The technique of non-redundant masking (NRM) transforms a conventional telescope into an interferometric array. In practice, this provides a much better constrained point-spread function than a filled aperture and thus higher resolution than traditional imaging methods. Here, we describe an NRM data reduction pipeline. We discuss strategies for NRM observations regarding dithering patterns and calibrator selection. We describe relevant image calibrations and use example Large Binocular Telescope data sets to show their effects on the scatter in the Fourier measurements. We also describe the various ways to calculate Fourier quantities, and discuss different calibration strategies. We present the results of image reconstructions from simulated observations where we adjust prior images, weighting schemes, and error bar estimation. We compare two imaging algorithms and discuss implications for reconstructing images from real observations. Finally, we explore how the current state of the art compares to next-generation Extremely Large Telescopes.

HD 11112 is an old, Sun-like star that has a long-term radial velocity (RV) trend indicative of a massive companion on a wide orbit. Here we present direct images of the source responsible for the trend using the Magellan Adaptive Optics system. We detect the object (HD 11112B) at a separation of 2 2 (100 au) at multiple wavelengths spanning 0.6-4 mu m. and show that it is most likely a gravitationally bound cool white dwarf. Modeling its spectral energy distribution suggests that its mass is 0.9-1.1M(circle dot), which corresponds to very high eccentricity, near edge-on orbits from a. Markov chain Monte Carlo analysis of the RV and imaging data together. The total age of the white dwarf is > 2 sigma, which is discrepant with that of the primary star under most assumptions. The problem can be resolved if the white dwarf progenitor was initially a double white dwarf binary that then merged into the observed high-mass white dwarf. HD 11112B is a unique and intriguing benchmark object that can be used to calibrate atmospheric and evolutionary models of cool white dwarfs and should thus continue to be monitored by RV and direct imaging over the coming years.

We analyze archival data from Bailey and co-workers from the Magellan adaptive optics system and present the first 0.9 mu m detection (z' = 20.3 +/- 0.4 mag; Delta z' = 13.0 +/- 0.4 mag) of the 11 M-Jup circumbinary planet HD 106906AB b, as well as 1 and 3.8 mu m detections of the debris disk around the binary. The disk has an east-west asymmetry in length and surface brightness, especially at 3.8 mu m where the disk appears to be one-sided. The spectral energy distribution of b, when scaled to the K-S-band photometry, is consistent with 1800 K atmospheric models without significant dust reddening, unlike some young, very red, low-mass companions such as CT Cha B and 1RXS 1609 B. Therefore, the suggested circumplanetary disk of Kalas and co-workers might not contain much material, or might be closer to face-on. Finally, we suggest that the widest (a greater than or similar to 100 AU) low mass ratio (M-p/M-star = q less than or similar to 0.01) companions may have formed inside protoplanetary disks but were later scattered by binary/planet interactions. Such a scattering event may have occurred for HD 106906AB b with its central binary star, but definitive proof at this time is elusive.

Stellar companions can influence the formation and evolution of planetary systems, but there are currently few observational constraints on the properties of planet-hosting binary star systems. We search for stellar companions around 77 transiting hot Jupiter systems to explore the statistical properties of this population of companions as compared to field stars of similar spectral type. After correcting for survey incompleteness, we find that 47% +/- 7% of hot Jupiter systems have stellar companions with semimajor axes between 50 and 2000 au. This is 2.9 times larger than the field star companion fraction in this separation range, with a significance of 4.4 sigma. In the 1-50 au range, only 3.9(-2.0)(+4.5)% of hot Jupiters host stellar companions, compared to the field star value of 16.4% +/- 0.7%, which is a 2.7 sigma difference. We find that the distribution of mass ratios for stellar companions to hot Jupiter systems peaks at small values and therefore differs from that of field star binaries which tend to be uniformly distributed across all mass ratios. We conclude that either wide separation stellar binaries are more favorable sites for gas giant planet formation at all separations, or that the presence of stellar companions preferentially causes the inward migration of gas giant planets that formed farther out in the disk via dynamical processes such as Kozai-Lidov oscillations. We determine that less than 20% of hot Jupiters have stellar companions capable of inducing Kozai-Lidov oscillations assuming initial semimajor axes between 1 and 5 au, implying that the enhanced companion occurrence is likely correlated with environments where gas giants can form efficiently.

