L’interférométrie optique/IR à longue base a été récemment mise en place comme une technique capable de résoudre spatialement les étoiles et leurs environnements circumstellaires au niveau de la milliseconde d'angle (mas). Cette haute résolution ouvre toute une nouvelle fenêtre pour l'étude des systèmes astrophysiques, fournissant des informations inaccessibles par d'autres techniques. Les disques astrophysiques sont observés dans une grande variété de systèmes, de galaxies jusqu'aux anneaux planétaires, partageant communément des processus physiques similaires. Deux disques particuliers sont étudiés dans la thèse: (i) les étoiles B He-riches qui présente des champs magnétiques de l'ordre de kG et que confine leurs vents dans des structures appelées magnétosphères; et (ii) les étoiles Be, rotateurs rapides qui présentent des disques circumstellaires épisodiques. Cette étude utilise la technique interférométrique pour étudier à la fois la photosphère et l'environnement circumstellaire de ces étoiles. L'objectif est de combiner l'interférométrie avec d'autres techniques d'observation (telles que la spectroscopie et la polarimétrie) pour effectuer une description physique complète et bien contraindre ces systèmes. Cette description est acquise par l'interprétation de l'ensemble des observations par des modèles de transfert radiatif. / Optical long baseline interferometry was recently established as a technique capable of resolving stars and their circumstellar environments at the milliarcsecond (mas) resolution level. This high-resolution opens an entire new window to the study of astrophysical systems, providing information inaccessible by other techniques. Astrophysical disks are observed in a wide variety of systems, from galaxies up to planetary rings, commonly sharing similar physical processes. Two particular disk like systems are studied in the thesis: (i) B He-rich stars that exhibits magnetic fields in order of kG and that trap their winds in structures called magnetospheres; and (ii) Be stars, fast rotating stars that create circumstellar viscous disks. This study uses the interferometric technique to investigate both the photosphere proper and the circumstellar environment of these stars. The objective is to combine interferometry with other observational techniques (such as spectroscopy and polarimetry) to perform a complete and well-constrained physical description of these systems. This description is accompanied by radiative transfer models.

Glacial till from the Mt. Achernar moraine (MAM) records pre- and post- last glacial maximum (LGM) compositional variability of an East Antarctic moraine sequence through time and space. Pebble lithology, detrital zircon geochronology, and till geochemistry were analyzed on samples from a 6.5 km transect. Hummocky topography occurs with the most recently exposed material along the active ice margin (Zone 1), followed by a relatively flat and low region (Zone 2), and then a series of ~2 m high parallel/sub-parallel ridges and troughs accompanied by distinct color changes that are directly related to the dominant lithology of the region (Zones 3–5). Zone 3 is dominated by ~38% more sedimentary rocks than adjacent zones and has an overall shape of a broad arch superimposed with smaller ridges. Zone 4 is composed of distinct colored bands that alternate between dominant sedimentary and mafic igneous lithologies. These dominant sedimentary and intermediate/mafic igneous rocks for all Zones are interpreted to be primarily the Beacon and Ferrar Supergroup rocks respectively. The U/Pb data from the till is consistent with a Beacon Supergroup source as samples consistently show significant populations from the Permian ~250-260 Ma, the Proterozoic ~565–600 Ma, ~950–1270 Ma, and ~2300-2320 Ma, as well as (and) the late Archean ~2700-2770 Ma. The Pagoda, Mackellar, Buckley, and Fremouw Formations are potential sources of the detrital zircons. When paired with surface exposure ages, the U/Pb data indicates that the debris source has been consistent over the past ~555 ka, implying relatively stable ice sheet behavior. However, ice sheet change is indicated by a trim line present on Mt. Achernar that can be traced back to the boundary between Zones 3 and 4, as well as a change in pebble lithology, geochemistry, and morphology of Zone 3. Zone 3 records a time of ice sheet thickening and a change in provenance during the LGM. Zone 4 is pre-LGM, Zone 2 records deglaciation, and Zone 1 is still actively connected to the Law Glacier. This study reveals the broader importance of using multiple provenance techniques when interpreting provenance changes in till over time.

