La première détection d'une Onde Gravitationnelle (OG) a été faite le 14 Septembre 2015 par la collaboration LIGO-Virgo avec les deux détecteurs de LIGO. Elle a été émise par la fusion de deux Trous Noirs, fournissant ainsi la première preuve directe de l’existence des Trous Noirs. Advanced Virgo est la version améliorée de l’interféromètre Virgo et il va rejoindre les détecteurs LIGO dans les mois qui suivent. Le passage d'une OG induit un changement différentiel de la distance entre masses-test (uniquement sensibles à la force gravitationnelle). Cette variation de distance est proportionnelle à l'amplitude de l'OG, néanmoins le déplacement le plus grand qui peut être observé depuis la Terre est de l'ordre de 10⁻¹⁹ m/sqrt(Hz) en terme de densité spectrale. C'est pour cela que l’interféromètre de Michelson est l'instrument idéal pour détecter cet effet différentiel. Les détecteurs d’OG utilisent des miroirs suspendus, qui se comportent comme masses-test. Le passage d'une OG va produire un changement dans la distance entre les miroirs qui va modifier la condition d’interférence et donc une variation de puissance lumineuse mesurée par la photodiode de détection. Cependant, un Michelson simple n'est pas assez sensible et des améliorations ont été ajoutées. La première génération de détecteurs a ajouté des cavités Fabry-Pérot dans les bras pour augmenter le chemin optique. De plus un nouveau miroir a été ajouté pour recirculer la lumière réfléchie vers le laser et augmenter la puissance effective, en créant une nouvelle cavité connue comme Power Recycling Cavity (PRC). Son effet est d’autant plus important que le Michelson est en fait optimalement réglé sur une frange noire. Tous les miroirs du détecteur ressentent le bruit sismique et les longueurs des cavités, entre autres, changent en permanence. Il est donc nécessaire de contrôler activement la position longitudinale et angulaire des cavités pour les maintenir en résonance. Pendant ma thèse j'ai étudié le contrôle de Advanced Virgo d’abord en simulation puis pendant le commissioning lui-même. D'abord j'ai simulé la stratégie de contrôle utilisée dans Virgo avec des simulations modales. L'objectif était de vérifier si la même stratégie pouvait être appliquée à Advanced Virgo ou s'il fallait l'adapter. Avec Advanced Virgo les cavités Fabry-Pérot ont une finesse plus grande ce qui entraîne de nouveaux effets dynamiques et qui demande une stratégie de contrôle spéciale, stratégie que j'ai modifiée pour l'adapter aux besoins du commissioning. Concernant la PRC, j’ai étudié l'impact de sa stabilité dans le fonctionnement de l’interféromètre. Comme elle est très proche de la région d’instabilité, l’onde lumineuse être très sensible à l'alignement et a l'adaptation du faisceau à la cavité. J’ai vérifié avec les simulations son impact sur les contrôles longitudinaux, qui peuvent devenir instables, et une solution a été validée. Ensuite j'ai utilisé cette information pour le commissioning d'Advanced Virgo. Dans cette thèse les détails du commissioning des contrôles longitudinal et angulaire de l’interféromètre sont présentés. La stabilisation en fréquence est aussi présentée, puisqu'elle joue un rôle très important dans le contrôle de l’interféromètre car étant le bruit dominant. / The first detection of a Gravitational Wave (GW) was done on September 14 th of 2015 by the LIGO-Virgo collaboration with the two LIGO detectors. It was emitted by the merger of a Binary Black Hole, providing the first direct proof of the existence of Black Holes. Advanced Virgo is the upgraded version of the Virgo interferometer and it will join the LIGO detectors in the next months. The passage of a GW on Earth induces a change on the distance between test masses (experiencing only the gravitational interaction) in a differential way. This distance variation is proportional to the amplitude of the GW however the largest displacement observable on Earth will be of the order of 10⁻¹⁹ m/sqrt(Hz). Taking this in account, a Michelson interferometer is the ideal instrument to detect this differential effect. GWs detectors will use suspended mirrors to behave as test masses. The passage of a GW will cause a change on the distance between the mirrors that will spoil the interference condition, allowing some light to leak to the detection photodiode. However, a simple Michelson interferometer does not provide enough sensitivity. For this reason the first generation of detectors added Fabry-Perot cavities in the arms, in order to increase the optical path. A second change was the addition of an extra mirror in order to recycle the light that comes back towards the laser, to increase the effective power, creating a new cavity also known as Power Recycling Cavity (PRC). Its effect is more important when the Michelson is tuned in an optimal way in a dark fringe. All the mirrors of the detector are affected by the seismic noise and so their distance is continuously changing. It is necessary to control the longitudinal and angular position of the cavities in order to keep them at resonance. During my thesis I have studied the control of Advanced Virgo using simulation and during the commissioning itself. First of all I have simulated the control strategy used in Virgo using modal simulations. The aim was to check if the same strategy could be applied to Advanced Virgo or if it needs adaptation. In Advanced Virgo the Fabry-Perot cavities have a higher finesse, which arises new dynamical problems and requires a special control strategy that I have modified to match the commissioning needs. Regarding the PRC, we have studied the impact of its stability on the performance of the interferometer. As it is very close from the instability region, the electrical field inside will be very sensitive to alignment and matching of the laser beam. We have checked using simulations its impact on the longitudinal controls, which can become unstable, and a solution has been validated. Then I have used this information during the commissioning of the Advanced Virgo detector. In this thesis the details of the commissioning of the longitudinal and angular control of the interferometer will be presented. It includes the frequency stabilization, which has a key role in the control of the interferometer, since it is the dominant noise.

