Depuis la première détection d'une planète extrasolaire autour d'une étoile de type solaire par Mayor et Queloz (1995), plus de 1500 planètes ont été découverts. Actuellement il existe un énorme intérêt à découvrir et caractériser des planètes semblables à la Terre, en particulier celles situées dans la zone habitable de leur étoile hôte (définie comme la distance à l'étoile hôte où la température de la planète permet l'existence d'eau liquide à la surface). La détection de planètes de type terrestre, et la recherche de biomarqueurs dans leurs atmosphères sont parmi les principaux objectifs de l'astronomie du vingt et unième siècle. La méthode des vitesses radiales (VR), consistant à mesurer le mouvement réflexe de l'étoile induit par des planètes en orbite, est une remarquable technique pour atteindre cet objectif.Pour atteindre les précisions nécessaire à la detection de telles planètes il est absolument nécessaire de concevoir des spectrographes extrêmement stables, d'avoir une très bonne compréhension de l'activité stellaire (qui peut mimer l'effet d'une planète), d'effectuer un traitement soigneux de l'atmosphère terrestre (laquelle inévitablement laisse des empreintes dans les spectres acquis depuis le sol), et de disposer d'une puissante technique pour extraire, à partir des spectres, autant d'information Doppler que possible. La recherche de planètes orbitant autour des étoiles de très faible masse, plutôt qu'autour des étoiles de type solaire, permet d'aborder dès maintenant la détection de planètes de faible masse dans la zone habitable. En effet, en gardant tout les autres paramètres égaux, le mouvement réflexe (et donc l'amplitude de la variation VR) sera plus grande si l'étoile centrale est de très faible masse. De plus les naines M ont une plus faible luminosité que les étoiles de type solaire, il en resulte des périodes orbitales courtes des planètes dans la zone habitable (~50 jours pour les naines M contre ~360 jours pour des étoiles de type solaire), entraînant à nouveau en une plus grande amplitude des VR. Une précision de ~1 m/s en VR permet la détection d'une planète dans la zone habitable d'une naine M, alors que ~0.1 m/s sont nécessaire dans le cas d'une étoile de type solaire.Cette thèse vise à optimiser l'extraction de VR des spectres des naines M à haute résolution acquis avec le spectrographe HARPS (avec une possibilité d'applications futures sur d'autres instruments comme SOPHIE, HARPS-N et le prochain spectrographe infrarouge SPIRou - prochainement mis en service au CFHT). Les effets de l'activité stellaire des naines M seront également analysées, dans le contexte de la technique des VR. Divers traceurs d'activité stellaire sont utilisés pour rejeter des fausses détections ou pour étudier les relations entre l'activité magnétique et la rotation. Dans cette thèse (Chap. 3) je calibre pour la première fois le flux dans les raies H et K du Calcium en fonction de la luminosité bolométrique et je détermine la relation entre cet estimateur R'HK et la période de rotation des naines M. Dans le chapitre 4 je décris l'implémentation d'une méthode d'extraction de VR par une minimisation du Chi-deux entre un template spectral et les spectres observés. Je démontre que cette méthode est plus précise que celle classiquement utilisée. Les raies telluriques qui affectent les mesures VR sont prises en compte dans les procédures d'analyse. Ces méthodes sont testées sur des systèmes avec des candidats planétaires, je discuterais l'analyse de certains de ces systèmes. / Since the first detection of an extrasolar planet orbiting a Sun-like star by Mayor and Queloz (1995), more than 1500 have been discovered. Enormous interest is currently focused on finding and characterising Earth-like planets, in particular those located in the habitable zone of their host star (defined as the distance from the host star where the planet temperature allows liquid water to flow on its surface). Both the detection of Earth-like planets, and the search for biomarkers in their atmospheres are among the main objectives of the twenty-first century's astronomy. The method known as radial velocities (RV), that consists in the measure of the star's reflex motion induced by orbiting planets, is a promising technique to achieve that quest.The main difficulties with the RV technique are the needs of an extremely stable spectrograph, a correct understanding of stellar activity (which can mimic the effect of a planet), a careful treatment of our Earth's atmosphere (which inevitable imprints spectra taken from the ground), and the need to dispose of a powerful algorithm to extract as much Doppler information as possible from the recorded spectra. Search for planets orbiting very low-mass stars (M dwarfs) can more easily reach the goal of detecting low-mass planets in the habitable zone of their parent star, compared to solar-type stars. Indeed, everything else being equal, a lower mass of the host star implies a larger reflex motion, and thus a larger RV amplitude. Moreover, the lower luminosity of M dwarfs compared to Sun-like stars, implies shorter orbital periods from planets in the habitable zone (~50 days against ~360 days, for M dwarfs compared to solar-type stars, respectively), resulting again in a larger RV amplitude. A RV precision of ~1 m/s allows a planet detection in the habitable zone of an M dwarf, whereas ~0.1 m/s is required in the case of a solar-type stars.This thesis aims to optimise the RV extraction from HARPS high-resolution spectra (and to open similar analysis on other instruments like SOPHIE, HARPS-N and the upcoming infrared spectrograph SPIRou -- to be commissioned to the 3.6-m CFH-Telescope). The effects of stellar activity will also be analysed, and contextualised in the RV technique. Stellar activity tracers are used to reject false detections or to study the relationships between the stellar magnetic activity and rotation. In this thesis (Chap.ref{chap:mag_activity}) I calibrate for the first time the ratio between the Ca textrm{small II} Htextrm{small &}K chromospheric lines and the bolometric luminosity for M dwarfs. I determine a relationship between the R^prime_{HK}-index and the rotation period of M dwarfs. In chapter~ref{chap:template_matching} I describe my algorithm to extract RVs through a chi^2-minimisation between a stellar template and the observed spectra. I demonstrate the improved accuracy of this method. Telluric spectral lines also affect the measurements of RV and are taken into account in the analysis procedures. I tested these methods on systems with planetary candidates, and for some systems, I took in charge the Keplerian analysis.

