scholarly journals Transonic structure of slowly rotating accretion flows with shocks around black holes

2016 ◽  
Vol 12 (S324) ◽  
pp. 23-26
Author(s):  
Petra Suková ◽  
Szymon Charzyński ◽  
Agnieszka Janiuk
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Time Scale ◽  
Mass Scale ◽  
Schwarzschild Black Hole ◽  
Transonic Flows ◽  
Accretion Flows ◽  
2D Structure ◽  
Sgr A

AbstractWe present recent results of the studies of low angular momentum accretion of matter onto Schwarzschild black hole using fully relativistic numerical simulations. We compare the resulting 2D structure of transonic flows with results of 1D pseudo-Newtonian computations of non-magnetized flow. The research has observable consequences on black holes on the whole mass scale, in particular it is related to the time-scale and shape of luminosity flares in Sgr A* or to the evolution of QPO frequency during outbursts of microquasars.

scholarly journals Transonic accretion and winds around Pseudo-Kerr black holes andcomparison with general relativistic solutions

2022 ◽  
Author(s):  
Abhrajit Bhattacharjee ◽  
Sandip Kumar Chakrabarti ◽  
Dipak Debnath
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Time Scale ◽  
Momentum Equation ◽  
Accretion Flows ◽  
Timing Properties ◽  
Surrounding Space ◽  
General Relativistic ◽  
Corotating Frame

Abstract Spectral and timing properties of accretion flows on a black hole depend on their density and temperature distributions, which, in turn come from the underlying dynamics. Thus, an accurate description of the flow which includes hydrodynamics and radiative transfer is a must to interpret the observational results. In the case of non-rotating black holes, Pseudo- Newtonian description of surrounding space-time enables one to make a significant progress in predicting spectral and timing properties. This formalism is lacking for the spinning black holes. In this paper, we show that there exists an exact form of ‘natural’ potential derivable from the general relativistic (GR) radial momentum equation written in the local corotating frame. Use of this potential in an otherwise Newtonian set of equations, allows us to describe transonic flows very accurately as is evidenced by comparing with solutions obtained from the full GR framework. We study the properties of the sonic points and the centrifugal pressure supported shocks in the parameter space spanned by the specific energy and the angular momentum, and compare with the results of GR hydrodynamics. We show that this potential can safely be used for the entire range of Kerr parameter −1 < a < 1 for modeling of observational results around spinning black holes. We assume the flow to be inviscid. Thus, it is non-dissipative with constant energy and angular momentum. These assumptions are valid very close to the black hole horizon as the infall time scale is much shorter as compared to the viscous time scale.

scholarly journals QUASINORMAL MODES AND LATE-TIME TAILS OF CANONICAL ACOUSTIC BLACK HOLES

2007 ◽  
Vol 16 (07) ◽  
pp. 1211-1218 ◽  
Author(s):  
PING XI ◽  
XIN-ZHOU LI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Wave Propagation ◽  
Angular Momentum ◽  
Numerical Method ◽  
Time Scale ◽  
Quasinormal Modes ◽  
Late Time ◽  
Classical Wave ◽  
Acoustic Black Holes

In this paper, we investigate the evolution of classical wave propagation in the canonical acoustic black hole by a numerical method and discuss the details of the tail phenomenon. The oscillating frequency and damping time scale both increase with the angular momentum l. For lower l, numerical results show the lowest WKB approximation gives the most reliable result. We also find that the time scale of the interim region from ringing to tail is not affected obviously by changing l.

scholarly journals The formation of bulges and black holes: lessons from a census of active galaxies in the SDSS

2005 ◽  
Vol 363 (1828) ◽  
pp. 621-643 ◽  
Author(s):  
Guinevere Kauffmann ◽  
Timothy M. Heckman
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Emission Line ◽  
Time Scale ◽  
Mass Scale ◽  
Growth Time ◽  
Normal Galaxies ◽  
Black Hole Accretion ◽  
Order Of Magnitude ◽  
Hole Accretion

