Black Hole Accretion Dynamics in Numerical Simulations

Black Hole Accretion Dynamics in Numerical Simulations
Author: Kenneth B. Henisey
Publisher:
Total Pages: 70
Release: 2011
Genre:
ISBN: 9781267020055

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Light curves from accreting black hole systems exhibit variability which has neither been conclusively explained by analytic models nor seen in numerical simulations of these flows. Until recently, these computational studies have uniformly assumed alignment between the angular momenta of a black hole and its accretion disk. In contrast, observational data suggests that these tilted configurations may exist in real astrophysical systems and theoretical work indicates that tilt is accompanied by disk eccentricity and warp capable of exciting trapped diskoseismological modes. This dissertation analyzes the spatial and temporal behavior of fluid in fully three-dimensional, general relativistic, magnetohydrodynamical simulations, the first of their kind, of both tilted and untilted black hole accretion flows. We uncover characteristically greater variability in tilted simulations at frequencies similar to those predicted by the formalism of trapped modes, but ultimately conclude that its spatial structure is inconsistent with a modal interpretation. We find instead that over-dense clumps orbiting on roughly Keplerian trajectories appear generically in our global simulations independent of tilt and that these blobs give rise to acoustic wakes inside and outside of their corotation radius. Our three dimensional analysis of the flow yields two additional results. First, we confirm the strongly asymmetric nature of the tilted configuration by further describing two previously identified standing shock structures in the background flow; second, we show that these shocks effectively amplify the blob-wake variability and thus explain the increased variability observed in our tilted datasets. Our identification of clumps, wakes, and wake-shock interactions in these tilted, fully general relativistic, magnetohydrodynamical simulations will certainly be relevant to those models which incorporate tilt as a way to explain the observed variability in black hole accretion flow.

Numerical Simulation of Viscous Shocked Accretion Flows Around Black Holes

Numerical Simulation of Viscous Shocked Accretion Flows Around Black Holes
Author: Kinsuk Giri
Publisher: Springer
Total Pages: 148
Release: 2014-08-30
Genre: Science
ISBN: 3319095404

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The work developed in this thesis addresses very important and relevant issues of accretion processes around black holes. Beginning by studying the time variation of the evolution of inviscid accretion discs around black holes and their properties, the author investigates the change of the pattern of the flows when the strength of the shear viscosity is varied and cooling is introduced. He succeeds to verify theoretical predictions of the so called Two Component Advective Flow (TCAF) solution of the accretion problem onto black holes through numerical simulations under different input parameters. TCAF solutions are found to be stable. And thus explanations of spectral and timing properties (including Quasi-Period Oscillations, QPOs) of galactic and extra-galactic black holes based on shocked TCAF models appear to have a firm foundation.

Black Hole Gravitohydromagnetics

Black Hole Gravitohydromagnetics
Author: Brian Punsly
Publisher: Springer Science & Business Media
Total Pages: 399
Release: 2008-12-15
Genre: Science
ISBN: 3540769579

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Black hole gravitohydromagnetics (GHM) is developed from the rudiments to the frontiers of research in this book. GHM describes plasma interactions that combine the effects of gravity and a strong magnetic field, in the vicinity (ergosphere) of a rapidly rotating black hole. This topic was created in response to the astrophysical quest to understand the central engines of radio loud extragalactic radio sources. The theory describes a "torsional tug of war" between rotating ergospheric plasma and the distant asymptotic plasma that extracts the rotational inertia of the black hole. The recoil from the struggle between electromagnetic and gravitational forces near the event horizon is manifested as a powerful pair of magnetized particle beams (jets) that are ejected at nearly the speed of light. This second edition of the book is updated throughout and contains a completely new chapter discussing state of the art and results of numerical simulations of ergospheric disk jets occurring in magnetohydrodynamic accretion flows.

