Sham, Yu Hin = 愛丁頓－玻恩－英費爾德重力理論和廣義相對論下的致密星 / 岑宇軒. / Thesis Ph.D. Chinese University of Hong Kong 2015. / Includes bibliographical references (leaves 137-143). / Abstracts also in Chinese. / Title from PDF title page (viewed on 15, September, 2016). / Sham, Yu Hin = Aidingdun-Boen-Yingfeierde zhong li li lun he guang yi xiang dui lun xia de zhi mi xing / Cen Yuxuan.

Tso Ka Yee = 致密星的研究 / 曹家怡. / Thesis submitted in: September 2006. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 86-88). / Abstracts in English and Chinese. / Tso Ka Yee = Zhi mi xing de yan jiu / Cao Jiayi. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Brief History of Neutron Stars --- p.1 / Chapter 1.2 --- The Proposal of Strange Quark Stars --- p.3 / Chapter 1.3 --- "Observation of Stellar Masses, Radii and Moment of Inertia" --- p.4 / Chapter 1.3.1 --- Radius Measurement --- p.5 / Chapter 1.3.2 --- Mass Measurement --- p.6 / Chapter 1.3.3 --- Moment of Inertia Measurement --- p.8 / Chapter 1.4 --- PSR B1828-11 --- p.8 / Chapter 1.5 --- Effect of rotation on a star's precession --- p.12 / Chapter 1.5.1 --- Reference Frames of the Star --- p.12 / Chapter 1.5.2 --- Dynamics of Free Precession --- p.14 / Chapter 1.6 --- Motivation --- p.17 / Chapter 2 --- Static structure of a compact star --- p.18 / Chapter 2.1 --- Equation of State that We Used --- p.18 / Chapter 2.1.1 --- Thomas-Fermi Model (TF96) --- p.18 / Chapter 2.1.2 --- MIT Bag Model --- p.19 / Chapter 2.1.3 --- Perturbative QCD Model --- p.21 / Chapter 2.2 --- Non-relativistic compact stars --- p.23 / Chapter 2.2.1 --- Lane-Emden Equation --- p.23 / Chapter 2.3 --- General Relativistic Approach --- p.24 / Chapter 2.3.1 --- The Oppenheimer-Volkoff Equations --- p.24 / Chapter 2.3.2 --- Properties of Compact Stars --- p.26 / Chapter 3 --- Non-relativistic rotating star --- p.29 / Chapter 3.1 --- Rotating Lane-Emden Equations --- p.29 / Chapter 3.2 --- The Moment of Inertia Tensor --- p.34 / Chapter 3.3 --- Models --- p.35 / Chapter 3.4 --- Results --- p.38 / Chapter 3.5 --- Summary --- p.46 / Chapter 4 --- Relativistic rotating star --- p.47 / Chapter 4.1 --- Rotating metric --- p.48 / Chapter 4.2 --- Frame Dragging Effect --- p.49 / Chapter 4.3 --- Hartle-Thorne Perturbative Solution --- p.52 / Chapter 4.4 --- Results --- p.56 / Chapter 4.5 --- Summary --- p.65 / Chapter 5 --- Effects of extra dimensions on non-rotating stars --- p.66 / Chapter 5.1 --- Background of Extra dimensional theories --- p.66 / Chapter 5.2 --- Results --- p.69 / Chapter 5.3 --- Summary --- p.82 / Chapter 6 --- Conclusion --- p.84 / Bibliography --- p.86

Chan, Pak On = 星體震動的分析方法 / 陳柏安. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (p. 117-119). / Abstracts in English and Chinese. / Chan, Pak On = Xing ti zhen dong de fen xi fang fa / Chen Boan. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Outline of the Content --- p.3 / Chapter 2 --- Preliminaries --- p.5 / Chapter 2.1 --- Einstein Equation --- p.5 / Chapter 2.1.1 --- Hydrostatic Equilibrium --- p.6 / Chapter 2.1.2 --- Linearized Stellar Pulsation --- p.7 / Chapter 2.1.3 --- Gravitational Radiation --- p.11 / Chapter 2.2 --- Classification of Modes --- p.13 / Chapter 2.2.1 --- Fundamental Mode --- p.14 / Chapter 2.2.2 --- Pressure Modes --- p.14 / Chapter 2.2.3 --- Gravity Modes --- p.14 / Chapter 2.3 --- Relativistic Cowling Approximation --- p.15 / Chapter 3 --- Stellar Structure of Quark Stars --- p.19 / Chapter 3.1 --- Ordinary Quark Stars --- p.19 / Chapter 3.1.1 --- Stellar Profile --- p.20 / Chapter 3.1.2 --- Radius and Mass --- p.27 / Chapter 3.1.3 --- Moment of Inertia --- p.30 / Chapter 3.2 --- Effects of Finite Strange Quark Mass and Finite Temperature --- p.32 / Chapter 3.2.1 --- Sommerfeld's Expansions --- p.33 / Chapter 3.2.2 --- Static EOS for Quark Matter --- p.35 / Chapter 3.2.3 --- Corrections to Ordinary Quark Stars --- p.37 / Chapter 3.2.4 --- Induced Buoyancy under Adiabaticity --- p.40 / Chapter 3.2.5 --- Induced Buoyancy under Fixed Composition --- p.45 / Chapter 3.3 --- Addition of Nuclear Crust --- p.47 / Chapter 4 --- Pressure Modes --- p.52 / Chapter 4.1 --- Sturm-Liouville Equation for p-modes --- p.52 / Chapter 4.2 --- Asymptotic Expansion --- p.54 / Chapter 4.3 --- "P""modes for Quark Stars" --- p.57 / Chapter 4.4 --- p-modes for Neutron Stars --- p.62 / Chapter 4.5 --- p-modes for Hybrid Stars --- p.65 / Chapter 5 --- Gravity Modes --- p.74 / Chapter 5.1 --- Sturm-Liouville Equation for modes --- p.74 / Chapter 5.2 --- Asymptotic Expansion --- p.76 / Chapter 5.3 --- g-modes for Quark Stars --- p.78 / Chapter 5.4 --- modes for Hybrid Stars --- p.83 / Chapter 5.5 --- Conditions on the modes --- p.88 / Chapter 6 --- Fundamental Mode --- p.93 / Chapter 6.1 --- Overview of the f-mode Universalities --- p.93 / Chapter 6.2 --- Relation between Real Part and Imaginary Part of Mwf --- p.95 / Chapter 6.3 --- New Universalities of f-mode --- p.96 / Chapter 7 --- Conclusions and Remarks --- p.104 / Chapter A --- Scattering Approximation --- p.106 / Chapter B --- Series Solution to Stellar Profile of Quark Stars --- p.108 / Chapter C --- AAKAS Formalism under Cowling Approximation --- p.113 / Chapter D --- Series Solutions to the Spectra of p-modes and g-modes --- p.114 / Bibliography --- p.117

Astrophysical compact objects --- white dwarfs (WDs), neutron stars (NSs), and stellar mass black holes (BHs) --- mark the endpoints of normal stellar evolution. Their birth is often associated with dramatic explosions known as core-collapse supernovae (SNe). Such SNe are archetypal ``transients'' --- astronomical events which produce detectable emission for only a limited period of time (measurable over human timescales). This dissertation investigates the astrophysical implications of the formation and destruction of compact objects with particular focus on the transient phenomena that may be produced in such events. Part I is devoted to the ``death'' of compact objects by their coalescence with a binary companion. Such compact object binaries are driven towards merger by the extraction of orbital energy in the form of gravitational-waves (GW), and are thus prime targets for current and future GW detectors. In the first two chapters of Part I we consider the merger of a WD with a NS companion, beginning with Chapter 2, in which we explore the nuclearly-reactive accretion flow produced in the aftermath of such mergers and the possible `SN-like' transient it may give rise to. We continue in Chapter 3 by proposing that the late-time evolution of this post-merger accretion disk may result in terrestrial planet formation, broadly consistent with the mysterious ``pulsar planets'' observed orbiting PSR B1257+12. We shift our attention in the next couple chapters of this first part of the dissertation to binary NS mergers. In Chapter 4 we address the question of disk formation in the aftermath of the collapse of a rigidly-rotating supramassive NS, which is directly applicable to various models of gamma-ray bursts (GRBs). In Chapter 5 we utilize both GW and electromagnetic signatures of the first observed NS merger GW170817 to place new constraints on the NS equation of state. Finally, in Part II of this dissertation, we explore the connection between transient phenomena ranging from long- and ultra-long- GRBs, to energetic super-luminous SNe (SLSNe) and fast radio bursts (FRB), and relate these to the ``birth'' of a rapidly rotating highly-magnetized NS, a millisecond ``magnetar''. In Chapter 6 we show that both jetted and thermal transients (namely a GRB and a SLSN) can be powered simultaneously by such magnetars, and explore the various observational implications of this connection. We end with Chapter 7 in which we study the photo-ionization of the medium surrounding a newly born magnetar, discussing the observational signatures related to the escape of this ionizing radiation. We additionally address the propagation of radio waves and the dispersion measure induced by such photo-ionization and apply these to show that FRBs are broadly consistent with having young magnetars as their progenitors.

