Showing papers on "Binary black hole published in 1982"

Pancake detonation of stars by black holes in galactic nuclei

Abstract: Recent efforts to understand exotic phenomena in galactic nuclei commonly postulate the presence of a massive black hole accreting gas produced by tidal or collisional disruption of stars. For black holes in the mass range 104–107 M⊙, individual stars penetrating well inside the Roche radius will undergo compression to a short-lived pancake configuration very similar to that produced by a high velocity symmetric collision of the kind likely to occur in the neighbourhood of black holes in the higher mass range ≳109 M⊙. Thermonuclear energy release ensuing in the more extreme events may be sufficient to modify substantially the working of the entire accretion process.

Are there black holes in quasars

Abstract: There are two main theoretical models for the central engine of quasars and other active galactic nuclei: the black hole model and the spinar model. Observations of the time scales of flux variations can rule out the black hole model and are therefore extremely important. The widely accepted argument of Elliot and Shapiro1 states that the maximal luminosity of the nucleus is given by the Eddington limit, LEdd = 1038 (M/M⊙) ergs−1, and the minimal time scale for periodicity is given by tmin = (gravitational radius)/(velocity of light) = 10−5 (M/M⊙) s. Therefore, the observed time scale of variations t, and the luminosity L must obey log t >log L −43. Variations on a time scale shorter than that would rule out the black hole model. We point out here that this statement is wrong in view of recent developments in the accretion disk theory: much shorter periodicities are still consistent with the black hole model.

Star clusters containing massive central black holes. IV. Galactic tidal fields

Abstract: Monte Carlo simulations of star cluster evolution are presented. The Monte Carlo scheme described previously is modified to incorporate a Galactic tidal radius r/sub t/, beyond which stars are stripped from the cluster. It is found that the late stages of cluster evolution are qualitatively unchanged by the introduction of a finite tidal cutoff. For clusters without a massive, central black hole the core collapses homologously with homology parameters independent of r/sub t/ and consistent with the recent findings of Cohn and of Lynden-Bell and Eggleton. For clusters possessing a central black hole, core collapse is eventually reversed by the heat flux from stellar disruption by the hole. The system attains a quasi-stationary, expanding state (by which time the hole has grown to several thousand solar masses). This state appears to be (roughly) independent of (i) the initial hole mass, (ii) the time during core evolution at which the hole is introduced and (iii) the value of r/sub t/. A simple homological model for core evolution with and without black holes is presented. The dynamical effects of those stars which diffuse outward during core collapse but are ''reencompassed'' during core reexpansion are incorporated. Numerical integrations of the resulting homological equationsmore » are in good agreement with the Monte Carlo ''data.'' When the homological equations are modified to include stellar ejections from the cusp due to occasional close encounters, the results are qualitatively unchanged. This finding suggests that the effects of close encounters in star cusps around massive black holes might not substantially alter results obtained with the present (Fokker-Planck) Monte Carlo scheme.« less

The suppression of gravitational radiation from finite-size stars falling into black holes

Abstract: We show that the gravitational radiation emitted in a head-on collision between a finite-size star and a black hole can be substantially less than might be expected on the basis of results for point mass-black hole collisions.

A radiating metric for evaporating black holes

Abstract: The evaporating black hole is described by a radiating metric. It is shown that in this way a better description of the intermediate phases of the evaporation is possible.

Black Holes and the Origin of Radio Sources

Abstract: Powerful, extragalactic radio sources might be fuelled by energy release near a massive black hole. In this article we describe some relativistic effects which may be relevant to this process. We use Newtonian language so far as possible and illustrate the effects with “simple” analogies. Specifically, we describe the gravitational field near a black hole, Lens-Thirring and geodetic precession, electromagnetic energy extraction of the spin energy of a black hole and the structure of accretion tori around a black hole.

Positron production near a 106 M⊙ black hole

Abstract: The annihilation line coming from the direction of the galactic center may be produced by positrons originating from the magnetosphere of a ∠106 M⊙ black hole.

Active Galactic Nuclei and Particle Acceleration in Accretion Disks Around Massive Black Holes

Abstract: The nuclei of active galaxies are compact power sources, mainly non-thermal. Much of the energy is emitted in the form of X-rays and γ-rays, and also of synchrotron radiation at radio and infrared wavelengths. From these galactic nuclei, radio lobes, jets and high-speed clouds are expelled. The central power source has been interpreted using models that invoke an ultra-massive black hole or, alternatively, a spinar. We examine here the acceleration processes near a black hole. An accretion disk around supermassive black hole in the center of an active galactic nucleus is shown to be a likely site of particle acceleration. Electrons can be accelerated to relativistic energies by various electromagnetic processes as well as by purely gravitational processes (e.g. Penrose pair production). Protons are accelerated to very high energies by the following mechanisms: 1) stochastic Fermi acceleration, 2) betatron acceleration, and possibly 3) shock wave acceleration. We find that, depending on the confinement time for the protons, different galactic nuclei would contribute to different parts of the rigidity spectrum. Examining the magnetic field strengths in different disk models we find that the betatron process can boost particle momenta by some 4 orders of magnitude. Finally, if shock waves can be sustained in an accretion disk (for example if the disk has a corona around it, or if supersonic turbulence can be sustained), such shock waves would also accelerate particles to cosmic-ray energies. Neutrinos would be a useful experimental probe of these models, whereas gamma-ray observations would be more useful for electron acceleration processes.

Inhomogeneity of the early Universe and formation of primordial black holes

Abstract: The dynamic role of primordial black holes in the early Universe is examined in terms of their formation and properties of the mass distribution. Particular attention is given to the early density perturbations caused by the presence of black holes. The disturbances in matter distribution are suggested to have led to the formation of galaxies and galactic clusters.An epoch is defined in which the turbulent energy density and the gaseous component of primordial black holes could predominate over effects of the background matter. A non-Friedmann expansion of the Universe would then be possible. The mass spectrum is described in terms of deviations of a random field expressed as the averaged value of the random field or perturbations in a volume of specified radius. Three possible variations are suggested for the Carr-Hawking criteria for black hole formation.

A semiquantitative general-relativistic model of quasar Markarian 205 interpreted as a massive black hole ejected from NGC 4319

Abstract: In 1979 I developed a special-relativistic analysis explaining the discrepancy of observed redshifts of spiral NGC 4319 and its companion quasar Markarian 205 by considering besides the Lorentz time dilatation also the gravitational redshift due to the gravitational field of Markarian 205 interpreted in terms of accretion of mass onto a black hole ejected from NGC 4319. In the present paper, a general-relativistic analysis is given. Numerical results of the special and general theories do not differ from each other significantly and admit the conclusion that the radius,r, of the radiating region of Markarian 205 is of the order of the tidal radius of black hole. Several models for various values of the ratio ofr to the Schwarzschild radius,rs, are constructed. Models with 8.5≲r/rs≲8.7 seem to be most realistic. It becomes clear that the interpretation of quasars in terms of huge black holes accreting stars can explain, in principle, the observed redshifts of quasars ejected from parent galaxies.