scholarly journals Tidal disruptions by rotating black holes: effects of spin and impact parameter

2019 ◽  
Vol 487 (4) ◽  
pp. 4790-4808 ◽  
Author(s):  
Emanuel Gafton ◽  
Stephan Rosswog
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Impact Parameter ◽  
Relativistic Effects ◽  
Momentum Spread ◽  
Tidal Forces ◽  
Wide Range ◽  
Tidal Disruptions ◽  
Self Gravity ◽  
The Impact

Abstract We present the results of relativistic smoothed particle hydrodynamics simulations of tidal disruptions of stars by rotating supermassive black holes, for a wide range of impact parameters and black hole spins. For deep encounters, we find that: relativistic precession creates debris geometries impossible to obtain with the Newtonian equations; part of the fluid can be launched on plunging orbits, reducing the fallback rate and the mass of the resulting accretion disc; multiple squeezings and bounces at periapsis may generate distinctive X-ray signatures resulting from the associated shock breakout; disruptions can occur inside the marginally bound radius, if the angular momentum spread launches part of the debris on non-plunging orbits. Perhaps surprisingly, we also find relativistic effects important in partial disruptions, where the balance between self-gravity and tidal forces is so precarious that otherwise minor relativistic effects can have decisive consequences on the stellar fate. In between, where the star is fully disrupted but relativistic effects are mild, the difference resides in a gentler rise of the fallback rate, a later and smaller peak, and longer return times. However, relativistic precession always causes thicker debris streams, both in the bound part (speeding up circularization) and in the unbound part (accelerating and enhancing the production of separate transients). We discuss various properties of the disruption (compression at periapsis, shape and spread of the energy distribution) and potential observables (peak fallback rate, times of rise and decay, duration of super-Eddington fallback) as a function of the impact parameter and the black hole spin.

scholarly journals X-ray properties of reverberation-mapped AGNs with super-Eddington accreting massive black holes

2019 ◽  
Vol 15 (S356) ◽  
pp. 143-143
Author(s):  
Jaya Maithil ◽  
Michael S. Brotherton ◽  
Bin Luo ◽  
Ohad Shemmer ◽  
Sarah C. Gallagher ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Accretion Rate ◽  
Time Lags ◽  
Black Hole Mass ◽  
Host Galaxies ◽  
Massive Black Holes ◽  
X Ray ◽  
Photon Index ◽  
The Impact

AbstractActive Galactic Nuclei (AGN) exhibit multi-wavelength properties that are representative of the underlying physical processes taking place in the vicinity of the accreting supermassive black hole. The black hole mass and the accretion rate are fundamental for understanding the growth of black holes, their evolution, and the impact on the host galaxies. Recent results on reverberation-mapped AGNs show that the highest accretion rate objects have systematic shorter time-lags. These super-Eddington accreting massive black holes (SEAMBHs) show BLR size 3-8 times smaller than predicted by the Radius-Luminosity (R-L) relationship. Hence, the single-epoch virial black hole mass estimates of highly accreting AGNs have an overestimation of a factor of 3-8 times. SEAMBHs likely have a slim accretion disk rather than a thin disk that is diagnostic in X-ray. I will present the extreme X-ray properties of a sample of dozen of SEAMBHs. They indeed have a steep hard X-ray photon index, Γ, and demonstrate a steeper power-law slope, ασx.

scholarly journals 2.4. Collisional stellar dynamics around a central galactic black hole

1998 ◽  
Vol 184 ◽  
pp. 65-66
Author(s):  
Marc Freitag ◽  
Willy Benz
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Stellar Dynamics ◽  
Stellar Cluster ◽  
Stellar Collisions ◽  
Galactic Black Hole ◽  
Tidal Disruptions

Massive but invisible black holes (BH) are often assumed to lurk in the center of many galaxies but definitive proof of their existence has not yet been established. However, in the surrounding stellar cluster stars are unavoidably being destroyed by tidal disruptions and stellar collisions liberating of order 1M⊙ in each event. The subsequent accretion of this gas by the BH could bring it back to “life” and reveal its presence.

scholarly journals Quasar Mass Functions Across Cosmic Time

2009 ◽  
Vol 5 (S267) ◽  
pp. 239-247
Author(s):  
Marianne Vestergaard
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmic Time ◽  
Wide Range ◽  
Mass Functions ◽  
Black Hole Masses ◽  
Cosmic History

AbstractI present mass functions of actively accreting black holes detected in different quasar surveys which in concert cover a wide range of cosmic history. I briefly address what we learn from these mass functions. I summarize the motivation for such a study and the methods by which we determine black hole masses.

scholarly journals Global embeddings and hydrodynamic properties of Kerr black hole

2016 ◽  
Vol 31 (35) ◽  
pp. 1650204
Author(s):  
Soon-Tae Hong
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Equatorial Plane ◽  
Kerr Black Hole ◽  
Kerr Spacetime ◽  
Stable Circular Orbit ◽  
Massive Particles ◽  
Flat Embedding ◽  
Bound Orbits ◽  
The Impact

