Dissertations / Theses on the topic 'Transits'

The search for extrasolar planets is strongly motivated by the goal of characterizing how frequent habitable worlds and life may be within the Galaxy. Whilst much effort has been spent on searching for Earth-like planets, large moons may also be common, temperate abodes for life as well. The methods to detect extrasolar moons, or “exomoons” are more subtle than their planetary counterparts and in this thesis I aim to provide a method to find such bodies in transiting systems, which offer the greatest potential for detection. Before one can search for the tiny perturbations to the planetary signal, an understanding of the planetary transit must be established. Therefore, in Chapters 3 to 5 I discuss the transit model and provide several new insights. Chapter 4 presents new analytic expressions for the times of transit minima and the transit duration, which will be critical in the later search for exomoons. Chapter 5 discusses two sources of distortion to the transit signal, namely blending (with a focus on the previously unconsidered self-blending scenario) and light curve smearing due to long integration times. I provide methods to compensate for both of these effects, thus permitting for the accurate modelling of the planetary transit light curve. In Chapter 6, I discuss methods to detect exomoons through their gravitational influence on the host planet, giving rise to transit timing and duration variations (TTV and TDV). The previously known TTV effect is updated with a new model and the associated critical problems are outlined. I then predict a new effect, TDV, which solves these problems, making exomoon detection viable. Chapter 7 presents a feasibility study for detecting habitable-zone exomoons with Kepler, where it is found that moons down to 0.2M⊕ are detectable. Finally, conclusions and future work are discussed in Chapter 8.

The maritime environment is one of the harshest and most dangerous in which to work, particularly for professional users (e.g. military and rescue services). The aims of this research were to: a) investigate the effects of marine transits conducted in high speed craft (HSC) on the subsequent physical performance of military passengers, b) assess mitigation techniques to limit any degradation in human physical performance.

The technique of searching for extra-solar planetary transits is investigated. This technique, which relies on detecting the brief, shallow eclipses caused by planets passing across the line of sight to the primary star, requires high-precision time-series photometry of large numbers of stars in order to detect these statistically rare events. Observations of ~ 18000 stars in the field including the intermediate-age open cluster NGC 6819 are presented. This target field contrasts with the stellar environment surveyed by the radial velocity technique, which concentrates on the Solar neighbourhood. I present the data-reduction techniques used to obtain high-precision photometry in a semi-automated fashion for tens of thousands of stars at a time, together with an algorithm designed to search the resulting lightcurves for the transit signatures of hot Jupiter type planets. I describe simulations designed to test the detection efficiency of this algorithm and, for comparison, predict the number of transits expected from this data, assuming that hot Jupiter planets similar to HD 209458 are as common in the field of NGC 6819 as they are in the Solar neighbourhood. While no planetary transits have yet been identified, the detection of several very low amplitude eclipses by stellar companions demonstrates the effectiveness of the method. This study also indicates that stellar activity and particularly blending are significant causes of false detections. A useful additional consequence of studying this time-series photometry is the census it provides of some of the variable stars in the field. I report on the discovery of a variety of newly-discovered variables, including Algol-type detached eclipsing binaries which are likely to consist of M-dwarf stars. Further study of these stars is strongly recommended in order to help constrain models of stellar structure at the very low mass end. I conclude with a summary of this work in the context of other efforts being made in this field and recommend promising avenues of further study.

En mesurant la vitesse radiale de l'étoile 51-Peg en 1995, Michel Mayor et Didier Queloz ont identifié pour la première fois une planète en dehors du système solaire, ou exoplanète. Depuis 12 ans, un formidable élan a amené le décompte des découvertes au-delà de 240. C'est désormais la caractérisation (rayon, densité, composition atmosphérique) qui est possible et qui motive cette thèse théorique et instrumentale. La recherche et l'étude des planètes en transit devant leur étoile revêtant une importance particulière, je présente tout d'abord dans cette thèse un simulateur de programmes de recherche de transits, destiné à la prédiction puis à l'interprétation scientifique de leurs résultats. Ce simulateur est utilisé en particulier pour prédire les événements attendus par la mission CoRoT en termes de planètes détectables et de "faux" transits. Les projets futurs de photométrie de planètes en transit devront permettre le suivi de planètes plus petites, ou la détection d'un très grand nombre d'objets. Une alternative à l'espace pour la photométrie des transits pourrait être dans ce cadre le site du Dôme C, en Antarctique. Je fais l'état du développement du projet A STEP, que j'ai proposé au cours de ma thèse, visant à caractériser la précision photométrique que l'on peut atteindre au Dôme C dès la nuit australe 2008. D'autres techniques de détection et de caractérisation d'exoplanètes sont complémentaires des transits. Je présente une méthode spectropolarimétrique pour détecter la lumière diffusée par l'atmosphère des exoplanètes, susceptible de caractériser leur albédo en lumière visible et leur taux de polarisation, indicatifs de leur composition atmosphérique. J'expose ensuite le concept du coronographe CIAXE : achromatique par nature, il conserve ses performances sur une large bande spectrale et pourrait être mis en place sur les projets futurs de détection d'exoplanètes. La méthode des transits nous permet progressivement de comprendre la formation et l'évolution des planètes. D'autres techniques sont nécessaires pour détecter des planètes à longue période correspondant aux critères - terriens - d"habitabilité". Nous pourrons ainsi déterminer si le système solaire, et plus encore la Terre, sont des cas communs, rares, ou même uniques dans la Galaxie
By measuring the radial velocity of the star 51-Peg in 1995. Michel Mayor and Didier Queloz identified for the first time a planet outside of the solar System, or exoplanet. The last 12 years have seen the discovery of over 240 exoplanets. The characterization of these planets (radius, density. Atmospheric composition) is now possible and motivates this theoretical and instrumental thesis. Because the search for planets in transit in front of their star and their study is of particular importance. I first present a Simulator of transit search missions, dedicated to the prediction and to the scientific interpretation of their results. This Simulator is in particular used to predict the yield of CoRoT mission in terms of detectable planets and "false" transits. Future photometric projects aimed at transiting planets will have to allow a follow-up of smaller planets. Or the detection of a very large number of planets. An alternative to space for transit photometry could then be the Dome C site, in Antarctica. I present the A STEP project. Its status and perspectives. A STEP will quantify the photometric accuracy at the Dome C site beginning in the Antarctic winter 2008. Other detection techniques are complementary to transits. I present a spetropolarimetric method to detect the light scattered by the atmosphere of exoplanets. In order to characterize their visible albedo and their polarization ratio, indicators of their atmospheric compositions. I then describe the CIAXE coronagraph : achromatic by nature, it keeps its performances on a large spectral band and could be inserted in future exoplanet detections projects. Transit method allows us to understand planetary formation and evolution, but other techniques are necessary to detect planets at longer periods that could harbour life. Considering earth-known criteria. We will then be able to determine if the Solar System, and furthermore the Earth. Are cornmon. Rare, or even unique in the Galaxy

Le transit sedimentaire dans les passes internes du bassin d'arcachon a ete etudie par le biais des dunes tidales. Cinq campagnes de geophysique ont permis de cartographier la repartition et la polarite des dunes a long terme. L'interpretation des donnees montre que la repartition des dunes suit une evolution saisonniere. En periode estivale, les formes a polarite de jusant sont dominantes. Le bassin se trouve dans une situation de deficit sedimentaire. La semelle caillouteuse, sur laquelle evoluent les dunes tidales, affleure en de nombreux points. A l'inverse, en periode hivernale, les dunes de flot sont majoritaires. La semelle caillouteuse est largement recouverte par le sable qui penetre dans le bassin sous l'action combinee des forts vents de secteur nord-ouest a sud-est et des vives-eaux. Les dunes, situees dans les zones d'inversion du transit sedimentaire residuel, peuvent changer de polarite sur une periode de quelques semaines, du moins superficiellement. Une etude detaillee d'un corps sedimentaire a ete menee afin de mieux cerner les mecanismes de progradation des dunes. Les dunes se deplaceraient de 16 a 248 metres par an. Leur deplacement represente un transit de sable au niveau de la dune de 1,7 a 13,9 tonnes/jour/metre lineaire. Les taux de migration observes (sur un cycle mortes-eaux vives-eaux) compares aux taux predits (a partir des mesures de courant) donnent des resultats assez concordants

