Dans le cadre de ma thèse, j’ai analysé les spectres de neuf étoiles Kepler obtenus avec les relevés de vitesse radiale (VR). Cela a permis la caractérisation de leur compagnons planétaires. J’ai analysé les spectres de 21 autres étoiles CoRoT et Kepler, probablement hôtes de naines M à faible masse. Cela a permis d’'élargir l'échantillon des étoiles à faible masse avec masse et rayon mesurés. J’ai calculé l’indice d’activité chromosphérique de 31 étoiles observées avec SOPHIE/OHP, en aidant l’étude des interactions étoile-planète. J’ai étudié le comportement de SOPHIE à bas signal à bruit (S/B). J’ai déterminé l’intervalle de S/B dans lequel un spectre stellaire est fiable pour la mesure des paramètres stellaires.Dans le cadre du consortium SOPHIE, j’ai suivi l’analyse complète du système Kepler-117. Ce système multi-planétaire montre variations des périodes orbitaux dues aux échanges dynamiques entre les planètes (TTV). Pour déterminer les paramètres du système, un approche spécifique a été développé pour l’ajustement simultané de transits, VR et TTV (Bruno et al. 2015).Finalement, je me suis intéressé à l’activité stellaire dans la photométrie de transit. J’ai impl ́ementé deux logiciels de modélisation de tâches stellaires dans un code MCMC, en ajoutant l’évolution des tâches dans l’un d’eux. J’ai appliqué les logiciels au Soleil, à CoRoT-7 et à CoRoT-2. J’ai amené un étude détaillé de la courbe de lumière de CoRoT-2, et exploré les effets des tâches dans les paramètres du transit (Bruno et al., en prep.). Avec la méthode FF’ (Aigrain et al. 2012), j’ai contribué à l’exploration du lien entre la signature des tâches de CoRoT-7 et dans la photométrie et dans les VR. / During my PhD, I analyzed the spectra of nine Kepler stars obtained by radial velocity (RV) observations. This allowed the characterization of their planetary companions. I analyzed the spectra of twenty-one other CoRoT and Kepler stars, likely orbited by low-mass M dwarfs. This helped widening the sample of low-mass stars with measured mass and radius. I calculated the chromospheric activity indfex of thirty-one stars observed with SOPHIE/OHP, helping the study of star-planet interactions. I studied the behavior of SOPHIE in low signal-to-noise ratio (SNR) regime. I determinhed the SNR range in which a stellar spectrum is reliable for the measure of the stellar parameters.Within the SOPHIE consortium, I followed the complete analysis of the Kepler-117 system. This multi-planetary system presents variations in the planetary orbital periods due to their mutual dynamical interacion (TTVs). To fit the system parameters, a specific fitting approach including TTV modeling was developed. We derived the system parameters by the simultaneous fit of transits, RVs, and TTVs (Bruno et al. 2015).Finally, I addressed the problem of stellar activity in transit photometry. I implemented two starspot modeling codes into an MCMC algorithm, adding spot evolution to oneof them. I applied the codes to the Sun, CoRoT-7, and CoRoT-2. I carried an extensive study on the light curve of CoRoT-2, and explored the effects of the spots on the transit parameters (Bruno et al., in prep.). With the FF’ method (Aigrain et al. 2012), I contributed to explore the connection between the photometric and RV signature of starspots in CoRoT-7.

The diploma thesis "The future of human exoplanet settlement from the present point of view" is focused on the analysis of the development of the urban compo-sition of the city for the purpose of finding the most suitable concept of the set-tlement. Its foundation is hypothetically put on some of the planets outside the solar system, where could be comparable conditions as on Earth. Installation in these extreme conditions is chosen deliberately so that the essential aspects of the urban layout come to the fore. In this way it is possible at the same time to verify the presumption of stability of the basic assumptions of a functional city and ap-ply the final conclusions in the current conditions as well.

