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The inner crust of a neutron star is explored, using nuclear models andimplementing them in an open quantum system formalism. The purposeof the investigation is to extract valuable dynamics of the predictednuclear clusters that may exist in this region. We begin by setting up thenuclear models to extract the total energy per particle per system in orderto see if the results are corroborated with the works of others. Thereafter,the single-particle energies of the nuclear clusters are extracted. Theseenergies are then used in the Lindblad formalism to work out the timedependenceof the density matrix, which will allow us to extract thetime-dependence of the average energy of the system in interaction withan environment. / Den inre skorpan hos en neutronstjärna utforskas genom att användakärnmodeller och implementera dem i en öppen kvantumsystemformalism.Syftet med undersökningen är att extrahera värdefulladynamiska egenskaper hos de förutsagda kärnkluster som kan existerai detta område. Vi börjar med att etablera kärnmodeller för att extrahera den totala energin per partikel per system för att se omresultaten överensstämmer med andras arbeten. Därefter extraherade enskilda partikelenergierna hos kärnklusterna. Dessa energieranvänds sedan i Lindblad-formalismen för att beräkna tidsberoendetav densitetsmatrisen, vilket kommer att tillåta oss att extraheratidsberoendet av systemets genomsnittliga energi i interaktion med en miljö.

Le Large Area Telescope (LAT) à bord du satellite Fermi, lancé le 11 Juin 2008, est sensible au rayonnement gamma de20 MeV à plus de 300 GeV. 148 pulsars gamma à ce jour ont été détectés avec le Fermi-LAT, dont 117 sont détaillés dansle Deuxième Catalogue de Pulsars gamma de Fermi (2PC). Les pulsars forment la plus grande classe de sources au GeVdans la Voie Lactée. Les études de pulsars gamma apportent des contraintes importantes sur les modèles d’émission gamma etpermettent des percées dans notre compréhension des pulsars.Cette thèse présente des détections de sept pulsars gamma faibles déjà connus en radio, dont quatre jeunes ou d’âgesmoyens et trois millisecondes (MSP). L’analyse spectrale et la caractérisation des courbes de lumiére sont décriteset comparées à la population de 2PC. Ces détections ont l’intérêt particulier de sonder et d’étendre l’espace desparamètres de la population actuelle. Elles illustrent la distorsion inhérente dans 2PC et marquent la transition de lapremière phase (pulsars brillants) à la seconde phase (pulsars faibles) d’opération de Fermi. Le développement desmodèles théoriques et un recensement complet de la population galactique des étoiles à neutrons bénéficieront de plusde détections de pulsars faibles dans les années à venir.Certains pulsars gamma dans 2PC manifestant de grande efficacité gamma sont étudiés dans cette thèse. L’examen desdifférents paramètres qui influencent l’efficacité conduit à quelques candidats pour lesquels un plus grand momentd’inertie est nécessaire afin de résoudre le paradoxe de grande efficacité. Les observations de Fermi en rayons gamma ontl’air à apporter des contraintes indépendantes sur le moment d’inertie et les équations d’état des étoiles à neutrons. / The Large Area Telescope (LAT) on board the Fermi satellite, launched on June 11 2008, is sensitive to g raysfrom 20 MeV to over 300 GeV. gamma-ray pulsations from 148 pulsars to date have been detected with the Fermi-LAT, 117are detailed in the Second Fermi-LAT Gamma-ray Pulsar Catalog (2PC). Pulsars are by far the largest GeV sourceclassin the Milky Way. Studies of the increasing gamma-ray pulsar sample bring important constraints on theoretical gamma-rayemission models and enable breakthroughs in our understanding of pulsars.This thesis presents detections of seven faint gamma-ray pulsars that are already known at radio wavelengths, includingfour young or middle aged pulsars and three millisecond pulsars (MSPs). Spectral analysis and light curve characterizationsare detailed and compared to the 2PC sample. These detections have the special interest of allowing us toprobe and extend the parameter space of the current population. They illustrate the inherent bias in 2PC and mark thetransition from the early part (bright pulsars) to the later part (faint pulsars) of the Fermi mission. Theoretical modeldevelopments and a complete census of Galactic neutron star populations will benefit from more detections of weakpulsars in the years to come.Some high gamma-ray efficiency pulsars in 2PC are studied in this thesis. Investigations on different parameters whichinfluence the efficiency result in a few candidates for which a large moment of inertia is necessary to cure the highefficiency paradox. Fermi gamma-ray observations seem to bring independent constraints on the moment of inertia andequations of state of neutron stars

