WorldCat Identities

Lopez, Bruno (astronome)

Overview
Works: 20 works in 28 publications in 2 languages and 38 library holdings
Genres: Academic theses 
Roles: Thesis advisor, Opponent, Author, Other
Publication Timeline
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Most widely held works by Bruno Lopez
ETUDE DE LA PERTE DE MASSE DES ETOILES EVOLUEES, APPORT DES MESURES A HAUTE RESOLUTION ANGULAIRE by Bruno Lopez( Book )

2 editions published in 1994 in French and held by 7 WorldCat member libraries worldwide

LA THESE PRESENTEE CONCERNE L'ETUDE DE LA PERTE DE MASSE DES ETOILES EVOLUEES. CETTE PHASE DE L'EVOLUTION STELLAIRE EST DETERMINANTE. ELLE PRECEDE LE STADE DE NEBULEUSES PLANETAIRES ET PARTICIPE A L'ENRICHISSEMENT DU MILIEU INTERSTELLAIRE EN MATERIAUX REFRACTAIRES. UNE ENVELOPPE DE GAZ ET DE POUSSIERES, RESULTANT DE L'EJECTION DE MATIERE, SE FORME AUTOUR DE L'ETOILE. IL EST A L'HEURE ACTUELLE POSSIBLE D'ETUDIER LA MORPHOLOGIE DES ENVELOPPES CIRCUMSTELLAIRES POUR QUELQUES SOURCES REPRESENTATIVES DE LA FAMILLE DES OBJETS EVOLUES. LES OUTILS UTILISES SONT: D'UNE PART, LES METHODES D'OBSERVATION EN HAUTE RESOLUTION ANGULAIRE (OPTIQUE ADAPTATIVE, TAVELOGRAPHIE, INTERFEROMETRIE LONGUE BASE); ET D'AUTRE PART, LES SIMULATIONS DU TRANSFERT RADIATIF DANS LES NUAGES DE POUSSIERES EN GEOMETRIE NON-SPHERIQUE. L'ETUDE DE TROIS OBJETS CARACTERISTIQUES EST ABORDEE. CETTE ANALYSE CONDUIT A L'ESTIMATION D'UN ENSEMBLE COHERENT DE PARAMETRES PHYSIQUES DEFINISSANT LES ENVELOPPES CIRCUMSTELLAIRES. UN TAUX DE PERTE DE MASSE DE 2.5 10##5 MASSES SOLAIRES PAR AN EST DEDUIT POUR L'ETOILE CARBONEE IRAS 15194-5115. LA STRUCTURE EN FORME DE DISQUE DE LA NEBULEUSE NOMMEE LE RECTANGLE ROUGE EST DETERMINEE AVEC PRECISION. UNE EBAUCHE DE MODELE EST EGALEMENT ELABOREE POUR O CETI, LE PROTOTYPE DES ETOILES DE TYPE MIRA. CETTE DERNIERE ETUDE EST FONDEE SUR DES OBSERVATIONS EFFECTUEES EN INTERFEROMETRIE LONGUE BASE. A LONG TERME, LA PERSPECTIVE PRINCIPALE DE CETTE RECHERCHE CONSISTE A MIEUX COMPRENDRE LES MECANISMES PHYSIQUES RESPONSABLES DU PHENOMENE DE LA PERTE DE MASSE
Transfert de rayonnement et formation de poussière dans les enveloppes circumstellaires by Gilles Niccolini( )

2 editions published between 2003 and 2007 in French and held by 4 WorldCat member libraries worldwide

Enveloppes circumstellaires des étoiles chaudes actives : modélisation et observations à haute résolution angulaire du phénomène Be et B[e] by Jamal Bittar( )

2 editions published in 2001 in French and held by 4 WorldCat member libraries worldwide

La haute résolution angulaire appliquée à l'étude des enveloppes de poussière circumstellaire d'étoiles évoluées by Jean-Luc Menut( Book )

2 editions published in 2008 in French and held by 2 WorldCat member libraries worldwide

The technic of High Angular Resolution by long baseline interferometry in optical wavelengths is a field of research in astronomy. It allows to reach the spatial resolution needed to have access to a more precise understanding of stellar sources. This is of relevance in particular for the study of the formation and evolutionary process of the dust environment of evolved stars, topic which catches my attention. With recent data and numerical modeling codes, we studied the envelopes of 5 astropysical targets : T Sgr, IRC+10216, HR4049, WR 95 et WR 106 for which, we obtained immediate results and we could show the progress allowed by the future instruments. These optical interferometry techniques are still young and in perpetual evolution. In this perspective, we partipated to the study of APreS-MIDI, an optical module for the MIDI interferometer, which since became the second generation VLTI instrument MATISSE. In this context, we also developed an interferometer mock-up as well as the bases for a new approach in image reconstruction from interferometry data called FrImage
Potentiel de l'Antarctique pour l'interférométrie optique : double champ & reconstruction d'images by Bruno Valat( Book )