LkCa 15 hosts a pre-transitional disk as well as at least one accreting protoplanet orbiting in its gap. Previous disk observations have focused mainly on the outer disk, which is cleared inward of similar to 50 au. The planet candidates, on the other hand, reside at orbital radii around 15 au, where disk observations have been unreliable until recently. Here, we present new J-band imaging polarimetry of LkCa 15 with SPHERE IRDIS, yielding the most accurate and detailed scattered-light images of the disk to date down to the planet-hosting inner regions. We find what appear to be persistent asymmetric structures in the scattering material at the location of the planet candidates, which could be responsible at least for parts of the signals measured with sparse-aperture masking. These images further allow us to trace the gap edge in scattered light at all position angles and search the inner and outer disks for morphological substructure. The outer disk appears smooth with slight azimuthal variations in polarized surface brightness, which may be due to shadowing from the inner disk or a two-peaked polarized phase function. We find that the near-side gap edge revealed by polarimetry matches the sharp crescent seen in previous ADI imaging very well. Finally, the ratio of polarized disk to stellar flux is more than six times larger in the J-band than in the RI bands.

Context. Radial velocity and transit methods are effective for the study of short orbital period exoplanets but they hardly probe objects at large separations for which direct imaging can be used. Aims. We carried out the international deep planet survey of 292 young nearby stars to search for giant exoplanets and determine their frequency. Methods. We developed a pipeline for a uniform processing of all the data that we have recorded with NIRC2/Keck II, NIRI/Gemini North, NICI/Gemini South, and NACO/VLT for 14 yr. The pipeline first applies cosmetic corrections and then reduces the speckle intensity to enhance the contrast in the images. Results. The main result of the international deep planet survey is the discovery of the HR8799 exoplanets. We also detected 59 visual multiple systems including 16 new binary stars and 2 new triple stellar systems, as well as 2279 point-like sources. We used Monte Carlo simulations and the Bayesian theorem to determine that 1.05(-0.70)(+2.80)% of stars harbor at least one giant planet between 0.5 and 14 MJ and between 20 and 300AU. This result is obtained assuming uniform distributions of planet masses and semi-major axes. If we consider power law distributions as measured for close-in planets instead, the derived frequency is 2.30(-1.55)(+5.95)%, recalling the strong impact of assumptions on Monte Carlo output distributions. We also find no evidence that the derived frequency depends on the mass of the hosting star, whereas it does for close-in planets. Conclusions. The international deep planet survey provides a database of confirmed background sources that may be useful for other exoplanet direct imaging surveys. It also puts new constraints on the number of stars with at least one giant planet reducing by a factor of two the frequencies derived by almost all previous works.

Nous allons assister au cours de la prochaine décennie, à la première lumière des nouveaux Extremely Large Telescopes. Leur grande taille (de 25 à 39 m de diamètre) permet d’augmenter à la fois leur sensibilité et leur résolution angulaire. Cependant, la résolution angulaire d'un télescope terrestre, est toujours limitée par la turbulence atmosphérique. Pour pallier à ce problème, les grands télescopes sont désormais équipés d'instruments d’Optique Adaptative (OA). L’OA est une technique qui permet d’analyser les effets de la turbulence et de les compenser en temps réel à l’aide de miroirs déformables. En complément, la plupart des télescopes de la génération 8-10 m sont maintenant équipés de systèmes d’étoiles lasers qui permettent d’augmenter la proportion du ciel pouvant bénéficier d’une correction par OA: on parle alors d'Optique Adaptative Grand Champ (OAGC). Malgré les excellentes performances de ces systèmes, la correction apportée aux images reste partielle et des résidus de correction limitent encore leur qualité. Pour extraire les meilleurs résultats scientifiques des images issues de l'OAGC, il est donc essentiel d'optimiser les outils de réduction et d'analyse de données. La première partie de cette thèse détaille une analyse astrophysique de données OAGC ayant pour but d'étudier la formation des étoiles massives dans un environnement extra-galactique. Au delà des résultats scientifiques nouveaux, cette étude a permis de mettre en évidence les termes d'erreur limitant l'analyse scientifique de données OAGC. La seconde partie de cette thèse est dédiée au développement d'un nouvel outil de correction de la distorsion permettant de réduire ces termes d'erreurs. / The next decade will see the first light of the new Extremely Large Telescopes. Their large diameter (from 25 to 39 meters across), increases both their sensitivity and their angular resolution. However, angular resolution of all sizes ground-based telescope is always strongly limited by the atmospheric turbulence. To tackle this problem and fully exploit their capabilities, large optical telescopes are now indissociable of their Adaptive Optics (AO) instruments. AO is a technic that consists in analyzing the effects of turbulence on the wavefront and compensating for it in real time, thanks to one or several deformable mirrors in order to restore the initial angular resolution of optical telescopes. In addition, most of the 8-10 meters telescopes are supplied with laser guide stars systems in order to increase the portion of the sky that can benefit for such an AO correction. Such systems are called Wide Field AO (WFAO). However, despite the excellent performance of such systems, the correction performed is not perfect and some residuals still limit the image quality. In order to get the best science results out of the WFAO images, dedicated and optimized reduction and analyses tools are needed. The first part of this document present an astrophysics analyses of WFAO images aiming to study massive star formation in an extra-galactic environment. In addition to new science results, the study carried out on these observations has enable to highlight the critical parameters that limit the scientific analyses of Wide Field AO data. The second part of this document is dedicated to the development of a new distorsion correction tool that aims to reduce these error terms.