The search for exo-planets is currently one of the most exiting and active topics in astronomy. Small and rocky planets are particularly the subject of intense research, since if they are suitably located from their host star, they may be warm and potentially habitable worlds. On the other hand, the discovery of giant planets in short-period orbits provides important constraints on models that describe planet formation and orbital migration theories. Several projects are dedicated to discover and characterize planets outside of our solar system. Among them, the Wide-Field Camera Transit Survey (WTS) is a pioneer program aimed to search for extra-solar planets, that stands out for its particular aims and methodology. The WTS has been in operation since August 2007 with observations from the United Kingdom Infrared Telescope, and represents the first survey that searches for transiting planets in the near-infrared wavelengths; hence the WTS is designed to discover planets around M-dwarfs. The survey was originally assigned about 200 nights, observing four fields that were selected seasonally (RA = 03, 07, 17 and 19h) during a year. The images from the survey are processed by a data reduction pipeline, which uses aperture photometry to construct the light curves. For the most complete field (19h-1145 epochs) in the survey, we produce an alternative set of light curves by using the method of difference imaging, which is a photometric technique that has shown important advantages when used in crowded fields. A quantitative comparison between the photometric precision achieved with both methods is carried out in this work. We remove systematic effects using the sysrem algorithm, scale the error bars on the light curves, and perform a comparison of the corrected light curves. The results show that the aperture photometry light curves provide slightly better precision for objects with J < 16. However, difference photometry light curves present a significant improvement for fainter stars. In order to detect transits in the WTS light curves, we use a modified version of the box-fitting algorithm. The implementation on the detection algorithm performs a trapezoid-fit to the folded light curve. We show that the new fit is able to produce more accurate results than the box-fit model. We describe a set of selection criteria to search for transit candidates that include a parameter calculated by our detection algorithm: the V-shape parameter, which has proven to be useful to automatically identify and remove eclipsing binaries from the survey. The criteria are optimized using Monte-Carlo simulations of artificial transit signals that are injected into the real WTS light curves and subsequently analyzed by our detection algorithm. We separately optimize the selection criteria for two different sets of light curves, one for F-G-K stars, and another for M-dwarfs. In order to search for transiting planet candidates, the optimized selection criteria are applied to the aperture photometry and difference imaging light curves. In this way, the best 200 transit candidates from a sample of ~ 475 000 sources are automatically selected. A visual inspection of the folded light curves of these detections is carried out to eliminate clear false-positives or false-detections. Subsequently, several analysis steps are performed on the 18 best detections, which allow us to classify these objects as transiting planet and eclipsing binary candidates. We report one planet candidate orbiting a late G-type star, which is proposed for photometric follow-up. The independent analysis on the M-dwarf sample provides no planet candidates around these stars. Therefore, the null detection hypothesis and upper limits on the occurrence rate of giant planets around M-dwarfs with J < 17 mag presented in a prior study are confirmed. In this work, we extended the search for transiting planets to stars with J < 18 mag, which enables us to impose a more strict upper limit of 1.1 % on the occurrence rate of short-period giant planets around M-dwarfs, which is significantly lower than other limit published so far. The lack of Hot Jupiters around M-dwarfs play an important role in the existing theories of planet formation and orbital migration of exo-planets around low-mass stars. The dearth of gas-giant planets in short-period orbit detections around M stars indicates that it is not necessary to invoke the disk instability formation mechanism, coupled with an orbital migration process to explain the presence of such planets around low-mass stars. The much reduced efficiency of the core-accretion model to form Jupiters around cool stars seems to be in agreement with the current null result. However, our upper limit value, the lowest reported sofar, is still higher than the detection rates of short-period gas-giant planets around hotter stars. Therefore, we cannot yet reach any firm conclusion about Jovian planet formation models around low-mass and cool main-sequence stars, since there are currently not sufficient observational evidences to support the argument that Hot Jupiters are less common around M-dwarfs than around Sun-like stars. The way to improve this situation is to monitor larger samples of M-stars. For example, an extended analysis of the remaining three WTS fields and currently running M-dwarf transit surveys (like Pan-Planets and PTF/M-dwarfs projects, which are monitoring up to 100 000 objects) may reduce this upper limit. Current and future space missions like Kepler and GAIA could also help to either set stricter upper limits or finally detect Hot Jupiters around low-mass stars. In the last part of this thesis, we present other applications of the difference imaging light curves. We report the detection of five faint extremely-short-period eclipsing binary systems with periods shorter than 0.23 d, as well as two candidates and one confirmed M-dwarf/M-dwarf eclipsing binaries. The etections and results presented in this work demonstrate the benefits of using the difference imaging light curves, especially when going to fainter magnitudes.
Die Suche nach Exoplaneten ist heute eine der interessantesten und aktivsten Forschungsgebiete in der Astronomie. Vor allem erdähnliche Planeten sind das Ziel diverser Forschungsprojekte, da diese, sofern sie in einem bestimmten Abstand um ihrem Mutter-Stern kreisen, eine Oberflächentemperatur aufweisen, die ein Vorkommen von Wasser in flüssiger Form ermöglicht und somit ``habitabel'' sind. Außerdem sorgt die Entdeckung von Gasriesen in kurzperiodischen Umlaufbahnen für wichtige Erkenntnisse zu Modellen, die die Planetenbildung und orbitale Migration beschreiben. Viele Projekte haben es sich zum Ziel gesetzt, Planeten außerhalb unseres Sonnensystems zu finden und zu charakterisieren. Eines dieser Projekte is der WFCam Transit Survey (WTS), ein Pionierprogramm, das sich durch eine besondere Zielsetzung und Methodik auszeichnet. Die Beobachtungen für WTS haben im August 2007 am United Kingdom Infrared Telescope in Hawaii begonnen. Der Survey unternimmt die erste Suche nach Exoplaneten im nah-infraroten Wellenlängenbereich, welcher für die Suche nach Planeten um M-Zwerge optimal ist. Ursprünglich waren für das Projekt etwa 200 Nächte geplant - verteilt auf insgesamt vier Felder, welche über das Jahr verteilt beobachtet wurden. Die gewonnen Daten werden in einer automatischen Pipeline prozessiert, um Lichtkurven mit Aperturphotometrie zu erstellen. Für das Feld mit den meisten Beobachtungen (``19h-Feld'' mit 1145 Belichtungen)erzeugen wir ein alternatives Set an Lichtkurven mit ``difference imaging'', einer photometrische Methode, die sich in der Vergangenheit für Felder mit hohen Sterndichten als überlegen herausgestellt hat. Ein quantitativer Vergleich zwischen der photometrischen Genauigkeit der beiden Methoden wurde in dieser Arbeit durchgeführt. Wir korrigieren ausserdem systematische Effekte unter Verwendung des ``sysrem'' Algorithmus, skalieren die unrealistischen Fehlerbalken in den Lichtkurven und vergleichen diese mit den ursprünglichen. Die Ergebnisse zeigen, dass die Lichtkurven der Aperturphotometrie geringfügig höhere Genauigkeit für Objekte mit J < 16 mag aufweisen. Difference imaging Lichtkurven zeigen dagegen eine deutliche Verbesserung für schwächere Sterne. Um Transits von Planeten zu detektieren, verwenden wir eine modifizierte Version des ``box-fitting'' Algorithmus. Unsere Implementierung erweitert den Algorithmus um einem Trapezoid-Fit des Transitbereichs in der gefalteten Lichtkurve. Wie wir zeigen, liefert dieser Fit bessere Resultate als der reine Box-Fit. Wir beschreiben ein Set von Selektionskriterien, mit welchem wir nach Transit-Kandidaten in den Lichtkurven suchen. Diese Kriterien beinhalten einen Parameter, der von unserem Detektionsalgorithmus berechnet wird: der V -Form Parameter. Dieser hat sich als sehr nützlich herausgestellt, um automatisch bedeckungsveränderliche Doppelsterne zu identifizieren und diese von der Suche nach Planeten auszuschliessen. Wir optimieren die Kriterien über Monte-Carlo Simulationen von künstlichen Transitsignalen, welche in die realen WTS Lichtkurven eingespeist und durch unseren Detektionsalgorithmus analysiert werden. Wir führen die Optimierung der Selektionskriterien separat für zwei getrennte Sets von Lichtkurven durch, jeweils eines für F-G-K Sterne und für M-Sterne. Um nach Transits von Planeten zu suchen, werden die optimierten Kriterien auf die Lichtkurven von Aperturphotometrie und difference imaging Photometrie angewendet. Auf diese Weise werden die 200 besten Transitkandidaten aus ~475 000 Quellen automatisch selektiert. Danach wird eine visuelle Untersuchung der gefalteten Lichtkurven vorgenommen, um klare Fehldetektionen zu entfernen. Anschließend werden weitere Analyseschritte für die vielversprechendsten 18 Kandidaten durchgeführt, was es uns ermöglicht, diese Objekte als Planeten-Kandidaten oder bedeckungsveränderliche Doppelsterne zu klassifizieren. Wir haben einen vielversprechenden Planetenkandidaten gefunden, der um einen späten G-Stern kreist, für welchen wir eine photometrische Nachbeobachtung vorschlagen. Die davon unabhängige Analyse der M-Stern Lichtkurven führte zu keiner Detektion. Damit können wir die Nullhypothese und die oberen Limits für die Häufigkeit von Gasriesen um M-Zwerge mit J < 17 mag aus einer früheren Studie bestätigen. In dieser Arbeit erweitern wir die Suche nach Planetentransits auf Sterne mit J < 18 mag, was es uns ermöglicht, ein Limit von 1.1 % für die Häufigkeit von kurzperiodischen Gasreisen um M-Zwerge zu setzen, was deutlich niedriger ist als die Limits anderer Publikationen. Der Mangel an Hot Jupiters um M-Zwerge spielt eine wichtige Rolle für die Theorien von Planetenentstehung von Exoplaneten um Sterne mit niedriger Masse. Das Fehlen von Gasriesen in kurzperiodischen Orbits um M-Sterne zeigt, dass der Disk-Instabilitätsmechanismus in Kombination mit einer Migration des Orbits nicht benötigt wird,um die Planetenbildung zu beschreiben. Die deutlich geringere Effizienz des ``Core Accretion'' Modells, Jupiter um kühle Sterne zu erzeugen, wird durch die Nullhypothese bestätigt. Unser oberes Limit ist jedoch immer noch höher als die Detektionsraten von kurzperiodigen Gasriesen um heißere Sterne. Wir können also keinen abschließendes Fazit über die Entstehungsmodelle von jupiterähnlichen Planeten um kühle, massearme Hauptreihensterne ziehen. Momentan gibt es noch nicht ausreichende Beobachtungen, um die Vorhersage, dass Hot Jupiters weniger häufig um M-Sterne als um sonnenähnliche Sterne sind, zu untermauern. Um dies zu erreichen, muss eine noch grössere Anzahl an M-Sternen beobachtet werden. Dies könnte durch eine umfassende Analyse aller vier WTS Felder erreicht werden oder aber durch andere momentan durchgeführte M-Zwerg Transit Surveys wie etwa Pan-Planets oder PTF/M-Dwarfs, welche nahezu 100 000 M-Sterne beobachten. Aktuelle und zukünftige Weltraummissionen wie Kepler und GAIA könnten ebenfalls weitere Erkenntnise über die Häufigkeit von Hot Jupiters um massearme Sterne liefern. Im letzten Teil dieser Arbeit präsentieren wir weitere Anwendungen der difference imaging Lichtkurven. Wir haben insgesamt fünf lichtschwache, bedeckungsveränderliche Doppelsternsysteme mit extrem kurzen Perioden unterhalb von 0.23 Tagen detektiert. Ausserdem konnten wir zwei weitere unbestätigte und ein bestätigtes bedeckungsveränderliches M-Zwerg/M-Zwerg Doppelstern-System finden. Alle in dieser Arbeit präsentierten Detektionen demonstrieren die Stärken der difference imaging Methode, welche vor allem bei lichtschwächeren Magnituden entscheidende Vorteile bringt.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2014.
234
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 237-261).
Over the past 20 years, approximately 1700 planets outside of the solar system have been found. Known as exoplanets, they represent a great opportunity to answer some of the deepest questions about the origin and evolution of our solar system. In this thesis I focus on transiting exoplanets, planets that eclipse their host star from our point of view, reducing momentarily the stellar flux detected by our telescopes. In the first part of this thesis, I develop a new method to measure obliquities, the angle between the spin axis of the star and orbital plane of each of the planets. In our solar system, the obliquity of all planets is within a few degrees of zero, a natural consequence of the standard theory of planet formation, in which a rotating envelope of gas collapses into a disk-shaped protoplanetary disk from which the planets form. But this is not the case for all exoplanets. Close-in gas giants are frequently found in orbits that are tilted respect to the spin axis, a sign that some process is altering the orbits of these planets.The new technique I develop in this thesis uses the passage of a transiting planet over starspots to obtain information about the obliquity of its host star. In particular, I show how to use this technique for close-in gas giants with low and high obliquities, and I extend it to longer orbital periods and multi-planet systems, where obliquity measurements are scarce and therefore more interesting. In the second part of this thesis I describe a survey to detect the shortest-period planets discovered with the Kepler space telescope. In this survey I take a different approach to discover ultra-short period transiting exoplanets. A simple Fourier transform is obtained for every Kepler star, and planets are detected by interpreting the amplitudes and frequencies of the different peaks of the Fourier spectrum. This technique has allowed us to detect Kepler-78b, currently the smallest planet with a mass and radius measurement, with an extreme orbital period of 8.5 hours. The last chapter of this thesis is devoted to the survey, from which a list of 106 planet candidates with orbital periods shorter than one day emerged. The properties of these planet candidates are ultimately used to understand the characteristics of ultra-short period planets in general.
by Roberto Sanchis Ojeda.
Ph. D.

