TWO FAMILIES OF EXACT DISKS WITH A CENTRAL BLACK HOLE

The gravitational field of a configuration formed by a static disk and a Schwarzschild black hole is analysed for two families of disks. The matter of the disks is made of counter-rotating particles with as many particles rotating to one side as to the other, in such a way that the net angular momentum is zero and the disk is static. The first family consists of peculiar disks, in the sense that they are generated by two opposite dipoles. The particles of the disk have no pressure or centrifugal support. However, when there is a central black hole, centrifugal balance in the form of counter-rotation appears. The second family is a one parameter family of self-similar disks which includes at one end a Newtonian disk, and at the other a topological defect of spacetime. The presence of the black hole impresses more rotational velocity to the particles. These two families are of infinite extent. Some interesting physical effects are studied.

Download Full-text

X-Ray Observations of M32 with ASCA

Symposium - International Astronomical Union ◽

10.1017/s0074180900115190 ◽

1998 ◽

Vol 188 ◽

pp. 291-292

Author(s):

T. Toneri ◽

K. Hayashida ◽

M. Loewenstein

Keyword(s):

Black Hole ◽

Mass Concentration ◽

Elliptical Galaxy ◽

Broad Band ◽

The Other ◽

Central Black Hole ◽

Massive Black Hole ◽

X Ray ◽

Eddington Limit

M32 is the nearest dwarf elliptical galaxy. Its center is known to have a mass concentration of 3 × 106 M⊙, which is usually interpreted as an evidence of a super massive black hole. We observed M32 with ASCA two times in July and August of 1996. An X-ray source was detected at the center of M32 and its first broad-band X-ray spectra were obtained. ASCA observations of M32 limit the activity of the central black hole to be less than 10−6 times of the Eddington limit. We also found two other bright sources within 12 arcmin from the M32 center. One is the newly appeared X-ray source and the other is G144. In this paper, we summarize the results on the new source and G144. For M32, please refer to the publication (Loewenstein et al. 1997).

Download Full-text

The Double Nucleus and Central Black Hole of M31

The Astrophysical Journal ◽

10.1086/307665 ◽

1999 ◽

Vol 522 (2) ◽

pp. 772-792 ◽

Cited By ~ 96

Author(s):

John Kormendy ◽

Ralf Bender

Keyword(s):

Black Hole ◽

Central Black Hole ◽

Double Nucleus

Download Full-text

Black Hole Algorithm for Sustainable Design of Counterfort Retaining Walls

Sustainability ◽

10.3390/su12072767 ◽

2020 ◽

Vol 12 (7) ◽

pp. 2767 ◽

Cited By ~ 13

Author(s):

Víctor Yepes ◽

José V. Martí ◽

José García

Keyword(s):

Black Hole ◽

Sustainable Design ◽

Retaining Walls ◽

The Other ◽

Trade Off ◽

Construction Company ◽

Geometric Variables ◽

The Stability ◽

The Cost ◽

Black Hole Algorithm

The optimization of the cost and CO 2 emissions in earth-retaining walls is of relevance, since these structures are often used in civil engineering. The optimization of costs is essential for the competitiveness of the construction company, and the optimization of emissions is relevant in the environmental impact of construction. To address the optimization, black hole metaheuristics were used, along with a discretization mechanism based on min–max normalization. The stability of the algorithm was evaluated with respect to the solutions obtained; the steel and concrete values obtained in both optimizations were analyzed. Additionally, the geometric variables of the structure were compared. Finally, the results obtained were compared with another algorithm that solved the problem. The results show that there is a trade-off between the use of steel and concrete. The solutions that minimize CO 2 emissions prefer the use of concrete instead of those that optimize the cost. On the other hand, when comparing the geometric variables, it is seen that most remain similar in both optimizations except for the distance between buttresses. When comparing with another algorithm, the results show a good performance in optimization using the black hole algorithm.

Download Full-text

Wandering of the central black hole in a galactic nucleus and correlation of the black hole mass with the bulge mass

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psab009 ◽

2021 ◽

Author(s):

Hajime Inoue

Keyword(s):