Zugl.: Hamburg, Univ., Diss., 2006

This thesis presents a literary study of three subtypes of the maiden stock character in Plautine Comedy: the silent virgo, the meretrix-virgo, and the virgo in transition. The comic maiden is remarkable in Roman Comedy, in that she is the female protagonist of most if not all of the plays in which she is a character, although she sometimes never appears onstage. The aim of this thesis is to investigate how the playwright manages and enrichens his portrayals of the virgo despite her limitations, and to analyze her significance in the broader themes of her plays. This has been done by detailed character analyses of three of Plautus’ plays, each of which features a virgo who represents one of the three subtypes of the comic maiden (i.e. Phaedria from Plautus’ Aulularia, Palaestra from Plautus’ Rudens, and Alcmena from Plautus’ Amphitruo respectively). Through the examination of the characters’ speeches and conversations, including those presented by the maiden herself when she appears onstage, it is evident that the virgo is a central figure in tensions and conclusions driving the plot. Because of her contradictory circumstances (i.e. her premarital pregnancy, slave status, or change in stock role), this integral function is contingent on her piety and innocence, which must be maintained throughout the play. Finally, the propitious resolution of the plot comes about in the restoration of the maiden’s status and the promise of marriage between her and the male lover. Because of this, she is also deeply connected to the underlying themes of morality and communal bonds governing the play. This research highlights the valuable and central role of a character in Plautine comedy, whose on-stage presence is often limited or even non-existent. / Thesis / Master of Arts (MA) / This thesis analyzes the portrayals of three subtypes of the virgo or maiden stock character in the comedies of Plautus, a Roman playwright who flourished in the late third to early second centuries BCE. More specifically, this thesis presents a detailed character study of Phaedria as the silent maiden in Aulularia, Palaestra as the prostitute-maiden (meretrix-virgo) in Rudens, and Alcmena the maiden in transition in Amphitruo. The aim is to investigate how Plautus manages and enrichens his characterization of these maidens, as well as their significance in the broader themes of the plays. Through the textual analyses of characters’ speeches and dialogues, this research highlights the centrality of the virgo in the tensions and resolutions driving the plot, and her connection to the underlying themes of morality and communal bonds in Plautus’ plays.

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.

