbiased estimator of H<SUB>0</SUB>. It is estimated that a precision better than 1% in H<SUB>0</SUB> may be possible if the rate of such events is sufficiently high, on the order of 20 to z=0.5.

[]

https://arxiv.org/pdf/0712.0618.pdf

2000PhRvD..62l4021F

Gravitational waves from a compact star in a circular, inspiral orbit, in the equatorial plane of a massive, spinning black hole, as observed by LISA

2000-01-01

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

[]

Results are presented from high-precision computations of the orbital evolution and emitted gravitational waves for a stellar-mass object spiraling into a massive black hole in a slowly shrinking, circular, equatorial orbit. The focus of these computations is inspiral near the innermost stable circular orbit (isco)-more particularly, on orbits for which the angular velocity Ω is 0.03&lt;~Ω/Ω<SUB>isco</SUB>&lt;=1.0. The computations are based on the Teuksolsky-Sasaki-Nakamura formalism, and the results are tabulated in a set of functions that are of order unity and represent relativistic corrections to low-orbital-velocity formulas. These tables can form a foundation for future design studies for the LISA space-based gravitational-wave mission. A first survey of applications to LISA is presented: Signal to noise ratios S/N are computed and graphed as functions of the time-evolving gravitational-wave frequency for the lowest three harmonics of the orbital period, and for various representative values of the hole's mass M and spin a and the inspiraling object's mass μ, with the distance to Earth chosen to be r<SUB>o</SUB>=1 Gpc. These S/N's show a very strong dependence on the black-hole spin, as well as on M and μ. Graphs are presented showing the range of the \{M,a,μ\} parameter space, for which S/N&gt;10 at r<SUB>0</SUB>=1 Gpc during the last year of inspiral. The hole's spin a has a factor of ~10 influence on the range of M (at fixed μ) for which S/N&gt;10, and the presence or absence of a white-dwarf-binary background has a factor of ~3 influence. A comparison with predicted event rates shows strong promise for detecting these waves, but not beyond about 1 Gpc if the inspiraling object is a white dwarf or neutron star. This argues for a modest lowering of LISA's noise floor. A brief discussion is given of the prospects for extracting information from the observed waves.

[]

https://arxiv.org/pdf/gr-qc/0007074.pdf

2005MNRAS.364..899C

A possible black hole in the γ-ray microquasar LS 5039

2005-01-01

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

[]

The population of high-energy and very high-energy γ-ray sources, detected with EGRET and the new generation of ground-based Cherenkov telescopes, forms a reduced but physically important sample. Most of these sources are extragalactic (e.g. blazars), while among the galactic ones there are pulsars and supernova remnants. The microquasar LS 5039, previously proposed to be associated with an EGRET source by Paredes et al., has recently been detected at TeV energies, confirming that microquasars should be regarded as a class of high-energy γ-ray sources. To model and understand how the energetic photons are produced and escape from LS 5039, it is crucial to unveil the nature of the compact object, which remains unknown. Here, we present new intermediate-dispersion spectroscopy of this source, which, combined with values reported in the literature, provides an orbital period of P<SUB>orb</SUB>= 3.90603 +/- 0.00017 d, a mass function f(M) = 0.0053 +/- 0.0009M<SUB>solar</SUB> and an eccentricity e= 0.35 +/- 0.04. Atmosphere model fitting to the spectrum of the optical companion, together with our new distance estimate of d= 2.5 +/- 0.1 kpc, yields R<SUB>O</SUB>= 9.3<SUP>+0.7</SUP><SUB>-0.6</SUB>R<SUB>solar</SUB>, log(L<SUB>O</SUB>/L<SUB>solar</SUB>) = 5.26 +/- 0.06 and M<SUB>O</SUB>= 22.9<SUP>+3.4</SUP><SUB>-2.9</SUB>M<SUB>solar</SUB>. These, combined with our dynamical solution and the assumption of pseudo-synchronization, yield an inclination and a compact object mass M<SUB>X</SUB>= 3.7<SUP>+1.3</SUP><SUB>-1.0</SUB>M<SUB>solar</SUB>. This is above neutron star masses for most of the standard equations of state and, therefore, we propose that the compact object in LS 5039 is a black hole. We finally discuss the implications of our orbital solution and new parameters of the binary system on the CNO products, the accretion/ejection energetic balance, the supernova explosion scenario and the behaviour of the very high-energy γ-ray emission with the new orbital period.

[]

https://arxiv.org/pdf/astro-ph/0507549.pdf

2012JHEP...03..065H

Asymptotic charged BTZ black hole solutions

2012-01-01

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

[]

The well-known (2 + 1)-dimensional Reissner-Nordström (BTZ) black hole can be generalized to three dimensional Einstein-nonlinear electromagnetic field, motivated from obtaining a finite value for the self-energy of a pointlike charge. Considering three types of nonlinear electromagnetic fields coupled with Einstein gravity, we derive three kinds of black hole solutions which their asymptotic properties are the same as charged BTZ solution. In addition, we calculate conserved and thermodynamic quantities of the solutions and show that they satisfy the first law of thermodynamics. Finally, we perform a stability analysis in the canonical ensemble and show that the black holes are stable in the whole phase space.

[]

https://arxiv.org/pdf/1405.4941.pdf

2007Natur.449..872O

A 15.65-solar-mass black hole in an eclipsing binary in the nearby spiral galaxy M 33

2007-01-01

['astrophysics']

[]

Stellar-mass black holes are found in X-ray-emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty producing black holes in close binaries with masses more than ten times that of the Sun (&gt;10; ref. 4), which is consistent with the fact that the most massive stellar black holes known so far all have masses within one standard deviation of 10. Here we report a mass of (15.65+/-1.45) for the black hole in the recently discovered system M 33 X-7, which is located in the nearby galaxy Messier 33 (M 33) and is the only known black hole that is in an eclipsing binary. To produce such a massive black hole, the progenitor star must have retained much of its outer envelope until after helium fusion in the core was completed. On the other hand, in order for the black hole to be in its present 3.45-day orbit about its (70.0+/-6.9) companion, there must have been a `common envelope' phase of evolution in which a significant amount of mass was lost from the system. We find that the common envelope phase could not have occurred in M 33 X-7 unless the amount of mass lost from the progenitor during its evolution was an order of magnitude less than what is usually assumed in evolutionary models of massive stars.

[]

https://arxiv.org/pdf/0710.3165.pdf

2000PhRvD..61f1502B

Mode sum regularization approach for the self-force in black hole spacetime

2000-01-01

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

[]

We present a method for calculating the self-force (the ``radiation reaction force'') acting on a charged particle moving in a strong field orbit in black hole spacetime. In this approach, one first calculates the contribution to the self-force due to each multipole mode of the particle's field. Then, the sum over modes is evaluated, subject to a certain regularization procedure. Here we develop this regularization procedure for a scalar charge on a Schwarzschild background, and present the results of its implementation for radial trajectories (not necessarily geodesic).

[]

https://arxiv.org/pdf/gr-qc/9912010.pdf

2014PhRvD..90d4066A

Slowly rotating black holes in Einstein-Dilaton-Gauss-Bonnet gravity: Quadratic order in spin solutions

2014-01-01

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

[]

We derive a stationary and axisymmetric black hole solution in Einstein-Dilaton-Gauss-Bonnet gravity to quadratic order in the ratio of the spin angular momentum to the black hole mass squared. This solution introduces new corrections to previously found nonspinning and linear-in-spin solutions. The location of the event horizon and the ergosphere are modified, as well as the quadrupole moment. The new solution is of Petrov type I, although lower order in spin solutions are of Petrov type D. There are no closed timelike curves or spacetime regions that violate causality outside of the event horizon in the new solution. We calculate the modifications to the binding energy, Kepler's third law, and properties of the innermost stable circular orbit. These modifications are important for determining how the electromagnetic properties of accretion disks around supermassive black holes are changed from those expected in general relativity.

[]

https://arxiv.org/pdf/1405.2133.pdf

2016ApJ...825L..19H

The Final Spin from Binary Black Holes in Quasi-circular Orbits

2016-01-01

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

[]

We revisit the problem of predicting the spin magnitude and direction of the black hole (BH) resulting from the merger of two BHs with arbitrary masses and spins inspiraling in quasi-circular orbits. We do this by analyzing a catalog of 619 recent numerical-relativity simulations collected from the literature and spanning a large variety of initial conditions. By combining information from the post-Newtonian approximation, the extreme mass-ratio limit, and perturbative calculations, we improve our previously proposed phenomenological formulae for the final remnant spin. In contrast with alternative suggestions in the literature, and in analogy with our previous expressions, the new formula is a simple algebraic function of the initial system parameters and is not restricted to binaries with spins aligned/anti-aligned with the orbital angular momentum but can be employed for fully generic binaries. The accuracy of the new expression is significantly improved, especially for almost extremal progenitor spins and for small mass ratios, yielding an rms error σ ≈ 0.002 for aligned/anti-aligned binaries and σ ≈ 0.006 for generic binaries. Our new formula is suitable for cosmological applications and can be employed robustly in the analysis of the gravitational waveforms from advanced interferometric detectors.