In the presence of a rotating Kerr black hole, we investigate hydrodynamics of the massive particles and massless photons to construct relations among number density, pressure and internal energy density of the massive particles and photons around the rotating Kerr black hole and to study an accretion onto the black hole. On equatorial plane of the Kerr black hole, we investigate the bound orbits of the massive particles and photons around the black hole to produce their radial, azimuthal and precession frequencies. With these frequencies, we study the black holes GRO J1655-40 and 4U 1543-47 to explicitly obtain the radial, azimuthal and precession frequencies of the massive particles in the flow of perfect fluid. We next consider the massive particles in the stable circular orbit of radius of 1.0 ly around the supernovas SN 1979C, SN 1987A and SN 2213-1745 in the Kerr curved spacetime, and around the potential supermassive Schwarzschild black holes M87, NGC 3115, NGC 4594, NGC 3377, NGC 4258, M31, M32 and Galatic center, to estimate their radial and azimuthal frequencies, which are shown to be the same results as those in no precession motion. The photon unstable orbit is also discussed in terms of the impact parameter of the photon trajectory. Finally, on the equatorial plane of the Kerr black hole, we construct the global flat embedding structures possessing (9 + 3) dimensionalities outside and inside the event horizon of the rotating Kerr black hole. Moreover, on the plane, we investigate the warp products of the Kerr spacetime.

scholarly journals Low-Complexity Security Algorithm Again Black-hole Attacking Node Considering Energy Balance for WSNs

2020 ◽  
Vol 18 (4.2) ◽  
pp. 26
Author(s):  
Phat Nguyen Huu
Keyword(s):  
Black Hole ◽  
Ad Hoc ◽  
Low Complexity ◽  
Network Simulator ◽  
Radio Waves ◽  
Rest Energy ◽  
Attack Model ◽  
Wired Networks ◽  
Wide Range ◽  
The Impact

Wireless sensor network (WSN) is a network through radio waves to link a large number of unevenly distributed nodes on a wide range of areas for the purpose of sensing, processing and collecting data.The data transmitted in WSNs is usually sensitive that needs to be protected. WSNs are more vulnerable to attacks due to network characteristics such as wireless transmission, changing network topologies, computing power, limited memory and power of nodes comparing to wired networks. There are many types of attacks on WSNs such as sinkhole attacks, data integrity attacks, wormhole attacks, Black hole attacks, etc. In this article, we will evaluate the impact of Black-hole attacks in the WSN network when using the AODV routing protocol (Ad-hoc On-demand Distance Vector routing). The Black hole attack model will be simulated by Network Simulator 2 (NS-2) by the number of lost packets by counting the number of packets sent by the sending node, receiving packets to destination, and rest energy of the nodes in two cases.

scholarly journals Probing correlation between photon orbits and phase structure of charged AdS black hole in massive gravity background

2019 ◽  
Vol 34 (35) ◽  
pp. 1950231 ◽  
Author(s):  
M. Chabab ◽  
H. El Moumni ◽  
S. Iraoui ◽  
K. Masmar
Keyword(s):  
Phase Transition ◽  
Black Holes ◽  
Black Hole ◽  
Phase Structure ◽  
Black Hole Solution ◽  
Massive Gravity ◽  
Direct Link ◽  
De Sitter ◽  
Thermodynamic Phase ◽  
The Impact

The phase structure of charged anti-de Sitter black hole in massive gravity is investigated using the unstable circular photon orbits formalism, concretely we establish a direct link between the null geodesics and the critical behavior thermodynamic of such black hole solution. Our analysis reveals that the radius and the impact parameter corresponding to the unstable circular orbits can be used to probe the thermodynamic phase structure. We also show that the latter are key quantities to characterize the order of Van der Waals-like phase transition. Namely, we found a critical exponent around [Formula: see text]. All these results support further that the photon trajectories can be used as a useful and crucial tool to probe the thermodynamic black holes criticality.

Further selected solutions

2020 ◽  
pp. 200-258
Author(s):  
Piotr T. Chruściel
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
De Sitter ◽  
Stationary Black Hole ◽  
Static Vacuum ◽  
Black Hole Spacetimes ◽  
Wide Range ◽  
Dimensional Black Hole ◽  
Horizon Topology ◽  
Basic Features

In previous chapters we presented the key notions associated with stationary black-hole spacetimes, as well as the minimal set of metrics needed to illustrate the basic features of the world of black holes. In this chapter we present some further black holes, selected because of their physical and mathematical interest. We start, in Section 5.1, with the Kerr–de Sitter/anti-de Sitter metrics, the cosmological counterparts of the Kerr metrics. Section 5.2 contains a description of the Kerr–Newman–de Sitter/anti-de Sitter metrics, which are the charged relatives of the metrics presented in Section 5.1. In Section 5.3 we analyse in detail the global structure of the Emparan–Reall ‘black rings’: these are five-dimensional black-hole spacetimes with R × S 1 × S 2-horizon topology. The Rasheed metrics of Section 5.4 provide an example of black holes arising in Kaluza–Klein theories. The Birmingham family of metrics, presented in Section 5.5, forms the most general class known of explicit static vacuum metrics with cosmological constant in all dimensions, with a wide range of horizon topologies.