No description available.

Esta dissertação versa sobre a incomunicabilidade humana. A pergunta problematizadora que temos como objetivo aprofundar é: o ser humano é, ontologicamente, um ser capaz de se comunicar? ou de outra forma: é possível a existência da comunicação? A hermenêutica imanente dos textos de natureza filosófica, seguida da reflexão analítica, nos aproxima da problemática sobre a incomunicabilidade humana, iluminando os enfoques chave do estado instaurado de incomunicação radical e generalizada, por outro lado a possibilidade do ser de relacionar-se e abrir a comunicação para sua existência. A possibilidade do ser humano de relacionar-se é mínima no sistema planetário de comunicação, o que nos faz concluir que vivemos na era da incomunicabilidade humana, por primeiro da incomunicabilidade entre eu e o outro. / This dissertation deals with human incommunicability. We intend to further study the following problematizing issue: Ontologically speaking, is the human being capable of communicating? In other words: can communication exist? The immanent hermeneutics of philosophical texts, followed by analytical reflection, leads us to the problem of human incommunicability, throws light on key approaches to the state of radical and generalized incommunication, and, on the other hand, the possibility for human beings to establish relationships and open lines of communication for their survival. The planets communication system allows for minimal possibilities of human beings establishing relationships; we have, therefore, to conclude that we live in an era of human incommunicability, starting with the incommunicability between the self and others.