[]

https://arxiv.org/pdf/1605.01938.pdf

2017MNRAS.468.1273R

Growing supermassive black holes in the late stages of galaxy mergers are heavily obscured

2017-01-01

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

[]

Mergers of galaxies are thought to cause significant gas inflows to the inner parsecs, which can activate rapid accretion on to supermassive black holes (SMBHs), giving rise to active galactic nuclei (AGN). During a significant fraction of this process, SMBHs are predicted to be enshrouded by gas and dust. Studying 52 galactic nuclei in infrared-selected local luminous and ultraluminous infrared galaxies in different merger stages in the hard X-ray band, where radiation is less affected by absorption, we find that the amount of material around SMBHs increases during the last phases of the merger. We find that the fraction of Compton-thick (CT, N<SUB> H</SUB> ≥ 10<SUP>24</SUP> cm<SUP>- 2</SUP>) AGN in late-merger galaxies is higher (f_ CT=65^{+12}_{-13}{per cent}) than in local hard X-ray selected AGN (f<SUB> CT</SUB> = 27 ± 4 per cent), and that obscuration reaches its maximum when the nuclei of the two merging galaxies are at a projected distance of D<SUB>12</SUB> ≃ 0.4-10.8 kpc (f_ CT=77_{-17}^{+13}{per cent}). We also find that all AGN of our sample in late-merger galaxies have N<SUB> H</SUB> &gt; 10<SUP>23</SUP> cm<SUP>- 2</SUP>, which implies that the obscuring material covers 95^{+4}_{-8}{per cent} of the X-ray source. These observations show that the material is most effectively funnelled from the galactic scale to the inner tens of parsecs during the late stages of galaxy mergers, and that the close environment of SMBHs in advanced mergers is richer in gas and dust with respect to that of SMBHs in isolated galaxies, and cannot be explained by the classical AGN unification model in which the torus is responsible for the obscuration.

[]

https://arxiv.org/pdf/1701.04825.pdf

1996PhLB..378...78J

Entropy of 4D extremal black holes

1996-01-01

['-', '-']

[]

We derive the Bekenstein-Hawking entropy formula for four-dimensional Reissner-Nordström extremal black holes in type II string theory. The derivation is performed in two separate (T-dual) weak coupling pictures. One uses a type IIB bound state problem of D5- and D1-branes, while the other uses a bound state problem of D0- and D4-branes with macroscopic fundamental type IIA strings. In both cases, the D-brane systems are also bound to a Kaluza-Klein monopole, which then yields the four-dimensional black hole at strong coupling.

[]

https://arxiv.org/pdf/hep-th/9603061.pdf

2016MNRAS.455.2253B

Disc formation from tidal disruptions of stars on eccentric orbits by Schwarzschild black holes

2016-01-01

['accretion', 'accretion disks', 'black hole physics', 'hydrodynamics', 'galaxies nuclei', '-']

[]

The potential of tidal disruption of stars to probe otherwise quiescent supermassive black holes cannot be exploited, if their dynamics is not fully understood. So far, the observational appearance of these events has been derived from analytical extrapolations of the debris dynamical properties just after disruption. By means of hydrodynamical simulations, we investigate the subsequent fallback of the stream of debris towards the black hole for stars already bound to the black hole on eccentric orbits. We demonstrate that the debris circularize due to relativistic apsidal precession which causes the stream to self-cross. The circularization time-scale varies between 1 and 10 times the period of the star, being shorter for more eccentric and/or deeper encounters. This self-crossing leads to the formation of shocks that increase the thermal energy of the debris. If this thermal energy is efficiently radiated away, the debris settle in a narrow ring at the circularization radius with shock-induced luminosities of ∼10-10<SUP>3</SUP> L<SUB>Edd</SUB>. If instead cooling is impeded, the debris form an extended torus located between the circularization radius and the semi-major axis of the star with heating rates ∼1-10<SUP>2</SUP> L<SUB>Edd</SUB>. Extrapolating our results to parabolic orbits, we infer that circularization would occur via the same mechanism in ∼1 period of the most bound debris for deeply penetrating encounters to ∼10 for grazing ones. We also anticipate the same effect of the cooling efficiency on the structure of the disc with associated luminosities of ∼1-10 L<SUB>Edd</SUB> and heating rates of ∼0.1-1 L<SUB>Edd</SUB>. In the latter case of inefficient cooling, we deduce a viscous time-scale generally shorter than the circularization time-scale. This suggests an accretion rate through the disc tracing the fallback rate, if viscosity starts acting promptly.

[]

https://arxiv.org/pdf/1501.04635.pdf

2005PhRvD..71j4027A

Charged rotating black holes on a 3-brane

2005-01-01

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

[]

We study exact stationary and axisymmetric solutions describing charged rotating black holes localized on a 3-brane in the Randall-Sundrum braneworld. The charges of the black holes are considered to be of two types, the first being an induced tidal charge that appears as an imprint of nonlocal gravitational effects from the bulk space and the second is a usual electric charge arising due to a Maxwell field trapped on the brane. We assume a special ansatz for the metric on the brane taking it to be of the Kerr-Schild form and show that the Kerr-Newman solution of ordinary general relativity in which the electric charge is superseded by a tidal charge satisfies a closed system of the effective gravitational field equations on the brane. It turns out that the negative tidal charge may provide a mechanism for spinning up the black hole so that its rotation parameter exceeds its mass. This is not allowed in the framework of general relativity. We also find a new solution that represents a rotating black hole on the brane carrying both charges. We show that for a rapid enough rotation the combined influence of the rotational dynamics and the local bulk effects of the “squared” energy-momentum tensor on the brane distort the horizon structure of the black hole in such a way that it can be thought of as composed of nonuniformly rotating null circles with growing radii from the equatorial plane to the poles. We finally study the geodesic motion of test particles in the equatorial plane of a rotating black hole with tidal charge. We show that the effects of negative tidal charge tend to increase the horizon radius, as well as the radii of the limiting photon orbit, the innermost bound and the innermost stable circular orbits for both direct and retrograde motions of the particles.

[]

https://arxiv.org/pdf/hep-th/0502223.pdf

2004NCimB.119..489V

Strong-field gravitational lensing by a Kerr black hole

2004-01-01

['-']

[]

We consider a Kerr black hole acting as a gravitational deflector in the strong-field regime within the geometrical optics and point source approximations. The Kerr black-hole gravitational lens geometry consists of an observer and a source located far away and placed at arbitrary inclinations with respect to the black hole's equatorial plane. For this geometry the null geodesics equations of our interest can go around the black hole several times before reaching the observer. Such photon trajectories are written in terms of the angular positions in the observer's sky and therefore become “lens equations". By performing an analysis of the null geodesic motion off the Kerr black-hole equatorial plane we found for any image a simple classification scheme based on two integers numbers: the number of turning points in the polar coordinate θ, and the number of windings around the black hole's rotation axis. As a numerical application, we consider a supermassive Kerr black hole at the galactic center as a gravitational deflector. In this case, we show that our proposed computational and graphical scheme to solve the “lens equations" works successfully by calculating the positions and magnifications of the relativistic images for different source-observer geometries. In particular, we consider observers located near the Kerr black-hole equatorial plane, at the poles, and at an angle of π/4.

[]

https://arxiv.org/pdf/gr-qc/0308023.pdf

2001JHEP...08..045H

Duality of the fermionic 2d black hole and N = 2 Liouville theory as mirror symmetry

2001-01-01

['-']

[]

We prove the equivalence of the SL(2,Bbb R)/U(1) Kazama-Suzuki model, which is a fermionic generalization of the 2d Black Hole, and Script N = 2 Liouville theory. We show that this duality is an example of mirror symmetry. The essential part of the derivation is to realize the fermionic 2d Black Hole as the low energy limit of a gauged linear sigma-model. Liouville theory is obtained by dualizing the charged scalar fields and taking into account the vortex-instanton effects, as proposed recently in non-dilatonic models. The gauged linear sigma-model we study has many useful generalizations which we briefly discuss. In particular, we show how to construct a variety of dilatonic superstring backgrounds which generalize the fermionic 2d Black Hole and admit a mirror description in terms of Toda-like theories.