We examine the relationship between galaxies, supermassive black holes and AGN using a sample of 23 000 narrow–emission–line (‘type 2’) active galactic nuclei (AGN) drawn from a sample of 123 000 galaxies from the Sloan Digital Sky Survey. We have studied how AGN host properties compare with those of normal galaxies and how they depend on the luminosity of the active nucleus. We find that AGN reside in massive galaxies and have distributions of sizes and concentrations that are similar to those of the early–type galaxies in our sample. The host galaxies of low–luminosity AGN have stellar populations similar to normal early types. The hosts of highluminosity AGN have much younger mean stellar ages, and a significant fraction have experienced recent starbursts. High–luminosity AGN are also found in lower–density environments. We then use the stellar velocity dispersions of the AGN hosts to estimate black hole masses and their [OIII]λ5007 emission–line luminosities to estimate black hole accretion rates.We find that the volume averaged ratio of star formation to black hole accretion is ∼1000 for the bulge–dominated galaxies in our sample. This is remarkably similar to the observed ratio of stellar mass to black hole mass in nearby bulges. Most of the present–day black hole growth is occurring in black holes with masses less than 3 × 10 7 M ⊙. Our estimated accretion rates imply that low–mass black holes are growing on a time–scale that is comparable with the age of the Universe. Around 50% this growth takes place in AGN that are radiating within a factor of five of the Eddington luminosity. Such systems are rare, making up only 0.2% of the lowmass black hole population at the present day. The remaining growth occurs in lower luminosity AGN. The growth time–scale increases by more than an order of magnitude for the most massive black holes in our sample. We conclude that the evolution of the AGN luminosity function documented in recent optical and X–ray surveys is driven by a decrease in the characteristic mass scale of actively accreting black holes.

scholarly journals Gravitational lensing by a quantum deformed Schwarzschild black hole

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Xu Lu ◽  
Yi Xie
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Renormalization Group ◽  
Gravitational Lensing ◽  
Galactic Center ◽  
Supermassive Black Holes ◽  
Quantum Deformation ◽  
Schwarzschild Black Hole ◽  
Sgr A

AbstractWe investigate the weak and strong deflection gravitational lensing by a quantum deformed Schwarzschild black hole and find their observables. These lensing observables are evaluated and the detectability of the quantum deformation is assessed, after assuming the supermassive black holes Sgr A* and M87* respectively in the Galactic Center and at the center of M87 as the lenses. We also intensively compare these findings with those of a renormalization group improved Schwarzschild black hole and an asymptotically safe black hole. We find that, among these black holes, it is most likely to test the quantum deformed Schwarzschild black hole via its weak deflection lensing observables in the foreseen future.

scholarly journals Gaseous Disks in the Nuclei of Elliptical Galaxies

1997 ◽  
Vol 163 ◽  
pp. 620-625 ◽  
Author(s):  
H. Ford ◽  
Z. Tsvetanov ◽  
L. Ferrarese ◽  
G. Kriss ◽  
W. Jaffe ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Elliptical Galaxies ◽  
Central Mass ◽  
Massive Black Holes ◽  
Radio Jets

AbstractHST images have led to the discovery that small (r ~ 1″ r ~ 100 – 200 pc), well-defined, gaseous disks are common in the nuclei of elliptical galaxies. Measurements of rotational velocities in the disks provide a means to measure the central mass and search for massive black holes in the parent galaxies. The minor axes of these disks are closely aligned with the directions of the large–scale radio jets, suggesting that it is angular momentum of the disk rather than that of the black hole that determines the direction of the radio jets. Because the disks are directly observable, we can study the disks themselves, and investigate important questions which cannot be directly addressed with observations of the smaller and unresolved central accretion disks. In this paper we summarize what has been learned to date in this rapidly unfolding new field.

Bound orbits around modified Hayward black holes

2021 ◽  
Author(s):  
Bo Gao ◽  
Xue-Mei Deng
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Gravitational Field ◽  
Periodic Orbits ◽  
Kerr Black Hole ◽  
Periodic Oscillations ◽  
Test Particles ◽  
Spin Parameter ◽  
Bound Orbits