Numerical Studies of Black Hole-neutron Star Binaries

Numerical Studies of Black Hole-neutron Star Binaries
Author: Francois Foucart
Publisher:
Total Pages: 226
Release: 2011
Genre:
ISBN:

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Black hole-neutron star mergers are extremely energetic events with the potential to generate gravitational waves detectable by ground-based detectors. They can also form massive, hot accretion discs around a remnant black hole, which could power short gamma-ray bursts. Due to the strength of the gravitational interactions around the time of merger, black hole-neutron star binaries can only be studied in a general relativistic framework -- and as we lack analytical solutions to Einstein's equations of general relativity in the case of binary systems, numerical simulations are required to determine their evolution. In this thesis, we study black hole-neutron star binaries using the SpEC code. We show how to efficiently and accurately determine the initial conditions for numerical simulations, and study the influence on the dynamics of black hole-neutron star mergers of both the equation of state of nuclear matter - which is unknown but could be constrained through observations of compact binaries - and the spin of the black hole. We find that the dynamics of mergers is strongly affected by the radius of the star: small stars are harder to disrupt, form lower-mass discs and emit waves longer (and at higher frequency) than large stars. The component of the black hole spin aligned with the orbital angular momentum of the binary also modifies the disk formation process: high spins let the star approach closer to the black hole without plunging into it, subjecting it to stronger tidal forces and making it easier for the star to disrupt and form a massive disk.

Theory of Black Hole Accretion Discs

Theory of Black Hole Accretion Discs
Author: Marek A. Abramowicz
Publisher: Cambridge University Press
Total Pages: 308
Release: 2010-08-26
Genre: Science
ISBN: 9780521152952

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This authoritative volume is the first to present a comprehensive and up-to-date review of our new understanding of accretion disks around black holes. Interest in black hole accretion disks has undergone a renaissance in recent years because of developments in three complementary areas: theoretical modeling of relativistic plasmas, numerical simulations with supercomputers, and observational tests now possible using new observatories such as the Japanese X-ray satellite, ASCAR. This volume presents review papers on all these topics from leading world authorities who gathered at an international conference in Reykjavik, Iceland. The authors are M. Abramowicz, P. Artymowicz, A. Brandenburg, G. Bjornsson, P. Charles, A. Fabian, J. Krolik, J.-P. Lasota, G. Madejski, R. Narayan, I. Novikov, J. Papaloizou, J. Poutanen, J. Pringle, M. Rees, E. Spiegel, R. Svensson, P. Witta. This timely volume provides an up-to-date review of the theory of black hole accretion disks for graduate students and researchers in astrophysics and theoretical physics.

The Physics and Evolution of Active Galactic Nuclei

The Physics and Evolution of Active Galactic Nuclei
Author: Hagai Netzer
Publisher: Cambridge University Press
Total Pages: 369
Release: 2013-09-16
Genre: Science
ISBN: 1107021510

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A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.

Black-Hole Accretion Disks

Black-Hole Accretion Disks
Author: 加藤正二
Publisher: Trans Pacific Press
Total Pages: 616
Release: 1998-02
Genre: Science
ISBN:

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Accretion Power in Astrophysics

Accretion Power in Astrophysics
Author: Juhan Frank
Publisher: Cambridge University Press
Total Pages: 390
Release: 2002-01-17
Genre: Science
ISBN: 9780521629577

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Accretion Power in Astrophysics examines accretion as a source of energy in both binary star systems containing compact objects, and in active galactic nuclei. Assuming a basic knowledge of physics, the authors describe the physical processes at work in accretion discs and other accretion flows. The first three chapters explain why accretion is a source of energy, and then present the gas dynamics and plasma concepts necessary for astrophysical applications. The next three chapters then develop accretion in stellar systems, including accretion onto compact objects. Further chapters give extensive treatment of accretion in active galactic nuclei, and describe thick accretion discs. A new chapter discusses recently discovered accretion flow solutions. The third edition is greatly expanded and thoroughly updated. New material includes a detailed treatment of disc instabilities, irradiated discs, disc warping, and general accretion flows. The treatment is suitable for advanced undergraduates, graduate students and researchers.

The Physics of Accretion onto Black Holes

The Physics of Accretion onto Black Holes
Author: Maurizio Falanga
Publisher: Springer
Total Pages: 483
Release: 2014-10-28
Genre: Science
ISBN: 1493922270

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Provides a comprehensive summary on the physical models and current theory of black hole accretion, growth and mergers, in both the supermassive and stellar-mass cases. This title reviews in-depth research on accretion on all scales, from galactic binaries to intermediate mass and supermassive black holes. Possible future directions of accretion are also discussed. The following main themes are covered: a historical perspective; physical models of accretion onto black holes of all masses; black hole fundamental parameters; and accretion, jets and outflows. An overview and outlook on the topic is also presented. This volume summarizes the status of the study of astrophysical black hole research and is aimed at astrophysicists and graduate students working in this field. Originally published in Space Science Reviews, Vol 183/1-4, 2014.