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Author: Koutarou Kyutoku
Publisher: Springer Science & Business Media
ISBN: 4431542019
Category : Science
Languages : en
Pages : 187
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Book Description
This thesis presents a systematic study of the orbital evolution, gravitational wave radiation, and merger remnant of the black hole–neutron star binary merger in full general relativity for the first time. Numerical-relativity simulations are performed using an adaptive mesh refinement code, SimulAtor for Compact objects in Relativistic Astrophysics (SACRA), which adopts a wide variety of zero-temperature equations of state for the neutron star matter. Gravitational waves provide us with quantitative information on the neutron star compactness and equation of state via the cutoff frequency in the spectra, if tidal disruption of the neutron star occurs before the binary merges. The cutoff frequency will be observed by next-generation laser interferometric ground-based gravitational wave detectors, such as Advanced LIGO, Advanced VIRGO, and KAGRA. The author has also determined that the mass of remnant disks are sufficient for the remnant black hole accretion disk to become a progenitor of short-hard gamma ray bursts accompanied by tidal disruptions and suggests that overspinning black holes may not be formed after the merger of even an extremely spinning black hole and an irrotational neutron star.
Author: Koutarou Kyutoku
Publisher: Springer Science & Business Media
ISBN: 4431542019
Category : Science
Languages : en
Pages : 187
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Book Description
This thesis presents a systematic study of the orbital evolution, gravitational wave radiation, and merger remnant of the black hole–neutron star binary merger in full general relativity for the first time. Numerical-relativity simulations are performed using an adaptive mesh refinement code, SimulAtor for Compact objects in Relativistic Astrophysics (SACRA), which adopts a wide variety of zero-temperature equations of state for the neutron star matter. Gravitational waves provide us with quantitative information on the neutron star compactness and equation of state via the cutoff frequency in the spectra, if tidal disruption of the neutron star occurs before the binary merges. The cutoff frequency will be observed by next-generation laser interferometric ground-based gravitational wave detectors, such as Advanced LIGO, Advanced VIRGO, and KAGRA. The author has also determined that the mass of remnant disks are sufficient for the remnant black hole accretion disk to become a progenitor of short-hard gamma ray bursts accompanied by tidal disruptions and suggests that overspinning black holes may not be formed after the merger of even an extremely spinning black hole and an irrotational neutron star.
Author: William H. Lee
Publisher:
ISBN:
Category : Black holes (Astronomy)
Languages : en
Pages : 5
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Book Description
Author: Matthew Karlson
Publisher:
ISBN:
Category : Black holes (Astronomy)
Languages : en
Pages : 106
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Book Description
The detection of gravitational waves from binary black hole and binary neutron star mergers has ushered in a new age of observational astronomy. Anticipation of detection from these coalescing compact binaries has led to the development of models for comparison using analytical and numerical techniques. Typically, these methods model gravitational-wave signals as small oscillations that grow over time, reach some maximum value, and eventually decay to zero. However, these models are incomplete: compact binaries can emit gravitational waves that decay to a non-zero value. This phenomenon is known as the gravitational-wave memory. In particular, the signal from compact binaries displays a nonlinear memory effect, which arises from gravitational waves produced by the previously emitted gravitational-wave energy. Using a semi-analytic approach we generate nonlinear memory signals for a range of binary black hole parameters, extending previous work. We also, for the first time, compute the nonlinear memory for binary neutron star mergers. Additionally, we perform the first comparison between our semi-analytic approach and full numerical relativity simulations of the nonlinear memory. These waveforms will be useful in future searches of the nonlinear memory in ground and space-based detectors.
Author: Francois Foucart
Publisher:
ISBN:
Category :
Languages : en
Pages : 226
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Book Description
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.
Author: H. Gursky
Publisher: Springer Science & Business Media
ISBN: 9401017670
Category : Science
Languages : en
Pages : 447
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Book Description
This book contains a set of articles based on a session of the annual meeting of the American Association for the Advancement of Science held in San Francisco in February, 1974. The reason for the meeting arose from the need to communicate to the largest possible scientific community the dramatic advances which have been made in recent years in the understanding of collapsed objects: neutron stars and black holes. Thanks to an unprecedented resonance between X-ray, y-ray, radio and optical astronomy and important new theoretical developments in relativistic astro physics, a new deep understanding has been acquired of the physical processes oc curring in the late stages of evolution of stars. This knowledge may be one of the greatest conquests of man's understanding of nature in this century. This book aims to give an essential and up-to-date view in this field. The analysis of the physics and astrophysics of neutron stars and black holes is here attacked from both theoretical and experimental points of view. In the experimental field we range from the reviews and catalogues of galactic X-ray sources (R. Gursky and E. Schreier) and pulsars (E. Groth) to the observations of the optical counter part of X-ray sources (P. Boynton) to finally the recently discovered gamma-ray bursts (I. Strong) and pulse astronomy R. B. Partridge).