Orientadores: Maximiliano Ujevic Tonino, Javier Fernando Ramos Caro, Carola Dobrigkeit Chinellato / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-20T00:26:31Z (GMT). No. of bitstreams: 1 AlarconLLacctarimay_CesarJuan_D.pdf: 2806949 bytes, checksum: 588125c56d514dbfd77030a564888461 (MD5) Previous issue date: 2012 / Resumo: Nesta tese pretendemos modelar a distribuição de matéria em um Anel estelar fino imerso no campo gravitacional de um e dois Satélites Shepherds (Satélites Pastores) usando a equação de Fokker-Planck. Em particular, estudamos a evolução de um anel fino ao redor de um monopolo central. Os coeficientes de difusão são aqui calculados e escritos em termos de um ¿potencial¿ semelhante aos usuais potencias de Rosenbluth. Neste caso, consideramos que as partículas campo obedecem uma distribuição Gaussiana. Resolvemos a equação de Fokker-Planck 1-dimensional para a função de distribuição das partículas teste que conformam o anel usando o método das diferenças finitas (versão Euler implícita). Demonstramos que o anel é uma configuração estável para uma evolução de longo tempo, tanto na ausência como na presença de shepherds. Estudamos também a variação da densidade de massa do anel para diferentes configurações. Em todos os casos é observada uma variação máxima e negativa da densidade perto da localização do shepherd devido a efeitos dinâmicos / Abstract: In this thesis we intend to model the distribution of matter in a thin stellar ring immersed in the gravitational field of one and two shepherd satellites using the Fokker-Planck equation. In particular, we study the evolution of a thin ring around a central monopole. The diffusion coefficients are calculated and written in terms of a ¿potential¿ similar to the usual Rosenbluth potentials. In this case, we consider that the particles follow a Gaussian distribution. We solve the 1-dimensional Fokker-Planck equation for the ring particles distribution function using the finite difference method (implicit Euler version). We show that the ring is a stable configuration for long time evolutions in the absence or in the presence of shepherds. We also studied the change in the mass density of the ring for different configurations. In all of the cases, it is observed a maximum negative variation of the density near the location of the shepherd due to dynamical effects / Doutorado / Física / Doutor em Ciências

OpenSpace is an interactive data visualization software system that portrays the entire known universe in a 3D simulation. Current navigation interface requires explanations, which prohibits OpenSpace to be displayed effectively in public exhibitions. Research has been shown that using large tangible touch surfaces with a multi-touch navigation interface is more engaging to users than mouse and keyboard as well as enhances the understanding of navigation control, thus decreasing the required instructions to learn the systems user interface. This thesis shows that combining a velocity-based interaction model together with a screen-space direct-manipulation formulation produces a user-friendly interface. Giving the user precise control of objects and efficient travels in between in the vastness of space. This thesis presents the work of integrating a multi-touch navigation interface with a combined formulation of velocity-based interaction and screen-space direct-manipulation into the software framework OpenSpace.

M dwarfs constitute around 70% of all stars in the local Galaxy. Their multitude together with their long main-sequence lifetimes make them important for studies of global properties of the Galaxy such as the initial mass function or the structure and kinematics of stellar populations. In addition, the exoplanet community is showing an increasing interest for those small, cold stars. However, very few M dwarfs are well characterized, and in the case of exoplanetary systems the stellar parameters have a direct influence on the derived planet properties. Stellar parameters of M dwarfs are difficult to determine because of their low surface temperatures that result in an optical spectrum dominated by molecular lines. Most previous works have therefore relied on empirical calibrations. High-resolution spectrographs operating in the infrared, a wavelength region less affected by molecular lines, have recently opened up a new window for the investigation of M dwarfs. In the two first papers of this thesis we have shown that we can determine the metallicity, and in some cases the effective temperature, using synthetic spectral fitting with improved accuracy. This method is time consuming and therefore not practical or even feasible for studies of large samples of M dwarfs. When comparing our results from the high-resolution studies with available photometric calibrations we find systematic differences. In the third paper we therefore used our sample to determine a new photometric metallicity calibration. Compared to previous calibrations our new photometric calibration shows improved statistical characteristics, and our calibration gives similar results as spectroscopic calibrations. In a comparison with theoretical calculations we find a good agreement of the shapes and slopes of iso-metallicity lines with our empirical relation. Applying the photometric calibration to a sample of M dwarfs with confirmed exoplanets we find a possible giant planet-metallicity correlation for M dwarfs.