2 editions published in 2011 in French and held by 2 WorldCat member libraries worldwide

Les instruments en astronomie offrent des sensibilités pour l'observation de plus en plus grandes. Corrélativement, ils deviennent aussi sensibles aux perturbations externes telles que la turbulence optique. Dans l'objectif d'optimiser le choix des sites en vue de l'installation de futurs instruments toujours plus performants, de nombreuses équipes se sont spécialisées dans la caractérisation de sites. Dans mon mémoire, j'ai étudié l'impact des mesures de sites en performances instrumentales du domaine de l'interférométrie optique. Les paramètres du site du Dôme C sont discutés et comparés à ceux du Cerro Paranal. Pour se faire, une expérience numérique capable de simuler la turbulence optique a été développée. Des études théoriques préliminaires ont révélé le Dôme C comme un site particulièrement adapté à l'interférométrie double champ. Le paramètre principal caractérisant ce mode d'observation est l'angle isopistonique. Son estimation actuelle se fait analytiquement et nécessite des approximations. C'est par l'intermédiaire d'une expérience numérique que je propose l'étude de ce paramètre. Les résultats obtenus renforcent l'approche analytique. Une des grandes percées envisagées par l'observation avec ce mode concerne les possibilités de reconstruction d'images. J'ai porté une attention particulière à cet aspect en réalisant des reconstructions issues de données simulées dans ce mode. Enfin, je présente un algorithme dont l'intérêt immédiat est l'accès aux visibilités absolues mesurées avec AMBER. L'algorithme permet de s'affranchir d'une partie des erreurs induites par le mouvement des franges durant le temps de pose sur le contraste des franges d'interférences
ETUDE DU REFLEXE DE HOFFMANN DANS LES HYPOTHYROIDIES NEO-NATALES DEPISTEES : INDEX DE MATURATION DU SYSTEME NERVEUX PERIPHERIQUE by Bruno Lopez( Book )

1 edition published in 1985 in French and held by 2 WorldCat member libraries worldwide

Intérêt de l'interférométrie infrarouge pour l'étude des constituants des systèmes planétaires : application à l'émission propre des astéroïdes et des planètes extrasolaires géantes by Alexis Matter( Book )

2 editions published between 2010 and 2011 in English and held by 2 WorldCat member libraries worldwide

This work is about the use of the high angular resolution capacities of the VLTI for the direct observation of the planetary systems components. By means of the MIDI instrument, we derived the first size measurements by long baseline interferometry of three asteroids: (951) Gaspra, (234) Barbara, and (41) Daphne. The application of a thermophysical model to MIDI data allowed to constrain several surface parameters (thermal inertia, roughness). Next, the study of extrasolar giant planets is addressed through the first attempt to observe a giant exoplanet, Gliese 86b, with the MIDI instrument. A new method of calibration of the chromatic effects of water vapour, using the simultaneous phase measurements of AMBER, is tested here. Because of several technical compromises related to the parallel operation of both instruments, the precision of MIDI data, along with the calibration accuracy from AMBER ones, currently stand at a factor 10 above the planetary signal. Using a dynamical model, i evaluated as well the impact of interactions between debris disks and planets, on the composition of planetary atmospheres. In the case of the giant planets of the solar system, the resulting enrichments are globally lower than the values currently observed, but remain significant for Uranus and Neptune. Finally, in a context of development of new generation interferometers, an analytical study is performed on the problem of parasitic interferences. Requirements are defined in relation to the detection of extrasolar giant planets
Transfert de rayonnement dans les enveloppes d'étoiles évoluées : étude de la nébuleuse " Frosty Leo by Gilles Niccolini( )

1 edition published in 1998 in French and held by 2 WorldCat member libraries worldwide

Préparation des observations de planètes extrasolaires by Juan Cabrera( Book )

2 editions published in 2008 in French and held by 2 WorldCat member libraries worldwide

