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Dissertations / Theses on the topic 'Compact object (Astronomy)'
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1
van, Spaandonk Lieke. "Exploring new emission line diagnostics for accreting compact objects." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/55659/.
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Theory predicts that a large fraction of CVs should have passed through the minimum period. The Sloan Digital Sky Survey (sdss) sample is finally unearthing these systems in large numbers. But due to their faint donor stars, the orbital period is often the only measurable system parameter for most CVs. The indirect measurable of the superhump period, and hence superhump excess, could potentially provide an indication of the mass ratio of the systems via the empirical relation between the two observables. While this relation is potentially very useful for the determination of mass ratios, the large scatter in the calibrators, especially at the low mass ratio end, prohibits a direct conversion between easy to measure light curve variability and the much sought after mass ratio. To place a short period CV firmly on the evolutionary track (e.g pre- or post bounce systems), more direct methods to determine the mass ratio are required, as well as a better calibration and validation of the relation between the superhump excess and mass ratio. We can achieve this, by constraining the mass ratios of short period CVs using dynamical constraints on the radial velocities of the binary components. The radial velocity of the WD (K1) is only occasionally directly measurable as the WD features are typically swamped by the strong disc features. As the disc is centred on the WD, measuring the disc radial velocity can give an indication of the WD radial velocity, but these measures tend to be biased by hotspots and other asymmetries in the disc. Measuring the radial velocity of the donor star (K2) is less straightforward and normally performed by either measuring the radial velocity of the donor absorption lines for earlier type donor stars, or via emission lines associated with the donor star, if irradiated by the disc and WD. The first method fails in short period CVs as the faint features from the late type donors in these systems are concealed in the accretion and WD dominated optical spectrum, even at very low mass loss rates. The second method comes with tight timing constraints as the irradiated donor is generally only visible on top of the double peaked disc emission shortly after outburst and data needs to be obtained via target of opportunity programs. In this thesis, we present a spectroscopic survey of short periods CVs and explore new techniques in addition to the traditional methods for the determination of the radial velocity components. We combine these new methods with the exploitation of the more `exotic' Ca ii triplet lines in the I-band in addition to the commonly used Balmer lines. We will show that, while it suffers from some of the same systematics as the Balmer lines, we can measure K1 better in Ca ii than in Balmer, especially when exploiting Doppler maps for these measures. More importantly for many systems, donor emission is visible in the Ca ii lines, which provides us with measures for the radial velocity amplitude of this feature (Kem). These, combined with K-correction models, yield a good measure of K2. We find that the determination of Kem is easy in Doppler maps, and that the K-correction, via irradiation methods, is fairly solid. We use these values to dynamically constrain the mass ratios for 13 CVs, including several eclipsing systems to test the validity of our method. The survey includes well known systems such as GW Lib, WZ Sge, OY Car and IP Peg.
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Huerta, Escudero Eliu Antonio. "Source modelling of extreme and intermediate mass ratio inspirals." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609770.
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Fang, Xiao. "Perturbation Theories in Astrophysics: From Large-Scale Structure To Compact Objects." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531217962535791.
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Völkel, Sebastian [Verfasser], and Kostas [Akademischer Betreuer] Kokkotas. "On the Gravitational Wave Spectrum of Compact Relativistic Objects / Sebastian Völkel ; Betreuer: Kostas Kokkotas." Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/1212024931/34.
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Efremov, Pavel [Verfasser], Volker [Akademischer Betreuer] Perlick, Volker [Gutachter] Perlick, and Domenico [Gutachter] Giulini. "Relativistic accretion onto compact objects / Pavel Efremov ; Gutachter: Volker Perlick, Domenico Giulini ; Betreuer: Volker Perlick." Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1164151983/34.
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Valente, Ema Filipa dos Santos. "A simple model of exotic compact objects : interaction with a scalar field." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/23655.