L'ère de l'astronomie gravitationnelle a commencé avec la première détection d'une onde gravitationnelle le 14 septembre 2015, par la collaboration LIGO-Virgo. Les premières détections proviennent de coalescences de trous noirs de quelques dizaines de masses solaires. Le détecteur européen Advanced Virgo a redémarré en 2017 pour participer aux prochaines détections d'ondes gravitationnelles et localiser les sources astrophysiques.Cette thèse a pour sujet les différentes étapes du processus de détection des ondes gravitationnelles : de l'étalonnage du détecteur Advanced Virgo à l'analyse en temps réel des données du réseau d'interféromètres LIGO-Virgo. Dans un premier temps, les objectifs, la méthode et les résultats de l'étalonnage du détecteur Advanced Virgo sont décrits. Cette étape est cruciale pour comprendre la sensibilité du détecteur et pour reconstruire l'amplitude de l'onde gravitationnelle. Un nouvel algorithme, SilenteC, développé pendant la thèse est ensuite détaillé : son objectif est d'identifier les sources de bruits non-stationnaires qui limitent la sensibilité des analyses. Certains bruits transitoires interviennent de façon non-linéaire et SilenteC tente de repérer ce type de contribution. Enfin, l'analyse MBTA à faible latence pour la recherche des signaux d'ondes gravitationnelles issus de coalescences de binaires compactes est décrite. En particulier, l'accent est mis sur la caractérisation de vétos permettant de distinguer les signaux astrophysiques à sélectionner et les bruits transitoires à rejeter le plus efficacement possible. / The era of gravitational astronomy began with the first detection of a gravitational wave on September 14, 2015, by the LIGO-Virgo collaboration. The first detections come from coalescences of black holes with masses of a few tens of solar masses. The European detector Advanced Virgo restarted in 2017 to participate in the next detections of gravitational waves and to locate the astrophysical sources.This thesis deals with the different stages of the gravitational waves detection process: from the calibration of the Advanced Virgo detector to low-latency analysis of the LIGO-Virgo interferometer network data. First, the objectives, method and results of the detector calibration are described. This step is crucial for understanding the sensitivity of the detector and for reconstructing the amplitude of the gravitational wave. A new algorithm, SilenteC, developed during the thesis is then detailed: its objective is to identify the sources of non-stationary noises that limit the sensitivity of the analysis. Some transient noises are non-linear and SilenteC tries to identify this type of contribution. Finally, low-latency MBTA analysis for the detection of gravitational wave signals from compact binary coalescences is described. In particular, emphasis is put on the study of vetos making it possible to distinguish the astrophysical signals to be selected and the transient noises to be rejected as efficiently as possible.

Cette thèse présente les résultats de la recherche de signaux d'ondes gravitationnelles transitoires de longue durée dans les données des deux premiers runs d'observation des détecteurs advanced LIGO et advanced Virgo. Ces ondes sont principalement émises par des étoiles à neutrons ou des trous noirs impliqués dans des phénomènes violents. Pour certaines sources, une modélisation impliquant une dynamique complexe et des instabilités hydrodynamiques peut prédire grossièrement la forme d'onde. Mais de manière générale, seulement l'information approximative sur la durée et la bande de fréquence est utilisée pour définir les limites de l'espace des paramètres de la recherche. Une méthode d'analyse temps-fréquence robuste aux incertitudes de la modélisation des signaux a donc été développé. En combinant les données de deux détecteurs de façon cohérente, la méthode permet de différencier les signaux recherchés du bruit de fond non gaussien des détecteurs. En l'absence de détection, nous avons placé des limites supérieures sur l'énergie émise et le taux attendu pour ces sources. Une recherche du signal attendu après la fusion de deux étoiles à neutrons observé en août 2017 (GW170817) a également était faite dans l'hypothèse où une étoile à neutrons supre-massive a été formée. Aucun signal n'a été identifié et j'ai montré que des détecteurs un ordre de grandeur plus sensibles auraient été nécessaires pour détecter un tel signal. / This thesis shows the results of the search of long duration transient gravitational waves using the data from the first two observation runs of advanced LIGO and advanced Virgo detectors. These long duration gravitational waves are mainly emitted by neutrons stars or black hole involved in extreme phenomena. For some sources, a modeling involving a complex dynamics and hydrodynamic instabilities can predict roughly the waveform. Nevertheless, for the general case, only a partial informations on the duration and frequency band are used to limits the parameters space. A time-frequency analysis, sturdy enough to modeling incertitude, has been developed and applied to the data. Combining data from two detectors in a coherent way, the analysis can distinguish between signal and detector's non gaussian background noise. In the absence of detection, we have placed upper limits on the energy emitted and the expected rate for these sources. A search for the expected signal emitted by the object created after the neutron stars coalescence and merger observed in August 2017 (GW170817) was also made assuming a supra-massive neutron star was created and survived hundred of seconds after the merger. No signal has been found and we have shown that detectors of an order of magnitude more sensible would have been required to detect a signal from this source.

