WorldCat Identities

Domiciano de Souza, Armando

Works: 6 works in 10 publications in 2 languages and 9 library holdings
Roles: Author, Opponent, Thesis advisor
Publication Timeline
Most widely held works by Armando Domiciano de Souza
Modélisation et observation en interférométrie stellaire : rotation, pulsation et taches by Armando Domiciano de Souza( Book )

3 editions published between 2003 and 2006 in French and held by 5 WorldCat member libraries worldwide

I present here my thesis researches and results on some mechanisms that govern stellar evolution, in particular rotation, pulsation and stellar activity. For this purpose I developed a numerical model oriented to Optical Long Baseline Interferometry (OLBI) combined to high spectral resolution. Thanks to this model I studied the morphology and the gravity darkening of stars rotating close to their critical velocity. I could then prepare, analyse and interpret our IR Interferometric observations on VLTI-VINCI. A major and unique result is the direct measure of the oblateness of the Be star Achernar, which shows an equatorial radius -50% larger than the polar one, in first approximation. This flattening comes certainly from the photosphere so that I could conclude that the Roche approximation cannot explain our observations. Differential rotation is the proposed alternative hypothesis, with multiple consequences on the transport and loss of the mass and angular momentum. This work motivated a spectro-interferometric study of the differential rotation, notably for VLTI-AMBER, where I show rate and the 3D orientation of the stellar rotation axis. Finally, I present a few prospective studies concerning the measure, by OBLI, of several kinds of surface inhomogeneities through complex visibility phases, direct imaging by telescope networks, as well as through interferometric Doppler imaging
Évolution stellaire en rotation rapide. Apports de l'interférométrie et de l'astérosismologie by Kévin Bouchaud( )

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

Observations et modélisations spectro-interférométriques longue base des étoiles et de leur environnement proche by Macinissa Hadjara( )

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

This thesis presents the results of rapidly rotating stars observations conducted on the AMBER spectro-interferometer VLTI in its high average spectral modes and resolutions. The measurements are estimated on three simultaneous visibility bases, differential phases depending on the wavelength and closure phases, with good coverage of the (u, v) plane for some nights. The data used are from several observation campaigns. These were highly degraded by the optical defects of AMBER, and assigned by standard optical interferometry long base IR noises: defects of the detector, reading noise, fringes follower instabilities, ... etc. Their analysis required the development of digital reduction of specific tools to achieve the necessary details to the interpretation of interferometric measurements. In interpreting these measures I developed a chromatic semi-analytical model of rapidly rotating star that allowed me to estimate, from the differential phases; the degree of flattening, the equatorial radius, speed of rotation, angle of inclination, the position angle of the star rotation axis in the sky, the local distribution of the actual temperature and the gravity to the surface of the star within the von Zeipel theorem. The results for four massive stars of spectral type B, A and F have allowed me to characterize the mechanisms discussed above and thus open framework for more systematic studies of similar objects subsequently extending these studies to the relationship photosphere circumstellar envelope
Une vie interférométrique des disques d'étoiles chaudes by Daniel Moser Faes( )

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

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
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

Caractéristiques spectrales et pulsationnelles d'étoiles Be à l'aide de données sol (VLT/GIRAFFE et X-SHOOTER) et espace (CoRoT) by Thierry Semaan( Book )

3 editions published between 2012 and 2019 in French and held by 0 WorldCat member libraries worldwide

Be stars are early-type stars having near critical rotation. They are surrounded by an equatorial disc fed by discrete mass-loss ejections from the central star. Be stars are good laboratories to study, on one hand, the impact of rotation on pulsations and, on the other hand, the role of pulsation on the recurrent mass ejections. During this thesis we focused on faint Be stars located in the first exoplanetary fields CoRoT satellite. In a first step we have identified the stars presenting the Be phenomenon among all the variable stars observed by CoRoT. We have thus been able to provide a sample of forty Be stars.Thanks to ground-based spectroscopic observations at VLT with GIRAFFE and X-SHOOTER instruments we have studied th spectral properties of half of them and determined their fundamental parameters by taking into account the effects of rapid rotation. Using the CoRoT light curves we have determined the frequencies and amplitudes of the pulsations that characterize the treated stars and studied their temporal variations. We have studied attentively the newly discovered stars presenting light outbursts. Thanks to the carried spectroscopic and photometric studies we have been able to investigate the properties of pulsations according to the stellar location in the HR diagram, and could identify some common properties among the Be stars of our sample
Audience Level
Audience Level
  General Special  
Audience level: 0.92 (from 0.90 for Modélisat ... to 1.00 for Caractéri ...)