Laboratoire d'Astrophysique de l'Observatoire de Grenoble
414, Rue de la Piscine
38041 Grenoble Cedex 09
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Chargé de recherche
|Titre / Statut - Title / Position
Docteur en Astrophysique / Chargé de Recherche au CNRS (CR2); Visiting Scientist at the Max Planck Institute fur Astronomie (2011 - 2012); Coordinateur du projet ANR-GuEPARD;
|Equipe - Team
Formation stellaire et planétaire, naines brunes
|Thèmes de Recherche - Research fields
My research activities are dedicated to the understanding of planetary formation, evolution and physics. Substellar objects like Giant Planets and Brown Dwarf companions are faint and located close to their hosting star. Consequently, a dedicated instrumentation is then needed to perform High Contrast (HC) and High Angular Resolution (HAR) observations. For large ground-based telescopes, the turbulence limits the resolution of the astronomical images and the use of Adaptive Optics (AO) systems is required to compensate for the wavefront distorsions. Such systems are presently used at the CFHT (3.6m), the Keck Observatory, the Subaru Telescope, the Gemini North and South Telescopes aa well as the VLT. During my PhD thesis, I had the chance to get involved into the NACO instrument, composed of NAOS (Nasmyth Adaptive Optics System) and the near-IR camera CONICA. NACO is actually installed at the 8.2m-UT4 of the ESO VLT Paranal Observatory. I was particularly interested in studying the AO system performances and limitations. I created an interesting tool to predict the detection limits expected during AO observations. This contrast model based on a simple analytical approach which takes into account standard noises such as photon, sky and read-out noises as well as the boiling speckle noise (Racine et al 1999) helped me to prepare HC and HAR observations.
During my Fellowship at ESO-Chile (2003-2007), as a member of the ESO Science Operation Team at the Parsanal VLT observatory, I was mainly involved into the maintenance, the observing and calibrating operations of the IR instruments NACO, SINFONI and ISAAC. I was also involved into the development, the tests and the use of new instrumental technics dedicated to Extremly High Contrast observations such as Interferential Coronagraphy, Pupil Apodisation, Differential Imaging, Polarimetry. And, in the perspective of the second generation of instruments for the VLT, I joined the Science Group of the SPHERE Planet Finder project to define its main scientific drivers, the observing strategy and the performances needed.
Detecting and characterizing substellar companions is then highly interesting:
- To study their physical structures and the chemical compositions of their atmosphere at different ages. Imaging and spectroscopy are then precious to test the evolutionary models which try to describe the fundamental parameters of these objects (effective temperature, mass, radius, luminosity) as well as the chemical compositions of their atmosphere (Methane, Water, Sodium, Carbon Monoxyde.....).
- To undestand the way Brown Dwarfs and Giant planets form. Several scenarii are presently proposed for these two categories of objects. Brown dwarfs may rapidly form as failed stars, ejected via dynamical interactions, or as "very low mass stars" via the fragmentation of dense and cold molecular clouds or disk fragmentation. On the other hand, Giant Planets are expected to form within a stable circumstellar disk at longer timescale, but the reality seems a bit more complicated. Although core accretion scenario is favored to explain the properties of planets detected in radial velocity or transit, disk fragmentation (or gravitational instability) may play a key role for the formation of giant planets at longer periods, for massive giant planets, and/or in binary systems. In this way, statistical studies are needed to study the substellar multiplicity around A, F, G, K, M stars and then derive the distributions as a function of the period, the mass ratio, the eccentricity, as well as the dependency on the primary mass and multiplicity.
Thesis: High Contrast and High Angular Resolution Imaging of Circumstellar Environments (in French),
|Mots Clés - Key words
Substellar Companion Detection and Characterization -- Brown Dwarfs and Giant Planets Formation -- High Contrast and High Angular Resolution Imaging -- Adaptive Optics -- Coronography -- Differential Imaging -- 3D-Spectroscopy
Voir les publications / See publications
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