L'objectif de cette thèse est d'étudier différents aspects microscopiques et macroscopiques liés à la présence de superfluidité dans les étoiles à neutrons. Dans un premier temps, nous avons calculé des configurations stationnaires d'étoiles à neutrons superfluides en rotation, en relativité générale, basées sur l'utilisation d'équations d'état réalistes. A l'aide de ces configurations d'équilibre, nous avons ensuite développé un modèle simple de glitch, en relativité générale, vu comme un transfert de moment cinétique entre les neutrons superfluides et les particules chargées constituant l'étoile. Cela nous a permis d'obtenir des temps caractéristiques de montée qui pourront être comparés à de futures observations précises de glitches afin d'apporter de meilleures contraintes sur l'intérieur de ces étoiles. Enfin, nous nous sommes également intéressés à la dynamique des vortex superfluides, en présence de tubes de flux, dans le cas où les protons dans le coeur des étoiles formeraient un supraconducteur de type II. / The aim of this thesis is to study different aspects, both microscopic and macroscopic, associated with the presence of a large amount of superfluid matter inside neutron stars. First, we computed stationary configurations of rotating superfluid neutron stars, in general relativity, using realistic equations of state. Based on these equilibrium configurations, we then developed a simple model of pulsar glitches, in general relativity, seen as angular momentum transfers between the superfluid neutrons and the charged particles composing the star. This enables us to infer spin-up time scales that could be compared with future accurate glitch observations, in order to get some constraints on the interior of neutron stars. Finally, we also focused on the dynamics of superfluid vortex lines, accounting for the presence of fluxtubes, if the protons are forming a type II superconductor in the core of neutron stars.

The main objective of the thesis is to study the properties of the Galactic population of radio-quiet and thermally emitting isolated neutron stars (INSs). This is done by studying further the existing neutron star sample of nearby seven sources, known as the Magnificent Seven (M7), as well as by searching for new candidates and constraining possible populations. During the thesis, we investigated the proper motions of three of the faintest M7 in X-rays with the satellite Chandra. This work allowed us to constrain the neutron star displacement in two cases as well as to accurately determine the high proper motion of a third source, for the first time in X-rays with a significance approaching 10 standard deviations (Motch, Pires, Haberl, & Schwope, 2007, Ap&SS, 308, 217; Motch, Pires, Haberl, Schwope, & Zavlin, 2009, A&A 497, 423). The search of new INS candidates in the serendipitous catalogue of the XMM-Newton Observatory, with more than 120,000 X-ray sources, had as well the aim to constrain the spatial density of thermally emitting sources located beyond the solar vicinity. This work allowed the long awaited discovery of a new thermally emitting INS with properties similar to those of the seven nearby sources discovered by ROSAT (Pires, Motch, Turolla, Treves, & Popov, 2009, A&A 498, 233). Moreover, deep optical observations with SOAR and the ESO-VLT have been obtained during the thesis work in order to optically identify a handful of INS candidates that have been selected among more than 72,000 sources (Pires, Motch, & Janot-Pacheco, 2009, A&A, 504, 185). Finally, population synthesis of Galactic thermally emitting INSs allows constraining the global properties of this population based on the whole sample of XMM-Newton observations. By estimating the density of similar sources at more remote distances in the Milky Way, the final objective is to determine whether the spatial density derived from the group of seven nearby sources is a local anomaly caused by the Suns current location near regions of active stellar formation of the Gould Belt. / O objetivo da tese é estudar as propriedades da população Galáctica de estrelas de nêutrons isoladas com emissão térmica em raios X mas silenciosas em rádio. Isto é feito iinvestigando-se a amostra existente de sete fontes próximas, conhecidas como Magnificent Seven (M7), assim como através da procura por novos candidatos e restringindo possíveis cenários e populações. Durante a tese, nós investigamos os movimentos próprios de três das mais fracas