Black Hole ◽

Loss Rate ◽

Energy Gain ◽

Stellar Disk ◽

Black Hole Mass ◽

Central Black Hole ◽

Massive Black Hole ◽

Stellar Cluster ◽

Upper Limit ◽

Simple Parameter

Abstract We investigate a mechanism for a super-massive black hole at the center of a galaxy to wander in the nucleus region. A situation is supposed in which the central black hole tends to move by the gravitational attractions from the nearby molecular clouds in a nuclear bulge but is braked via the dynamical frictions from the ambient stars there. We estimate the approximate kinetic energy of the black hole in an equilibrium between the energy gain rate through the gravitational attractions and the energy loss rate through the dynamical frictions in a nuclear bulge composed of a nuclear stellar disk and a nuclear stellar cluster as observed from our Galaxy. The wandering distance of the black hole in the gravitational potential of the nuclear bulge is evaluated to get as large as several 10 pc, when the black hole mass is relatively small. The distance, however, shrinks as the black hole mass increases, and the equilibrium solution between the energy gain and loss disappears when the black hole mass exceeds an upper limit. As a result, we can expect the following scenario for the evolution of the black hole mass: When the black hole mass is smaller than the upper limit, mass accretion of the interstellar matter in the circumnuclear region, causing the AGN activities, makes the black hole mass larger. However, when the mass gets to the upper limit, the black hole loses the balancing force against the dynamical friction and starts spiraling downward to the gravity center. From simple parameter scaling, the upper mass limit of the black hole is found to be proportional to the bulge mass, and this could explain the observed correlation of the black hole mass with the bulge mass.

Download Full-text

Isothermal Bondi Accretion in Two-component Jaffe Galaxies with a Central Black Hole

The Astrophysical Journal ◽

10.3847/1538-4357/aae97d ◽

2018 ◽

Vol 868 (2) ◽

pp. 91 ◽

Cited By ~ 4

Author(s):

Luca Ciotti ◽

Silvia Pellegrini

Keyword(s):

Black Hole ◽

Central Black Hole ◽

Two Component

Download Full-text

The Merger Rate of Black Holes in a Primordial Black Hole Cluster

Physics ◽

10.3390/physics3020026 ◽

2021 ◽

Vol 3 (2) ◽

pp. 372-378

Author(s):

Viktor D. Stasenko ◽

Alexander A. Kirillov

Keyword(s):

Black Holes ◽

Black Hole ◽

Mass Spectrum ◽

Star Clusters ◽

Primordial Black Hole ◽

Primordial Black Holes ◽

Central Black Hole ◽

Solar Mass ◽

Merger Rate

In this paper, the merger rate of black holes in a cluster of primordial black holes (PBHs) is investigated. The clusters have characteristics close to those of typical globular star clusters. A cluster that has a wide mass spectrum ranging from 10−2 to 10M⊙ (Solar mass) and contains a massive central black hole of the mass M•=103M⊙ is considered. It is shown that in the process of the evolution of cluster, the merger rate changed significantly, and by now, the PBH clusters have passed the stage of active merging of the black holes inside them.

Download Full-text

Refining the mass estimate for the intermediate-mass black hole candidate in NGC 3319

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2021.23 ◽

2021 ◽

Vol 38 ◽

Author(s):

Benjamin L. Davis ◽

Alister W. Graham

Keyword(s):

Black Holes ◽

Black Hole ◽

Meta Analysis ◽

Rotational Velocity ◽

Logarithmic Spiral ◽

Star Cluster ◽

Black Hole Mass ◽

Intermediate Mass ◽

Mass Scaling ◽

Cluster Mass

Abstract Recent X-ray observations by Jiang et al. have identified an active galactic nucleus (AGN) in the bulgeless spiral galaxy NGC 3319, located just $14.3\pm 1.1$ Mpc away, and suggest the presence of an intermediate-mass black hole (IMBH; $10^2\leq M_\bullet/\textrm{M}_{\odot}\leq 10^5$ ) if the Eddington ratios are as high as 3 to $3\times10^{-3}$ . In an effort to refine the black hole mass for this (currently) rare class of object, we have explored multiple black hole mass scaling relations, such as those involving the (not previously used) velocity dispersion, logarithmic spiral arm pitch angle, total galaxy stellar mass, nuclear star cluster mass, rotational velocity, and colour of NGC 3319, to obtain 10 mass estimates, of differing accuracy. We have calculated a mass of $3.14_{-2.20}^{+7.02}\times10^4\,\textrm{M}_\odot$ , with a confidence of 84% that it is $\leq $ $10^5\,\textrm{M}_\odot$ , based on the combined probability density function from seven of these individual estimates. Our conservative approach excluded two black hole mass estimates (via the nuclear star cluster mass and the fundamental plane of black hole activity—which only applies to black holes with low accretion rates) that were upper limits of ${\sim}10^5\,{\textrm M}_{\odot}$ , and it did not use the $M_\bullet$ – $L_{\textrm 2-10\,\textrm{keV}}$ relation’s prediction of $\sim$ $10^5\,{\textrm M}_{\odot}$ . This target provides an exceptional opportunity to study an IMBH in AGN mode and advance our demographic knowledge of black holes. Furthermore, we introduce our novel method of meta-analysis as a beneficial technique for identifying new IMBH candidates by quantifying the probability that a galaxy possesses an IMBH.

Download Full-text