Les mécanismes physiques de la perte de masse des étoiles évoluées sont encore largement inconnus. Ce processus essentiel est pourtant le moteur principal de l'évolution chimique du milieu interstellaire. Pour les supergéantes rouges (SGR), le déclenchement de l'éjection de la matière et les mécanismes de condensation de la poussière demeurent mal compris. La façon dont les géantes rouges parviennent à former des nébuleuses planétaires non-Sphériques est aussi inconnue. Au cours de ma thèse j'ai étudié des étoiles évoluées grâce à des techniques de haute résolution angulaire permettant de détailler leur surface et leur environnement proche où se trouve l'origine de la perte de masse. À partir d'observations interférométriques en infrarouge (IR), j'ai caractérisé l'enveloppe de vapeur d'eau et de monoxyde de carbone de la SGR Bételgeuse. J'ai également suivi l'évolution d'un point chaud à sa surface et analysé la structure de sa convection ainsi que celle d'Antarès (une autre SGR très proche) grâce à des simulations hydrodynamiques radiatives. L'imagerie à la limite de diffraction (optique adaptative en IR, télescope spatial en ultraviolet) m'a permis d'étudier l'évolution des inhomogénéités de l'enveloppe circumstellaire de Bételgeuse et découvrir un disque circumstellaire autour de L2 Puppis, une étoile de la branche asymptotique des géantes. Ces observations multi-Longueurs d'onde, répétées à plusieurs époques, m'ont permis d'initier un suivi temporel et d'apporter des informations sur la dynamique en jeu. Renouvelé sur un plus grand échantillon d'étoiles dans les années à venir, ce programme permettra de mieux appréhender la perte de masse des étoiles évoluées. / Mass loss of evolved stars is still largely mysterious, despite its importance as the main evolution engine for the chemical composition of the interstellar medium. For red supergiants (RSG), the triggering of the outflow and the mechanism of dust condensation remain unknown. Concerning red giant stars, we still do not know how their mass loss is able to form a bipolar planetary nebula. During my PhD thesis, I observed evolved stars with high angular resolution techniques. They allowed us to study the surface and the close environment of these stars, from where mass loss originates. With near-Infrared interferometric observations, I characterized the water vapor and carbon monoxide envelope of the nearby RSG Betelgeuse. I also monitored a hot spot on its surface and analyzed the structure of its convection, as well as that of Antares (another very nearby supergiant) thanks to radiative hydrodynamical simulations. Diffraction-Limited imaging techniques (near-Infrared adaptive optics, ultraviolet space telescope) allowed me to observe the evolution of inhomogeneities in the circumstellar envelope of Betelgeuse and to discover a circumstellar disk around L2 Puppis, an asymptotic giant branch star. These multi-Scale and multi-Wavelength observations obtained at several epochs allowed us to monitor the evolution of the structures and to derive information on the dynamics of the stellar environment. With a wider stellar sample expected in the next few years, this observing program will allow a better understanding of the mass loss of evolved stars.