fontes em raios X com o satélite Chandra. Este trabalho nos permitiu restringir o deslocamento da estrela de nêutrons em dois casos assim como medir com grande precisão o alto valor de movimento próprio de uma terceira fonte, pela primeira vez em raios X com uma precisão alcançando 10 desvios-padrão (Motch, Pires, Haberl & Schwope, 2007, Ap&SS, 308, 217; Motch, Pires, Haberl, Schwope & Zavlin, 2009, A&A 497, 423). A procura por novos candidatos a estrelas de nêutrons isoladas no catálogo de fontes do satélite XMM-Newton, com mais de 120.000 fontes de raios X, teve igualmente como objetivo restringir a densidade espacial de fontes com emissão térmica situadas além da vizinhança solar. Este trabalho levou à aguardada descoberta de uma nova estrela de nêutrons isolada em processo de resfriamento, a qual exibe propriedades similares às sete fontes descobertas pelo ROSAT (Pires, Motch, Turolla, Treves, & Popov, 2009, A&A 498, 233). Mais ainda, observações óticas profundas com os telescópios SOAR e ESO-VLT foram obtidas durante a tese de maneira a identificar no óptico a amostra mais brilhante de candidatos a estrelas de nêutrons, os quais foram selecionados entre mais de 72.000 fontes (Pires, Motch, & Janot-Pacheco, 2009, A&A, 504, 185). Finalmente, a síntese de população de estrelas de nêutrons isoladas Galácticas permite restringir as propriedades globais da população com base na amostra total de observações em raios X realizadas com o satélite XMM-Newton. Estimando-se a densidade de fontes similares a maiores distâncias na Via Láctea, o objetivo final é determinar se a densidade espacial derivada do grupo de sete estrelas próximas corresponde a uma anomalia local causada pela proximidade do Sol em relação a regiões de ativa formação estelar do Cinturão de Gould.

La première détection des ondes gravitationnelles en 2015 a ouvert un nouveau plan d'étude pour l'astrophysique des étoiles binaires compactes. En utilisant les données des détections faites par les détecteurs terrestres advanced LIGO et advanced Virgo, il est possible de contraindre les paramètres physiques de ces systèmes avec une analyse Bayésienne et ainsi approfondir notre connaissance physique des étoiles binaires compactes. Cependant, pour pouvoir être en mesure d'obtenir de tels résultats, il est essentiel d’avoir des algorithmes performants à la fois pour trouver les signaux de ces ondes gravitationnelles et pour l'estimation de paramètres. Le travail de cette thèse a ainsi été centré autour du développement d’algorithmes performants et adaptées au problème physique à la fois de la détection et de l'estimation des paramètres pour les ondes gravitationnelles. La plus grande partie de ce travail de thèse a ainsi été dédiée à l'implémentation d’un algorithme de type Hamiltonian Monte Carlo adapté à l'estimation de paramètres pour les signaux d’ondes gravitationnelles émises par des binaires compactes formées de deux étoiles à neutrons. L'algorithme développé a été testé sur une sélection de sources et a été capable de fournir de meilleures performances que d'autres algorithmes de type MCMC comme l'algorithme de Metropolis-Hasting et l'algorithme à évolution différentielle. L'implémentation d'un tel algorithme dans les pipelines d’analyse de données de la collaboration pourrait augmenter grandement l'efficacité de l'estimation de paramètres. De plus, il permettrait également de réduire drastiquement le temps de calcul nécessaire, ce qui est un facteur essentiel pour le futur où de nombreuses détections sont attendues. Un autre aspect de ce travail de thèse a été dédié à l'implémentation d'un algorithme de recherche de signaux gravitationnelles pour les binaires compactes monochromatiques qui seront observées par la future mission spatiale LISA. L'algorithme est une mixture de plusieurs algorithmes évolutionnistes, avec notamment l'inclusion d'un algorithme de Particle Swarm Optimisation. Cette algorithme a été testé dans plusieurs cas tests et a été capable de trouver toutes les sources gravitationnelles comprises dans un signal donné. De plus, l'algorithme a également été capable d'identifier des sources sur une bande de fréquence aussi grande que 1 mHz, ce qui n'avait pas été réalisé au moment de cette étude de thèse. / The first detection of gravitational waves in 2015 has opened a new window for the study of the astrophysics of compact binaries. Thanks to the data taken by the ground-based detectors advanced LIGO and advanced Virgo, it is now possible to constrain the physical parameters of compact binaries using a full Bayesian analysis in order to increase our physical knowledge on compact binaries. However, in order to be able to perform such