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              Direct imaging is currently the only available method to characterize the atmosphere of long-period exoplanets (≥1 AU). This technique is difficult to carry out because it requires high contrasts at short angular separations (10^6-10^10 at ~0,2''). During my PhD thesis, I focused on two instruments : the SPICES mission and the VLT/NaCo instrument. SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a project of space coronagraph which aims to characterize in spectro-polarimetry cold exoplanets and faint circumstellar disks (≥1 zodi). I determined the science performance of the mission using numerical simulations. SPICES could characterize Jupiters at separations ≤5 AU and distances ≤10 pc, super-Earths at 1-2 AU for a few stars within 4-5 pc and possibly Earths around α Centauri A. Considering all stellar types, I estimated an amount of ~300 potential targets. In the second part of my PhD thesis, I analyzed images taken in coronagraphic and differential imaging modes of the NaCo instrument. The objective was to search for gas giant planets as cool as 500-1300 K at separations of 5-10 AU around a selected sample of young and nearby stars (<200 Myr, <25 pc). Median detection limits give contrasts of ~10−5 at 1'', corresponding to effective temperatures and masses of 1100 K and 10 MJ, and complement statistical studies based on radial velocities.
            """ ;
    dct:identifier "tel-00750252" ;
    dct:issued "2026-05-11T08:24:21.261028"^^xsd:dateTime ;
    dct:language "fr" ;
    dct:modified "2026-05-11T08:24:21.261033"^^xsd:dateTime ;
    dct:publisher <https://rec.harvest-normandie.data4citizen.com/organization/cce9db95-46d9-4dc2-84b6-764215d0a002> ;
    dct:title "Exoplanet characterization using ground-based and space-based direct imaging: Application to the SPICES mission and the VLT/NaCo instrument" ;
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    dcat:keyword "angular-differential-imaging",
        "coronagraphy",
        "coronographie",
        "exoplanetes",
        "exoplanets",
        "high-contrast-imaging",
        "imagerie-differentielle-angulaire",
        "imagerie-differentielle-spectrale",
        "imagerie-haute-dynamique",
        "infoeu-reposemanticsdoctoralthesis",
        "physastrimphysics-physicsastrophysics-astro-phinstrumentation-and-methods-for-astrophysic",
        "sduastrimsciences-of-the-universe-physicsastrophysics-astro-phinstrumentation-and-methods",
        "spectral-differential-imaging",
        "theses" ;
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    dct:title "Exoplanet characterization using ground-based and space-based direct imaging: Application to the SPICES mission and the VLT/NaCo instrument" ;
    dcat:accessURL <https://theses.hal.science/tel-00750252> .

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