[]

https://arxiv.org/pdf/hep-th/0104202.pdf

2007PhLB..646...63N

Quantum-corrected black hole thermodynamics to all orders in the Planck length

2007-01-01

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

[]

We investigate the effects to all orders in the Planck length from a generalized uncertainty principle (GUP) on black holes thermodynamics. We calculate the corrected Hawking temperature, entropy, and examine in details the Hawking evaporation process. As a result, the evaporation process is accelerated and the evaporation end-point is a zero entropy, zero heat capacity and finite non-zero temperature black hole remnant (BHR). In particular we obtain a drastic reduction of the decay time, in comparison with the results obtained in the Hawking semi classical picture and with the GUP to leading order in the Planck length.

[]

https://arxiv.org/pdf/0704.1261.pdf

2012MNRAS.419L..69N

Observational evidence for a correlation between jet power and black hole spin

2012-01-01

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

[]

We show that the 5-GHz radio flux of transient ballistic jets in black hole binaries correlates with the dimensionless black hole spin parameter a<SUB>*</SUB> estimated via the continuum-fitting method. The data suggest that jet power scales either as the square of a<SUB>*</SUB> or as the square of the angular velocity of the horizon Ω<SUB>H</SUB>. This is the first direct evidence that jets may be powered by black hole spin energy. The observed correlation validates the continuum-fitting method of measuring spin. In addition, for those black holes that have well-sampled radio observations of ballistic jets, the correlation may be used to obtain rough estimates of their spins.

[]

https://arxiv.org/pdf/1112.0569.pdf

2012PhRvD..86d4037Y

Slowly rotating black holes in dynamical Chern-Simons gravity: Deformation quadratic in the spin

2012-01-01

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

[]

We derive a stationary and axisymmetric black hole solution to quadratic order in the spin angular momentum. The previously found, linear-in-spin terms modify the odd-parity sector of the metric, while the new corrections appear in the even-parity sector. These corrections modify the quadrupole moment, as well as the (coordinate-dependent) location of the event horizon and the ergoregion. Although the linear-in-spin metric is of Petrov type D, the quadratic-order terms render it of type I. The metric does not possess a second-order Killing tensor or a Carter-like constant. The new metric does not possess closed timelike curves or spacetime regions that violate causality outside of the event horizon. The new, even-parity modifications to the Kerr metric decay less rapidly at spatial infinity than the leading order in spin, odd-parity ones, and thus, the former are more important when considering black holes that are rotating moderately fast. We calculate the modifications to the Hamiltonian, binding energy and Kepler’s third law. These modifications are crucial for the construction of gravitational wave templates for black hole binaries, which will enter at second post-Newtonian order, just like dissipative modifications found previously.

[]

https://arxiv.org/pdf/1206.6130.pdf

2007IJMPA..22...11S

Thermodynamic Geometry and Critical Behavior of Black Holes

2007-01-01

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

[]

Based on the observations that there exists an analogy between the Reissner-Nordström-Anti-de Sitter (RN-AdS) black holes and the van der Waals-Maxwell liquid-gas system, in which a correspondence of variables is (ϕ,q) ↔ (V,P), we study the Ruppeiner geometry, defined as Hessian matrix of black hole entropy with respect to the internal energy (not the mass) of black hole and electric potential (angular velocity), for the RN, Kerr and RN-AdS black holes. It is found that the geometry is curved and the scalar curvature goes to negative infinity at the Davies' phase transition point for the RN and Kerr black holes. Our result for the RN-AdS black holes is also in good agreement with the one about phase transition and its critical behavior in the literature.

[]

https://arxiv.org/pdf/gr-qc/0512035.pdf

2014Sci...345...64K

A fast and long-lived outflow from the supermassive black hole in NGC 5548

2014-01-01

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

[]

Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution x-ray and ultraviolet (UV) observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six space observatories shows the nucleus to be obscured by a long-lasting, clumpy stream of ionized gas not seen before. It blocks 90% of the soft x-ray emission and causes simultaneous deep, broad UV absorption troughs. The outflow velocities of this gas are up to five times faster than those in the persistent outflow, and, at a distance of only a few light days from the nucleus, it may likely originate from the accretion disk.

[]

https://arxiv.org/pdf/1406.5007.pdf

2020PhRvD.102f4001P

Setting the cornerstone for a family of models for gravitational waves from compact binaries: The dominant harmonic for nonprecessing quasicircular black holes

2020-01-01

['-', '-']

[]

In this paper we present IMRPHENOMXAS, a thorough overhaul of the IMRPHENOMD [S. Husa et al., Phys. Rev. D 93, 044006 (2016), 10.1103/PhysRevD.93.044006; S. Khan et al., Phys. Rev. D 93, 044007 (2016), 10.1103/PhysRevD.93.044007] waveform model, which describes the dominant l =2 , |m |=2 spherical harmonic mode of nonprecessing coalescing black holes in terms of piecewise closed form expressions in the frequency domain. Improvements include in particular the accurate treatment of unequal spin effects, and the inclusion of extreme mass ratio waveforms. IMRPHENOMD has previously been extended to approximately include spin precession [M. Hannam et al., Phys. Rev. Lett. 113, 151101 (2014), 10.1103/PhysRevLett.113.151101] and subdominant spherical harmonics [L. London et al., Phys. Rev. Lett. 120, 161102 (2018), 10.1103/PhysRevLett.120.161102], and with its extensions it has become a standard tool in gravitational wave parameter estimation. Improved extensions of IMRPHENOMXAS are discussed in companion papers [C. García-Quirós et al., Phys. Rev. D 102, 064002 (2020), 10.1103/PhysRevD.102.064002; G. Pratten et al., arXiv:2004.06503].

[]

https://arxiv.org/pdf/2001.11412.pdf

1999CQGra..16L...1A

LETTER TO THE EDITOR: Isolated horizons: a generalization of black hole mechanics

1999-01-01

['-']

[]

A set of boundary conditions defining a non-rotating isolated horizon are given in Einstein-Maxwell theory. A spacetime representing a black hole which itself is in equilibrium but whose exterior contains radiation admits such a horizon. Physically motivated, (quasi-)local definitions of the mass and surface gravity of an isolated horizon are introduced. Although these definitions do not refer to infinity, the quantities assume their standard values in Reissner-Nordström solutions. Finally, using these definitions, the zeroth and first laws of black hole mechanics are established for isolated horizons.

[]

https://arxiv.org/pdf/gr-qc/9812065.pdf

2012MNRAS.425.2799R

Investigating stellar-mass black hole kicks

2012-01-01

['black hole physics', 'stars binaries general', '-', 'stars novae;cataclysmic variables', 'galaxy kinematics and dynamics', 'astronomy x rays', '-', '-']

[]

We investigate whether stellar-mass black holes have to receive natal kicks in order to explain the observed distribution of low-mass X-ray binaries containing black holes within our Galaxy. Such binaries are the product of binary evolution, where the massive primary has exploded forming a stellar-mass black hole, probably after a common envelope phase where the system contracted down to separations of the order of 10-30 R<SUB>⊙</SUB>. We perform population synthesis calculations of these binaries, applying both kicks due to supernova mass-loss and natal kicks due to the newly formed black hole. We then integrate the trajectories of the binary systems within the Galactic potential. We find that natal kicks are in fact necessary to reach the large distances above the Galactic plane achieved by some binaries. Further, we find that the distribution of natal kicks would seem to be similar to that of neutron stars, rather than one where the kick velocities are reduced by the ratio of black hole to neutron star mass (i.e. where the kicks have the same momentum). This result is somewhat surprising; in many pictures of stellar-mass black hole formation, one might have expected black holes to receive kicks having the same momentum (rather than the same speed) as those given to neutron stars.

[]

https://arxiv.org/pdf/1203.3077.pdf

1999ApJ...514..388W

Frame Dragging and Other Precessional Effects in Black Hole Pulsar Binaries

1999-01-01

['stars binaries general', 'black hole physics', 'gravitation', '-', '-', 'stars binaries general', 'black hole physics', 'gravitation', '-', '-', 'astrophysics', '-']

[]

For radio pulsars in orbit with a compact companion, pulsar timing observations have proved to be a powerful tool for identifying the physical nature of the companion. Unfortunately, perhaps the most intriguing system where such a tool could be used, a pulsar in orbit with a black hole, has yet to be discovered. In this paper we give a detailed investigation of what one can learn about the black hole companion via timing observations of the pulsar. We present an analytic calculation for the propagation delay caused by the frame-dragging effect and show that it has the same functional behavior as the modulation of the observed rotational phase of the pulsar caused by the deflection of the radio signals in the gravitational field of the companion (bending delay). Thus, contrary to statements of other authors, the frame-dragging delay is unlikely to be separately measurable in pulsar binaries where the companion is a stellar-mass black hole. We demonstrate, however, that the precession of the binary orbit caused by the relativistic spin-orbit coupling can lead to observable effects that can be used to set a lower limit to the black hole spin or possibly allow the determination of its magnitude and orientation. We give parameter estimates for two possible systems, a 10 M<SUB>solar</SUB> black hole in orbit either with a young (~0.1 s) pulsar or with a millisecond pulsar. Finally, we discuss the measurability of the quadrupole moment of the rotating black hole companion that would test the presence of a Kerr black hole. As an interesting side result of our calculations, we can give a further argument why the companion of PSR J0045-7319 cannot be a Kerr black hole.