Une manière efficace de contraindre la formation des planètes est l'étude des disques protoplanétaires. Les premières images de ces disques ont été obtenues dans les années 80 en infrarouge et en millimétrique. Ces images dévoilaient pour la première fois la morphologie de l'excès infrarouge vu dans les distributions spectrales d'énergies des étoiles jeunes. Depuis, de nets progrès ont été faits et, outre la détection directe de planètes, nous sommes capables de distinguer les perturbations que celles-ci pourraient engendrer dans ces disques. La région interne de ces disques, où la majorité des planètes sont détectées, est complexe car étant le théâtre de nombreux phénomènes encore mal contraints (sublimation de la poussière, vents, accrétion). Pour les étoiles jeunes les plus proches, observer ces régions revient à atteindre une résolution angulaire de l'ordre de la milliseconde d'arc, inatteignable avec un télescope monolithique. L'interférométrie optique permet de satisfaire cette contrainte. Cette technique consiste à combiner la lumière de deux télescopes ou plus afin de la faire interférer. Ces interférences permettent de contraindre la morphologie de l'objet observé à l'aide de modèles. Mais afin de comprendre les phénomènes en jeu il est nécessaire d'avoir une image indépendante de ces modèles. La reconstruction d'images est possible avec l'avènement récent d'interféromètres à 4 télescopes ou plus. Les premières images ont ainsi pu être reconstruites. Cependant, l'étoile centrale ne permet pas d'accéder facilement à l'image de l'environnement. Ma thèse a donc consisté à outrepasser cette difficulté en développant une méthode de reconstruction d'image adaptée à l'environnement protoplanétaire des étoiles jeunes. Elle consiste à séparer l'étoile centrale de l'image afin de reconstruire son environnement tout en prenant en compte la différence de température entre ces deux éléments. Grâce à cette méthode et aux instruments interférométriques du VLTI, j'ai pu reconstruire les images des premières unités astronomiques d'une douzaine d'étoiles de Herbig et de révéler leurs morphologies. J'ai ainsi pu appliquer une analyse géométrique originale afin de les caractériser. Enfin, j'ai analysé plus en détail un étoile particulière, MWC158, dont j'ai imagé la variabilité qui pourrait être interprétée comme une éjection de matière. Ma thèse démontre l'importance de la prise en compte des aspects chromatiques dans la reconstruction d'image ainsi que de l'adaptation de cette méthode à la spécificité des étoiles jeunes. / An effective way to understand the formation of planets is the study of protoplanetary disks. The first images of these disks were obtained in the infrared and the millimeter in the 80s. These images unveiled for the first time the morphology of the infrared excess seen in the spectral energy distributions of young stellar objects. Since then, significant progress has been made and, in addition to the direct detection of planets, we are able to distinguish the disruption they could cause in these disks. The inner region of these disks, where the majority of planets are found, is complex as being the scene of many phenomena still poorly constrained (dust sublimation, winds, accretion). For the closest young stars, observing these regions amounts to achieve an angular resolution of the order of a milliarcsecond, unattainable with monolithic telescopes. The optical interferometry can reach such a small angle. This technique consists in combining the light of two or more telescopes to make it interfere. These interferences can be used to constrain the morphology of the observed object by using models. But to understand the phenomena involved in the inner parts of young stellar objects, it is necessary to have an independent image. Image reconstruction is possible with the recent advent of interferometers with 4 or more telescopes. The first images were able to be rebuilt. However, the central star does not allow easy access to the environment morphology. The goal of my thesis was to bypass this difficulty by developing a method of image reconstruction which is adapted to the protoplanetary environment of young stars. It consists in separating the central star of the image to reconstruct its environment while taking into account the temperature difference between the two. With this method and the VLTI interferometric instruments, I reconstructed the images of the first astronomical unit of a dozen of Herbig stars and revealed their morphologies. I was able to apply a novel geometric analysis to characterize them. Finally, I have analyzed in more detail a particular star, MWC158, which I imaged the variability that could be interpreted as a matter ejection. My thesis demonstrates the importance of the inclusion of chromatic aspects in image reconstruction and adaptation of this method to the specific characteristics of young stars.