In this thesis, I report on the effects that magnetic stellar activity of solar-type stars induces on stellar light curves involved in the photometric technique for the detection and characterization of transiting extra-solar planets that is one of the most effective detection methods, the first being the radial velocity technique. Stellar magnetic activity is a source of noise in the study of the transits of extra-solar planets since it induces flux variations that significantly affect the transit depth determination and the derivations of planetary and stellar parameters. Surface brightness inhomogeneities, such as starspots or bright faculae, on star disc have an intrinsic dependence on wavelength and thus on the stellar colours. The colour dependence of stellar activity may significantly influence the characterization of planetary atmospheres since it produces stellar flux variations that may mimic those due to the presence of molecular or atomic species in the transmitted planetary spectra. In this thesis I focus on the effects due essentially to stellar spots present in the visible hemisphere of solar-type stars. The proposed method is a theoretical one, aiming to predict the starspot-induced effects with the use of stellar atmospheric models and I present a systematic approach to quantify the corresponding stellar flux variations as a function of wavelength bands. Therefore I consider a star with spots covering a given fraction of its disc and model the variability in both the UBVRIJHK photometric system and the Spitzer/IRAC wavebands for dwarf stars from G to M spectral types. Then I compare starspot-induced flux variations in these different passbands with planetary transits and quantify how they affect the determination of the planetary radius and the analysis of the transmission spectroscopy in the study of planetary atmospheres. My results suggest that the monitoring of the systems by using broad-band photometry, from visible to infrared, helps to constrain spots effects by estimating the R parameter, i.e. the ratio of the relative variations in the stellar fluxes at short wavelength optical bands (e.g., U or B) to near-infrared ones (e.g., J or K). Its numerical value can be used to distinguish starspot brightness dips from planetary transits in a single stellar light curve. In addition to the perturbations in the measurement of the planetary radius, the perturbations in the transit light curve profiles due to starspots can affect the determinations of orbital parameters, i.e., the relative semi-major axis and the inclination of the planetary orbit, that are directly derived by fitting procedure of the transit light curves. These distortions in the transit light curves have a significant impact on the derivation of stellar parameters and, above all, on the stellar density thus bothering the stellar evolutionary estimates. The results derived from the synthetic photometric analysis are presented and discussed in Ballerini et al. 2012.

Le mini-satellite Corot lancé en 2006 utilisera la méthode des transits :
Une exoplanète signe son passage devant l'étoile par une brève baisse de flux inférieure au millième. La stabilité et continuité de mesure seront assurées sur 150 jours pour 60.000 étoiles afin d'augmenter le nombre de configurations favorables. La photométrie d'ouverture intègre chaque flux dans un masque de lecture adapté aux multiples bruits, limité `a 250 formes différentes pour 12.000 cibles. J'ai étudié des méthodes autorisant cette réduction sans perte notable de signal `a bruit. Le tri efficace de masques aléatoires s'avère la plus satisfaisante.

Pour la détection, j'ai développé une méthode qui rehausse le contraste des transits en éliminant les composantes des effets collectifs et de certains artefacts. Après détection temporelle les systématiques sont identifiées, même celles d'origine et de poids inconnus. On fait émerger de nouvelles détections en jaugeant la dispersion autour de ces composantes.

