scholarly journals Black holes formed by direct collapse: observational evidences

2016 ◽  
Vol 12 (S324) ◽  
pp. 303-306 ◽  
Author(s):  
I. F. Mirabel
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Three Dimensions ◽  
Binary Black Holes ◽  
Galactic Black Hole ◽  
X Ray Binaries ◽  
The Universe ◽  
Dimensions Of Space ◽  
Stellar Density

AbstractBinary black holes as the recently detected sources of gravitational waves can be formed from massive stellar binaries in the field or by dynamical interactions in clusters of high stellar density, if the black holes are the remnants of massive stars that collapsed without natal kicks that would disrupt the binary system or eject the black holes from the cluster before binary black hole formation. Here are summarized and discussed the kinematics in three dimensions of space of five Galactic black hole X-ray binaries. For Cygnus X-1 and GRS 1915+105 it is found that the black holes of ~15 M⊙ and ~10 M⊙ in these sources were formed in situ, without energetic kicks. These observations suggest that binary black holes with components of ~10 M⊙ may have been prolifically produced in the universe.

scholarly journals The black hole spin in coalescing binary black holes and high-mass X-ray binaries

2018 ◽  
Vol 14 (S346) ◽  
pp. 426-432
Author(s):  
Y. Qin ◽  
T. Fragos ◽  
G. Meynet ◽  
P. Marchant ◽  
V. Kalogera ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
High Spin ◽  
High Mass ◽  
Binary Black Holes ◽  
X Ray ◽  
Black Hole Spin ◽  
Spin Properties ◽  
X Ray Binaries

AbstractThe six LIGO detections of merging black holes (BHs) allowed to infer slow spin values for the two pre-merging BHs. The three cases where the spins of the BHs can be determined in high-mass X-ray binaries (HMXBs) show that those BHs have high spin values. We discuss here scenarios explaining these differences in spin properties in these two classes of object.

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 Black Holes in the Universe

1998 ◽  
Vol 11 (1) ◽  
pp. 28-41
Author(s):  
I.D. Novikov
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Stars ◽  
Supernova Explosions ◽  
The Universe

Some 30 years ago very few scientists thought that black holes may really exist. Attention focussed on the black hole hypothesis after neutron stars had been discovered. It was rather surprising that astrophysicists immediately ‘welcomed’ black holes. They found their place not only in the remnants of supernova explosions but also in the nuclei of galaxies and quasars.

scholarly journals Symmetry and the Arrow of Time in Theoretical Black Hole Astrophysics

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
David Garofalo
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Time Reversal ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Arrow Of Time ◽  
Time Symmetry ◽  
The Universe

While the basic laws of physics seem time-reversal invariant, our understanding of the apparent irreversibility of the macroscopic world is well grounded in the notion of entropy. Because astrophysics deals with the largest structures in the Universe, one expects evidence there for the most pronounced entropic arrow of time. However, in recent theoretical astrophysics work it appears possible to identify constructs with time-reversal symmetry, which is puzzling in the large-scale realm especially because it involves the engines of powerful outflows in active galactic nuclei which deal with macroscopic constituents such as accretion disks, magnetic fields, and black holes. Nonetheless, the underlying theoretical structure from which this accreting black hole framework emerges displays a time-symmetric harmonic behavior, a feature reminiscent of basic and simple laws of physics. While we may expect such behavior for classical black holes due to their simplicity, manifestations of such symmetry on the scale of galaxies, instead, surprise. In fact, we identify a parallel between the astrophysical tug-of-war between accretion disks and jets in this model and the time symmetry-breaking of a simple overdamped harmonic oscillator. The validity of these theoretical ideas in combination with this unexpected parallel suggests that black holes are more influential in astrophysics than currently recognized and that black hole astrophysics is a more fundamental discipline.

scholarly journals High-Mass X-ray Binaries: progenitors of double compact objects

2018 ◽  
Vol 14 (S346) ◽  
pp. 1-13
Author(s):  
Edward P. J. van den Heuvel
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Stars ◽  
Compact Objects ◽  
High Mass ◽  
X Ray ◽  
Future Evolution ◽  
Short Period ◽  
Orbital Periods ◽  
X Ray Binaries

AbstractA summary is given of the present state of our knowledge of High-Mass X-ray Binaries (HMXBs), their formation and expected future evolution. Among the HMXB-systems that contain neutron stars, only those that have orbital periods upwards of one year will survive the Common-Envelope (CE) evolution that follows the HMXB phase. These systems may produce close double neutron stars with eccentric orbits. The HMXBs that contain black holes do not necessarily evolve into a CE phase. Systems with relatively short orbital periods will evolve by stable Roche-lobe overflow to short-period Wolf-Rayet (WR) X-ray binaries containing a black hole. Two other ways for the formation of WR X-ray binaries with black holes are identified: CE-evolution of wide HMXBs and homogeneous evolution of very close systems. In all three cases, the final product of the WR X-ray binary will be a double black hole or a black hole neutron star binary.

scholarly journals The MEMO project: Combining all microlensing surveys to search for intermediate-mass Galactic black holes

2018 ◽  
Vol 618 ◽  
pp. L4 ◽  
Author(s):  
A. Mirhosseini ◽  
M. Moniez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Milky Way ◽  
Detection Efficiency ◽  
Large Magellanic Cloud ◽  
Detection Algorithm ◽  
Intermediate Mass ◽  
Detection Rates ◽  
Galactic Black Hole ◽  
The Individual