analysis, it is essential to have efficient algorithms both to search for the signals and for parameter estimation. The main part of this thesis has been dedicated to the implementation of a Hamiltonian Monte Carlo algorithm suited for the parameter estimation of gravitational waves emitted by compact binaries composed of neutron stars. The algorithm has been tested on a selection of sources and has been able to produce better performances than other types of MCMC methods such as Metropolis-Hastings and Differential Evolution Monte Carlo. The implementation of the HMC algorithm in the data analysis pipelines of the Ligo/Virgo collaboration could greatly increase the efficiency of parameter estimation. In addition, it could also drastically reduce the computation time associated to the parameter estimation of such sources of gravitational waves, which will be of particular interest in the near future when there will many detections by the ground-based network of gravitational wave detectors. Another aspect of this work was dedicated to the implementation of a search algorithm for gravitational wave signals emitted by monochromatic compact binaries as observed by the space-based detector LISA. The developed algorithm is a mixture of several evolutionary algorithms, including Particle Swarm Optimisation. This algorithm has been tested on several test cases and has been able to find all the sources buried in a signal. Furthermore, the algorithm has been able to find the sources on a band of frequency as large as 1 mHz which wasn’t done at the time of this thesis study

In this thesis, we present the spectral and timing variabilities of anomalous X-ray pulsar 1E 2259+586 observed with European Photon Imaging PN Camera (EPIC PN) on board X-ray Multi Mirror Mission (XMM), Proportional Counter Array (PCA) on board Rossi X-ray Timing Explorer (RXTE) and Advanced CCD Imaging Spectrometer (ACIS) on board Chandra X-ray Observatory. We presented the results of spectral analysis of 2000 January 11 ACIS observation. Pulse phase spectroscopy was performed on two XMM observations before and after the outburst. Pulse profiles of two XMM observations before the outburst and three XMM observations after the outburst were studied. Results are consistent with the those presented by Patel et al. (2001) and Woods et al. (2004). We searched for the spectral variations versus spin rate during the outburst. Long-term spectral, frequency and spin-down rate variations are presented between 1996 and 2006 including 98 RXTE and 4 XMM observations. However, except outburst region (Woods et al. 2004) no significant spectral and spin rate variabilities were seen. Around the outburst region we confirmed the spectral hardening with increasing spin rate and flux.

In this thesis, X-ray spectral and pulse timing analysis of the high mass X-ray binary pulsar 4U 1907+09, based on the observations with Rossi X-ray Timing Explorer (RXTE) and International Gamma-Ray Astrophysics Laboratory (INTEGRAL), are presented. INTEGRAL (October 2005 - November 2007) and RXTE (June 2007 - December 2008) observations confirm that the luminosity of the source is highly variable such that, flaring and dipping activities are observed. The results of time-averaged energy spectra of RXTE and INTEGRAL observations are consistent with the previous studies. Orbital phase resolved spectroscopy with RXTE data, reveals that the Hydrogen column density varies through the orbit reaching to its maximum value just after periastron. This variation approves that the location of the absorbing material is the accretion flow. A slight spectral softening with increasing luminosity is aslo observed. 4U 1907+09 had been steadily spinning down for more than ~15 years with a rate of -3.54x10-14 Hz s-1. RXTE observations of the source in 2001 showed a ~60% decrease in the spin-down rate and INTEGRAL observations in 2003 showed a reversal to spin-up. The timing analysis presented in this thesis reveals a new spin-down episode with a rate of -3.59x10-14 Hz s-1, which is close to the previous steady spin-down rate. This result implies that a recent torque reversal before June 2007 has taken place. The reversal is a rare event for 4U 1907+09 and it indicates the variations in the mass accretion rate and/or geometry. Using RXTE observations, 24 new pulse periods are measured to demonstrate the period evolution. Energy resolved pulse profiles confirm that the profile has a double peak sinusoidal shape at energies below 20 keV, whereas the leading peak significantly loses its intensity above 20 keV. This energy dependence indicates that the physical circumstances of the two polar caps are different.