[]

https://arxiv.org/pdf/astro-ph/9811052.pdf

2003PhRvD..67j3006B

Quasiequatorial gravitational lensing by spinning black holes in the strong field limit

2003-01-01

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

[]

Spherically symmetric black holes produce, by strong field lensing, two infinite series of relativistic images, formed by light rays winding around the black hole at distances comparable to the gravitational radius. In this paper we address the relevance of the black hole spin for the strong field lensing phenomenology, focusing on trajectories close to the equatorial plane for simplicity. In this approximation, we derive a two-dimensional lens equation and formulas for the position and the magnification of the relativistic images in the strong field limit. The most outstanding effect is the generation of a nontrivial caustic structure. Caustics drift away from the optical axis and acquire finite extension. For a high enough black hole spin, depending on the source extension, we can practically observe only one image rather than two infinite series of relativistic images. In this regime, additional nonequatorial images may play an important role in the phenomenology.

[]

https://arxiv.org/pdf/gr-qc/0210109.pdf

2007JHEP...12..068K

Higher-order corrections to mass-charge relation of extremal black holes

2007-01-01

['-']

[]

We investigate the hypothesis that the higher-derivative corrections always make extremal non-supersymmetric black holes lighter than the classical bound and self-repulsive. This hypothesis was recently formulated in the context of the so-called swampland program. One of our examples involves an extremal heterotic black hole in four dimensions. We also calculate the effect of general four-derivative terms in Maxwell-Einstein theories in D dimensions. The results are consistent with the conjecture.

[]

https://arxiv.org/pdf/hep-th/0606100.pdf

2003MNRAS.342..355Z

Correlations between X-ray and radio spectral properties of accreting black holes

2003-01-01

['accretion', 'accretion disks', 'radiation', 'stars binaries general', 'galaxies seyfert', 'astronomy x rays', 'astronomy x rays', 'astrophysics']

[]

We study correlations between the X-ray spectral index, the strength of Compton reflection, and X-ray and radio fluxes in accreting black holes (Seyferts and black hole binaries). We critically evaluate the evidence for the correlation of the X-ray spectral index with the strength of Compton reflection and consider in detail statistical and systematic effects that can affect it. We study patterns of spectral variability (in particular, pivoting of a power-law spectrum) corresponding to the X-ray index-flux correlation. We also consider implications of the form of observed X-ray spectra and their variability for interpretation of the correlation between the radio and X-ray fluxes. Finally, we discuss accretion geometries that can account for the correlations and their overall theoretical interpretations.

[]

https://arxiv.org/pdf/astro-ph/0209363.pdf

2016CQGra..33q4001C

Testing the black hole ‘no-hair’ hypothesis

2016-01-01

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

[]

Black holes (BHs) in general relativity (GR) are very simple objects. This property, that goes under the name of ‘no-hair’, has been refined in the last few decades and admits several versions. The simplicity of BHs makes them ideal testbeds of fundamental physics and of GR itself. Here we discuss the no-hair property of BHs, how it can be measured in the electromagnetic or gravitational window, and what it can possibly tell us about our Universe.

[]

https://arxiv.org/pdf/1607.03133.pdf

2006ApJ...646..754D

The Star-forming Torus and Stellar Dynamical Black Hole Mass in the Seyfert 1 Nucleus of NGC 3227

2006-01-01

['galaxies active', 'galaxies', 'galaxies nuclei', 'galaxies seyfert', 'galaxies starburst', 'astronomy infrared', 'astrophysics']

[]

We report R~4300 VLT SINFONI adaptive optics integral field K-band spectroscopy of the nucleus of the Seyfert 1 galaxy NGC 3227 at a spatial resolution of 0.085" (7 pc). We present the morphologies and kinematics of emission lines and absorption features and give the first derivation of a black hole mass in a Seyfert 1 nucleus from stellar dynamics (marginally resolving the black hole's sphere of influence). We show that the gas in the nucleus has a mean column density of order 10<SUP>24</SUP> cm<SUP>-2</SUP> and that it is geometrically thick, in agreement with the standard ``molecular torus'' scenario. We discuss possible heating processes responsible for maintaining the vertical height of the torus. We also resolve the nuclear stellar distribution and find that within a few parsecs of the AGN there has been an intense starburst, the most recent episode of which began ~40 Myr ago but has now ceased. The current luminosity of stars within 30 pc of the AGN, ~3×10<SUP>9</SUP> L<SUB>solar</SUB>, is comparable to that of the AGN. We argue that the star formation has been occurring in the obscuring material. Finally, we apply Schwarzschild orbit superposition models to our full two-dimensional data and derive the mass of the black hole, paying careful attention to the input parameters, which are often uncertain. Our models yield a 1 σ range for the black hole mass of M<SUB>BH</SUB>=7×10<SUP>6</SUP>-2×10<SUP>7</SUP> M<SUB>solar</SUB>. <P />Based on observations at the European Southern Observatory VLT (074.B-9012).

[]

https://arxiv.org/pdf/astro-ph/0604125.pdf

2021ARA&A..59..117R

Observational Constraints on Black Hole Spin

2021-01-01

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

[]

The spin of a black hole is an important quantity to study, providing a window into the processes by which a black hole was born and grew. Furthermore, spin can be a potent energy source for powering relativistic jets and energetic particle acceleration. In this review, I describe the techniques currently used to detect and measure the spins of black holes. It is shown that: Two well-understood techniques, X-ray reflection spectroscopy and thermal continuum fitting, can be used to measure the spins of black holes that are accreting at moderate rates. There is a rich set of other electromagnetic techniques allowing us to extend spin measurements to lower accretion rates. Many accreting supermassive black holes are found to be rapidly spinning, although a population of more slowly spinning black holes emerges at masses above as expected from recent structure formation models. Many accreting stellar-mass black holes in X-ray binary systems are rapidly spinning and must have been born in this state. The advent of gravitational wave astronomy has enabled the detection of spin effects in merging binary black holes. Most of the premerger black holes are found to be slowly spinning, a notable exception being an object that may itself be a merger product. The stark difference in spins between the black hole X-ray binary and the binary black hole populations shows that there is a diversity of formation mechanisms.Given the array of new electromagnetic and gravitational wave capabilities currently being planned, the future of black hole spin studies is bright.

[]

https://arxiv.org/pdf/2011.08948.pdf

2020ApJ...888...36R

A New Sample of (Wandering) Massive Black Holes in Dwarf Galaxies from High-resolution Radio Observations

2020-01-01

['-', 'galaxies dwarf', 'astronomy radio', 'techniques interferometric', 'galaxies active', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-', '-']

[]

We present a sample of nearby dwarf galaxies with radio-selected accreting massive black holes (BHs), the majority of which are non-nuclear. We observed 111 galaxies using sensitive, high-resolution observations from the Karl G. Jansky Very Large Array (VLA) in its most extended A-configuration at X band (∼8-12 GHz), yielding a typical angular resolution of ∼0.″25 and rms noise of ∼15 μJy. Our targets were selected by crossmatching galaxies with stellar masses M <SUB>⋆</SUB> ≤ 3 × 10<SUP>9</SUP> M <SUB>⊙</SUB> and redshifts z &lt; 0.055 in the NASA-Sloan Atlas with the VLA Faint Images of the Radio Sky at Twenty centimeters Survey. With our new high-resolution VLA observations, we detect compact radio sources toward 39 galaxies and carefully evaluate possible origins for the radio emission, including thermal H II regions, supernova remnants, younger radio supernovae, background interlopers, and active galactic nuclei (AGNs) in the target galaxies. We find that 13 dwarf galaxies almost certainly host active massive BHs, despite the fact that only one object was previously identified as having optical signatures of an AGN. We also identify a candidate dual radio AGN in a more massive galaxy system. The majority of the radio-detected BHs are offset from the center of the host galaxies, with some systems showing signs of interactions/mergers. Our results indicate that massive BHs need not always live in the nuclei of dwarf galaxies, confirming predictions from simulations. Moreover, searches attempting to constrain BH seed formation using observations of dwarf galaxies need to account for such a population of “wandering” BHs.

[]

https://arxiv.org/pdf/1909.04670.pdf

2017ApJ...851L..25F

Where Are LIGO’s Big Black Holes?