Les Jupiters chauds sont des exoplanètes si proches de leur étoile que leur atmosphère peut perdre du gaz par échappement hydrodynamique. Les géantes gazeuses qui transitent sont un excellent moyen de comprendre ce processus, mais il faut étudier d'autres types de planètes pour déterminer son impact sur la population exoplanétaire. Cette thèse propose d'utiliser la spectroscopie du transit pour observer l'atmosphère de plusieurs planètes, étudier leurs propriétés et caractériser l'échappement hydrodynamique. Des raies de l'ultraviolet observées avec le télescope Hubble sont analysées avec le modèle numérique de la haute atmosphère que nous avons développé. Grâce à la raie Ly-? nous mettons en évidence les interactions énergétiques et dynamiques entre l'atmosphère des Jupiters chauds HD209458b et HD189733b et leurs étoiles. Nous étudions la dépendance de l'échappement à l'environnement d'une planète et à ses propriétés physiques, en observant une super-Terre et un Jupiter tiède dans le système 55Cnc. Grâce à des observations de HD209458b nous montrons que les raies du magnésium permettent de sonder la région de formation de l'échappement. Nous étudions le potentiel de la spectroscopie du transit dans le proche UV pour détecter de nouveaux cas d'échappement. Ce mécanisme est favorisé par la proximité d'une planète à son étoile, ce qui rend d'autant plus important la compréhension des processus de formation et de migration, qui peuvent être étudiés par l'alignement d'un système planétaire. Grâce à des mesures des spectrographes HARPS-N et SOPHIE nous étudions les alignements de 55Cnc e et du candidat Kepler KOI-12.01, dont nous cherchons aussi à valider la nature planétaire.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
A pesquisa Cartografias de um estrangeiro: trânsitos e afetos nas ruas do Rio de Janeiro tem o intuito de (re)criar os trânsitos de um narrador estrangeiro, que passa a morar no Rio a partir de agosto de 2013. Seguido o método proposto por Gilles Deleuze e Félix Guattari (1995), o desejo é construir, com um texto acompanhado de ilustrações, fotografias e colagens, uma cartografia deste corpo, aberto às surpresas que transbordam das dobras da cidade. O trabalho busca nas ruas o que desloque o olhar, não só no sentido físico e decorativo, mas também como possibilidade de sensibilizar de afetar e quebrar a rotina. Assim, a dissertação investiga os múltiplos encontros proporcionados em uma cidade. É possível pensar esse narrador que veio de fora como alguém mais inserido/ inscrito na capital carioca ao caminhar pelas rotas afetivas do espaço urbano? Ao se deslocar, principalmente, por bairros da Zona Sul, Centro e Zona Norte, sua narrativa busca uma visão aberta e ativa, desdobrada em quatro eixos teóricos: 1) cidade; 2) o outro, estrangeiro de mim mesmo; 3) caminhada; 4) afetos. Leitura de estudos sócio-históricos, geográficos e filosóficos sobre as palavras-chave citadas acima, assim como questões suscitadas pelos atravessamentos dele no Rio, é convite para explorar uma pesquisa construída e experimentada.
The research Cartography of a foreigner: transits and affections in the streets of Rio de Janeiro have the intention of (re)creating the transits of a foreign narrator, who starts living in Rio since August of 2013. Starting from the method proposed by Gilles Deleuze and Félix Guattari (1995), the desire is to construct, with a text accompanied by illustrations, photographies and collages, a cartography of this body, open to the surprises that overflow the city s folds. The work searches in the streets what dislocates the eye, not only in the physical and decorative sense, but also with possibility of sensitizing, of affecting and breaking the routine. This way, the dissertation investigates the multiple encounters proportioned in a city. Is it possible to think if this narrator who came from outside feels more inserted/registered in the capital of Rio while walking through the affective routes of urban space? While dislocating, mainly by neighborhoods of South Zone, Downtown and North Zone, his narrative searches for an open and active sight, constructing narratives that unfold in four theoretical axes: 1) city; 2) the other, foreigner of own self ; 3) the walk 4) affections. Lectures of socio-historical, geographical and philosophical aspects of the keywords cited above, as well as questions raised by his passage in Rio, are invitations for the research to be built and experimented.

Le travail de recherche proposé dans cette thèse porte sur la question de la transmission psychique inconsciente, l’objet de recherche s’attachant plus précisément à définir les différentes modalités de transit de la réalité psychique. C’est à partir d’une clinique auprès d’enfants suivis en hôpital de jour ou en centre médico-psychologique que sont interrogées les formes, les voies et les fonctions des transits, des échanges qui s’organisent entre les différentes scènes subjectives, qu’il s’agisse de la scène du rêve, du jeu, du corps, mais encore celle de l’autre de la relation. La scène psychique au regard de sa croissance, de son développement, ne peut se penser sans l’objet, aussi le modèle proposé en appui sur la théorie psychanalytique mais explorant aussi d’autres épistémologies comme la phénoménologie, les neurosciences, l’embryologie, est un modèle intersubjectif. A la suite des auteurs kleiniens mais aussi des travaux des groupalistes, il a pour objet de construire une représentation de l’espace intermédiaire ou espace « entre », situé entre les scènes et à partir duquel s’organisent les transactions et la transmission psychique. Il est possible de caractériser ce lieu de la connexion, d’en proposer une métaphore, une topologie, de montrer qu’il a une concrétude et des processus spécifiques. Penser l’entre-deux et l’alternance entre les scènes subjectives sur lesquelles se montre la réalité psychique amène aussi à interroger les modes de représentation de la conflictualité, à penser en termes de scénalité, d’inter-scénalité, de trans-scénalité, à rechercher également qu’elle est l’instance intrapsychique organisatrice de sa mise en jeu et de sa mise en scène. Parce que le moi est un être frontière et assure une fonction d’articulation, on peut décrire, en usant de la métaphore théâtrale, un moi dramaturge et scénographe et montrer comment les scènes subjectives interconnectées permettent alors de retrouver un lien associatif et une continuité narrative. Lorsque la souffrance psychique est trop grande et ne peut être psychisée, la scène éloignée (par exemple la scène phobique), se révèle être un puissant attracteur de la réalité psychique et donne une forme au conflit. Du fait d’une coïncidence, d’une mêmeté ou autre, elle vient en relais, elle est à penser comme un lieu où se déposent et se déchargent les tensions à l’instar d’une zone de transits ou parfois d’une zone de quarantaine maintenant à distance le surcroit de douleur et évitant une contamination de l’ensemble. Certains mécanismes identificatoires jouent un rôle fondamental dans la transmission psychique, notamment l’identification projective qui permet que se véhicule la souffrance et notamment qu’elle soit communiquée au thérapeute. De fait, la scène thérapeutique parce qu’elle attire à elle des contenus psychiques toxiques, non-élaborés, ceux-ci pouvant être liés à une transmission transgénérationnelle, opère aussi comme une scène à distance où s’organise un partage des expériences affectives et émotionnelles, cela étant à penser dans le cadre d’une relation transféro-contre-transférentielle. La prise en compte des jeux d’alternance impliquant souvent plusieurs scènes interconnectées entre elles comme les scènes thérapeutique, transférentielle mais aussi corporelle, onirique, fantasmatique, qui sont autant de lieux possibles d’expression du conflit psychique, amène en dernier lieu et en guise d’ouverture à un prochain travail de recherche à envisager une autre modalité d’associativité que nous nommons associativité inter-scénale
The research work proposed within the framework of this thesis focuses upon the unconscious psychic transmission, with a particular emphasis on the various forms of transits of psychological reality. Based on The forms, channels and the roles of the transits, the interaction between the various subjective scenes, be they the dream scene, the game scene, the body scene or the Other in the relationship, have been studied in a child clinic with children in a day hospital or in a medical psychological centre. The psychological scene in view of its growth, its development, is unthinkable without the object, that is why the model proposed on the psychoanalytical theory, but also investigating other epistemologies such as phenomenology, neurosciences, embryology, is an intersubjective model. Following the kleinian authors, but also the groupalists’ work, its purpose is to build a representation of the intermediary space, or space in between, located between the scenes and from which psychological transactions and transmissions organize themselves. It is possible to characterize this place of connection, to propose a metaphor for it, a topology, to show it is real, with specific processes. Considering the between-two and the alternating between the subjective scenes on which the psychological reality shows, also leads us to ask questions about the modes of representation of conflicts, to think in terms of scenality, inter-scenality, trans-scenality, also to investigate the intrapsychic occurrence which articulates its operation and staging. Because the self is a border being and it has a function of articulation, one could evoke, with a theatrical metaphor, a dramatist and scenographer self, and show how the interconnected subjective scenes then allow to get back to an associative link and a narrative continuity.When mental suffering is too acute and it cannot be psychologized, the remote scene (the phobic scene for instance) proves to be a powerful attraction of psychic reality, and it gives a shape to the conflict. Because of a coincidence, a sameness, or other, it is a relay, one should think about it as a place where tensions lay and discharge as in a transit area or sometimes a quarantine zone keeping the excess pain away and avoiding a contamination of the whole.Some identifiable mechanisms play a key role in the psychologicaltransfer, particularlythe projective identification which ensures pain is carried out and, especially, communicated to the therapist. Indeed, because the therapeutic scene attracts undeveloped toxic psychic contents which may be linked to a transgenerational transmission, it also operates like a distant scene in which a sharing of the affective and emotional experiences takes place. The coverage of the alternation games often involving several scenes interconnected together such as the therapeutic scenes, transferential as well as corporeal, oniric, fantasmal, which represent as many potential places of expression of psychological conflict, finally leads us, thus opening up to a future research work, to consider another method of associativity which we name inter-scenal associativity