Author: Nicholas Anthony Tacik
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The inspiral and merger of binary neutron stars (BNS) is one of the most promising potential sources of gravitational waves for ground-based detectors like Advanced LIGO. BNS mergers are also likely a source of counterpart electromagnetic radiation. It is important to perform simulations of BNS to better understand and model their gravitational wave emission as well as their electromagnetic emission. The parameter space of BNS binaries is quite large, and one aspect that has not been well studied in neutron star spin. In this thesis, we focus on investigating spinning neutron stars in compact object binaries. Using the SpEC code, developed by the SXS collaboration, we begin by presenting a new code to create initial data for binary neutron stars with arbitrary spins. We introduce a novel method of measuring neutron star spin, and show that it is accurate and robust. We evolve several spinning binary configurations and show that their properties agree remarkably well with Post-Newtonian predictions. We also show that we are able to control the eccentricity of the binaries to ~0.1%. Thereafter, we proceed to extend our code to black hole--neutron star (BHNS) binaries. We create many data sets across the BHNS parameter space, varying neutron star spin magnitude, spin direction, compactness, and black hole mass, spin and spin direction. We are able to create initial data sets with neutron star spins near the mass-shedding limit, and nearly extremal black hole spins. Finally, we investigate spurious gravitational radiation in binary black hole systems. We study its parameter space dependence, by introducing three diagnostics, investigating them as a function of black hole spin and black hole separation, and comparing two different methods of constructing initial data.
Author: Arun Kenath
Publisher: Springer Nature
ISBN: 3031304632
Category : Science
Languages : en
Pages : 61
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Book Description
This book provides a concise introduction to the physics of gravitational waves. It is aimed at graduate-level students and PhD scholars. Ever since the discovery of gravitational waves in 2016, gravitational wave astronomy has been adding to our understanding of the universe. Gravitational waves have been detected in the past few years from several transient events such as merging stellar-mass black holes, binary neutron stars, etc. These waves have frequencies in a band ranging from a few hundred hertz to around a kilohertz to which LIGO type instruments are sensitive. LISA will be sensitive to much lower range of frequencies from SMBH mergers. Apart from these cataclysmic burst events, there are innumerable sources of radiation which are continuously emitting gravitational waves of all frequencies. These include a whole mass range of compact binary and isolated compact objects and close planetary stellar entities. This book discusses the gravitational wave background produced in typical frequency ranges from such sources emitting over a Hubble time and the fluctuations in the h values measured in the usual devices. Also discussed are the high-frequency thermal background gravitational radiation from hot stellar interiors and newly formed compact objects. The reader will also learn how gravitational waves provide a testing tool for various theories of gravity, i.e. general relativity and extended theories of gravity, and will be the definitive test for general relativity.
Author: Koutarou Kyutoku
Publisher:
ISBN: 9784431542025
Category : Black holes (Astronomy)
Languages : en
Pages : 194
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Book Description
Author: Serena Vinciguerra
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The revolutionary discoveries of the last few years have opened a new era of astronomy. With the detection of gravitational-waves, we now have the opportunity of investigating new phenomena, such as mergers of black-holes. Furthermore, multi-messenger observations now allow us to combine information from different channels, providing insight into the physics involved. With this rapid evolution and growth of the field, many challenges need to be faced. In this thesis we propose three data analysis strategies to efficiently study the coalescences of compact binaries. First we propose an algorithm to reduce the computational cost of Bayesian inference on gravitational-wave signals. Second we prove that machine-learning signal classification could enhance the significance of gravitational-wave candidates in unmodelled searches for transients. Finally we develop a tool, saprEMo, to predict the number of electromagnetic events, which according to a specific emission model, should be present in a particular survey.
Author: Rosalba Perna
Publisher: Frontiers Media SA
ISBN: 2889669416
Category : Science
Languages : en
Pages : 73
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Book Description