Les planètes rocheuses achèvent leur formation dans des processus collisionnels très énergétiques.L'énergie libérée lors des impacts majeurs a vraisemblablement fondu la surface des planètes, formant ainsi un océan de roches en fusion. Le refroidissement et la solidification de cet « océan de magma » conditionnent la différentiation chimique du manteau et la distribution des éléments volatils entre les différents réservoirs de la planète. C'est lors de cette phase évolutive, commune aux planètes rocheuses, que l'atmosphère est formée par dégazage des volatils et que les conditions initiales de l'évolution future des planètes se mettent en place. C'est ainsi une phase évolutive de première importance pour comprendre l'apparition des océans d'eau primitifs, le démarrage de la convection thermique du manteau et l'actuelle diversité des planètes telluriques.Un modèle numérique couplant l'évolution thermique de l'océan de magma en interaction avec l'atmosphère a été utilisé pour étudier le refroidissement de la planète et les conditions de surface résultantes. Nous avons investigué l'influence du contenu initial en volatil combiné avec la distance orbitale de la planète sur la formation des premiers océans d'eau à la fin du refroidissement, pour des atmosphères avec et sans nuages. Cette approche a ensuite été étendue aux planètes rocheuses extra-solaires orbitant des étoiles froides.Le contenu relatif en H2O et CO2 de l'atmosphère peut empêcher la formation d'océans, menant à des planètes ayant une surface solide sans océans d'eau. Des lois d'échelle prédisent la formation d'océans en fonction du contenu initial en volatil. Une épaisse couche nuageuse diminue la température de surface et maintient des conditions clémentes plus proche de l'étoile rendant ainsi possible la formation d'océan sur Vénus. Ces conditions de surface tempérées pourraient alors être favorable à l'émergence de la vie et suggèrent qu'en fonction de la couverture nuageuse, la Terre et Vénus pourraient être dans un état relativement similaire à la fin de la phase océan de magma, contrairement à ce qui est généralement admis.Pour les étoiles froides, la formation d'océans d'eau n'est possible qu'à des flux stellaires plus faibles que dans notre système solaire, correspondant à des distances étoile-planète relativement plus importantes.L'effet refroidissant des nuages est atténué pour les étoiles froides autour desquelles la bordure intérieure de la zone d'habitabilité tend à être indépendante de la couverture nuageuse. / At the end of the accretion phase, rocky planets grow through high energetic impact processes. Combined with other heat sources, they most likely melt the surface of the planets, forming an ocean of molten rocks. The cooling and solidification of this early so-called magma ocean strongly influences the earliest compositional differentiation and volatile distribution of the planet. Indeed, this common early evolution stage of rocky planets witnesses the degassing of the atmosphere and sets the initial conditions for the long-term evolution of the planets. It is thus of major importance in understanding the formation of the primitive water ocean, the onset of thermally driven mantle convection and the diversity of observed terrestrial planets.Using a coupled magma ocean-atmosphere thermal evolution model, we investigated the cooling of the planet and the surface conditions reached at the end of this early stage. We studied how the initial volatile content and the distance from the star influence the formation of a water ocean at the end of the cooling for both cloud-free and cloudy atmospheres. We extended this approach to planets orbiting colder stars than the Sun.The relative amount of H2O and CO2 in the atmosphere can preclude water ocean formation, leading to solid surface planets without water ocean. Scaling laws are derived to predict the formation of a water ocean as a function of the initial volatile content.The presence of a thick cloud cover extends clement surface conditions close to the star and allows for water ocean formation on early Venus. Such temperate conditions might be suitable for the emergence of life and suggest that, depending on the cloud cover, the Earth and Venus might not be as different as previously thought at the end of the magma ocean stage.For stars colder than the Sun, water ocean formation is shifted to farther star distances. The cooling effect of clouds becomes less efficient for cold stars whose inner edge of the temperate zone tends to be independent of the cloud cover.