scholarly journals CLASSICAL AND QUANTUM SCATTERING OF MAXIMALLY CHARGED DILATON BLACK HOLES

1993 ◽  
Vol 02 (01) ◽  
pp. 59-77 ◽  
Author(s):  
KIYOSHI SHIRAISHI
Keyword(s):  
Black Holes ◽  
Impact Parameter ◽  
Critical Value ◽  
Quantum Scattering ◽  
Dilaton Coupling ◽  
The Impact ◽  
Dilaton Black Holes

The classical and the quantum scattering of two maximally-charged dilaton black holes which have low velocities are studied. We find a critical value for the dilaton coupling, a2=1/3. For a2>1/3, two black holes are always scattered away and never coalesce together, regardless of the value of the impact parameter.

scholarly journals The Radio Scream from black holes at Cosmic Dawn: a semi-analytic model for the impact of radio-loud black holes on the 21 cm global signal

2019 ◽  
Vol 492 (4) ◽  
pp. 6086-6104 ◽  
Author(s):  
Aaron Ewall-Wice ◽  
Tzu-Ching Chang ◽  
T Joseph W Lazio
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Point Sources ◽  
Absorption Feature ◽  
Analytic Model ◽  
Supermassive Black Hole ◽  
Global Signal ◽  
Deep Point ◽  
Large Populations ◽  
The Impact

ABSTRACT We use a semi-analytic model to explore the potential impact of a brief and violent period of radio-loud accretion on to black holes (The Radio Scream) during the Cosmic Dawn on the H i hyperfine 21 cm signal. We find that radio emission from supermassive black hole seeds can impact the global 21 cm signal at the level of tens to hundreds of per cent provided that they were as radio loud as $z$ ≈ 1 black holes and obscured by gas with column depths of NH ≳ 1023 cm−2. We determine plausible sets of parameters that reproduce some of the striking features of the EDGES absorption feature including its depth, timing, and side steepness while producing radio/X-ray backgrounds and source counts that are consistent with published limits. Scenarios yielding a dramatic 21 cm signature also predict large populations of ∼$\mu$Jy point sources that will be detectable in future deep surveys from the Square Kilometer Array (SKA). Thus, 21 cm measurements, complemented by deep point-source surveys, have the potential to constrain optimistic scenarios where supermassive black hole progenitors were radio loud.

scholarly journals ALMA observations of molecular tori around massive black holes

2019 ◽  
Vol 623 ◽  
pp. A79 ◽  
Author(s):  
F. Combes ◽  
S. García-Burillo ◽  
A. Audibert ◽  
L. Hunt ◽  
A. Eckart ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Spatial Resolution ◽  
Center Of Mass ◽  
Host Galaxy ◽  
Molecular Outflow ◽  
Wide Range ◽  
Liner Galaxies ◽  
Circumnuclear Disk ◽  
Sphere Of Influence

We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO(3-2) emission in a sample of seven Seyfert/LINER galaxies at the unprecedented spatial resolution of 0.″1 = 4−8 pc. Our aim is to explore the close environment of active galactic nuclei (AGN), and the dynamical structures leading to their fueling, through the morphology and kinematics of the gas inside the sphere of influence of the black hole. The selected galaxies host low-luminosity AGN and have a wide range of activity types (Seyferts 1 to 2, LINERs), and barred or ringed morphologies. The observed maps reveal the existence of circumnuclear disk structures, defined by their morphology and decoupled kinematics, in most of the sample. We call these structures molecular tori, even though they often appear as disks without holes in the center. They have varying orientations along the line of sight, unaligned with the host galaxy orientation. The radius of the tori ranges from 6 to 27 pc, and their mass from 0.7 × 107 to 3.9 × 107 M⊙. The most edge-on orientations of the torus correspond to obscured Seyferts. In only one case (NGC 1365), the AGN is centered on the central gas hole of the torus. On a larger scale, the gas is always piled up in a few resonant rings 100 pc in scale that play the role of a reservoir to fuel the nucleus. In some cases, a trailing spiral is observed inside the ring, providing evidence for feeding processes. More frequently, the torus and the AGN are slightly off-centered with respect to the bar-resonant ring position, implying that the black hole is wandering by a few 10 pc amplitude around the center of mass of the galaxy. Our spatial resolution allows us to measure gas velocities inside the sphere of influence of the central black holes. By fitting the observations with different simulated cubes, varying the torus inclination and the black hole mass, it is possible to estimate the mass of the central black hole, which is in general difficult for such late-type galaxies, with only a pseudo-bulge. In some cases, AGN feedback is revealed through a molecular outflow, which will be studied in detail in a subsequent article.

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