Parmi les 3000 exoplanètes détectées à ce jour, seule une cinquantaine ont été observées par imagerie dont l’avantage est de donner accès à la lumière des exoplanètes, ce qui ouvre la voie aux études spectrales de leur atmosphère et de leur surface. L’imagerie est aussi la seule méthode permettant d’étudier des exoplanètes situées dans les parties externes des systèmes stellaires ainsi que les disques circumstellaires, ce qui est fondamental pour comprendre les différentes étapes de la formation planétaires. Cependant, ces techniques doivent relever deux défis : la faible séparation angulaire qui existe entre une exoplanète et son étoile, ainsi que le contraste entre ces deux objets qui est de l’ordre de 10-4 dans l'infrarouge proche pour des Jupiter jeunes et de l'ordre de 10-10 dans le visible pour des planètes matures telles la Terre et Jupiter. Les instruments actuels utilisent des coronographes pour filtrer la lumière de l'étoile hôte et observer son voisinage ténu. Ils utilisent également des techniques actives qui compensent les effets des aberrations de surface d’onde pour minimiser le niveau des tavelures dans l'image finale. Couplés à des techniques d'imagerie différentielle, ces instruments ont permis la découverte et l'étude d'exoplanètes jeunes et massives, et de disques circumstellaires. Cependant, pour détecter des exoplanètes moins lumineuses et plus proches de leur étoile, les techniques d’imagerie font aujourd’hui l’objet d'une recherche active en laboratoire. Par exemple, l’Observatoire de Paris a développé le banc très haute dynamique (THD) pour tester et optimiser l’association de plusieurs techniques d’imagerie haute dynamique comme le four quadrants phase masque (FQPM) ou la self-coherent camera (SCC) qui est une technique d’analyse de surface d’onde en plan focal.Au début de ma thèse, mes travaux se sont concentrés sur le développement et l’étude de coronographes et d’analyseurs en plan focal pouvant travailler en larges bandes spectrales (typiquement 12,5 % à 40 %). J’ai testé sur le banc THD deux coronographes, le multi four-quadrant phase-mask (MFQPM) et le dual-zone phase-mask (DZPM). J’ai prouvé que le DZPM peut atteindre des contrastes de l’ordre de 4 10-8 pour des séparations angulaires comprises entre 7 et 16 λ/D et une bande spectrale de 250 nm centrée à 640 nm. J’ai également développé et testé une version de la SCC moins sensible au chromatisme appelée multireference self-coherent camera (MRSCC). En la combinant au DZPM, j’ai réussi à atteindre en boucle fermée des contrastes de l’ordre de 4.5 10-8 entre 5 et 17 λ/D pour une bande spectrale de 80 nm centrée à 640 nm. Ces deux résultats sont importants, car ils montrent qu'il est possible de construire un instrument qui atténue la lumière et contrôle activement les aberrations optiques directement à partir de l'image scientifique en large bande spectrale. À la fin de ma thèse, nous avons mis en place une collaboration visant à tester la SCC sur le télescope Hale du mont Palomar. Lors de deux missions auxquelles j’ai participé, nous avons prouvé que la SCC pouvait être associée avec un coronographe de type vortex ce qui n’avait jamais était fait auparavant. De plus, suite aux résultats obtenus sur source interne, nous prévoyons une démonstration sur ciel à l'automne 2016 / Among the 3000 exoplanets detected at this time, about 50 have been observed by direct imaging. The benefit of direct imaging is to give access to exoplanet light, paving the way for spectroscopic study of their atmospheres and surfaces. Moreover, direct imaging is also the only method that enables the study of exoplanets located in the outer parts of the stellar systems as well as circumstellar disks, which are fundamental to understand the different stages of planetary formation. However, there are two challenges : the small angular separation between an exoplanet and its star (less than a fraction of 1’’), and the contrast between the two objects which is of the order of 10-4 in near infrared for young Jupiter and of the order of 10-10 in visible light for Earth like planets. Existing instruments use coronagraphs to filter light from the host star and observe its tenuous neighborhood. They also use active techniques in order to minimize, in the final image, the brightness of speckles induced by wavefront aberrations. Coupled with differential imaging techniques, these instruments led to the discovery and study of young and massive exoplanets and circumstellar disks. However, to detect fainter exoplanets closer to their star, imaging techniques are now at the heart of an active research. For example, the Paris Observatory developed the banc très haute dynamique (THD bench) aiming at testing several high contrast imaging techniques and their associations as the four quadrants phase masque (FQPM) and the self-coherent camera (SCC) which is a focal plane wavefront sensor.At the beginning of my PHD, I mainly focused my work on the development and the study of coronagraphs and focal plane wavefront sensors able to work in broadband (between 12,5 % and 40 %). I tested on the THD bench two coronagraphs, the multi four-quadrant phase-mask (MFQPM) and the dual-zone phase-mask (DZPM). I proved that the DZPM is able to reach contrasts of 4 10-8 at angular separations ranging from 7 to 16 λ/D using a spectral bandwidth of 250 nm centered on 640 nm (40 %). I also developed and tested a new version of the SCC, less sensitive to chromatism, called the multireference self-coherent camera (MRSCC). By combining both DZPM and MRSCC, I reached in closed loop contrasts of 4.5 10-8 between 5 and 17 λ/D for a spectral bandwidth of 80 nm centered on 640 nm (12,5 %). These two results are important because they show that it is possible to build an instrument able to reduce the stellar light and actively control optical aberrations directly from a scientific image registered in a large spectral bandwidth which is requiered for the next generation of instruments. During my PHD, we also strated a collaboration to install the SCC at the Palomar Observatory. During two missions in which I took part, we proved, for the first time, that the SCC can be associated with a vortex coronagraph. Finally, based on these results, we plan to demonstrate the SCC concept on sky in the fall of this year