Imager une exo-terre à proximité d’une étoile est une tâche complexe : le signal de la planète est noyé dans le flux immense de l’étoile, très proche. Doivent donc être combinés :- de grands télescopes spatiaux segmentés. La segmentation du miroir primaire facilite le transport mais crée des erreurs liées à l’alignement.- un coronographe, permettant d’éteindre la lumière stellaire. - enfin, toute aberration optique crée un résidu lumineux nuisible dans l’image. La mesure et le contrôle des aberrations d’un système coronographique, notamment celles liées à la segmentation du télescope, sont donc primordiaux et constituent le sujet de ma thèse.Tout d’abord, j’ai développé PASTIS, un modèle simplifié du contraste d’un coronographe en présence d’une pupille segmentée, permettant d’analyser facilement les performances pour contraindre les aberrations optiques lors du design de l’instrument. PASTIS prend en compte les spécificités des instruments : structure de la pupille, aberrations optiques dues à la segmentation, coronographe. Je l’ai appliqué au télescope LUVOIR afin d’analyser les modes limitant le contraste et ainsi mieux répartir les contraintes sur les segments. Par la suite, j’ai travaillé sur l’analyse de front d’onde coronographique en présence d’un télescope segmenté sur le banc expérimental HiCAT avec une première démonstration de l’analyseur COFFEE permettant de reconstruire les erreurs de phasage avec une grande précision. Enfin, j’ai mené une analyse comparative des multiples méthodes de contrôle de front d’onde existantes et validé l’une d’elles (Dark Hole Non Linéaire) expérimentalement dans un cadre simplifié sur le banc MITHIC du LAM / Direct imaging of exo-Earths is extremely complex: the star is by far brighter and very close to the planet. Several tools have to be combined:- a giant primary mirror. For manufacturing and transportation reasons, we tend to use segmented mirrors, ie. mirrors made of smaller mirrors but that have to be well-aligned and stabilised.- a coronagraph, enabling to remove the starlight.- the smallest residual wavefront aberration into residual light that decreases the image quality. The measurement and control of the aberrations, including the ones due to the telescope segmentation, are crucial and consist in the topic of my thesis.First, I developed PASTIS, a model of the contrast of a coronagraphic system in presence of a segmented pupil, enabling to analyze the performance to set up constraints on the optical aberrations during the instrument design. PASTIS takes into account the specificities of high-contrast instruments: pupil structure, optical aberrations due to the segmentation, coronagraph. I applied it to the LUVOIR telescope to analyze the main modes limiting the contrast and therefore optimizing the repartition of the constraints on the segments. In parallel, I worked on the analysis of the coronagraphic wavefront in presence of a segmented telescope on the experimental testbed called HiCAT, with a first demonstration of the COFFEE sensor enabling to reconstruct phasing errors with a high precision.Eventually, I ran a comparative analysis of existing methods of wavefront control and experimentally validated one of them (Non Linear Dark Hole) in a simplified case on the MITHIC testbed at LAM

In this licentiate thesis, I consider debris disks from an observational, astronomical viewpoint, but also discuss a potential astrobiological application. Debris disks are essentially disks of dust and rocks around main-sequence stars, analogue to the Kuiper- or the asteroid belt in our solar system. Their observation and theoretical modeling can help to constrain planet formation models and help in the understanding of the history of the solar system. After a general introduction into the field of debris disks and some basic debris disk physics, the thesis concentrates on the observation of gas in debris disks. The possible origins of this gas and its dynamics are discussed and it is considered what it can tell us about the physical conditions in the disk and possibly about the dust composition. In this way, the paper associated with this thesis (dealing with the gas in the β Pic debris disk) is set into context. More in detail, we observed the CII emission originating from the carbon-rich β Pic disk with Herschel HIFI and attempted to constrain the spatial distribution of the gas from the shape of the emission line. This is necessary since the gas production mechanism is currently unknown, but can be constraint by obtaining information about the spatial profile of the gas. The last part of the thesis describes our preliminary studies of the possibility of a debris disk containing biomarkers, created by a giant impact on a life-bearing exoplanet.