The Citizen Continental-America Telescopic Eclipse (CATE) Experiment established a standardized set of observation procedures and 72 volunteer observation teams with identical equipment along the path of the 2017 total solar eclipse. CATE successfully imaged the solar corona from 66 of the 72 observation sites resulting in a high dynamic range animation of 90 minutes of solar corona data collected by volunteer citizen science teams. A subgroup of CATE began work in the fall of 2017 to evaluate use of the standard CATE observation setup for exoplanet transit observations. Light curves and analysis of data using AstroImageJ of two well know transiting exoplanets, HD209458b (V = 7.65, depth = 1.5%) and HD189733b (V= 7.67, depth=2.4%) are presented along with modifications to CATE telescopes required for successful exoplanet follow up observations.

We present results from 30 nights of observations of the intermediate-age Solar-metallicity open cluster NGC 7789 with the WFC camera on the INT telescope in La Palma. From ~900 epochs, we obtained lightcurves and Sloan r' - i' colours for ~33000 stars, with ~2400 stars with better than 1% precision. We find 24 transit candidates, 14 of which we can assign a period. We rule out the transiting planet model for 21 of these candidates using various robust arguments. For 2 candidates we are unable to decide on their nature, although it seems most likely that they are eclipsing binaries as well. We have one candidate exhibiting a single eclipse for which we derive a radius of 1.81+/0.09- Three candidates remain that require follow-up observations in order to determine their nature. Monte Carlo simulations reveal that we expected to detect ~2 transiting 3d to 5d hot Jupiter planets from all the stars in our sample if 1% of stars host such a companion and that a typical hot Jupiter radius is similar to that of HD 209458b. Our failure to find good transiting hot Jupiter candidates allows us to place an upper limit on the 3d to 5d hot Jupiter fraction of 2.6% for all stars at the 1% significance level, and similar useful limits on the hot Jupiter fraction of the different star types in our sample.

Over the last decade, 135 extrasolar planets have been discovered, the vast majority found by ongoing radial velocity searches. Of the stars sampled in these searches, 1% have `Hot Jupiter' planets associated with them. Having masses equivalent to Jupiter yet orbital periods of only a few days, this new class of planet is clearly unlike anything in our Solar System.¶ Hot Jupiters present us with an intriguing prospect. If the orientation of the planetary orbit is close to edge-on, the planet will periodically transit across the face of its star, resulting in a small drop in brightness. This transit phenomenon has been successfully used for planet detection over the last couple of years, allowing determination of the planetary radius and accurate mass estimates when coupled with radial velocity observations.¶ To aid understanding of the effect stellar environment plays on Hot Jupiter formation and survivability, this thesis presents the results of a wide-field search for transiting Hot Jupiters in the globular cluster 47 Tucanae. This cluster presents many thousands of stars in a moderate field of view and provides the perfect target for a search of this nature. One previous transit search has been made in the central core of 47 Tuc; using the HST for 8.3 continuous days, Gilliland et.al (2000) expected 17 transits yet found none. This null result suggests that either system metallicity or stellar density may be inhibiting Hot Jupiter formation or survivability in the cluster.¶ This thesis presents a search for transits with a field of view 250 times larger than the HST search and samples the uncrowded outer halo of the cluster (previously unsampled for transits), providing important constraints on the effect of environment on Hot Jupiter formation. If planets are found, then stellar density would seem responsible for the Gilliland et.al (2000) core null result. If no planets are found to a significant level, the survey would provide strong evidence that system metallicity is the dominant factor. Using the ANU 40'' (1m) telescope at Siding Spring Observatory, a 30.4 night observing run was executed and photometry was derived via differential imaging. The dataset numbers 109,000 cluster (and field) stars for photometric analysis, of which 22,000 are suitable for the transit search. With a custom-written transit detection algorithm and extensive Monte Carlo simulations to model the dataset, seven planets should be detectable if the occurrence rate of Hot Jupiters is the same in the cluster as in the Solar Neighbourhood.¶ Despite a detailed search, no transit signatures were identified. This result strongly indicates that the low metallicity of the cluster is the dominant factor inhibiting planet formation in 47 Tuc. Current results in the Solar Neighbourhood show that planet frequency is strongly biased towards stars of high metallicity. This thesis shows that the metallicity trend is likely a universal phenomenon, not only limited to the immediate Solar Neighbourhood and raises questions of whether planets were much rarer in the earlier Universe.¶ As a side result of the search, 100 variable stars were identified in the field, 69 of which are new discoveries. Subsequent analysis reveals a strong period segregation among the cluster eclipsing binaries, indicating previously unobserved dynamical effects in the cluster. Distance estimates for both 47 Tuc and the SMC are in agreement with previously published values and an independent identification of the binary period-colour relation was observed. Two binaries seem to have low-luminosity companions worthy of followup and one variable is likely a star in the early phases of planetary nebula formation. All of the results presented in this thesis have been published in three separately refereed research papers.

This study presents the development of an observing program to pursue the idea of looking for transiting exoplanets in eclipsing binary stars. The various kinds of orbits a planet might have in a binary system are explored. From this it is shown how to anticipate the possible orbits a planet might have in a given star system. The potential detectability of a planet in a binary system is also analyzed. Together these guidelines enable observers to rank targets by the likelihood that a detectable planet might exist in the system. The results of observations by a team at Ball State University of five binary star systems chosen with these guidelines are presented.
Department of Physics and Astronomy

Cette thèse est consacrée à l'étude d'algorithmes de détection et d'estimation de transits planétaires. La recherche des planètes extrasolaires, c'est-à-dire des planètes en orbite autour d'autres étoiles que le Soleil, constitue un des grands défis de l'astrophysique contemporaine. L'une des méthodes de détection des exoplanètes consiste à rechercher les éventuelles variations photométriques d'une étoile dues aux passages consécutifs de la planète devant son disque. La première étape de notre travail était de modéliser des courbes de lumière aussi réalistes que possible, en supposant que les signaux étaient produits par un instrument similaire à celui développé pour la future mission COROT, qui prévoit dès 2004 de poser en continu pendant cinq mois sur des milliers d'étoiles. Nous avons ensuite mis au point et testé sur ces courbes de lumière divers algorithmes de détection et d'estimation de transits. Dans le cas d'un transit unique et d'un seul canal de détection, l'utilisation simultanée d'un filtre adapté et d'un filtre "optimal" devrait constituer une méthode de détection rigoureuse. L'utilisation de deux canaux de détection permettra d'améliorer la détection notamment pour des valeurs élevées de l'activité stellaire et, sans doute, de construire une méthode de discrimination. Dans le cas de transits multiples, l'application de deux méthodes complémentaires de détection et d'estimation de la forme du transit, respectivement le filtre adapté et la méthode d'estimation bayésienne, devrait permettre de détecter des planètes de taille terrestre avec un excellent degré de confiance
This thesis is devoted to the study of algorithms to locate and estimate planetary transits. The search for extrasolar planets, that is to say planets orbiting Sun-like stars, constitute one of the leading challenge of the contemporary astrophysic. One of the detection method consists to search the eventual photometric variations of a star due to the transit of the planet across its star. The first step to our work was to simulate light curves as realistic as possible on the assumption that the signal of the stars is produced by an instrument similar to that developed for the COROT space mission, which expects since 2004 to observe continuously during five months thousands of stars. Then, we have built and test on this curves many algorithms to locate and estimate transits. Concerning the detection of a single transit with one detection channel, the simultaneous use of a matched filter and of an "optimal" filter might constitute a strict detection method. Using two detection channels will permit to improve the detection especially for the largest level of the stellar variability and, perhaps, to develop a discriminative method. Concerning the detection of multitransits, the application of two complementary methods to locate and estimate transits, respectively the matched filter and the bayesian method, might permit to detect terrestrial planets with a great confidence level