In this thesis, X-ray observations of four accretion powered pulsars are presented. Using RXTE observations of 4U 1907+09, we found three new pulse periods of the source. We found that the source spun-down almost at a constant rate of $dot nu$ = (-3.54 $pm 0.02) times 10^{-14}$ Hz s$^{-1}$ for more than 15 years. Using RXTE observations, X-ray flux related spectral and timing features in 2S 1417-62 were, in general, interpreted as a sign of a disc accretion with a similar geometry with a varying mass accretion rate, whereas spectral and timing features of the low X-ray flux regions were interpreted as a sign of possible temporary accretion geometry change prior to the next periastron. Using XMM-Newton and RXTE observations of SAX J2103.5+4545, we discovered quasi periodic oscillations around 0.044 Hz (22.7 sec) while the source was spinning-up with a rate of $(7.4pm0.9)times10^{-13}$Hz s$^{-1}$. In the X-ray spectrum, we also found a soft component consistent with a blackbody emission with ${rm{kT}}sim1.9$keV. Using RXTE observations, we also studied spectral evolution of Her X-1

Κύριο αντικείμενο μελέτης της παρούσας μεταπτυχιακής διπλωματικής εργασίας είναι οι περιστρεφόμενοι αστέρες νετρονίων. Λόγω του ότι οι κλασικές διαταρακτικές μέθοδοι που εφαρμόζονται για την εύρεση της ακτίνας ενός περιστρεφόμενου πολυτροπικού μοντέλου περιορίζονται, από την επιφάνεια του αστέρα, αναπτύξαμε μία μέθοδο για τον υπολογισμό ποσοτήτων πέραν αυτού του ορίου. Αυτή η γενικευμένη μέθοδος χρησιμοποιεί τις μετανευτώνειες παραμέτρους ως όρους διαταραχής. Υλοποιώντας έναν κώδικα σε γλώσσα προγραμματισμού Fortran, υπολογίσαμε εκτεταμένους πίνακες ποσοτήτων και σταθερών. Μέσω της γενικευμένης αυτής μεθόδου επιτυγχάνεται η εύρεση της ακριβούς τιμής της ακτίνας ενός τέτοιου μοντέλου καθώς και ο καθορισμός της κρίσιμης παραμέτρου περιστροφής, η οποία αποτελεί μία μετανευτώνεια παράμετρο. Ο υπολογισμός της κρίσιμης παραμέτρου διαταραχής επιτυγχάνεται με ευκολία, κυρίως εκ του λόγου ότι η μέθοδος έχει υπολογίσει εκτεταμένους πίνακες συναρτησιακών τιμών. Οι υπολογιζόμενες κρίσιμες παράμετροι διαταραχής είναι μεγαλύτερες των αντιστοίχων τιμών της βιβλιογραφίας (κυρίως σε σύγκριση με τους Fahlman-Anand [55]), και φαίνεται να συμφωνούν καλύτερα με τις τιμές που υπολογίζονται από τις λεγόμενες επαναληπτικές μεθόδους. Τα αποτελέσματα επαληθεύουν με μεγάλη ακρίβεια τιμές συναρτήσεων και παραμέτρων σε σύγκριση με την κλασική βιβλιογραφία. Η παρούσα εργασία χωρίζεται σε πέντε μέρη, τα οποία αναπτύσσονται στα κεφάλαια 1, 2, 3, 4 και 5. Στο πρώτο κεφάλαιο, περιγράφεται ο αστέρας νετρονίων ως αστροφυσικό αντικείμενο. Δίνεται βάρος τόσο στη δομή του όσο και στα φυσικά χαρακτηριστικά του. Η ύπαρξη των αστέρων νετρονίων είναι απόλυτα συνδεδεμένη με τους πάλσαρς. Αυτοί αποτελούν ένα «ζωντανό» παράδειγμα περιστρεφομένων αστέρων νετρονίων; έτσι, γίνεται αναφορά στις φυσικές ιδιότητες και στις διεργασίες που πραγματοποιούνται σε αυτούς. Στο δεύτερο κεφάλαιο, αναφερόμαστε στις καταστατικές εξισώσεις που διέπουν το εσωτερικό των αστέρων νετρονίων, και στην έννοια του πολυτρόπου. Αφενός μεν, διότι δεν μπορεί να πραγματοποιηθεί μία μελέτη για αυτούς τους αστέρες χωρίς να υιοθετηθεί κάποια καταστατική εξίσωση, αφετέρου δε διότι μία από τις πλέον ενδεικτικές για την περιγραφή τους (και την οποία εμείς υιοθετούμε) είναι αυτή του πολυτρόπου. Επιπλέον, αναλύουμε τις εξισώσεις που διέπουν το αδιατάρακτο πολυτροπικό μοντέλο, όπως και αυτές που περιγράφουν το αντίστοιχο