2017-01-01

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

[]

In LIGO’s O1 and O2 observational runs, the detectors were sensitive to stellar-mass binary black hole (BBH) coalescences with component masses up to 100 {M}<SUB>⊙ </SUB>, with binaries with primary masses above 40 {M}<SUB>⊙ </SUB> representing ≳90% of the total accessible sensitive volume. Nonetheless, of the 5.9 detections (GW150914, LVT151012, GW151226, GW170104, GW170608, and GW170814) reported by LIGO-Virgo, the most massive binary detected was GW150914 with a primary component mass of ∼ 36 {M}<SUB>⊙ </SUB>, far below the detection mass limit. Furthermore, there are theoretical arguments in favor of an upper mass gap, predicting an absence of black holes in the mass range 50≲ M≲ 135 {M}<SUB>⊙ </SUB>. We argue that the absence of detected binary systems with component masses heavier than ∼ 40 {M}<SUB>⊙ </SUB> may be preliminary evidence for this upper mass gap. By allowing for the presence of a mass gap, we find weaker constraints on the shape of the underlying mass distribution of BBHs. We fit a power-law distribution with an upper mass cutoff to real and simulated BBH mass measurements, finding that the first 3.9 BBHs favor shallow power-law slopes α ≲ 3 and an upper mass cutoff {M}<SUB>\max </SUB>∼ 40 {M}<SUB>⊙ </SUB>. This inferred distribution is entirely consistent with the two recently reported detections, GW170608 and GW170814. We show that with ∼10 additional LIGO-Virgo BBH detections, fitting the BH mass distribution will provide strong evidence for an upper mass gap if one exists.

[]

https://arxiv.org/pdf/1709.08584.pdf

2019PhRvD..99j3521B

Testing primordial black holes as dark matter with LISA

2019-01-01

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

[]

The idea that primordial black holes (PBHs) can comprise most of the dark matter of the Universe has recently reacquired a lot of momentum. Observational constraints, however, rule out this possibility for most of the PBH masses, with a notable exception around 10<SUP>-12</SUP> M<SUB>⊙</SUB>. These light PBHs may be originated when a sizable comoving curvature perturbation generated during inflation reenters the horizon during the radiation phase. During such a stage, it is unavoidable that gravitational waves (GWs) are generated. Since their source is quadratic in the curvature perturbations, these GWs are generated fully non-Gaussian. Their frequency today is about a millihertz, which is exactly the range where the LISA mission has the maximum of its sensitivity. This is certainly an impressive coincidence. We show that this scenario of PBHs as dark matter can be tested by LISA by measuring the GW two-point correlator. On the other hand, we show that the short observation time (as compared to the age of the Universe) and propagation effects of the GWs across the perturbed Universe from the production point to the LISA detector suppress the bispectrum to an unobservable level. This suppression is completely general and not specific to our model.

[]

https://arxiv.org/pdf/1810.12224.pdf

2009ApJ...692..411N

Direct Calculation of the Radiative Efficiency of an Accretion Disk Around a Black Hole

2009-01-01

['accretion', 'accretion disks', 'black hole physics', 'mhd', 'radiative transfer', 'astrophysics']

[]

Numerical simulation of magnetohydrodynamic (MHD) turbulence makes it possible to study accretion dynamics in detail. However, special effort is required to connect inflow dynamics (dependent largely on angular momentum transport) to radiation (dependent largely on thermodynamics and photon diffusion). To this end, we extend the flux-conservative, general relativistic MHD (GRMHD) code HARM from axisymmetry to full three dimensions. The use of an energy conserving algorithm allows the energy dissipated in the course of relativistic accretion to be captured as heat. The inclusion of a simple optically thin cooling function permits explicit control of the simulated disk's geometric thickness as well as a direct calculation of both the amplitude and location of the radiative cooling associated with the accretion stresses. Fully relativistic ray-tracing is used to compute the luminosity received by distant observers. For a disk with aspect ratio H/r sime 0.1 accreting onto a black hole with spin parameter a/M = 0.9, we find that there is significant dissipation beyond that predicted by the classical Novikov-Thorne model. However, much of it occurs deep in the potential, where photon capture and gravitational redshifting can strongly limit the net photon energy escaping to infinity. In addition, with these parameters and this radiation model, significant thermal and magnetic energy remains with the gas and is accreted by the black hole. In our model, the net luminosity reaching infinity is 6% greater than the Novikov-Thorne prediction. If the accreted thermal energy were wholly radiated, the total luminosity of the accretion flow would be sime20% greater than the Novikov-Thorne value.

[]

https://arxiv.org/pdf/0808.3140.pdf

2005ApJ...635..853B

The Relationship between Stellar and Black Hole Mass in Submillimeter Galaxies

2005-01-01

['galaxies evolution', 'galaxies formation', 'galaxies photometry', 'galaxies starburst', 'astrophysics']

[]

We analyze deep X-ray, optical, and mid-infrared Spitzer observations of the CDF-N/GOODS-N region to study a sample of 13 submillimeter-detected galaxies with spectroscopic redshifts (median z=2.2). These galaxies are among the most active and massive at this epoch. We find evidence for a power-law correlation between the estimated stellar and X-ray luminosity, implying that masses of the black holes may be related to the stellar masses of their host galaxies. We derive the rest-frame UV-near-infrared spectral energy distributions for these galaxies, believed to be young spheroids, and fit them with model templates. Using the rest-frame near-infrared luminosities, which are relatively insensitive to uncertainties in stellar ages and reddening in these young dusty galaxies, and theoretical mass-to-light ratios, we can estimate their stellar masses. Although the submillimeter emission implies that these galaxies are undergoing an epoch of intense star formation, the Spitzer data reveal a massive stellar population already in place. We find that our submillimeter galaxies have a median stellar mass of ~10<SUP>11</SUP> M<SUB>solar</SUB>, which is roughly 10 times more massive than typical UV-selected star-forming systems at similar redshifts. These stellar masses are then compared to previously published black hole mass estimates derived from the X-ray luminosities under the assumption of Eddington-limit accretion. We find that the black hole masses for our high-redshift sample are approximately 1-2 orders of magnitude smaller than galaxies of comparable stellar mass in the local universe. Although our estimates of black hole masses will increase if the accretion is sub-Eddington, and our stellar masses will decrease if we assume a much younger stellar population or a different initial mass function, we find that only through a combination of effects is it possible to shift the high-redshift galaxies such that they lie on the local relation. This suggests that the black holes need to grow substantially between z=2.2 and the present day, with much of the black hole growth occurring after the current obscured, far-infrared luminous phase of activity, which is likely associated with the formation of the spheroid. This interpretation supports a scenario in which submillimeter galaxies pass through a subsequent accretion-dominated phase, where they would appear as optically bright quasars.

[]

https://arxiv.org/pdf/astro-ph/0507610.pdf

2007ApJ...661..430H

Gravitational Recoil from Spinning Binary Black Hole Mergers

2007-01-01

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

[]

The inspiraling and merger of binary black holes will likely involve black holes with not only unequal masses but also arbitrary spins. The gravitational radiation emitted by these binaries will carry angular as well as linear momentum. A net flux of emitted linear momentum implies that the black hole produced by the merger will experience a recoil or kick. Previous studies have focused on the recoil velocity from unequal-mass, nonspinning binaries. We present results from simulations of equal-mass but spinning black hole binaries and show how a significant gravitational recoil can also be obtained in these situations. We consider the case of black holes with opposite spins of magnitude a aligned and antialigned with the orbital angular momentum, with a the dimensionless spin parameter of the individual holes. For the initial setups under consideration, we find a recoil velocity of V=475a km s<SUP>-1</SUP>. Supermassive black hole mergers producing kicks of this magnitude could result in the ejection of the final hole produced by the collision from the core of a dwarf galaxy.

[]

https://arxiv.org/pdf/gr-qc/0701143.pdf

2011MNRAS.414L..60U

The causal connection between disc and power-law variability in hard state black hole X-ray binaries

2011-01-01

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

[]

We use the XMM-Newton EPIC-pn instrument in timing mode to extend spectral time-lag studies of hard state black hole X-ray binaries into the soft X-ray band. We show that variations of the disc blackbody emission substantially lead variations in the power-law emission, by tenths of a second on variability time-scales of seconds or longer. The large lags cannot be explained by Compton scattering but are consistent with time delays due to viscous propagation of mass accretion fluctuations in the disc. However, on time-scales less than a second the disc lags the power-law variations by a few milliseconds, consistent with the disc variations being dominated by X-ray heating by the power law, with the short lag corresponding to the light traveltime between the power-law emitting region and the disc. Our results indicate that instabilities in the accretion disc are responsible for continuum variability on time-scales of seconds or longer and probably also on shorter time-scales.

[]

https://arxiv.org/pdf/1104.0634.pdf

2003PhRvD..68f4011F

Particle and light motion in a space-time of a five-dimensional rotating black hole

2003-01-01

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

[]

We study the motion of particles and light in a space-time of a five-dimensional rotating black hole. We demonstrate that the Myers-Perry metric describing such a black hole, in addition to three Killing vectors, also possesses a Killing tensor. As a result, the Hamilton-Jacobi equations of motion allow a separation of variables. Using first integrals we present the equations of motion in the first-order form. We describe different types of motion of particles and light and study some interesting special cases. We prove that there are no stable circular orbits in equatorial planes in the background of this metric.