Lau, Hoi Kwan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 208-212). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Gravitational wave astronomy --- p.1 / Chapter 1.2 --- Stellar pulsation and gravitational radiation --- p.3 / Chapter 1.3 --- Outline --- p.5 / Chapter 2 --- Hydrostatic stellar structure --- p.8 / Chapter 2.1 --- Structural equation --- p.9 / Chapter 3 --- Finite temperature equations of state of nuclear matter --- p.13 / Chapter 3.1 --- Finite temperature ordinary nuclear matter --- p.13 / Chapter 3.2 --- Strange Quark Matter --- p.15 / Chapter 3.3 --- Equilibrium and Dynamic EOS --- p.16 / Chapter 4 --- Stellar pulsation and gravitational radiation --- p.19 / Chapter 4.1 --- Linearized theory of general relativity --- p.19 / Chapter 4.2 --- Stellar oscillation --- p.25 / Chapter 4.3 --- Quasi-normal Mode --- p.28 / Chapter 4.3.1 --- f mode --- p.29 / Chapter 4.3.2 --- p mode --- p.29 / Chapter 4.3.3 --- g mode --- p.30 / Chapter 4.3.4 --- w mode --- p.31 / Chapter 5 --- Gravitational wave spectrum of hot compact stars --- p.32 / Chapter 5.1 --- Numerical results --- p.32 / Chapter 5.1.1 --- Temperature effect on QNM --- p.32 / Chapter 5.1.2 --- Temperature effect and QS model --- p.38 / Chapter 5.1.3 --- QNM shift due to phase transition --- p.41 / Chapter 5.2 --- Summary and prospective --- p.48 / Chapter 6 --- Universality of fundamental mode and spacetime mode --- p.50 / Chapter 6.1 --- Review --- p.50 / Chapter 6.2 --- Generic proposal of universalities --- p.53 / Chapter 6.2.1 --- Moment of Inertia --- p.54 / Chapter 6.2.2 --- Gravitational wave spectrum --- p.57 / Chapter 6.3 --- Universality on moment of inertia --- p.63 / Chapter 6.4 --- Origin of universality --- p.70 / Chapter 6.4.1 --- Tolman VII model --- p.71 / Chapter 6.4.2 --- Polytropic Model --- p.76 / Chapter 6.5 --- Application of universality --- p.82 / Chapter 6.6 --- Summary --- p.89 / Chapter 7 --- Quark star properties and gravity mode oscillation --- p.92 / Chapter 7.1 --- Introduction --- p.92 / Chapter 7.2 --- g mode frequencies of quark stars --- p.94 / Chapter 7.2.1 --- Temperature profile and p mode frequency --- p.96 / Chapter 7.2.2 --- Strange quark mass and Yp mode frequency --- p.104 / Chapter 7.3 --- Summary --- p.108 / Chapter 8 --- Gravitational radiation excitation by infalling shell --- p.111 / Chapter 8.1 --- Introduction --- p.111 / Chapter 8.2 --- Formalism --- p.116 / Chapter 8.2.1 --- Connection between star and vacuum --- p.117 / Chapter 8.2.2 --- Matter source --- p.121 / Chapter 8.2.3 --- Geodesic --- p.124 / Chapter 8.2.4 --- Source of infalling dust shell --- p.126 / Chapter 8.2.5 --- Green's function --- p.127 / Chapter 8.3 --- Gravitational Wave excitation by collapsing shell --- p.130 / Chapter 8.4 --- Features of radiation --- p.138 / Chapter 8.4.1 --- Power spectrum --- p.138 / Chapter 8.4.2 --- Wave function --- p.144 / Chapter 8.4.3 --- Energy of excitation --- p.147 / Chapter 8.5 --- Non-adiabatic oscillation --- p.153 / Chapter 8.5.1 --- Mathematical Background --- p.154 / Chapter 8.5.2 --- Numerical results --- p.158 / Chapter 8.6 --- General relativistic simulation --- p.163 / Chapter 8.6.1 --- Technical briefing --- p.163 / Chapter 8.6.2 --- Numerical results --- p.166 / Chapter 8.7 --- Summary --- p.174 / Chapter 9 --- Conclusion and remarks --- p.178 / Chapter A --- Unit conversions --- p.183 / Chapter B --- Series expansion of quark star EOS --- p.185 / Chapter C --- Accuracy of simplified mode extraction scheme --- p.188 / Chapter D --- Computation of moment of inertia --- p.193 / Chapter E --- Comment of exactness of inference scheme --- p.195 / Chapter E.1 --- Precision of the mass inferred --- p.195 / Chapter E.2 --- Accuracy of universality combinations --- p.199 / Chapter F --- Calculation of sound speed --- p.202 / Chapter G --- Mode extraction of non-adiabatic oscillation --- p.204 / Bibliography --- p.208

No description available.