abstract: One strategic objective of the National Aeronautics and Space Administration (NASA) is to find life on distant worlds. Current and future missions either space telescopes or Earth-based observatories are frequently used to collect information through the detection of photons from exoplanet atmospheres. The primary challenge is to fully understand the nature of these exo-atmospheres. To this end, atmospheric modeling and sophisticated data analysis techniques are playing a key role in understanding the emission and transmission spectra of exoplanet atmospheres. Of critical importance to the interpretation of such data are the opacities (or absorption cross-sections) of key molecules and atoms. During my Doctor of Philosophy years, the central focus of my projects was assessing and leveraging these opacity data. I executed this task with three separate projects: 1) laboratory spectroscopic measurement of the infrared spectra of CH4 in H2 perturbing gas in order to extract pressure-broadening and pressure-shifts that are required to accurately model the chemical composition of exoplanet atmospheres; 2) computing the H2O opacity data using ab initio line list for pressure and temperature ranges of 10^-6–300 bar and 400–1500 K, and then utilizing these H2O data in radiative transfer models to generate transmission and emission exoplanetary spectra; and 3) assessing the impact of line positions in different H2O opacities on the interpretation of ground-based observational exoplanetary data through the cross-correlation technique. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2019

Les atmosphères de Jupiter chaudes reçoivent des quantitées extrêmes de radiation de leur étoile hôte, ce qui nous permet d’étudier les processus chimiques et dynamiques d’atmosphères dans un régime d’énergie qui n’est pas accessible par l’étude du système solaire. La spectroscopie de transit et d’éclipse secondaire permet la caractérisation de ces atmosphères. Toutefois, ces méthodes ne considèrent pas la variation spatiale des abondances moléculaires, du profil de température et des nuages dans l’atmosphère. À l’aide de la méthode de cartographie par éclipse secondaire à plusieurs longueurs d’ondes, il est possible de mesurer la distribution spatiale des paramètres atmosphériques. À ce jour, cette méthode n’a été appliquée qu’à la Jupiter chaude HD 189733 b à partir d’observations photométriques du télescope spatial Spitzer à 8 μm. Avec le lancement prochain du JWST, des observations à haute précision spectrophotométrique sont attendues, ce qui renforce le besoin pour une méthode permettant la simulation et l’analyse statistique d’observations d’éclipse secondaire à plusieurs longueurs d’ondes. Nous présentons une nouvelle méthode afin de simuler des courbes de lumière à plusieurs longueurs d’ondes, ainsi qu’une méthode statistique pour déterminer la distribution atmosphérique à partir d’observations. La simulation des courbes de lumière à plusieurs longueurs d’ondes est discrétisée pour permettre le calcul rapide des modèles nécessaire à l’analyse statistique d’observations. Nous appliquons cette méthode à des observations simulées de JWST NIRSpec pour la planète WASP-33 b à diverses distributions spatiales de coefficient de dissociation de l’eau. Nos résultats indiquent que 5 observations d’éclipse secondaire sont suffisantes pour mesurer la distribution spatiale du coefficient de dissociation de l’eau en longitude et latitude. L’application de la méthode de cartographie par éclipse secondaire à plusieurs longueurs d’ondes va permettre d’appronfondir d’avantage notre connaissance des processus dynamiques des atmosphères de Jupiter chaudes. / Hot Jupiter atmospheres, receiving extreme amounts of irradiation from their host star, enable us to study the atmospheric chemistry and dynamics of atmospheres at regimes that would otherwise be inaccessible from solar system observations. Transmission and emission spectroscopy of these atmospheres enables their characterization. However, these methods do not consider the spatial distribution of the molecular abundances, temperature profile, and clouds. Using multi-wavelength secondary eclipse mapping, it is possible to measure the spatial distribution of the atmospheric parameters. Secondary eclipse mapping has only been applied for photometric Spitzer/IRAC 8 μm observations of HD 189733 b so far. With the imminent launch of JWST, high-precision spectrophotometric observations of hot Jupiters are expected, reinforcing the need for a framework that can simulate and retrieve secondary eclipse mapping observations. We present a novel method to simulate secondary eclipse light curves for non-uniform atmospheres at multiple wavelengths, as well as a statistical method to retrieve the distribution from observations. The simulation of the multi-wavelength light curves is discretized to enable the fast computation necessary for statistical analysis of observations. We apply these methods to simulated JWST NIRSpec observations of WASP-33 b for various distributions of the water dissociation coefficient and conclude that 5 secondary eclipse observations are sufficient to constrain significant spatial variations in longitude and latitude. The application of the multi-wavelength secondary eclipse mapping to JWST will further deepen our understanding of the atmospheric dynamics processes to which hot Jupiter atmospheres are subjected.