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Mestrado em FísicaModelos de objetos compactos exóticos (OCEs) foram propostos nas últimas décadas como alternativas aos buracos negros. Esses modelos visam reproduzir a fenomenologia que caracteriza os (candidatos a) buracos negros observados. No entanto, para superar os problemas associados ao horizonte de eventos (e à consequente singularidade de curvatura, de acordo com o teorema de Penrose), estes OCEs não possuem horizonte de eventos. Nesta dissertação, exploramos um modelo simples de um OCE, descrito pela métrica de Kerr-Newman no exterior de uma superfície com condições de fronteira reflectivas, localizada fora do horizonte de eventos de Kerr-Newman. Nesta geometria, estudamos OCEs que podem estar em equilíbrio com con figurações estáticas de um campo escalar. Consideramos um campo escalar sem massa, tanto no caso eletricamente não carregado como no caso carregado, e obtemos, através de métodos analíticos, um conjunto discreto de raios críticos da superfície do OCE que podem suportar con figurações estáticas não triviais do campo escalar. Dentro deste conjunto discreto, o OCE com maior raio crítico separa os OCEs estáveis e instáveis relativamente à instabilidade superradiante, induzida por um campo escalar. O conjunto discreto de raios críticos da superfície do OCE foi construído para os três regimes diferentes da métrica de Kerr-Newman: regime sub-extremo, regime extremo e regime super-extremo. Estes espectros de ressonância dependem dos parâmetros físicos {a, Q, q, l,m }
Models of exotic compact objects (ECOs) have been proposed in the past decades as alternatives to black holes. These models aim at reproducing the phenomenology that characterises the observed black hole (candidates). However, to overcome the problems associated to the event horizon (and the consequent curvature singularity, following from Penrose's singularity theorem), these ECOs do not possess an event horizon. In this thesis, we explore a simple ECO model, described by the Kerr-Newman metric in the exterior of a surface wherein re ective boundary conditions are imposed, placed outside the event horizon of the Kerr-Newman geometry. We then study, on this geometry, ECOs that may be in equilibrium with static scalar eld con- gurations. We consider both electrically charged and uncharged massless scalar elds, and, using analytical methods, we obtain a discrete set of critical ECO surface radii that can support static scalar eld con gurations. Within this discrete set, the ECO with the largest critical surface radius separates stable and unstable Kerr-Newman-type ECOs against the superradiant instability induced by a scalar eld. The discrete set of ECO critical surface radii was constructed for three di erent regimes of the Kerr-Newman metric: sub-extremal regime, extremal regime and super-extremal regime. These resonance spectra are dependent on the physical parameters {a,Q,q,l,m}
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Nativi, Lorenzo. "Jet-wind interaction in neutron star mergers." Licentiate thesis, Stockholms universitet, Institutionen för astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-189245.
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Besides being sources of gravitational waves, there has been evidence that neutron starmergers release neutron-rich material suitable for the production of heavy r-process nuclei.The radioactive decay of these freshly synthesised elements powers a rapidly evolvingthermal transient, the “macronova” (also known as “kilonova”). Its spectral propertiesstrongly depend on the ejecta composition, since neutron rich material synthesises heavyr-process elements that can efficiently trap radiation inside the ejecta producing a longlasting signal peaking in the red part of the spectrum. The first detection of a binaryneutron star merger was also accompanied by the evidence of a relativistic jet. Despitebeing ascertained the presence of these two dynamical components, neutron-rich ejectaand ultra-relativistic jet, the observational consequences of the interplay between the twois still unclear. In the paper we investigate such interaction through dedicated specialrelativistic hydrodynamic simulations, starting from a realistic environment obtained byprevious works. Light curves are then constructed up to the time scale of days by postprocessing the hydrodynamic results adopting proper radiative transfer. I show thatjet propagation within such environment can significantly affect the observation of theradioactive transient. A relativistic outflow can in fact “punch-away” a fraction of highopacity material before the brightening of the macronova, resulting in the transient beingbrighter and bluer for on-axis observers in the first few days. In this way the jet impactsboth time scale and luminosity of the macronova peak, that are the two main observablesallowing the estimate of the ejecta properties.
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Rosado, González Pablo Antonio [Verfasser]. "Gravitational wave background from compact objects and a new search for supermassive black hole binaries / Pablo Antonio Rosado González." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2013. http://d-nb.info/1047352435/34.
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Hanke, Manfred [Verfasser], and Jörn [Akademischer Betreuer] Wilms. "Probing the Environment of Accreting Compact Objects = Untersuchung der Umgebung von akkretierenden kompakten Objekten / Manfred Hanke. Betreuer: Jörn Wilms." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2011. http://d-nb.info/1015474926/34.
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Waisberg, Idel Reis [Verfasser], and Reinhard [Akademischer Betreuer] Genzel. "Optical interferometry of compact objects : testing general relativity and the extremes of accretion / Idel Reis Waisberg ; Betreuer: Reinhard Genzel." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1193924197/34.