Since the first observation of a gravitational-wave (GW) in 2015, the LIGO and Virgo detectors reported tens of astrophysical signals interpreted as mergers of compact objects. These observations provide invaluable tests of the General Relativity and open a new era of astronomy, unveiling compact objects’ nature. The focus of the thesis is the detection and the characterization of GW transients with minimal assumptions on the GW sources. To identify astrophysical signals embedded in detector noise, there are two main approaches: template-based and unmodelled searches. The firsts look for GW signals with a time-frequency evolution consistent to the waveform models contained in extensive template banks. Instead, unmodelled or burst searches do not assume a waveform model, but look for excess of power that is coherent on multiple GW detectors. Burst search are fundamental to observe GWs from various astrophysical sources. Unmodelled searches observe GWs originated from the coalescence of compact binaries, and might observe GWs that are expected by other sources such as supernovae, isolated neutron stars, and cosmic strings. Burst searches also provide the reconstruction of the GW waveform with minimal assumptions, and are able to identify discrepancies between theoretical models and measured data, which may reveal new physics. A well-known software for burst searches is Coherent WaveBurst (cWB). cWB identifies excess of power with respect to the detector noise that are coherent in the GW detectors network. Within this framework, the thesis presents three author’s original contributions to this field. The first is the search sensitivity of three-detectors network in burst searches. Having more detectors participating in the GW observations generally improves the source localization and the characterization of the GW signals. The capability of burst searches to distinguish between potential signals and transient noise depends on the orientation of the detectors and on their relative sensitivities. In literature, the cWB search sensitivity of the three-detectors network composed of the LIGO and Virgo detectors (HLV) is lower than the one achieved using only LIGO detectors (HL). cWB uses likelihood regulators to force the reconstruction of the GW component observed by the LIGO aligned detectors. These regulators successfully reduce the false alarm rate of the HL coherent analysis, but to make full use of a third, not-aligned detector, they should be relaxed. The fifth chapter investigates the impact of the likelihood regulators in cWB for HLV network, first in a simplified case assuming Gaussian noise only, and then in the data from the third LIGO-Virgo-KAGRA observing run. Thanks to latest cWB enhancements and relaxed likelihood regulators, we show that the HLV network reduces significantly the gap w.r.t. HL, having a higher sensitivity for several waveforms tested on average over the sky directions. Moreover, we investigate the use of the HLV network to test the consistency between cWB unmodelled signal reconstruction and the GW waveform models. The second original contribution is the development of an autoencoder neural network integrated into GW burst searches to improve the rejection of noise transients GW data contains short-duration disturbances, called glitches, which can mimic astrophysical signals. Mitigation of glitches is particularly difficult for unmodelled algorithm, such as cWB, that do not use GW waveform models to filter the data, but are sensitive to the widest possible range of morphologies. Noise mitigation is a long-term effort in cWB, which led to the introduction of specific estimators and a machine-learning based signal-noise classification algorithm. The sixth chapter presents an autoencoder neural network, integrated into cWB, that learns transient noise morphologies from GW time-series and it improves their rejection. An autoencoder is an unsupervised learning neural network that compresses the input data into a lower dimensional space, called latent space, and then re-constructs an output with the original dimensions. Here, the autoencoder is trained on time-series belonging to a single