The neutral time-like particle’s bound orbits around modified Hayward black holes have been investigated. We find that both in the marginally bound orbits (MBO) and the innermost stable circular orbits (ISCO), the test particle’s radius and its angular momentum are all more sensitive to one of the parameters [Formula: see text]. Especially, modified Hayward black holes with [Formula: see text] could mimic the same ISCO radius around the Kerr black hole with the spin parameter up to [Formula: see text]. Small [Formula: see text] could mimic the ISCO of small-spinning test particles around Schwarzschild black holes. Meanwhile, rational (periodic) orbits around modified Hayward black holes have also been studied. The epicyclic frequencies of the quasi-circular motion around modified Hayward black holes are calculated and discussed with respect to the observed Quasi-periodic oscillations (QPOs) frequencies. Our results show that rational orbits around modified Hayward black holes have different values of the energy from the ones of Schwarzschild black holes. The epicyclic frequencies in modified Hayward black holes have different frequencies from Schwarzschild and Kerr ones. These might provide hints for distinguishing modified Hayward black holes from Schwarzschild and Kerr ones by using the dynamics of time-like particles around the strong gravitational field.

Accretion onto a Black Hole

2014 ◽  
Author(s):  
Charles D. Bailyn
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Gas Flow ◽  
Gravitational Potential Energy ◽  
Spherically Symmetric ◽  
Potential Well ◽  
Accretion Flows ◽  
Flow Geometry

This chapter explores the ways that accretion onto a black hole produces energy and radiation. As material falls into a gravitational potential well, energy is transformed from gravitational potential energy into other forms of energy, so that total energy is conserved. Observing such accretion energy is one of the primary ways that astrophysicists pinpoint the locations of potential black holes. The spectrum and intensity of this radiation is governed by the geometry of the gas flow, the mass infall rate, and the mass of the accretor. The simplest flow geometry is that of a stationary object accreting mass equally from all directions. Such spherically symmetric accretion is referred to as Bondi-Hoyle accretion. However, accretion flows onto black holes are not thought to be spherically symmetric—the infall is much more frequently in the form of a flattened disk.

scholarly journals Shocks in relativistic viscous accretion flows around Kerr black holes

2019 ◽  
Vol 488 (2) ◽  
pp. 2412-2422 ◽  
Author(s):  
Indu K Dihingia ◽  
Santabrata Das ◽  
Debaprasad Maity ◽  
Anuj Nandi
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Shock Front ◽  
Critical Point ◽  
Parameter Space ◽  
Accretion Flows ◽  
Flow Parameters ◽  
Flow Motion ◽  
Present Formalism ◽  
Kerr Black Holes

ABSTRACT We study the relativistic viscous accretion flows around the Kerr black holes. We present the governing equations that describe the steady-state flow motion in full general relativity and solve them in 1.5D to obtain the complete set of global transonic solutions in terms of the flow parameters, namely specific energy (${\mathcal E}$), specific angular momentum (${\mathcal L}$), and viscosity (α). We obtain a new type of accretion solution which was not reported earlier. Further, we show for the first time to the best of our knowledge that viscous accretion solutions may contain shock waves particularly when flow simultaneously passes through both inner critical point (rin) and outer critical point (rout) before entering into the Kerr black holes. We examine the shock properties, namely shock location (rs) and compression ratio (R, the measure of density compression across the shock front) and show that shock can form for a large region of parameter space in ${\cal L}\!-\!{\cal E}$ plane. We study the effect of viscous dissipation on the shock parameter space and find that parameter space shrinks as α is increased. We also calculate the critical viscosity parameter (αcri) beyond which standing shock solutions disappear and examine the correlation between the black hole spin (ak) and αcri. Finally, the relevance of our work is conferred where, using rs and R, we empirically estimate the oscillation frequency of the shock front (νQPO) when it exhibits quasi-periodic (QP) variations. The obtained results indicate that the present formalism seems to be potentially viable to account for the QPO frequency in the range starting from milli-Hz to kilo-Hz as $0.386~{\rm Hz}\le \nu _{\mathrm{ QPO}} (\frac{10\, \mathrm{M}_\odot }{M_{\mathrm{ BH}}}) \le 1312$ Hz for ak = 0.99, where MBH stands for the black hole mass.

scholarly journals WHAT IS THE TOPOLOGY OF A SCHWARZSCHILD BLACK HOLE?

2012 ◽  
Vol 18 ◽  
pp. 125-129 ◽  
Author(s):  
EDMUNDO M. MONTE
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Space Time ◽  
Higher Dimension ◽  
Schwarzschild Black Hole

We investigate the topology of Schwarzschild's black holes through the immersion of this space-time in space of higher dimension. Through the immersions of Kasner and Fronsdal we calculate the extension of the Schwarzschilds black hole.

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