The detection of Earth-like exoplanets and the characterization of their atmospheres is a challenge one needs to solve to assess their habitability and the presence of life in the universe. If this challenge is still unresolved today, even in the era of giant telescopes, it is mainly because of the very high contrast between these exoplanets and their host star and also their proximity. To overcome both of these constraints, a new method combining high-dispersion spectroscopy and nulling interferometry has been imagined. The idea is to use the nulling interferometry to attenuate the star light emission and detect the inner rocky planets with a high angular resolution. The high-dispersion spectroscopy is increasing the exoplanet detectability significantly which enables to relax the star attenuation requirement for an Earth-like observation. Our simulation made for an exoplanet similar to the Earth orbiting Proxima Centauri is giving a condition for the star attenuation ∼10−4 to detect it. Given this condition, we are able to evaluate the unability of a photonic device at our disposal to achieve such performance without dealing with its limitations. If a future project manages to overcome these limitations, this device could be part of a precursor instrument at IPAG to demonstrate experimentally the performance of high-dispersion nulling interferometry. / Upptäckten av jordliknande exoplaneter och karakteriseringen av deras atmosfärer är en utmaning man behöver lösa för att bedöma deras beboelighet och närvaron av liv i universum. Om denna utmaning fortfarande inte är löst idag, även i jätteteleskopens tid, beror det främst på den mycket höga kontrasten mellan dessa exoplaneter och deras värdstjärna och också deras närhet. För att övervinna båda dessa begränsningar har en ny metod som kombinerar högdispersionsspektroskopi och nullingsinterferometri föreställts. Idéen är att använda nullingsinterferometrin för att minska stjärnljusemissionen och upptäcka de inre steniga planeterna med hög vinkelupplösning. Spektroskopin med hög dispersion ökar exoplanetens detekterbarhet betydligt vilket gör det möjligt att minska stjärndämpningsbehovet för en jordliknande observation. Vår simulering för en exoplanet som liknar jorden som kretsar omkring Proxima Centauri ger ett tillstånd för stjärndämpningen att ∼10−4 för att upptäcka den. Med tanke på detta villkor kan vi utvärdera oförmågan hos en fotonisk enhet till vårt förfogande för att uppnå sådan prestanda utan att hantera dess begränsningar. Om ett framtida projekt lyckas övervinna dessa begränsningar kan den här enheten vara en del av ett föregångarinstrument på IPAG för att experimentellt visa prestanda för högdispersionsnullningsinterferometri.

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Le nombre de systèmes planétaires connus ne cesse de croître depuis la découverte de la première exoplanète il y a déjà quelques décennies. Cependant, ces systèmes connaîtront éventuellement la mort de leur étoile, s’ils ne l’ont pas déjà connue. Ces étoiles deviendront des naines blanches. Pourtant, peu de planètes ont été découvertes autour de naines blanches. Une théorie populaire propose la survie des planètes géantes autour de celles-ci. Il est toutefois difficile de rechercher des planètes autour de naines blanches, entre autres, à cause de leurs petits rayons et de leurs raies spectrales peu nombreuses. L’imagerie de noyaux de phase est une méthode prometteuse pour la recherche d’exoplanètes autour de naines blanches puisqu’elle permet l’exploration à des séparations angulaires très petites allant jusqu’à la moitié de la limite de diffraction. Il s’agit de détecter un signal astrophysique par l’entremise de l’annulation des erreurs de phase instrumentales produites par le télescope. Ce projet vise à évaluer les performances de l’instrument MIRI du JWST pour détecter des exoplanètes autour de naines blanches avec cette technique. Pour ce faire, les observations de quatre naines blanches ont été analysées. Ce projet a permis de découvrir deux exoplanètes candidates, soient WD 1202−232 b et WD 2105−820 b sur un échantillon de quatre naines blanches. Elles ont été détectées par imagerie directe standard, mais aussi par imagerie de noyaux de phase. Les candidates se trouvent respectivement à une séparation de 1230 ± 20 mas et 2210 ± 20 mas de leur étoile et leurs rapports de flux sont de 63 ± 2 pour le système WD 1202−232 et de 29 ± 3 pour le système WD 2105−820. Si les