glitch family, known as blip, and the network learns that specific morphology. The autoencoder improves cWB discrimination between blip-like glitches and potential GW signals, reducing the background trigger at low frequencies. We inject in the LIGO detectors’ data from the third Advanced LIGO-Virgo observing run a wide range of simulated signals, and we evaluate the cWB search sensitivity including the autoencoder output in the cWB ranking statistics. At a false alarm rate of one event per 50 years, the sensitivity volume increases up to 30% for signal morphologies similar to blip glitches. Finally, the thesis presents the search for hyperbolic encounters between compact objects in the data from the third LIGO-Virgo-KAGRA observing run. As GW detectors sensitivity increases, new astrophysical sources could emerge. Close hyperbolic encounters (HE) are one such source class: scattering of stellar mass compact objects is expected to manifest as GW burst signals in the frequency band of current detectors. The seventh chapter presents the search for GWs from HE in the data from the second-half of the third observing run using cWB. No significant event has been identified in addition to known detections of GW events. We inject third Post-Newtonian order accurate HE waveforms with component masses between [2,100]M ⊙ . For the first time, we report the sensitivity volume achieved for such sources, i.e. the portion of the Universe in which the proposed analysis would have detected a HE signal with a certain significance, if any. The sensitivity volume peaks at 3.9±1.4×10 5 Mpc3 year for compact objects with masses between [20, 40] M ⊙, corresponding to a rate density upper limit of 0.589±0.094 ×10 −5 Mpc −3 year −1. Moreover, the sensitive volume prospects for the next observing runs of current detectors are discussed. All the result shown are based on the latest publicly available data from the third observing run of the LIGO-Virgo-KAGRA collaboration.

We present new models for two low-mass X-ray binaries (LMXB), 4U 1822-371 and V1408 Aql (= 4U 1957+115). The eclipsing LMXB 4U 1822-371 is the prototypical accretion disk corona (ADC) system. We have obtained new time-resolved UV spectroscopy of 4U 1822-371 with the Advanced Camera for Surveys/Solar Blind Channel on the Hubble Space Telescope and new V- and J- band photometry with the 1.3-m SMARTS telescope at Cerro Tololo Inter-American Observatory. We use the new data to construct the UV/optical spectral energy distribution of 4U 1822-371 and its orbital light curve in the UV, V , and J bands. We derive an improved ephemeris for the optical eclipses and confirm that the orbital period is changing rapidly, indicating extremely high rates of mass flow in the system; and we show that the accretion disk in the system has a strong wind with projected radial velocities up to 4400 km s⁻¹. We show that the disk has a vertically extended, optically thick component at optical wavelengths. This component extends almost to the edge of the disk and has a height equal to ~0.5 of the disk radius. As it has a low brightness temperature, we identify it as the optically thick base of the disk wind, not as the optical counterpart of the ADC. Like previous models of 4U 1822-371, ours needs a tall obscuring wall near the edge of the accretion disk, but we interpret the wall as a layer of cooler material at the base of the disk wind, not as a tall, luminous disk rim. V1408 Aql is a black hole candidate. We have obtained new optical photometry of this system in 2008 and 2009 with the Argos photometer on the 2.1-m Otto Struve telescope and optical spectra with the low resolution spectrometer on the Hobby Eberly telescope. From the data we derive an improved optical orbital ephemeris and a new geometric model for the system. The model uses only a simple thin disk without the need for a warped disk or a large disk rim. The orbital variation is produced by the changing aspect of the irradiated secondary star with orbital phase. The new model leaves the orbital inclination unconstrained and allows for inclinations as low as 20 degrees. The spectra is largely featureless continuum with He II and occasionally H[alpha] emission lines, and an absorption line from Na D. The lines are highly variable in strength and wavelength, but the variations do not correlate with orbital phase. / text