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Gold, Roman [Verfasser], Bernd [Akademischer Betreuer] Brügmann, Luis [Akademischer Betreuer] Lehner, and Deirdre [Akademischer Betreuer] Shoemaker. "Eccentric binaries of compact objects in strong-field gravity / Roman Gold. Gutachter: Bernd Brügmann ; Luis Lehner ; Deirdre Shoemaker." Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2012. http://d-nb.info/1019969563/34.
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Lehebel, Antoine. "Objets astrophysiques compacts en gravité modifiée." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS204/document.
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Vingt années se sont écoulées depuis la découverte de l'expansion accélérée de l'Univers, ravivant l'intérêt pour les théories alternatives de la gravité. Ajouter un champ scalaire à la métrique habituelle de la relativité générale est l'une des manières les plus simples de modifier notre théorie de la gravité. En parallèle, nos connaissances sur les trous noirs et les étoiles à neutrons sont en plein essor, grâce notamment au développement de l'astronomie par ondes gravitationnelles. Cette thèse se situe au carrefour entre les deux domaines : elle étudie les propriétés des objets compacts dans les théories tenseur-scalaire généralisées. Je commence par rappeler les théorèmes d'unicité essentiels établis depuis les années soixante-dix. Après avoir présenté le théorème d'unicité pour les trous noirs en théorie de Horndeski, je l'étends aux étoiles. La deuxième partie de cette thèse détaille les différentes manières de contourner ce théorème. Parmi elles, je présente des solutions où la dépendance temporelle du champ scalaire permet de le raccorder à une solution cosmologique, mais aussi des trous noirs statiques et asymptotiquement plats. Dans la troisième partie, j'établis un critère important pour la stabilité de ces solutions, qui s'appuie sur leur structure causale. C'est aussi l'occasion d'étudier la propagation des ondes gravitationnelles au voisinage de trous noirs, et de sélectionner les théories dans lesquelles les ondes gravitationnelles se propagent à la même vitesse que la lumièreTwenty years have passed since the discovery of the accelerated expansion of the Universe, reviving the interest for alternative theories of gravity. Adding a scalar degree of freedom to the usual metric of general relativity is one of the simplest ways to modify our gravitational theory. In parallel, our knowledge about black holes and neutron stars is booming, notably thanks to the advent of gravitational wave astronomy. This thesis is at the crossroads between the two fields, investigating the properties of compact objects in extended scalar-tensor theories. I start by reviewing essential no-hair results established since the seventies. After discussing the no-hair theorem proposed for black holes in Horndeski theory, I present its extension to stars. The second part of the thesis investigates in detail the various ways to circumvent this theorem. These notably include solutions with a time-dependent scalar field in order to match cosmological evolution, but also static and asymptotically flat configurations. In a third part, I establish an important stability criterion for these solutions, based on their causal structure. It is also the occasion to study the propagation of gravitational waves in black hole environments, and to select the theories where gravitational waves travel at the same speed as light
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Schroven, Kris Inken [Verfasser], Claus [Akademischer Betreuer] Lämmerzahl, Claus [Gutachter] Lämmerzahl, and Jutta [Gutachter] Kunz. "The Role of Electric Charge in Relativistic Accretion onto Compact Objects : an Analytical Approach / Kris Inken Schroven ; Gutachter: Claus Lämmerzahl, Jutta Kunz ; Betreuer: Claus Lämmerzahl." Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1171420455/34.
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Droulans, Robert. "Étude de l'émission haute énergie des objets compacts avec SPI-INTEGRAL." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1234/.