In this paper, we present the analysis of incoherent non-thermal radio emission from a sample of hot magnetic stars, ranging from early-B to early-A spectral type. Spanning a wide range of stellar parameters and wind properties, these stars display a commonality in their radio emission which presents new challenges to the wind scenario as originally conceived. It was thought that relativistic electrons, responsible for the radio emission, originate in current sheets formed, where the wind opens the magnetic field lines. However, the true mass-loss rates from the cooler stars are too small to explain the observed non-thermal broad-band radio spectra. Instead, we suggest the existence of a radiation belt located inside the inner magnetosphere, similar to that of Jupiter. Such a structure explains the overall indifference of the broad-band radio emissions on wind mass-loss rates. Further, correlating the radio luminosities from a larger sample of magnetic stars with their stellar parameters, the combined roles of rotation and magnetic properties have been empirically determined. Finally, our sample of early-type magnetic stars suggests a scaling relationship between the non-thermal radio luminosity and the electric voltage induced by the magnetosphere's co-rotation, which appears to hold for a broader range of stellar types with dipole-dominated magnetospheres (like the cases of the planet Jupiter and the ultracool dwarf stars and brown dwarfs). We conclude that well-ordered and stable rotating magnetospheres share a common physical mechanism for supporting the generation of non-thermal electrons.

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

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2008. / Includes bibliographical references (p. 207-221). / This thesis studies the dynamics of a rotating compressible gas sphere, driven by internal convection, as a model for the dynamics on the giant planets. We develop a new general circulation model for the Jovian atmosphere, based on the MITgcm dynamical core augmenting the nonhydrostatic model. The grid extends deep into the planet's interior allowing the model to compute the dynamics of a whole sphere of gas rather than a spherical shell (including the strong variations in gravity and the equation of state). Different from most previous 3D convection models, this model is anelastic rather than Boussinesq and thereby incorporates the full density variation of the planet. We show that the density gradients caused by convection drive the system away from an isentropic and therefore barotropic state as previously assumed, leading to significant baroclinic shear. This shear is concentrated mainly in the upper levels and associated with baroclinic compressibility effects. The interior flow organizes in large cyclonically rotating columnar eddies parallel to the rotation axis, which drive upgradient angular momentum eddy fluxes, generating the observed equatorial superrotation. Heat fluxes align with the axis of rotation, contributing to the observed flat meridional emission. We show the transition from weak convection cases with symmetric spiraling columnar modes similar to those found in previous analytic linear theory, to more turbulent cases which exhibit similar, though less regular and solely cyclonic, convection columns which manifest on the surface in the form of waves embedded within the superrotation. We develop a mechanical understanding of this system and scaling laws by studying simpler configurations and the dependence on physical properties such as the rotation period, bottom boundary location and forcing structure. These columnar cyclonic structures propagate eastward, driven by dynamics similar to that of a Rossby wave except that the restoring planetary vorticity gradient is in the opposite direction, due to the spherical geometry in the interior. / (cont.) We further study these interior dynamics using a simplified barotropic annulus model, which shows that the planetary vorticity radial variation causes the eddy angular momentum flux divergence, which drives the superrotating equatorial flow. In addition we study the interaction of the interior dynamics with a stable exterior weather layer, using a quasigeostrophic two layer channel model on a beta plane, where the columnar interior is therefore represented by a negative beta effect. We find that baroclinic instability of even a weak shear can drive strong, stable multiple zonal jets. For this model we find an analytic nonlinear solution, truncated to one growing mode, that exhibits a multiple jet meridional structure, driven by the nonlinear interaction between the eddies. Finally, given the density field from our 3D convection model we derive the high order gravitational spectra of Jupiter, which is a measurable quantity for the upcoming JUNO mission to Jupiter. / by Yohai Kaspi. / Ph.D.