Sous l'action des vents, courants et de la houle, les sediments cotiers sont mis en mouvement et transportes. Pour quantifier les transits sableux plusieurs approches sont possibles, celles-ci passent par le biais: d'experiences de terrain, l'utilisation de fonctions de quantification, de la mise au point et d'application de modeles de transport de sable. Les experiences de terrains realisees dans le cadre de cette etude montrent que: il existe des mouvements de courte duree (cycle de maree) sur la zone de jet de rive; ils sont caracterises par des ondes de sedimentation-erosion qui se deplacent avec la maree. Le profil de plage s'erode a maree montante et se sedimente a maree descendante. La morphologie du profil de plage est le resultat de la dynamique cotiere; ainsi on distingue le profil de beau temps (convexe) et de mauvais temps (concave). En milieu mesotidal, le profil cotier est caracterise par une barre sous-marine simple ou double, festonnee ou rectiligne, puis des sillons prelittoraux. En milieu microtidal, la barre sous-marine est toujours simple rarement festonnee. L'utilisation des fonctions de quantification ne va pas sans la realisation d'experiences de terrain qui permettent de caracteriser au mieux le regime hydrosedimentaire et de recueillir les donnees entrant dans ces fonctions. La derniere partie de ce memoire est un exemple d'application d'etude morphosedimentaire et dynamique d'une zone cotiere comportant un systeme lagunaire, des cordons et des plages sableuses. Cette etude a ete realisee sur le systeme lagunaire de pirartininga et d'itaipu (bresil)

Exoplanets that transit nearby M dwarfs allow us to measure the sizes, masses, and atmospheric properties of distant worlds. Between 2008 and 2013, we searched for such planets with the MEarth Project, a photometric survey of the closest and smallest main-sequence stars. This thesis uses the first planet discovered with MEarth, the warm 2.7 Earth radius exoplanet GJ1214b, to explore the possibilities that planets transiting M dwarfs provide.
Astronomy

Approved for public release; distribution is unlimited
A simulation model was specified. It examines United States Navy Antisubmarine Warfare Screen alternative dispositions for Carrier Battlegroups. The scenario posed is open ocean transit under the threat of an attack from foreign submarine hulls built in the 1990s. The investigation raises the issue of the appropriateness of current Navy practices and suggests that new tactics be developed. The author's thoughts are that there will be ever newer, more lethal, unpredictable threats to United States' maritime independence than current doctrine addresses. The full implementation of the simulation program has not been accomplished. A segment of verification output is shown for expository purposes only. A discussion is given on the adequacy of the model's abstractions along with the possible impact on potential results of experiments.

STEREO’s imager, HI-1A, monitors nearly 500,000 stars down to 4th magnitude as it orbits the Sun. The resulting light curves offer unique characteristics and repeatability, which could make significant contributions to stellar variability surveys and the hunt for transiting planets. The HI-1A trend removal pipeline (TRP) was constructed to counteract systematic and observationsal effects and thereby increase the potential of a transit search. This pipeline uses a non-linear iterative filter to provide an adaptable noise-reduction process, without effecting transit-like signals. The TRP reduces the point-to-point scatter by up to 50 % for the brightest targets (R ≤ 6) and 25 % for the faintest (R ≥ 9). The correlated noise on transit timescales was found to be negligible for most targets and only 20 % of the total noise for the brightest stars, which amount to < 3 % of the sample. In an automated search for planet candidates, several transit signals were detected in the HI-1A light curves. Further testing suggests that none of these were veritable planet candidates. However the results show that Neptune-sized planets are certainly detectable and that a more effective reduction of solar-noise will lead to a successful planet search in the future.

The first transiting planetesimal orbiting a white dwarf was recently detected in K2 data of WD 1145+017 and has been followed up intensively. The multiple, long and variable transits suggest the transiting objects are dust clouds, probably produced by a disintegrating asteroid. In addition, the system contains circumstellar gas, evident by broad absorption lines, mostly in the u' band, and a dust disc, indicated by an infrared excess. Here we present the first detection of a change in colour of WD 1145+017 during transits, using simultaneous multiband fast-photometry ULTRACAM measurements over the u'g'r'i' bands. The observations reveal what appears to be 'bluing' during transits; transits are deeper in the redder bands, with a u' - r' colour difference of up to similar to-0.05 mag. We explore various possible explanations for the bluing, including limb darkening or peculiar dust properties. 'Spectral' photometry obtained by integrating over bandpasses in the spectroscopic data in and out of transit, compared to the photometric data, shows that the observed colour difference is most likely the result of reduced circumstellar absorption in the spectrum during transits. This indicates that the transiting objects and the gas share the same line of sight and that the gas covers the white dwarf only partially, as would be expected if the gas, the transiting debris and the dust emitting the infrared excess are part of the same general disc structure (although possibly at different radii). In addition, we present the results of a week-long monitoring campaign of the system using a global network of telescopes.

Parmi les méthodes qui permettent de détecter des exoplanètes, la photométrie des transits est celle qui a connu le plus grand essor ces dernières années grâce à l’arrivée des télescopes spatiaux CoRoT (en 2006) puis Kepler (en 2009). Ces deux satellites ont permis de détecter des milliers de transits potentiellement planétaires. Étant donnés leur nombre et l’effort nécessaire à la confirmation de leur nature, il est essentiel d’effectuer, à partir des données photométriques, un classement efficace permettant d’identifier les transits les plus prometteurs et qui soit réalisable en un temps raisonnable. Pour ma thèse, j’ai développé un outil logiciel, rapide et automatisé, appelé BART (Bayesian Analysis for the Ranking of Transits) qui permet de réaliser un tel classement grâce une estimation de la probabilité que chaque transit soit de nature planétaire. Pour cela, mon outil s’appuie notamment sur le formalisme bayésien des probabilités et l’exploration de l’espace des paramètres libres par méthode de Monte Carlo avec des chaînes de Markov (mcmc).Une fois les exoplanètes détectées, l’étape suivante consiste à les caractériser. L’étude du système solaire nous a démontré, si cela était nécessaire, que l’information spectrale est un point clé pour comprendre la physique et l’histoire d’une planète. L’interférométrie annulante est une solution technologique très prometteuse qui pourrait permettre cela. Pour ma thèse, j’ai travaillé sur le banc optique Nulltimate afin d’étudier la faisabilité de certains objectifs technologiques liés à cette technique. Au-delà de la performance d’un taux d’extinction de 3,7.10^-5 en monochromatique et de 6,3.10^-4 en polychromatique dans l’infrarouge proche, ainsi qu’une stabilité de σN30 ms = 3,7.10^-5 estimée sur 1 heure, mon travail a permis d’assainir la situation en réalisant un budget d’erreur détaillé, une simulation en optique gaussienne de la transmission du banc et une refonte complète de l’informatique de commande. Tout cela m’a finalement permis d’identifier les faiblesses de Nulltimate
From all exoplanet detection methods, transit photometry went through the quickest growth over the last few years thanks to the two space telescopes, CoRoT (in 2006) and Kepler (in 2009). These two satellites have identified thousands of potentially planetary transits. Given the number of detected transits and the effort required to demonstrate their natures, it is essential to perform, from photometric data only, a ranking allowing to efficiently identify the most promising transits within a reasonable period of time. For my thesis, I have developed a quick and automated software called bart (Bayesian Analysis for the Ranking of Transits) which realizes such a ranking thanks to the estimation of the probability regarding the planetary nature of each transit. For this purpose, I am relying on the Bayesian framework and free parameter space exploration with Markov Chain Monte Carlo (mcmc) methods.Once you have detected exoplanets, the following step is to characterise them. The study of the solar system demonstrated, if it was necessary, that the spectral information is a crucial clue for the understanding of the physics and history of a planet. Nulling interferometry is a promising solution which could make this possible. For my thesis, I worked on the optical bench Nulltimate in order to study the feasibility of certain technological requirements associated with this technique. Beyond the obtention of a nulling ratio of 3,7.10^-5 in monochromatic light and 6,3.10^-4 in polychromatic light in the near infrared, as well as a stability of σN30 ms = 3,7.10^-5 estimated on 1 hour, my work allowed to clarify the situation thanks to a detailed error budget, a simulation of the transmission based on Gaussian beam optics and a complete overhaul of the computer control system. All of this finally resulted in the identification of the weaknesses of Nulltimate