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L'étude de l'émission haute énergie est indispensable pour comprendre les processus radiatifs inhérents aux flots d'accrétion sur les objets compacts (trous noirs et étoiles à neutrons). Le continuum X/gamma d'un tel système est généralement interprété selon deux composantes. La première traduit la présence d’un disque d'accrétion alors que la deuxième, à plus haute énergie (>20 keV), peut s'expliquer par des diffusions Compton entre électrons chauds et photons de plus basse énergie. Les mécanismes de chauffage des électrons et la structure du milieu de Comptonisation restent cependant mal connus. Pour approfondir notre compréhension de ces aspects, nous avons tiré profit des données issues de l'instrument SPI, un spectromètre haute énergie (20 keV – 8 MeV) développé au CESR (désormais IRAP, Toulouse, France) pour la mission INTEGRAL de l'ESA. Au-dessus de 150 keV, SPI réunit une résolution spectrale et une sensibilité sans précédent et constitue donc un outil idéal pour l'étude de l'émission haute énergie des objets compacts. Dans cette thèse, je présente les résultats d'une étude spectrale et temporelle de trois systèmes individuels. Malgré les différences dans leurs propriétés principales (nature de l'objet compact, stabilité du flot d'accrétion etc. ), les trois sources montrent un excès à haute énergie par rapport aux lois habituellement utilisées pour décrire leur spectre. Les possibles origines physiques de cet excès d'émission sont présentées et discutées, concluant que tous les états lumineux peuvent être expliqués par un milieu de Comptonisation magnétique de type couronne alimenté par des processus d'accélération non-thermiquesThe study of the high energy emission (>20 keV) is essential for understanding the radiative processes inherent to accretion flows onto compact objects (black holes and neutron stars). The X/gamma-ray continuum of these systems is successfully interpreted in terms of two components. The first component corresponds to blackbody emission from a geometrically thin optically thick accretion disk while the second component is generally associated to Compton scattering of the thermal disk flux off hot electrons. Despite considerable advances throughout the years, the heating mechanisms as well as the structure of the Comptonizing medium remain poorly understood. In order to enhance our understanding of these aspects, we take advantage of the data archive accumulated by the SPI instrument, a high energy spectrometer (20 keV – 8 MeV) developed at the CESR (now IRAP, Toulouse, France) for the INTEGRAL mission. Above 150 keV, SPI combines a unique spectral resolution with unequalled sensitivity, being thus an ideal tool to study the high energy emission of accreting compact objects. This thesis comprises the results of timing and spectral studies of three individual systems. Despite major differences in their main properties (nature of the compact object, stability of the accretion flow etc. ), all three systems show a significant high energy excess with respect to the emission laws that are commonly used to describe their spectra. In the lights of the SPI results, the possible physical origins of the high energy emission of stellar-size compact objects are presented and discussed, showing that all luminous states can be explained by a non-thermal magnetized corona model
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Pradel, Nicolas. "Etude des objets compacts symétriques en VLBI : imagerie et astrométrie par référence de phase." Toulouse 3, 2005. http://www.theses.fr/2005TOU30242.
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Ce travail de thèse présente l'étude des objets compacts symétriques (CSO), une catégorie bien précise de noyaux actifs de galaxies présentant à très haute résolution angulaire (mas) une structure symétrique atypique, réalisée en interférométrie à très longue base (VLBI). L'étude de la précision astrométrique de la technique d'astrométrie par référence de phase montre que la précision de cette technique est d'environ 50 µas. L'ensemble des CSO sont ensuite décrits. L'étude des CSO a porté sur deux voix : une étude VLBI classique sur une longue base de temps et une étude de 8 CSO par référence de phase. L'étude classique a porté sur le CSO OQ208 et a permis de mettre en évidence des mouvements apparents avec une précision de 10 µas/an. L'étude par référence de phase a permis d'imager avec une résolution angulaire proche du mas les 8 CSO observés et de permettre d'effectuer l'astrométrie de chaque composante des CSO avec une précision de 20 à 30 µasThis study is about compact symetric objects (CSO). These objects are a specific type of active galactic nuclei only observed at a very accurate angular resolution (milliarsecond). This resolution is only obtained with the very long baseline interferometry (VLBI). CSO present a specific geometry with symetric jets on this scale. A presentation of the forty known CSO is included in this study. A preliminary study of an astrometric VLBI technique (phase-referencing) used in this study showed that this technique is accurate at a 50 microarcseconds level. In the first part of the study, classical VLBI observations of the CSO OQ208 showed apparent motions of the components with an accuracy of 10 µas/yr. In the second part of the study, phase referencing observation of 8 CSO produced maps with an 1 mas angular resolution and the accuracy of the phase-referencing astrometry of all components of the 8 CSO was about 20 to 30 µas
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Malzac, Julien. "Modélisation de l'émission X et Gamma des objets compacts par les méthodes Monte-Carlo." Phd thesis, Université Paul Sabatier - Toulouse III, 1999. http://tel.archives-ouvertes.fr/tel-00010420.