By virtue of its proximity, the Virgo Cluster is an ideal laboratory for us to test our understanding of the formation of structure in our Universe. In this spirit, we present a dynamical study of 33 gas-poor and 34 gas-rich Virgo galaxies as part of the Spectroscopic and H-band Imaging of Virgo survey. Our final spectroscopic data set was acquired at the 3.5-m telescope at the Apache Point Observatory. Hα rotation curves for the gas-rich galaxies were modelled with a multi-parameter fit function from which various velocity measurements were inferred. Analog values were measured off of the observed rotation curves, but yielded noisier scaling relations, such as the luminosity-velocity relation (also known as the Tully-Fisher relation). Our best i-band Tully-Fisher relation has slope α=-7.2 ± 0.5 and intercept M_i(2.3)=-21.5 ± 1.1 mag, matching similar previous studies. Our study takes advantage of our own, as well as literature, data; we plan to continue expanding our compilation in order to build the largest Tully-Fisher relation for a cluster to date. Following extensive testing of the IDL routine pPXF, extended velocity dispersion profiles were extracted for our gas-poor galaxies. Considering the lack of a common standard for the measurement of a fiducial galaxy velocity dispersion in the literature, we have endeavoured to rectify this situation by determining the radius at which the measured velocity dispersion, coupled with the galaxy luminosity, yields the tightest Faber-Jackson relation. We found that radius to be 1.5 R_e, which exceeds the extent of most dispersion profiles in other works. The slope of our Faber-Jackson relation is α=-4.3 ± 0.2, which closely matches the virial value of 4. This analysis will soon be applied to a study of the Virgo Cluster Fundamental Plane. Rotation correction of our dispersion profiles will also permit the study of galaxies' velocity dispersion profile shapes in an attempt to refine our understanding of the overall manifold of galaxy structural parameters. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-12-22 19:09:06.192

NIL

No description available.

L’objectif de la thèse est de développer une nouvelle technique d’optique adaptive pour les interferomètres gravitationels avancés, basée sur un nouveau type de miroir pour le faisceau d’injection de l’interferomètre. Le miroir déformable, basé sur une actuation thermique, doit etre un outil compatible ultra-vide, qui fonctionne sans bruit électronique ou mécanique, bon marché et permettre la correction des modes d’ordre supérieurs afin d’améliorer le matching des faisceaux de haute puissance dans les cavités laser du détecteur sous ultra-vide. Un montage experimental de caractérisation du miroir déformable a été mis en place afin d’effectuer les tests de validation du premier prototype sous air. L’élaboration d’une procédure de caractérisation des propriétés du miroir et d’une boucle de controle a permis de développer une approche efficace pour déterminer les possibilités et les limites du miroir. Nous avons ainsi pu faire la démonstration de sa capacite a corriger les aberrations de phase d’un faisceau laser infrarouge a différentes fréquences spatiales. Nous avons également démontré que le miroir vérifie les performances de stabilité, de reproductibilité et de linearité attendues. Nous avons ensuite validé l’amélioration du mode matching d’un faisceau laser sur une cavité de réference par le miroir thermiquement déformable / In this thesis we develop a new technique of adaptive optics for the Advanced Gravitational Interferometers, based on a new type of deformable mirror for the injection beam of the interferometer. This deformable mirror, based on a thermal actuation, has to be a high vacuum compatible and low-cost device, that is working without any electronic or mechanic noise. It has to allow the correction of high order modes to improve the matching of high power laser beams in the interferometer.An experimental setup has been made to characterize the first prototype on air. An efficient process and a control loop have allowed to determine the possibilities and limits of the device. We have demonstrated its ability to correct high order modes of an infrared laser beam. Afterwards, we have validated the improvement of mode matching into a fixed cavity.