The first part of this thesis considers the three body problem. In a first approximation of the hierarchical restricted three body problem, it is studied the motion of a star gravitationally linked to a distant binary. This perturbation can mimic the reflex motion of a star caused by a planet, provoking a false detection by astrometric or radial velocity methods. Then, in the case of a multiple planet system, the perturbations in the time of arrival of the transit signals as well as their influence in the planetary detection are considered. Next, the photometric signal produced by a stellar spot is analyzed to recognize its differences with planetary transits : in some configurations spots can produce a similar signal. The techniques developed are applied to the study of planetary photometry. In particular, the mutual phenomena between a planet and a satellite (occultations and projections of shadows) are examined and the detailed analysis of the signal of a transit. Finally, an important part of the thesis has been devoted to the analysis of the data supplied by the mission CoRoT, committed to the search for extrasolar planets. Four times a year, the satellite furnishes ten thousand light-curves that must be filtered of instrumental noise and stellar activity prior to the search for planetary signals. Eventually, the candidates are followed photometrically and spectroscopically from ground to determine their mass. In the systems where a planet has been found, the time of arrival of the transits is studied looking for the perturbations described in the first part of the thesis
Interférométrie et astrométrie différentielles chromatiques et observation de planètes extrasolaires géantes chaudes avec le VLTI et le NGST by Martin Vannier( Book )

2 editions published in 2003 in French and held by 1 WorldCat member library worldwide

Imagerie optique à très haut contraste : une approche instrumentale optimale by Mathilde Beaulieu( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

This thesis aims to optimize high-contrast imaging performance in visible and near infrared for exoplanet detection. The main study focuses on high-contrast at small separation, to image exoplanets in their habitable zone. This direct detection is achievable with the next Extremely Large Telescopes and with the development of coronagraph providing high performance at small separation. The approach adopted for this study creates a high-contrast region (a dark hole) with the combination of coronagraphy and wavefront shaping (wavefront control of both phase and amplitude with 2 deformable mirrors) but is limited by the Fresnel propagation of phase aberrations. The goal of this work is to define the wavefront shaping limitation in optical configuration (deformable mirrors location, component optical quality, beam diameter). A semi-analytic approach followed by a Monte-Carlo analysis of numerical end-to-end simulations is studied, resulting in the definition of the optimal configuration. Results are then applied to SPEED, a test bench to optimize and test high-contrast imaging at small separation with a segmented pupil. Another aspect of this thesis is a contribution to a stability study to treat the temporal stability as a crucial parameter in high-contrast imaging instrumentation, at the conception level. A preliminary work is initiated during the thesis to analyse the stability of the measuring instrument itself. A metrology tool and its thermal behaviour are thus studied. Finally, the last part of this thesis is a performance analysis of a new differential imaging technique, developed to improve high contrast with observations with different diaphragm sizes
Imagerie directe de systèmes planétaires avec SPHERE et prédiction des performances de MICADO sur l'E-ELT by Clément Perrot( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

This thesis is performed in the context of the study of the formation and evolution of planetary systems using high contrast imaging, also known as direct imaging in contrast to so-called "indirect" detection methods. The work I present in this manuscript is divided into two distinct parts.The first part concerns the observational component of my thesis, using the SPHERE instrument installed at Very LargeTelescope. This work was done as part of the consortium of the same name. The purpose of the SPHERE instrument is to detect and characterize young and massive exoplanets, but also circumstellar disks ranging from very young protoplanetary disks to older debris disks. In this manuscript, I present my contribution to the program SHINE, a large survey with an integration time of 200 nights' worth of observation, the goal of which is the detection of new exoplanets and the spectral and orbital characterization of some previously-known companions. I also present the two studies of circumstellar disks that I made, around the stars HD 141569 and HIP 86598. The first study allowed the discovery of concentric rings at about ten AU of the star along with an unusual flux asymmetry in the disk. The second study is about the discovery of a debris disk that also has an unusual flux asymmetry. The second part concerns the instrumental component of my thesis work done within the MICADO consortium, in charge of the design of the camera of the same name which will be one of the first light instruments of the European Extremely Large Telescope (ELT). In this manuscript, I present the study in which I define the design of some components of the coronagraphic mode of MICADO while taking into account the constraints of the instrument - which is not dedicated to high contrast imaging, unlike SPHERE
Mécanismes de transport dans les disques protoplanétaires et impact sur la formation des premiers solides by Nicolás Cuello( )

1 edition published in 2015 in French and held by 1 WorldCat member library worldwide