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L'étude des processus de production de rayonnement de haute énergie dans les plasmas relativistes constituant l'environnement des objets compacts nécéssite des outils numériques relativement lourds. Je présente des codes dédiés à la simulation de ces processus (diffusions Compton multiples, production et annihilation de paires Èlectron-positon, raie de fluorescence du fer...). D'une part, des codes basés sur des méthodes Monte-Carlo standards (linéaires) permettent de calculer le spectre Èmis par Comptonisation dans un plasma chaud ou réflexion sur de la matière froide. Ces calculs sont effectuÈs pour une géométrie et une distribution des électrons fixée. D'autre part, un code Monte-Carlo nonlinéaire a été développé. Ce code évite les hypothèses sur la distribution des électrons (ou paires) qui est calculée de manière autocohérente en utilisant à la fois le bilan énergétique et le bilan de création/annihilation des paires, et en tenant compte du couplage avec la matière froide présente dans l'environnement de la région active. Les paramètres libres sont alors la puissance fournie au plasma et la façon dont cette énergie est fournie (chauffage thermique, injection/accélération de particules à haute énergie...). Les spectres calculés, comparés aux observations, donnent des informations sur la distribution des particules et les processus de dissipation d'énergie. Ce code permet également d'étudier des situations hors équilibre, dépendant du temps et notamment de calculer les courbes de lumière associées à une perturbation. Des applications aux différents modèles proposès pour rendre compte des observations X et gamma sont présentées (modèles thermiques, non-thermiques, modèle d'illumination anisotrope et modèles de couronne thermique radiativement couplèe au disque d'accrétion). Je montre comment de tels outils numériques peuvent mettre des contraintes sur la géométrie et les conditions physiques qui règnent dans les sources compactes de rayonnement X et gamma.
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Antognini, Joseph M. "Adventures in the Kozai-Lidov Mechanism." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1450697815.
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Limousin, François. "Etude de systemes binaires d'objets compacts : etoiles a neutrons, etoiles de quarks etranges et trous noirs." Paris 6, 2005. http://www.theses.fr/2005PA066524.
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Postnikov, Sergey A. "Topics in the Physics and Astrophysics of Neutron Stars." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1259174094.
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"Topics in compact stars." 2007. http://library.cuhk.edu.hk/record=b5893136.
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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
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"Compact stars in Eddington-inspired Born-Infeld gravity and general relativity." 2015. http://repository.lib.cuhk.edu.hk/en/item/cuhk-1291276.
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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.
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"alytic approach to pulsations of compact stars." 2011. http://library.cuhk.edu.hk/record=b5894655.
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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
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Margalit, Ben. "Transients from the Birth and Death of Compact Objects." Thesis, 2018. https://doi.org/10.7916/D8QG09QH.
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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.
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Li, Hui. "Particle acceleration near astrophysical compact objects--Several problems in high energy astrophysics." Thesis, 1995. http://hdl.handle.net/1911/19101.
Full textAbstract:
Particle acceleration in astrophysical plasmas has been a longstanding and challenging problem and it has been both intensively and extensively highlighted by the recent observations from Compton Gamma Ray Observatory on various astrophysical objects, including Gamma Ray Bursts (GRBs), Active Galactic Nuclei (AGNs) and Galactic Black Hole Candidates (gBHCs).
In this work, I study the stochastic particle acceleration due to the resonant interactions between the turbulent plasma waves and particles. I employ the particle orbital theory approach by treating the effects of various waves as perturbations to particle's zeroth-order Hamiltonian. The particle's momentum and pitch angle diffusion coefficients ($D\sb{pp},\ D\sb{\mu\mu})$ are derived for interactions of proton/Alfven-wave, electron/fast-magnetosonic-wave and electron /whistler-wave, though the formalism can be generalized to other type of waves. Based on the Monte Carlo code I have developed, which solves the coupled time-dependent wave, particle, and photon kinetic equations, these results have been or are being applied to the central region of both AGNs and gBHCs, with applications for gamma-ray production and energetic particle outflows.
By calculating the particle trajectories under the influence of gravity and radiation pressure near the center of galactic black hole accretion disk, I show that the recent discoveries of relativistic outflows from several X-ray binaries (e.g., GRS1915+105 and GROJ1655$-$40) can be well explained by radiation acceleration. The calculated final jet velocity is in good agreement with the observations and further constraints can be put on the composition and the power of those jets.
The isotropic but inhomogeneous distribution of GRBs over the whole sky apparently requires more exotic explanations. A novel model for GRBs from high velocity neutron stars, which escape into our Galactic halo, has been developed. I show, in detail, the difficulties the halo models are facing and propose several scenarios to overcome them. This model predicts that bright burst distribution should deviate from isotropy and it still awaits confrontation with the observations.
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"Gravitational waves and dynamical processes in hot newborn compact stars." 2010. http://library.cuhk.edu.hk/record=b5894287.
Full textAbstract:
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
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"A study on non-radial fluid oscillation modes in compact stars." Thesis, 2013. http://repository.lib.cuhk.edu.hk/en/item/cuhk-1291489.
Full textAbstract:
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.