Transits of exoplanets observed in the near-UV have been used to study the scattering properties of their atmospheres and possible star-planet interactions. We observed the primary transits of 15 exoplanets (CoRoT-1b, GJ436b, HAT-P-1b, HAT-P-13b, HAT-P-16b, HAT-P-22b, TrES-2b, TrES-4b, WASP-1b, WASP-12b, WASP-33b, WASP-36b, WASP-44b, WASP-48b, and WASP-77Ab) in the near-UV and several optical photometric bands to update their planetary parameters, ephemerides, search for a wavelength dependence in their transit depths to constrain their atmospheres, and determine if asymmetries are visible in their light curves. Here, we present the first ground-based near-UV light curves for 12 of the targets (CoRoT-1b, GJ436b, HAT-P-1b, HAT-P-13b, HAT-P-22b, TrES-2b, TrES-4b, WASP-1b, WASP-33b, WASP-36b, WASP-48b, and WASP-77Ab). We find that none of the near-UV transits exhibit any non-spherical asymmetries, this result is consistent with recent theoretical predictions by Ben-Jaffel et al. and Turner et al. The multiwavelength photometry indicates a constant transit depth from near-UV to optical wavelengths in 10 targets (suggestive of clouds), and a varying transit depth with wavelength in 5 targets (hinting at Rayleigh or aerosol scattering in their atmospheres). We also present the first detection of a smaller near-UV transit depth than that measured in the optical in WASP-1b and a possible opacity source that can cause such radius variations is currently unknown. WASP-36b also exhibits a smaller near-UV transit depth at 2.6 sigma. Further observations are encouraged to confirm the transit depth variations seen in this study.

The characterization of exoplanetary atmospheres is the new frontier in the field of exoplanets. Transit and eclipse spectroscopy are invaluable sources of information, as they may reveal the chemical composition, the presence of clouds, and the temperature and pressure profiles of the atmospheres of exoplanets. A photometric precision of about one part in 104 is necessary to make statistically significant inferences. The native calibration of current observatories, except Kepler, is not sufficient to reach this precision. In the past, parametric models have been used extensively by most teams to remove instrumental systematics. This approach has caused many debates regarding the use of different parametric choices for the removal of systematic errors. Parametric models decorrelate the systematic noise with the aid of auxiliary information on the instrument: the so-called optical state vectors (OSVs). Such OSVs can include inter- and intra-pixel position of the star or its spectrum, instrument temperatures and inclinations, and/or other parameters. The choice of the parameters to include in the OSVs is somewhat arbitrary, as is the choice of the functional forms to approximate the dependence of systematic noise on those parameters. The solution to many of the issues deriving from the use of OSVs lies in the use of `blind', non-parametric techniques. Such methods do not require a model for the systematics, and for this reason, they can be applied to any instrument with few changes (if any). In this Thesis, I focus on the Independent Component Analysis (ICA) of multiple time series, which performs a linear transformation of those series into maximally independent components. The use of ICA to detrend instrument systematics in exoplanetary light-curves was first proposed by Waldmann (2012). They experimented with spectroscopic light-curves taken with HST/NICMOS and sequential Kepler observations as input light-curves for the ICA. In this Thesis, I present two novel approaches to detrend single photometric observations in a self-consistent way (pixel-ICA), and scanning-mode spectroscopic observations without mixing the signals at different wavelengths (stripe-ICA). The two techniques that I pioneered extend the applicability of ICA to single observations with different instrument design. Some unsupervised preprocessing steps are also tested. The better performances of these algorithms compared to other ones in the literature are demonstrated over a series of Spitzer and Hubble observations, and synthetic data sets. The (re)analysis of archive and new data with similar techniques will cast new light on the characterization of exoplanets.

The transit method, employed by Microvariability and Oscillation of Stars (MOST), Kepler, and various ground-based surveys has enabled the characterization of extrasolar planets to unprecedented precision. These results are precise enough to begin to measure planet atmosphere composition, planetary oblateness, starspots, and other phenomena at the level of a few hundred parts per million. However, these results depend on our understanding of stellar limb darkening, that is, the intensity distribution across the stellar disk that is sequentially blocked as the planet transits. Typically, stellar limb darkening is assumed to be a simple parameterization with two coefficients that are derived from stellar atmosphere models or fit directly. In this work, we revisit this assumption and compute synthetic planetary-transit light curves directly from model stellar atmosphere center-to-limb intensity variations (CLIVs) using the plane-parallel Atlas and spherically symmetric SAtlas codes. We compare these light curves to those constructed using best-fit limb-darkening parameterizations. We find that adopting parametric stellar limb-darkening laws leads to systematic differences from the more geometrically realistic model stellar atmosphere CLIV of about 50–100 ppm at the transit center and up to 300 ppm at ingress/egress. While these errors are small, they are systematic, and they appear to limit the precision necessary to measure secondary effects. Our results may also have a significant impact on transit spectra.

2013 - 2014
Nature always offers astonishing shows to the humankind. Gravitational lensing is one of the most intriguing effects which can be observed, and the astrophysical applications of such a phenomenon span from particle physics to cosmology, to the search for new worlds. Although, since its formulation in the early 1900, gravitational lensing was underestimated and poorly investigated, in the last thirty years the observation of different phenomena related to gravitational lenses have revealed the real potentiality of the study of the effects of gravity on the light. Our comprehension of the Universe has been largely improved since we have studied the cosmological implications of lensing by clusters of galaxies, lensing of quasars, or effects of microlensing by non-luminous objects. The structure of the Universe, constraints on its formation theories, the mass distribution, and even proofs of the nature of dark matter can be studied by investigating magnification patterns and the effects due to gravitational lenses. Additionally, gravitational microlensing provides a unique tool to search for planetary systems in a region of the physical parameter space not probed by other methods. By observing microlensing effects to stars towards the Galactic bulge, we are able to look for small rocky planets orbiting stars in the Galactic disk or, more in general, along the line of sight. What we observe is the source lightcurve, i.e. the measured flux as a function of time. The presence of a foreground mass, or a system of masses, between the observer and a background source, causes an amplification of the source flux, so giving to the lightcurve specific features and shapes which can be attributed to different kinds of lens (single, binary, planetary, etc...). The study of this specific effect is likely to attain more promising results with the launch of space missions like EUCLID or WFIRST, since those telescopes will be able to detect Earth-like and smaller planets in their habitable zone, i.e. at a distance from their host star allowing the planet to have an equilibrium temperature at which liquid water can exist. This thesis work propose an insight into the gravitational microlensing, by starting with a theoretical work on the classification of binary microlensing lightcurves, and then by presenting the results of the modelling of one event from the 2013 observing season. A brief summary of some hot-Jupiter discovered with the transit method, and observed by the author, is finally presented at the end of the work. [edited by author]
XIII n.s.