[]

https://arxiv.org/pdf/gr-qc/0301016.pdf

2013PhLB..719..419D

Black holeʼs 1/N hair

2013-01-01

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

[]

According to the standard view classically black holes carry no hair, whereas quantum hair is at best exponentially weak. We show that suppression of hair is an artifact of the semi-classical treatment and that in the quantum picture hair appears as an inverse mass-square effect. Such hair is predicted in the microscopic quantum description in which a black hole represents a self-sustained leaky Bose-condensate of N soft gravitons. In this picture the Hawking radiation is the quantum depletion of the condensate. Within this picture we show that quantum black hole physics is fully compatible with continuous global symmetries and that global hair appears with the strength B/N, where B is the global charge swallowed by the black hole. For large charge this hair has dramatic effect on black hole dynamics. Our findings can have interesting astrophysical consequences, such as existence of black holes with large detectable baryonic and leptonic numbers.

[]

https://arxiv.org/pdf/1203.6575.pdf

1999ApJ...515L..73K

Magnetized Accretion inside the Marginally Stable Orbit around a Black Hole

1999-01-01

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

[]

Qualitative arguments are presented in order to demonstrate that the energy density of magnetic fields in matter accreting onto a black hole inside the marginally stable orbit is automatically comparable to the rest-mass energy density of the accretion flow. Several consequences follow: magnetic effects must be dynamically significant but cannot be so strong as to dominate; the outward energy transport in Alfvén waves may alter the effective efficiency of energy liberation; and vertical magnetic stresses in this region may contribute to ``coronal'' activity.

[]

https://arxiv.org/pdf/astro-ph/9902267.pdf

2016MNRAS.459.3738I

Hyper-Eddington accretion flows on to massive black holes

2016-01-01

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

[]

We study very high rate, spherically symmetric accretion flows on to massive black holes (BHs; 10<SUP>2</SUP> ≲ M<SUB>BH</SUB> ≲ 10<SUP>6</SUP> M<SUB>⊙</SUB>) embedded in dense metal-poor clouds, performing one-dimensional radiation hydrodynamical simulations. We find solutions from outside the Bondi radius at hyper-Eddington rates, unimpeded by radiation feedback when (n<SUB>∞</SUB>/10<SUP>5</SUP> cm<SUP>-3</SUP>) &gt; (M<SUB>BH</SUB>/10<SUP>4</SUP> M<SUB>⊙</SUB>)<SUP>-1</SUP>(T<SUB>∞</SUB>/10<SUP>4</SUP> K)<SUP>3/2</SUP>, where n<SUB>∞</SUB> and T<SUB>∞</SUB> are the density and temperature of ambient gas. Accretion rates in this regime are steady, and larger than 5000L<SUB>Edd</SUB>/c<SUP>2</SUP>, where L<SUB>Edd</SUB> is the Eddington luminosity. At lower Bondi rates, the accretion is episodic due to radiative feedback and the average rate is below the Eddington rate. In the hyper-Eddington case, the solution consists of a radiation-dominated central core, where photon trapping due to electron scattering is important, and an accreting envelope which follows a Bondi profile with T ≃ 8000 K. When the emergent luminosity is limited to ≲ L<SUB>Edd</SUB> because of photon trapping, radiation from the central region does not affect the gas dynamics at larger scales. We apply our result to the rapid formation of massive BHs in protogalaxies with a virial temperature of T<SUB>vir</SUB> ≳ 10<SUP>4</SUP>K. Once a seed BH forms at the centre of the galaxy, it can grow to a maximum ∼10<SUP>5</SUP>(T<SUB>vir</SUB>/10<SUP>4</SUP> K) M<SUB>⊙</SUB> via gas accretion independent of the initial BH mass. Finally, we discuss possible observational signatures of rapidly accreting BHs with/without allowance for dust. We suggest that these systems could explain Lyα emitters without X-rays and nearby luminous infrared sources with hot dust emission, respectively.

[]

https://arxiv.org/pdf/1511.02116.pdf

2018PhRvL.121x1301A

Quantum Transfiguration of Kruskal Black Holes

2018-01-01

['-', '-']

[]

We present a new effective description of macroscopic Kruskal black holes that incorporates corrections due to quantum geometry effects of loop quantum gravity. It encompasses both the "interior" region that contains classical singularities and the "exterior" asymptotic region. Singularities are naturally resolved by the quantum geometry effects of loop quantum gravity, and the resulting quantum extension of the full Kruskal space-time is free of all the known limitations of previous investigations of the Schwarzschild interior. We compare and contrast our results with these investigations and also with the expectations based on the AdS /CFT duality.

[]

https://arxiv.org/pdf/1806.00648.pdf

2003PhRvD..67b4009Y

Black hole formation in the grazing collision of high-energy particles

2003-01-01

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

[]

We numerically investigate the formation of D-dimensional black holes in high-energy particle collisions with the impact parameter and evaluate the total cross section of black hole production. We find that the formation of an apparent horizon occurs when the distance between the colliding particles is less than 1.5 times the effective gravitational radius of each particle. Our numerical result indicates that although both the one-dimensional hoop and the (D-3)-dimensional volume corresponding to the typical scale of the system give a fairly good condition for horizon formation in the higher-dimensional gravity, the (D-3)-dimensional volume provides a better condition to judge the existence of the horizon.

[]

https://arxiv.org/pdf/gr-qc/0209003.pdf

2006ApJ...651..775B

A Reverberation-based Mass for the Central Black Hole in NGC 4151

2006-01-01

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

[]

We have undertaken a new ground-based monitoring campaign to improve the estimates of the mass of the central black hole in NGC 4151. We measure the lag time of the broad Hβ line response compared to the optical continuum at 5100 Å and find a lag of 6.6<SUP>+1.1</SUP><SUB>-0.8</SUB> days. We combine our data with the recent reanalysis of UV emission lines by Metzroth and coworkers to calculate a weighted mean of the black hole mass, M<SUB>BH</SUB>=(4.57<SUP>+0.57</SUP><SUB>-0.47</SUB>)×10<SUP>7</SUP> M<SUB>solar</SUB>. The absolute calibration of the black hole mass is based on normalization of the AGN black hole mass-stellar velocity dispersion (MBH-σ<SUB>*</SUB>) relationship to that of quiescent galaxies by Onken and coworkers. The scatter in the MBH-σ<SUB>*</SUB> relationship suggests that reverberation-mapping-based mass measurements are typically uncertain by a factor of 3-4.

[]

https://arxiv.org/pdf/astro-ph/0607085.pdf

2006CMaPh.266..571G

A Generalization of Hawking's Black Hole Topology Theorem to Higher Dimensions

2006-01-01

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

[]

Hawking's theorem on the topology of black holes asserts that cross sections of the event horizon in 4-dimensional asymptotically flat stationary black hole spacetimes obeying the dominant energy condition are topologically 2-spheres. This conclusion extends to outer apparent horizons in spacetimes that are not necessarily stationary. In this paper we obtain a natural generalization of Hawking's results to higher dimensions by showing that cross sections of the event horizon (in the stationary case) and outer apparent horizons (in the general case) are of positive Yamabe type, i.e., admit metrics of positive scalar curvature. This implies many well-known restrictions on the topology, and is consistent with recent examples of five dimensional stationary black hole spacetimes with horizon topology S<SUP>2</SUP> × S<SUP>1</SUP>. The proof is inspired by previous work of Schoen and Yau on the existence of solutions to the Jang equation (but does not make direct use of that equation).

[]

https://arxiv.org/pdf/gr-qc/0509107.pdf

2006ApJ...651..392S

Interaction of Massive Black Hole Binaries with Their Stellar Environment. I. Ejection of Hypervelocity Stars

2006-01-01

['black hole physics', 'methods numerical', 'stars kinematics and dynamics', 'astrophysics']

[]

We use full three-body scattering experiments to study the ejection of hypervelocity stars (HVSs) by massive black hole binaries (MBHBs) at the centers of galaxies. Ambient stars drawn from a Maxwellian distribution unbound to the binary are expelled by the gravitational slingshot. Accurate measurements of thermally averaged hardening, mass ejection, and eccentricity growth rates (H, J, and K) for MBHBs in a fixed stellar background are obtained by numerical orbit integration from initial conditions determined by Monte Carlo techniques. Three-body interactions create a subpopulation of HVSs on nearly radial orbits, with a spatial distribution that is initially highly flattened in the inspiral plane of the MBHB, but becomes more isotropic with decreasing binary separation. The degree of anisotropy is smaller for unequal mass binaries and larger for stars with higher kick velocities. Eccentric MBHBs produce a more prominent tail of high-velocity stars and break planar symmetry, ejecting HVSs along a broad jet perpendicular to the semimajor axis. The jet two-sidedness decreases with increasing binary mass ratio, while the jet opening angle increases with decreasing kick velocity and orbital separation. The detection of a numerous population of HVSs in the halo of the Milky Way by the next generation of large astrometric surveys such as Gaia may provide a unique signature of the history, nature, and environment of the MBH at the Galactic center.