Optical long baseline interferometry was recently established as a technique capable of resolving stars and their circumstellar environments at the milliarcsecond (mas) resolution level. This high-resolution opens an entire new window to the study of astrophysical systems, providing information inaccessible by other techniques. Astrophysical disks are observed in a wide variety of systems, from galaxies up to planetary rings, commonly sharing similar physical processes. Two particular disk like systems are studied in the thesis: (i) B He-rich stars that exhibits magnetic fields in order of kG and that trap their winds in structures called magnetospheres; and (ii) Be stars, fast rotating stars that create circumstellar viscous disks. This study uses the interferometric technique to investigate both the photosphere proper and the circumstellar environment of these stars. The objective is to combine interferometry with other observational techniques (such as spectroscopy and polarimetry) to perform a complete and well-constrained physical description of these systems. This description is accompanied by radiative transfer models performed by the HDUST code. / Interferometria óptica de longa linha de base recentemente estabeleceu-se como uma técnica capaz de resolver estrelas e seus ambientes circunstelares no nível de mili segundos de arcos (\\textit). Esta alta resolução abre uma janela inteiramente nova para o estudo de sistemas astrofísicos, fornecendo informações inacessíveis por outras técnicas. Discos astrofísicos são observados numa ampla variedade de sistemas, de galáxias à discos planetários, em geral compartilhando de processos físicos similares. Dois sistemas de discos foram estudados nesta tese: (i) o estrelas B ricas em He e que possuem campos magnéticos da ordem de kG e que confinam seus ventos em estruturas chamadas magnetosferas; e (ii) estrelas Be, estrelas de rotação rápida que criam um disco circumstelar viscoso. Este estudo usa a técnica interferométrica para investigar ambas a própria fotosfera e o ambiente circunstelar destas estrelas. O objetivo é combinar a interferometria com outras técnicas observacionais (tal como espectroscopia e polarimetria) para realizar uma descrição física completa e precisa destes sistemas. Esta descrição é acompanhada por modelos de transferência radiativa executados pelo código HDUST.

Optical long baseline interferometry was recently established as a technique capable of resolving stars and their circumstellar environments at the milliarcsecond (mas) resolution level. This high-resolution opens an entire new window to the study of astrophysical systems, providing information inaccessible by other techniques. Astrophysical disks are observed in a wide variety of systems, from galaxies up to planetary rings, commonly sharing similar physical processes. Two particular disk like systems are studied in the thesis: (i) B He-rich stars that exhibits magnetic fields in order of kG and that trap their winds in structures called magnetospheres; and (ii) Be stars, fast rotating stars that create circumstellar viscous disks. This study uses the interferometric technique to investigate both the photosphere proper and the circumstellar environment of these stars. The objective is to combine interferometry with other observational techniques (such as spectroscopy and polarimetry) to perform a complete and well-constrained physical description of these systems. This description is accompanied by radiative transfer models performed by the HDUST code. / Interferometria óptica de longa linha de base recentemente estabeleceu-se como uma técnica capaz de resolver estrelas e seus ambientes circunstelares no nível de mili segundos de arcos (\\textit). Esta alta resolução abre uma janela inteiramente nova para o estudo de sistemas astrofísicos, fornecendo informações inacessíveis por outras técnicas. Discos astrofísicos são observados numa ampla variedade de sistemas, de galáxias à discos planetários, em geral compartilhando de processos físicos similares. Dois sistemas de discos foram estudados nesta tese: (i) o estrelas B ricas em He e que possuem campos magnéticos da ordem de kG e que confinam seus ventos em estruturas chamadas magnetosferas; e (ii) estrelas Be, estrelas de rotação rápida que criam um disco circumstelar viscoso. Este estudo usa a técnica interferométrica para investigar ambas a própria fotosfera e o ambiente circunstelar destas estrelas. O objetivo é combinar a interferometria com outras técnicas observacionais (tal como espectroscopia e polarimetria) para realizar uma descrição física completa e precisa destes sistemas. Esta descrição é acompanhada por modelos de transferência radiativa executados pelo código HDUST.