The main goal of this work is to study new transport mechanisms of solids in protoplanetary disks and its implications for the composition of the first solids. The motion of solids inside the disk leads to the so-called radial-drift barrier caused by the gas aerodynamic drag, which is a severe problem for planet formation theory. In this context, it is hard to explain how sub-mm grains reach planetesimal sizes during the disk lifespan. First of all, I study the effects of photophoresis on the dust grains illuminated by the stellar radiation and quantify the efficiency of radial transport as a function of the particle properties. Then, I study the ejection of particles from the inner regions of the disk via the so-called stellar fountain model. Due to the stellar magnetic field which threads the disk, solid particles enter a jet that sends them outwards up to a few astronomical units. Both processes, photophoresis and jets, have important implications for the composition of meteorites which are discussed within the Solar Nebula scenario. In the last chapter, I study dust dynamics in multi-planetary systems through SPH simulations. The formation of particle traps in a disk with two planets is treated in detail and compared to previous work considering a single planet. Then I consider the case of HD 100546, a star with a disk which might harbor two planets according to recent observations, and study the disk evolution in different scenarios. By considering different grains sizes it is then possible to establish a link with interferometric observations of the system. We consider models with different planetary masses and radial distances in order to better constrain these quantities. The study of these mechanisms reveals that, according to particle size and composition, grains can pile up at different radial distances in the disk. This prevents the accretion by the central star by stopping the radial drift of solids, which shows that these mechanisms are good candidates to solve the radial-drift barrier. Future observations using ALMA, SPHERE and MATISSE will provide insights into the efficiency of these transport processes in protoplanetary disks
Imagerie et analyse hyperspectrales d'observations interférométriques d'environnement circumstellaires by Gaetan Dalla Vedova( )

1 edition published in 2016 in French and held by 1 WorldCat member library worldwide

L'observation des planètes extrasolaires, ainsi que l'étude de l'environnementcircumstellaire demandent des instruments très performants en matière dedynamique et de résolution angulaire. L'interférométrie classique et annulanteoffrent une solution. En particulier, dans le cas de l'interférométrie annulante,le flux de l'étoile sur l'axe de l'interféromètre est fortement réduit et permetainsi aux structures plus faibles hors axe d'émerger et être plus facilementdétectables. Dans ce contexte, la reconstruction d'image est un outilfondamental. Le développement d'interféromètres à haute résolution spectraletelle que AMBER, et bientôt MATISSE et GRAVITY, fait de la reconstruction d'imagepolychromatique une priorité.Cette thèse a comme objectif de développer et d'améliorer des techniques dereconstruction d'image hyperspectrale. Le travail présenté s'articule en deuxparties. En premier, nous discutons le potentiel de l'interférométrie annulantedans le cadre de la résolution du problème inverse. Ce travail repose sur dessimulations numériques et sur l'exploitation de données collectées sur le bancinterférométrique annulant PERSEE. Ensuite, nous avons adapté et développé desméthodes de reconstruction d'images monochromatique et polychromatique. Cestechniques ont été appliquées pour étudier l'environnement circumstellaire dedeux objets évolués, Achernar et Eta Carina, à partir de données PIONIER etAMBER.Ce travail apporte des éléments méthodologiques sur la reconstruction d'image etl'analyse hyperspectrale, ainsi que des études spécifiques sur l'environnementd'Achernar et d'Eta Carina
Étude des nébuleuses spirales de poussière autour des étoiles Wolf-Rayet by Anthony Soulain( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