This work describes the most relevant steps undertaken for the development and installation of the survey APACHE (A PAthway toward the Characterization of Habitable Earths), and some of the main results obtained after the first observing season are presented. APACHE is the first long-term observing campaign based in Europe which is devised expressly for detecting extrasolar planets orbiting well selected, nearby M dwarfs by using the photometric transit method. The project was conceived at the end of 2008 and he survey makes use of an array of five automated 40 cm telescopes which started routine observations between July 2012 and March 2013. In the Thesis introduction some key issues are discussed which in the last years have placed the cool stars at the centre of the planet hunters’ interests, producing an increase in the number of photometric and high resolution spectroscopic surveys targeted on red dwarfs. In Chapters 1 and 2 the milestones which led to the preparation and initial design of APACHE are presented (the feasibility and pilot study), while Chapter 3 is focused on the description of the most relevant characteristics of the survey structure, as the accurate definition of the catalogue of eligible targets (the APACHE Input Catalogue) and observing strategy, and the implementation of the software package used for obtaining and analyzing the light curves. In Chapter 4 the preliminary results obtained after the first observing season at regime are presented and discussed, with the analysis mainly focused on the study of the photometric variability of more than 130 M dwarfs. Three targets showed evidence of stellar flares, and rotation periods have been measured for five stars through the analysis of their light curve periodograms. A simple single-spot model has been applied to the time series of these stars to describe the observed sinusoidal-like modulation in terms of stellar spots/active regions, obtaining in particular an estimate of the spin-axis inclination angle relative to the line of sight. The Chapter ends with a presentation of more than 90 new variable stars discovered in the stellar fields observed by the APACHE telescopes during the first year. The Thesis concludes with Chapter 5, where the strategic synergy established between APACHE and the large National observing programme GAPS (Global Architecture of Planetary Systems) is described. GAPS observations are carried out with the high resolution spectrograph HARPS-N at the Telescopio Nazionale Galileo (TNG, @ La Palma island in the Canary archipelago) for an extensive study in the field of extrasolar planets. Among the goals of GAPS, of particular relevance is the detection of planets orbiting M dwarfs by analyzing the time variations of the stellar radial velocities, and in Chapter 5 preliminary results are presented for a sample of targets in common with the APACHE project. In particular, it is highlighted the importance of having photometric light curves as a support for a correct interpretation of periodical signals found in the radial velocity time series which could be due to the gravitational effects induced on the star by a planetary mass companion. The results discussed in this Thesis should demonstrate how effectively a large photometric database such that of APACHE is expected to contribute to both the exoplanet science and the physics of the cool stars
In questo lavoro sono descritti i passi più importanti che hanno portato allo sviluppo e alla messa in funzione della survey APACHE (A PAthway toward the Characterization of Habitable Earths), e vengono presentati alcuni dei principali risultati ottenuti dopo la prima stagione osservativa. APACHE è la prima campagna osservativa di lunga durata con base in Europa finalizzata alla ricerca di pianeti in orbita attorno a stelle nane rosse nelle vicinanze del Sole accuratamente selezionate, utilizzando il metodo fotometrico del transito. Il progetto è stato concepito alla fine del 2008 e la schiera di cinque telescopi automatici di 40 cm di diametro utilizzati per le ricerche sono entrati in funzione tra luglio 2012 e marzo 2013. L’introduzione presenta alcuni aspetti chiave che negli ultimi anni hanno portato le nane rosse al centro degli interessi dei cacciatori di mondi alieni, determinando la crescita del numero di campagne osservative dedicate al monitoraggio delle stelle pi`ù fredde, sia fotometricamente che tramite spettroscopia ad alta risoluzione. Vengono poi ripercorse le tappe fondamentali che sono servite per preparare e definire il design iniziale della survey APACHE (studio di fattibilità e studio pilota, discussi nei Capitoli 1 e 2), mentre il Capitolo 3 si concentra sulla descrizione delle caratteristiche più rilevanti dell’impianto della campagna osservativa, come la definizione del catalogo con i potenziali target osservativi (APACHE Input Catalogue) e della strategia osservativa, e la costruzione del software utilizzato per ottenere e analizzare le curve di luce. Nel Capitolo 4 sono presentati i risultati preliminari ottenuti dopo il primo anno di osservazioni a regime, e l’analisi si concentra soprattutto sullo studio della variabilità fotometrica di oltre 130 nane rosse. Tre target hanno mostrato evidenza di brillamenti stellari, e sono stati misurati periodi di rotazione attorno al proprio asse di cinque stelle attraverso l’analisi dei periodogrammi relativi alle loro curve di luce. Alle serie temporali fotometriche di queste stelle è stato applicato un semplice modello a singola macchia per descrivere la modulazione quasi-sinusoidale osservata in termini di macchie stellari/regioni attive, ottendo in particolare una stima dell’angolo di inclinazione dell’asse di rotazione rispetto alla linea di vista. Il Capitolo si conclude con la presentazione di più di 90 nuove stelle variabili scoperte da APACHE nel corso del primo anno. Il lavoro si chiude con il Capitolo 5, dove viene descritta la strategica sinergia instaurata tra il progetto APACHE e l’esteso programma osservativo nazionale GAPS (Global Architecture of Planetary Systems) che fa uso dello spettrografo ad alta risoluzione HARPS-N montato al Telescopio Nazionale Galileo (Isola di La Palma, arcipelago delle Canarie) per ricerche nell’ambito dei pianeti extrasolari. Tra gli obiettivi di GAPS c’è quello di scoprire pianeti in orbita attorno a nane rosse attraverso l’analisi delle variazioni temporali delle velocità radiali stellari, e il Capitolo 5 presenta i risultati preliminari ottenuti per i target in comune con il progetto APACHE. In particolare, viene sottolineata l’importanza delle serie temporali fotometriche come aiuto per una corretta interpretazione di segnali periodici trovati nelle serie temporali di velocità radiali che potrebbero essere dovuti agli effetti gravitazionali indotti sulla stella da un compagno di massa planetaria. I risultati discussi in questa Tesi dovrebbero dimostrare l’importante contributo che un ricco archivio di dati come quello prodotto dalla survey APACHE potrà assicurare sia alla scienza dei pianeti extrasolari che allo studio delle nane rosse

In the mid-eighteenth century, the primary and most urgent astronomical problem was to determine the exact value of the Earth-Sun distance (the so-called Astronomical Unit, A.U.). With that value in hand, thanks to Kepler’s third law, all the planet distances would have been easily derived and, as a consequence the entire solar system real dimension would have been determined too. The most promising methods for measuring the A.U., due to Halley and Delisle, were taking advantage of a rare phaenomenon: Venus transit over the Sun. It would have been sufficient that two observers, located in the two Earth hemispheres, had taken accurate measures of the transit to derive from the solar parallax and hence the A.U. The phaenomenon is rare but occurs always in close pairs and thus the attention of the whole scientific community was engaged twice in the eighteenth century: in 1761 and in 1769. While the European powers were fighting in the Seven Years War and in the subsequent struggles for colonial hegemony, 250 astronomers and scholars from different nations, animated by a common purpose in the spirit of Enlightenment, gave life to a joint venture, never attempted before, leaving for the farthest and most inaccessible locations of the known world, such as Siberia, the island of Newfoundland and the mysterious Australia, to observe Venus transit. Along with the astronomical results, those expeditions also improved geographical knowledges, discovered new lands, gave an impulse to the production of scientific instruments, resulted in collection of natural samples and, above all, constituted the first international and collaborative project in the whole history of science. At the crucial point, some astronomers faced a desolately cloudy sky, one passed out from his emotions, others had not even reached their destination, and someone never returned home. This is their story.

Parmi les méthodes qui permettent de détecter des exoplanètes, la photométrie des transits est celle qui a connu le plus grand essor ces dernières années grâce à l'arrivée des télescopes spatiaux CoRoT (en 2006) puis Kepler (en 2009). Ces deux satellites ont permis de détecter des milliers de transits potentiellement planétaires. Étant donnés leur nombre et l'effort nécessaire à la confirmation de leur nature, il est essentiel d'effectuer, à partir des données photométriques, un classement efficace permettant d'identifier les transits les plus prometteurs et qui soit réalisable en un temps raisonnable. Pour ma thèse, j'ai développé un outil logiciel, rapide et automatisé, appelé BART (Bayesian Analysis for the Ranking of Transits) qui permet de réaliser un tel classement grâce une estimation de la probabilité que chaque transit soit de nature planétaire. Pour cela, mon outil s'appuie notamment sur le formalisme bayésien des probabilités et l'exploration de l'espace des paramètres libres par méthode de Monte Carlo avec des chaînes de Markov (mcmc).Une fois les exoplanètes détectées, l'étape suivante consiste à les caractériser. L'étude du système solaire nous a démontré, si cela était nécessaire, que l'information spectrale est un point clé pour comprendre la physique et l'histoire d'une planète. L'interférométrie annulante est une solution technologique très prometteuse qui pourrait permettre cela. Pour ma thèse, j'ai travaillé sur le banc optique Nulltimate afin d'étudier la faisabilité de certains objectifs technologiques liés à cette technique. Au-delà de la performance d'un taux d'extinction de 3,7.10^-5 en monochromatique et de 6,3.10^-4 en polychromatique dans l'infrarouge proche, ainsi qu'une stabilité de σN30 ms = 3,7.10^-5 estimée sur 1 heure, mon travail a permis d'assainir la situation en réalisant un budget d'erreur détaillé, une simulation en optique gaussienne de la transmission du banc et une refonte complète de l'informatique de commande. Tout cela m'a finalement permis d'identifier les faiblesses de Nulltimate.

This PhD thesis presents the analysis of a large sample of photometric data relative to the super metal-rich open clusters NGC6791 and NGC6253. The main goal of the surveys was the search for extrasolar planets using the transits method. I contributed to the extrasolar planet search by making numerical simulations in order to estimate the number of expected transiting planets. Moreover I analyzed the entire sample of light curves in order to find variable stars. I discovered 260 new variable stars in the field of NGC6791 and 597 in the field of NGC6253. The classification of all variables is presented and discussed in this work.