[]

https://arxiv.org/pdf/astro-ph/0604299.pdf

2008ApJ...675.1048R

Broad Iron-Kα Emission Lines as a Diagnostic of Black Hole Spin

2008-01-01

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

[]

We address the ability of broad iron emission lines from black hole accretion disks to diagnose the spin of the black hole. Using a high-resolution three-dimensional MHD simulation of a geometrically thin accretion disk in a pseudo-Newtonian potential, we show that both the mid-plane density and the vertical column density of the accretion flow drop dramatically over a narrow range of radii close to the innermost stable circular orbit (ISCO). We argue that this drop of density is accompanied by a sharp increase in the ionization parameter of the X-ray photosphere, and that the resulting imprint of the ISCO on the X-ray reflection spectrum can be used to constrain spin. Motivated by this simulation, we construct a simplified toy model of the accretion flow within the ISCO of a Kerr black hole, and use this model to estimate the systematic error on inferred black hole spin that may result from slight bleeding of the iron line emission to the region inside of the ISCO. We find that these systematic errors can be significant for slowly spinning black holes but become appreciably smaller as one considers more rapidly rotating black holes.

[]

https://arxiv.org/pdf/0711.4158.pdf

2009PhRvD..80l6003B

Black holes in asymptotically Lifshitz spacetimes with arbitrary critical exponent

2009-01-01

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

[]

Recently, a class of gravitational backgrounds in 3+1 dimensions have been proposed as holographic duals to a Lifshitz theory describing critical phenomena in 2+1 dimensions with critical exponent z≥1. We numerically explore black holes in these backgrounds for a range of values of z. We find drastically different behavior for z&gt;2 and z&lt;2. We find that for z&gt;2 (z&lt;2) the Lifshitz fixed point is repulsive (attractive) when going to larger radial parameter r. For the repulsive z&gt;2 backgrounds, we find a continuous family of black holes satisfying a finite energy condition. However, for z&lt;2 we find that the finite energy condition is more restrictive, and we expect only a discrete set of black hole solutions, unless some unexpected cancellations occur. For all black holes, we plot temperature T as a function of horizon radius r<SUB>0</SUB>. For z⪅1.761 we find that this curve develops a negative slope for certain values of r<SUB>0</SUB> possibly indicating a thermodynamic instability.

[]

https://arxiv.org/pdf/0905.3183.pdf

2008PhLB..661..370L

Dirac particles tunneling from BTZ black hole

2008-01-01

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

[]

We calculated the Dirac particles' Hawking radiation from the outer horizon of BTZ black hole via tunneling formalism. Applying WKB approximation to the Dirac equation in (2 + 1)-dimensional BTZ spacetime background, we obtain the radiation spectrum for fermions and Hawking temperature of BTZ black hole. The results obtained by taking the fermion tunneling into account are consistent with the previous literatures.

[]

https://arxiv.org/pdf/0802.3954.pdf

2007JHEP...03..110C

Flow equations for non-BPS extremal black holes

2007-01-01

['-']

[]

We exploit some common features of black hole and domain wall solutions of (super)gravity theories coupled to scalar fields and construct a class of stable extremal black holes that are non-BPS, but still can be described by first-order differential equations. These are driven by a ``superpotential'', which replaces the central charge Script Z in the usual black hole potential. We provide a general procedure for finding this class and deriving the associated ``superpotential''. We also identify some other cases which do not belong to this class, but show a similar behaviour.

[]

https://arxiv.org/pdf/hep-th/0702088.pdf

2010PhRvL.104b1101J

Spinning Black Holes as Particle Accelerators

2010-01-01

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

[]

It has recently been pointed out that particles falling freely from rest at infinity outside a Kerr black hole can in principle collide with an arbitrarily high center of mass energy in the limiting case of maximal black hole spin. Here we aim to elucidate the mechanism for this fascinating result, and to point out its practical limitations, which imply that ultraenergetic collisions cannot occur near black holes in nature.

[]

https://arxiv.org/pdf/0911.3363.pdf

2001PhRvD..64f4004H

Evolution of circular, nonequatorial orbits of Kerr black holes due to gravitational-wave emission. II. Inspiral trajectories and gravitational waveforms

2001-01-01

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

[]

The inspiral of a ``small'' (μ~1-100 M<SUB>solar</SUB>) compact body into a ``large'' (M~10<SUP>5-7</SUP> M<SUB>solar</SUB>) black hole is a key source of gravitational radiation for the space-based gravitational-wave observatory LISA. The waves from such inspirals will probe the extreme strong-field nature of the Kerr metric. In this paper, I investigate the properties of a restricted family of such inspirals (the inspiral of circular, inclined orbits) with an eye toward understanding observable properties of the gravitational waves that they generate. Using results previously presented to calculate the effects of radiation reaction, I assemble the inspiral trajectories (assuming that radiation reacts adiabatically, so that over short time scales the trajectory is approximately geodesic) and calculate the wave generated as the compact body spirals in. I do this analysis for several black hole spins, sampling a range that should be indicative of what spins we will encounter in nature. The spin has a very strong impact on the waveform. In particular, when the hole rotates very rapidly, tidal coupling between the inspiraling body and the event horizon has a very strong influence on the inspiral time scale, which in turn has a big impact on the gravitational wave phasing. The gravitational waves themselves are very usefully described as ``multi-voice chirps'': the wave is a sum of ``voices,'' each corresponding to a different harmonic of the fundamental orbital frequencies. Each voice has a rather simple phase evolution. Searching for extreme mass ratio inspirals voice-by-voice may be more effective than searching for the summed waveform all at once.

[]

https://arxiv.org/pdf/gr-qc/0104041.pdf

2014MNRAS.437.2554M

Precise mass and spin measurements for a stellar-mass black hole through X-ray timing: the case of GRO J1655-40

2014-01-01

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

[]

We present a systematic analysis of the fast time variability properties of the transient black hole binary GRO J1655-40, based on the complete set of Rossi X-ray Timing Explorer observations. We demonstrate that the frequencies of the quasi-periodic oscillations and of the broad-band noise components and their variations match accurately the strong field general relativistic frequencies of particle motion in the close vicinity of the innermost stable circular orbit, as predicted by the relativistic precession model.We obtain high-precision measurements of the black hole mass [M = (5.31 ± 0.07) M<SUB>⊙</SUB>, consistent with the value from optical/NIR observations] and spin (a = 0.290 ± 0.003), through the sole use of X-ray timing.

[]

https://arxiv.org/pdf/1309.3652.pdf

2019PhRvD.100b4059K

Phenomenological model for the gravitational-wave signal from precessing binary black holes with two-spin effects

2019-01-01

['-']

[]

The properties of compact binaries, such as masses and spins, are imprinted in the gravitational waves (GWs) they emit and can be measured using parametrized waveform models. Accurately and efficiently describing the complicated precessional dynamics of the various angular momenta of the system in these waveform models is the object of active investigation. One of the key models extensively used in the analysis of LIGO and Virgo data is the single-precessing-spin waveform model IMRPhenomPv2. In this article we present a new model IMRPhenomPv3, which includes the effects of two independent spins in the precession dynamics. Whereas IMRPhenomPv2 utilizes a single-spin frequency-dependent post-Newtonian rotation to describe precession effects, the improved model, IMRPhenomPv3, employs a double-spin rotation that is based on recent developments in the description of precessional dynamics. Besides double-spin precession, the improved model benefits from a more accurate description of precessional effects. We validate our new model against a large set of precessing numerical-relativity simulations. We find that IMRPhenomPv3 has better agreement with the inspiral portion of precessing binary-black-hole simulations and is more robust across a larger region of the parameter space than IMRPhenomPv2. As a first application we analyze the gravitational-wave event GW151226 with an efficient frequency-domain waveform model that describes two-spin precession. Within statistical uncertainty our results are consistent with published results. IMRPhenomPv3 will allow studies of the measurability of individual spins of binary black holes using GWs and can be used as a foundation upon which to build further improvements, such as modeling precession through merger, extending to higher multipoles, and including tidal effects.