Massive stars are one of the major contributors to the enrichment of galaxies in heavy elements and interstellar dust. The last stage of their evolution is represented by the Wolf-Rayet phase (WR). WR stars generate a dense radiative stellar wind, which can interact with the wind from a close companion and cause a spiral dust environment called pinwheel nebula. The orders of magnitude associated with this kind of object are spectacular: with a dust formation rate equivalent to the mass of the planet Mars produced each year, WR stars compete with the historical dust producers, like the stars of the asymptotic giant branch (AGB) or the supernovae (SN). Dusty WR stars could thus answer a well-known problem: where does the dust observed in galaxies come from? This thesis aims at enriching our knowledge about this problem using all aspects of the scientific chain: from observation to data analysis by using different levels of sophistication in numerical modelling (analytical, radiative transfer and hydrodynamics). The first aspect explored by this thesis concerns the modelling of spiral dust nebulae. I first developed an analytical model for the spiral to constrain the geometrical aspects of the spiral, including a number of physical hypothesis like the dust sublimation radius and different types of internal structure. The next step consisted to include the radiative transfer in the geometrical model in order to link the intensity distribution of the object (the image) to its density distribution. This 3-D model of spiral allow to study the opacity and shadowing effects related to the dust mass considered. Similarly, I developed a 3-D axisymmetric radiative transfer model to mimic the spiral into a series of concentric rings. This model aims to reproduce the intensity distribution of a spiral at a given azimuth and allows a direct comparison with the radial intensity profiles derived from observations. Finally, we implemented a 3-D hydrodynamic model of a wind-wind interacting binary to get a realistic idea of the physical conditions in places around the dust nucleation zone. The second aspect addressed by this thesis focuses to the study of the prototype of the pinwheel nebula, called WR104. Such object is an ideal laboratory to study the problem of dust nucleation around massive stars. I explored all spatial scales of WR 104: From the large scale with VLT/VISIR to study the link with the interstellar medium, to the internal regions with VLTI/AMBER to probe the dust nucleation zone, including intermediate angular resolution to study the pinwheel structure with extreme adaptive optics instrument VLT/SPHERE. The third and last aspect deals with the second generation of the instrument installed at the European Very Large Telescope Interferometer (VLTI): MATISSE. It is the first instrument operating simultaneously in the L, M and N bands by recombining the light coming from four telescopes. MATISSE was developed to study different scientific cases: protoplanetary disks, the circumstellar environments and the active galactic nuclei. To prepare the first observation programs, I developed an automated tool, called PREVIS, to determine the observability of objects according to their magnitude and celestial coordinate. In the context of spiral nebulae, I explored the image reconstruction capabilities of the instrument by testing different aspects: geometric (size, inclination, opening angle, etc.) and observational (coverage (u-v), sampling). The unprecedented spatial resolution of MATISSE of 3 mas at 3.5 µm will allow to study these objects in a unique way, resolving for the first time the thickness of the spiral arm, its internal structure or the exact position of the sublimation radius
Disques et vents des étoiles chaudes : Apport de la spectroscopie et de l'interférométrie multi-bandes by Elisson Saldanha Da Gama De Almeida( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

Accrétion du gaz sur planètes géantes by Judit Szulágyi( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

This thesis is focusing on the runaway gas accretion phase of giant planet formation with hydrodynamic simulations. A Jupiter-mass planet is simulated embedded in a circumstellar disk around a Solar-mass star. Thanks to the JUPITER-code nested meshing technique, the planet vicinity is resolved with high resolution allowing to study the circumplanetary disk formed around the giant planet. Isothermal, 3-dimensional simulations revealed that the accretion is truly 3D process, with 90% of the gas accreted from the vertical direction through the planetary gap. This vertical influx is part of a meridional circulation between the circumstellar and circumplanetary disks. The accretion rate to planet was determined from inviscid simulation, in order to account for the presumably low viscosity environment in the forming planet's vicinity. In this inviscid limit, the mass doubling time in the runaway phase can be as long as half a million years, competing with the gas dispersal timescale, hence providing a possible solution for the missing population of massive (>3 Jupiter-mass) giant planets. Incorporating the thermal effects into the JUPITER-code, radiative simulations with more realistic temperature information were carried out as well. These simulations revealed that the planetary temperature greatly determines the properties of the circumplanetary material. Even a gap-opening giant planet could only form a circumplanetary, pressure-supported envelope, if the planet temperature is high (~13,000 Kelvin), similarly to low-mass planets. In contrary, in the simulations were the central temperatures were capped at 1000-2000 Kelvins, circumplanetary disks were formed
Aspects de la synthèse d'ouverture en infrarouge, dans le plan pupille by Bruno Lopez( )

1 edition published in 1989 in French and held by 1 WorldCat member library worldwide

Une étude multi longueur d'onde des disques protoplanétaires à l'échelle de l'unité astronomique by Narges Jamialahmadi( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Planetary systems are born in circumstellar gas and dust disks surrounding Young Stellar Objects (YSOs). To understand how planetary systems form, a detailed knowledge of the structure and evolution of these disks is required. Although, this is almost well understood for the regions of the disks observed with a spatial resolution of several AUs, the structure of these disks probed at a few AU scale and especially inward of 1 AU remains a puzzle. In recent years, it has become possible to directly spatially resolve the inner region of protoplanetary disks with optical interferometry technique. The context of this thesis is a multi-wavelength investigation of the protoplanetary disks evolution by determining their density distribution, their temperature distribution, the size and com- position of the dust components and finally the kinematics of the gas. I have developed my thesis following three complementary wavelength domains: study of the photosphere of the star and its nearby gaseous disk through visible interferometry, study of the radial and vertical structure of the inner rim of a pre-transitional disk at fractions of an AU through near-IR interferometry, and, the characterization of the disk regions at a few AUs from the central star through spectroscopic and mid-IR interferometry. To analyse the visible-, near- and mid-IR interferometric observations, I have focused my attention on three well known sources, 51 OPh, HD 100546 and MWC 480 respectively that they have not been observed in these wavelengths
 
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Languages
French (23)

English (5)