διαταραγμένο, σύμφωνα με τη θεωρία που ανέπτυξε ο Chandrasekhar. Στο τρίτο κεφάλαιο, χρησιμοποιούμε τη Γενική Θεωρία της Σχετικότητας στη μελέτη του πολυτροπικού μοντέλου, εστιάζοντας κυρίως στον τρόπο με τον οποίο τροποποιείται η κλασική θεώρηση, στο πώς μετασχηματίζονται η βασικές ποσότητες του μοντέλου, και στο πώς προκύπτουν οι σχέσεις της μετανευτώνειας προσέγγισης. Εξάγουμε τις μετανευτώνειες εξισώσεις της υδροδυναμικής και αναπτύσσουμε το διαταρακτικό μοντέλο επίλυσης, από το οποίο προκύπτουν οι εξισώσεις που επιλύουμε αριθμητικά. Στο τέταρτο κεφάλαιο, κάνουμε αναφορά στις διάφορες αριθμητικές μεθόδους που έχουν αναπτυχθεί για την μελέτη του σχετικιστικά περιστρεφόμενου πολυτροπικού μοντέλου. Στο πέμπτο κεφάλαιο, παρουσιάζουμε πίνακες αποτελεσμάτων και ενδιαφέρουσες γραφικές παραστάσεις. Δίνουμε επίσης ορισμένες αλγοριθμικές λεπτομέρειες για το πρόγραμμά μας. Συγκεκριμένα, γενικεύουμε τη μέθοδο των μετανευτωνείων προσεγγίσεων και αναλύουμε τα πλεονεκτήματα της. Ακολούθως, παραθέτουμε μία περιγραφή της αριθμητικής διαπραγμάτευσης της μεθόδου και την πορεία υλοποίησής της. Τέλος, παρατίθενται οι πίνακες των αποτελεσμάτων και τα τελικά συμπεράσματα. / In the present Thesis, we study rotating neutron stars. Due to the fact that the classical perturbation methods implemented to compute the radius of a polytropic rotating model are restricted by the star's surface, we develop a method for continuing integrations beyond this limit. This general approach utilises the postnewtonian parameters in terms of disturbance. By the application of a code written in Fortran, we calculate extensive tables of quantities and constants. Furthermore, we compute the radius as well as the critical rotation parameter, which plays the role of a postnewtonian term. This Thesis is organized in five chapters. In the first chapter, the neutron star is presented as an astrophysical object. Its structure and physical characteristics are of a great importance. Moreover, the existence of neutron stars is linked to pulsars, which are "living" examples of rotating neutron stars. Therefore, the physical characteristics of these objects are discussed in this chapter. The second chapter refers to the equations that describe the structure of the neutron stars and to the concept of polytropes. First, due to the difficulty in implementing a study for these stars without the adoption of any equation of state as well as due to the most indicative one for their description which is that of the polytrope. Second, the equations that refer to the undistorted and those that describe the corresponding distorted configurations are analysed in this chapter, in accordance with Chandrasekhar's perturbation theory. In the third chapter, the General Theory of Relativity is used to the study of the polytropic model, focusing on how the classical theory is corrected, on how the basic model's quantities are transformed and on how the equations of the postnewtonian approach are derived. The equations to be solved result from the latter ones. Furthermore, a a discussion on the various numerical methods that have been developed for studying the relativistic rotating polytopric model is given in the fourth chapter. In the fifth chapter of this Thesis, a number of tables illustrating results as well as some interesting diagrams are included. Certain algorithmic details for our program are given. We also discuss the generalisation of the postnewtonian approach and its advantages.