[]

https://arxiv.org/pdf/1809.10113.pdf

2015PhR...548....1M

The masses and spins of neutron stars and stellar-mass black holes

2015-01-01

['accretion disks', 'black hole physics', 'gravitational waves', 'neutron', '-']

[]

Stellar-mass black holes and neutron stars represent extremes in gravity, density, and magnetic fields. They therefore serve as key objects in the study of multiple frontiers of physics. In addition, their origin (mainly in core-collapse supernovae) and evolution (via accretion or, for neutron stars, magnetic spindown and reconfiguration) touch upon multiple open issues in astrophysics. <P />In this review, we discuss current mass and spin measurements and their reliability for neutron stars and stellar-mass black holes, as well as the overall importance of spins and masses for compact object astrophysics. Current masses are obtained primarily through electromagnetic observations of binaries, although future microlensing observations promise to enhance our understanding substantially. The spins of neutron stars are straightforward to measure for pulsars, but the birth spins of neutron stars are more difficult to determine. In contrast, even the current spins of stellar-mass black holes are challenging to measure. As we discuss, major inroads have been made in black hole spin estimates via analysis of iron lines and continuum emission, with reasonable agreement when both types of estimate are possible for individual objects, and future X-ray polarization measurements may provide additional independent information. We conclude by exploring the exciting prospects for mass and spin measurements from future gravitational wave detections, which are expected to revolutionize our understanding of strong gravity and compact objects.

[]

https://arxiv.org/pdf/1408.4145.pdf

1995PhRvD..52.6997L

Black hole complementarity versus locality

1995-01-01

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

[]

The evaporation of a large mass black hole can be described throughout most of its lifetime by a low-energy effective theory defined on a suitably chosen set of smooth spacelike hypersurfaces. The conventional argument for information loss rests on the assumption that the effective theory is a local quantum field theory. We present evidence that this assumption fails in the context of string theory. The commutator of operators in light-front string theory, corresponding to certain low-energy observers on opposite sides of the event horizon, remains large even when these observers are spacelike separated by a macroscopic distance. This suggests that degrees of freedom inside a black hole should not be viewed as independent from those outside the event horizon. These nonlocal effects are only significant under extreme kinematic circumstances, such as in the high-redshift geometry of a black hole. Commutators of spacelike separated operators corresponding to ordinary low-energy observers in Minkowski space are strongly suppressed in string theory.

[]

https://arxiv.org/pdf/hep-th/9506138.pdf

2001PhRvD..65b3521N

Cosmological and black hole brane-world universes in higher derivative gravity

2001-01-01

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

[]

A general model of multidimensional R<SUP>2</SUP> gravity including a Riemann tensor square term (nonzero c case) is considered. The number of brane-worlds in such a model is constructed (mainly in five dimensions) and their properties are discussed. The thermodynamics of a Schwarzschild-anti-deSitter (S-AdS) BH (with boundary) is presented when perturbation on c is used. The entropy, free energy, and energy are calculated. For a nonzero c the entropy (energy) is not proportional to the area (mass). The equation of motion of the brane in a BH background is presented as a FRW equation. Using a dual CFT description it is shown that the dual field theory is not a conformal one when c is not zero. In this case the holographic entropy does not coincide with the BH entropy (they coincide for Einstein gravity or c=0 HD gravity where the AdS/CFT description is well applied). An asymmetrically warped background (an analogue of a charged AdS BH) where Lorentz invariance violation occurs is found. The cosmological 4D dS brane connecting two dS bulk spaces is formulated in terms of the parameters of R<SUP>2</SUP> gravity. Within the proposed dS/CFT correspondence the holographic conformal anomaly from five-dimensional higher derivative gravity in a de Sitter background is evaluated.

[]

https://arxiv.org/pdf/hep-th/0108172.pdf

1999JHEP...06..036E

AdS/CFT duals of topological black holes and the entropy of zero-energy states

1999-01-01

['-']

[]

The horizon of a static black hole in anti-de Sitter space can be spherical, planar, or hyperbolic. The microscopic dynamics of the first two classes of black holes have been extensively discussed recently within the context of the AdS/CFT correspondence. We argue that hyperbolic black holes introduce new and fruitful features in this respect, allowing for more detailed comparisons between the weak and strong coupling regimes. In particular, by focussing on the stress tensor and entropy of some particular states, we identify unexpected increases in the entropy of Super-Yang-Mills theory at strong coupling that are not accompanied by increases in the energy. We describe a highly degenerate state at zero temperature and zero energy density. We also find that the entanglement entropy across a Rindler horizon in exact AdS<SUB>5</SUB> is larger than might have been expected from the dual SYM theory. Besides, we show that hyperbolic black holes can be described as thermal Rindler states of the dual conformal field theory in flat space.

[]

https://arxiv.org/pdf/hep-th/9906040.pdf

2002PhRvD..66b4023K

Calculable corrections to brane black hole decay: The scalar case

2002-01-01

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

[]

In the context of brane-world theories, the production cross section for black holes may be greatly enhanced. Such black holes can in principle lead to detectable signals via their Hawking evaporation to brane-localized modes. We calculate, in the semiclassical approximation, the leading corrections to the energy spectrum (the greybody factors) for decay into scalar fields, as a function of the number of toroidally compactified extra dimensions, and partial wave number.

[]

https://arxiv.org/pdf/hep-ph/0203223.pdf

2009ApJ...706..404G

The Fundamental Plane of Accretion onto Black Holes with Dynamical Masses

2009-01-01

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

[]

Black hole accretion and jet production are areas of intensive study in astrophysics. Recent work has found a relation between radio luminosity, X-ray luminosity, and black hole mass. With the assumption that radio and X-ray luminosities are suitable proxies for jet power and accretion power, respectively, a broad fundamental connection between accretion and jet production is implied. In an effort to refine these links and enhance their power, we have explored the above relations exclusively among black holes with direct, dynamical mass-measurements. This approach not only eliminates systematic errors incurred through the use of secondary mass measurements, but also effectively restricts the range of distances considered to a volume-limited sample. Further, we have exclusively used archival data from the Chandra X-ray Observatory to best isolate nuclear sources. We find log L<SUB>R</SUB> = (4.80 ± 0.24) + (0.78 ± 0.27)log M <SUB>BH</SUB> + (0.67 ± 0.12)log L<SUB>X</SUB> , in broad agreement with prior efforts. Owing to the nature of our sample, the plane can be turned into an effective mass predictor. When the full sample is considered, masses are predicted less accurately than with the well-known M-σ relation. If obscured active galactic nuclei are excluded, the plane is potentially a better predictor than other scaling measures.

[]

https://arxiv.org/pdf/0906.3285.pdf

1994PhRvD..49..966S

Gedanken experiments involving black holes

1994-01-01

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

[]

Analysis of several gedanken experiments indicates that black hole complementarity cannot be ruled out on the basis of known physical principles. Experiments designed by outside observers to disprove the existence of a quantum-mechanical stretched horizon require knowledge of Planck-scale effects for their analysis. Observers who fall through the event horizon after sampling the Hawking radiation cannot discover duplicate information inside the black hole before hitting the singularity. Experiments by outside observers to detect baryon number violation will yield significant effects well outside the stretched horizon.

[]

https://arxiv.org/pdf/hep-th/9308100.pdf

1998PhRvD..57.6050K

Primordial black hole formation in a double inflation model in supergravity

1998-01-01

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

[]

It has been recently pointed out that the initial value problem in new inflation models is naturally solved by supergravity effects if there exists a preinflation before the new inflation. We study this double inflation model in detail and find that density fluctuations on small cosmological scales are much larger than those on large scales due to the peculiar property of the new inflation. We show that this results in the production of primordial black holes which have ~1M<SUB>solar</SUB> masses in a certain parameter region of the double inflation model. We stress that these black holes may be identified with massive compact halo objects observed in the halo of our galaxy.

[]

https://arxiv.org/pdf/hep-ph/9710259.pdf

2018PDU....22..137C

Seven hints for primordial black hole dark matter

2018-01-01

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

[]

Seven observations point towards the existence of primordial black holes (PBH), constituting the whole or an important fraction of the dark matter in the Universe: the mass and spin of black holes detected by Advanced LIGO/VIRGO, the detection of micro-lensing events of distant quasars and stars in M31, the non-detection of ultra-faint dwarf satellite galaxies with radius below 15 parsecs, evidences for core galactic dark matter profiles, the correlation between X-ray and infrared cosmic backgrounds, and the existence of super-massive black holes very early in the Universe's history. Some of these hints are newly identified and they are all intriguingly compatible with the re-constructed broad PBH mass distribution from LIGO events, peaking on PBH mass m<SUB>PBH</SUB> ≈ 3M<SUB>⊙</SUB> and passing all other constraints on PBH abundances. PBH dark matter also provides a new mechanism to explain the mass-to-light ratios of dwarf galaxies, including the recent detection of a diffuse galaxy not dominated by dark matter. Finally we conjecture that between 0.1% and 1% of the events detected by LIGO will involve a PBH with a mass below the Chandrasekhar mass, which would unambiguously prove the existence of PBH.

[]

https://arxiv.org/pdf/1711.10458.pdf