candidates sont confirmées, la masse de WD 1202−232 b se situerait entre 1 et 7 \(M_J\), alors que la masse de WD 2105−820 b se situerait entre 1 et 2 \(M_J\). Des analyses et des simulations ont aussi été faites dans le but de tester les performances de l’imagerie par noyaux de phase avec les observations du JWST/MIRI à différents régimes de signal sur bruit. / The number of known planetary systems has been continuously increasing since the discovery of the first exoplanet several decades ago. However, these systems will eventually experience the death of their star, if they have not already. These stars will become white dwarfs. Yet, few planets have been discovered around white dwarfs. A favored theory suggests the survival of giant planets around them. However, it is challenging to search for planets around white dwarfs, among other reasons, due to their small radii and limited number of spectral lines. Kernel phase imaging is a promising method for the search for exoplanets around white dwarfs as it allows exploration at very small angular separations down to half the diffraction limit. This involves detecting an astrophysical signal through the cancellation of instrumental phase errors produced by the telescope. This project aims to evaluate the performance of JWST’s MIRI instrument in detecting exoplanets around white dwarfs using this technique. To achieve this, the observations of four white dwarfs were analyzed. This project has led to the discovery of two candidate exoplanets, namely WD 1202−232 b and WD 2105−820 b, in a sample of four white dwarfs. They were detected through standard direct imaging but also through kernel phase imaging. The candidates are located at a separation of 1230 ± 20 mas and 2210 ± 20 mas from their star, with flux ratios of 63 ± 2 for the WD 1202−232 system and 29 ± 3 for the WD 2105−820 system. If confirmed, the mass of WD 1202−232 b would be between 1 and 7 \(M_J\), while the mass of WD 2105−820 b would be between 1 and 2 \(M_J\). Analyses and simulations were also conducted to test the performance of kernel phase imaging with JWST/MIRI observations under various signal-to-noise regimes.

Thanks to a range of discovery methods that are sensitive to different regions of parameter space, we now know of over 900 planets in over 700 planetary systems. This large population has allowed exoplanetary scientists to move away from a focus on simple discovery, and towards efforts to study the bigger pictures of planetary system formation and evolution. The interactions between planets and their host stars have proven to be varied in both mechanisms and scope. In particular, tidal interactions seem to affect both the physical and dynamical properties of planetary systems, but characterising the broader implications of this has proven challenging. In this thesis I present work that investigates different aspects of tidal interactions, in order to uncover the scope of their influence of planetary system evolution. I compare two different age calculation methods using a large sample of exoplanet and brown dwarf host stars, and find a tendency for stellar model fitting to supply older age estimates than gyrochronology, the evaluation of a star's age through its rotation (Barnes 2007). Investigating possible sources of this discrepancy suggests that angular momentum exchange through the action of tidal forces might be the cause. I then select two systems from my sample, and investigate the effect of tidal interactions on their planetary orbits and stellar spin using a forward integration scheme. By fitting the resulting evolutionary tracks to the observed eccentricity, semi-major axis and stellar rotation rate, and to the stellar age derived from isochronal fitting, I am able to place constraints on tidal dissipation in these systems. I find that the majority of evolutionary histories consistent with my results imply that the stars have been spun up through tidal interactions as the planets spiral towards their Roche limits. I also consider the influence of tidal interactions on the alignment between planetary orbits and stellar spin, presenting new measurements of the projected spin-orbit alignment angle, λ, for six hot Jupiters. I consider my results in the context of the full ensemble of measurements, and find that they support a previously identified trend in alignment angle with tidal timescale, implying that tidal realignment might be responsible for patterns observed in the λ distribution.