Aims. The microlensing surveys MACHO, EROS, MOA and OGLE (hereafter called MEMO) have searched for microlensing toward the Large Magellanic Cloud for a cumulated duration of 27 years. We study the potential of joining these databases to search for very massive objects, that produce microlensing events with a duration of several years. Methods. We identified the overlaps between the different catalogs and compiled their time coverage to identify common regions where a joint microlensing detection algorithm can operate. We extrapolated a conservative global microlensing detection efficiency based on simple hypotheses, and estimated detection rates for multi-year duration events. Results. Compared with the individual survey searches, we show that a combined search for long timescale microlensing should detect about ten more events caused by 100 M⊙ black holes if these objects have a major contribution to the Milky Way halo. Conclusions. Assuming that a common analysis is feasible, meaning that the difficulties that arise from using different passbands can be overcome, we show that the sensitivity of such an analysis might enable us to quantify the Galactic black hole component.

scholarly journals Gas filaments of the cosmic web located around active galaxies in a protocluster

Science ◽  
2019 ◽  
Vol 366 (6461) ◽  
pp. 97-100 ◽  
Author(s):  
H. Umehata ◽  
M. Fumagalli ◽  
I. Smail ◽  
Y. Matsuda ◽  
A. M. Swinbank ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Star Formation ◽  
Ionizing Radiation ◽  
Rest Frame ◽  
Active Galaxies ◽  
Intergalactic Gas ◽  
Supermassive Black Hole ◽  
The Universe ◽  
Intense Star Formation

Cosmological simulations predict that the Universe contains a network of intergalactic gas filaments, within which galaxies form and evolve. However, the faintness of any emission from these filaments has limited tests of this prediction. We report the detection of rest-frame ultraviolet Lyman-α radiation from multiple filaments extending more than one megaparsec between galaxies within the SSA22 protocluster at a redshift of 3.1. Intense star formation and supermassive black-hole activity is occurring within the galaxies embedded in these structures, which are the likely sources of the elevated ionizing radiation powering the observed Lyman-α emission. Our observations map the gas in filamentary structures of the type thought to fuel the growth of galaxies and black holes in massive protoclusters.

scholarly journals Gravitational waves from Population III binary black holes formed by dynamical capture

2020 ◽  
Vol 495 (2) ◽  
pp. 2475-2495 ◽  
Author(s):  
Boyuan Liu ◽  
Volker Bromm
Keyword(s):  
Black Holes ◽  
Binary Stars ◽  
First Generation ◽  
High Redshift ◽  
Ex Situ ◽  
Binary Black Holes ◽  
Formation Pathway ◽  
Einstein Telescope ◽  
Population Iii

ABSTRACT We use cosmological hydrodynamic simulations to study the gravitational wave (GW) signals from high-redshift binary black holes (BBHs) formed by dynamical capture (ex situ formation channel). We in particular focus on black holes (BHs) originating from the first generation of massive, metal-poor, so-called Population III (Pop III) stars. An alternative (in situ) formation pathway arises in Pop III binary stars whose GWligi signature has been intensively studied. In our optimistic model, we predict a local GW event rate density for ex situ BBHs (formed at z > 4) of ∼0.04 yr−1 Gpc−3. This is comparable to or even higher than the conservative predictions of the rate density for in situ BBHs ∼0.01–0.1 yr−1 Gpc−3, indicating that the ex situ formation channel may be as important as the in situ one for producing GW events. We also evaluate the detectability of our simulated GW events for selected planned GW instruments, such as the Einstein Telescope (ET). For instance, we find the all-sky detection rate with signal-to-noise ratios above 10 to be ${\lesssim} 100\, \rm {yr^{-1}}$ for the xylophone configuration of ET. However, our results are highly sensitive to the subgrid models for BBH identification and evolution, such that the GW event efficiency (rate) is reduced by a factor of 4 (20) in the pessimistic case. The ex situ channel of Pop III BBHs deserves further investigation with better modelling of the environments around Pop III-seeded BHs.

scholarly journals Formation of Low-Mass Black Hole X-Ray Transients

1998 ◽  
Vol 11 (2) ◽  
pp. 775-778
Author(s):  
Simon Portegies Zwart ◽  
Frank Verbunt ◽  
Ene Ergma
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Formation Rate ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

We study the formation of low-mass X-ray binaries with a black hole as accreting object. The performed semi-analytic analysis reveals that the formation rate of black holes in low-mass X-ray binaries is about two orders of magnitude smaller than that of systems with a neutron star as accretor. This is contradicted by the six observed systems, which are all transients, which suggest that the majority of these systems has not been seen jet. The birthrate for both type of objects are expected to be similar (for reviews see Cowley 1992, Tanaka & Lewin 1995).

The Odd Couple: Quasars & Black Holes

Daedalus ◽  
2014 ◽  
Vol 143 (4) ◽  
pp. 103-113 ◽  
Author(s):  
Scott Tremaine
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Solar System ◽  
Total Mass ◽  
Host Galaxy ◽  
The Sun ◽  
Central Black Hole ◽  
Frictional Forces ◽  
The Universe

Quasars emit more energy than any other object in the universe, yet are not much bigger than our solar system. Quasars are powered by giant black holes of up to ten billion (1010) times the mass of the sun. Their enormous luminosities are the result of frictional forces acting upon matter as it spirals toward the black hole, heating the gas until it glows. We also believe that black holes of one million to ten billion solar masses – dead quasars – are present at the centers of most galaxies, including our own. The mass of the central black hole appears to be closely related to other properties of its host galaxy, such as the total mass in stars, but the origin of this relation and the role that black holes play in the formation of galaxies are still mysteries.

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