<p>Neutron stars are some of the most fascinating objects in Nature. Essentially all aspects of physics seems to be represented inside them. Their cores are likely to contain deconfined quarks, hyperons and other exotic phases of matter in which the strong interaction is the dominant force. The inner region of their solid crust is penetrated by superfluid neutrons and their magnetic fields may reach well over 10¹²Gauss. Moreover, their extreme mean densities, well above the densities of nuclei, and their rapid rotation rates makes them truly relativistic both in the special as well as in the general sense. This thesis deals with a small subset of these phenomena. In particular the exciting possibility of trapping of gravita-tional waves is examined from a theoretical point of view. It is shown that the standard condition <i>R</i> < 3<i>M</i> is not essential to the trapping mechanism. This point is illustrated using the elegant tool provided by the optical geometry. It is also shown that a realistic equation of state proposed in the literature allows stable neutron star models with closed circular null orbits, something which is closely related to trapped gravitational waves. Furthermore, the general relativistic theory of elasticity is reviewed and applied to stellar models. Both static equilibrium as well as radially oscillating configurations with elasticsources are examined. Finally, Killing tensors are considered and their applicability to modeling of stars is discussed</p>

The objective of this thesis is to study the fluid oscillation modes in compact stars, understand their properties and infer stellar structures from their frequencies. The first part of the thesis focuses on the Newtonian theory of stellar pulsation and the Cowling approximation (CA), which neglects the change in gravitational potential. We modify the conventional CA, devise a more accurate version of the CA and calculate the first-order correction to the conventional CA. In the second part, we apply the variational approximation method proposed by Chandrasekhar [Astrophys. J. 139,664 (1963)] and δ-perturbation expansion proposed by Bender et. al. [J. Maths. Phys. 30, 1447 (1989)] to explain the universality in the relationships between the fundamental mode frequency and the moment of inertia of neutron stars, which was discovered by Lau et. al. [Astrophys. J. 714, 1234 (2010)]. We reveal that stiff equations of state are the conditions for the observed universality. In the third part, we consider the relativistic pulsation formulation and relativistic CAs for compact stars. We unify several known CAs with a single second-order differential equation. We also extend the modified CA derived from the formalism established by Allen et. al. [Phys. Rev. D 58, 124012 (1998)] to include the effect of buoyancy. Finally, we find the first-order and the second-order post-Newtonian expansions for the nonradial pulsations in quark stars. We derive an analytic formula expressing the fundamental mode frequency in terms of the compactness of quark stars. As a result, we are able to verify the universality mentioned above for quark stars. / 這論文是對在牛頓力學以及相對論框架下緻密星流體振盪的研究結果。論文第一部分集中討論牛頓力學下流體振盪以及近似方法。這近似方法忽略重力勢的擾動，令系統由四階微分方程減少為二階微分方程。我們修正了已往的近似方法和提出一個更精準的近似方法。第二部分包括變分近似方法。我們利用該方法和δ微擾理論解釋基本模式頻率的普通性。第三部分包括相對論框架下緻密星流體振盪和近似方法。我們以一條二階微分方程總結之前出現的近似方法並且在近似方法中加入浮力。最後，我們執行一階和二階的後牛頓展開，以分析夸克星的基本模式。我們驗證了展開的準確度和發現了基本模式頻率的方程。 / Chan, Tsang Keung = 有關在緻密星中流體振盪的研究 / 陳增強. / Thesis M.Phil. Chinese University of Hong Kong 2013. / Abstracts also in Chinese. / Title from PDF title page (viewed on 07, October, 2016). / Chan, Tsang Keung = You guan zai zhi mi xing zhong liu ti zhen dang de yan jiu / Chen Zengqiang. / Detailed summary in vernacular field only.