# Lettre de l'AT Exosystèmes n°11 (16 septembre 2025)
Chères et chers collègues,
Voici les nouvelles de l’AT Exosystèmes du 2025-09-16 :
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1. Soutenances de thèse / PhD thesis defenses
2. PhD thesis defense - Salomé Grouffal
3. Reminder: Roman Coronagraph School Europe 2026
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Pour transmettre vos annonces ou résultats scientifiques que vous souhaitez diffuser à la communauté, écrivez-nous à l’adresse <newsletter-at-exos@services.cnrs.fr>
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1. Annonce des soutenances de thèse
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L'AT Exosystèmes a à coeur d'offrir de la visibilité aux étudiants en thèse. N'hésitez pas à nous faire parvenir vos annonces de soutenance qui seront retransmises en visioconférence.
[Transmis par l'AT Exosystèmes]
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2. PhD thesis defense - Salomé Grouffal
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Title: Detection and characterisation of long-period exoplanets: toward Earth-like planets
Date: Friday, 26th September at 9:00
Zoom link: https://univ-amu-fr.zoom.us/j/99659697908?pwd=UXuJ69PhAC5u5MoPErHD1Ela7YagaZ.1
The defence will be held in English.
Jury composition:
Émeline BOLMONT (Observatoire de Genève) - Reviewer
Tristan GUILLOT (Observatoire de la Côte d’Azur) - Reviewer
Susana BARROS (Instituto de Astrofísica e Ciências do Espaço) - Examiner
Lucile MIGNON (Institut de Planétologie et d'Astrophysique de Grenoble) - Examiner
Amaury TRIAUD (University of Birmingham) - Examiner
Stéphane UDRY (Observatoire de Genève) - Examiner
Vincent LE BRUN (Laboratoire d’Astrophysique de Marseille) - President
Alexandre SANTERNE (Laboratoire d’Astrophysique de Marseille) - PhD supervisor
Abstract:
Thirty years after the discovery of the first exoplanet around a main-sequence star, over 5800 exoplanets have been confirmed. These discoveries, made using a variety of techniques, have revealed a remarkable diversity of planetary systems and reshaped our understanding of planetary formation and evolution. Among them, transiting planets, those that pass in front of their host stars, offer unique opportunities to precisely measure both mass and radius, as well as probe their atmosphere via transmission spectroscopy. Increasingly detailed studies of multi-planet systems enable comparative planetology both across systems and within them. Despite these advances, no system resembling the Solar System has yet been detected. This is largely due to observational biases that favour short-period planets in current detection methods, such as radial velocity and transits. Addressing the question of the uniqueness of the Solar System, and the Earth in particular, requires detecting longer-period planets in the habitable zones of Sun-like stars. The PLATO mission (ESA) aims to achieve this goal. In the meantime, ground-based instruments are improving their precision to characterise low-mass, long-period planets. Together, these efforts will expand exoplanet characterisation and enable comparisons with Solar System planets. In this context, this thesis addresses the challenges of detecting and characterising long-period exoplanets through a comprehensive study of a multi-planet system using different techniques.
The first part focuses on the characterisation of the HIP 41378 system, a bright F-type star hosting five transiting planets with periods up to 542 days. This system is a perfect testbed for the targets of the upcoming PLATO mission. The orbital periods of planets observed with only one or two transits are first determined, before combining transit data, radial velocities, and transit timing variations to constrain the orbital parameters and masses of the system’s seven low-mass planets. Particular attention is given to HIP 41378 f, a cold giant on a 542-day orbit. A multi-instrument observational campaign yields a measurement of the projected spin-orbit angle via the Rossiter–McLaughlin effect, revealing a misalignment. In addition, the planet’s unexpectedly low density challenges standard models of internal structure and formation. This case study provides key insights for the design of future observations with PLATO as well as ground-based follow-up strategies for long-period planets.
The second part addresses exoplanet detection with the radial velocity method. A new approach is developed to correct instrumental variations in the SOPHIE spectrograph using environmental monitoring of pressure and temperature, enhancing sensitivity to low-mass planets. The work also includes a contribution to the KOBE survey, which targets habitable-zone planets around K-dwarf stars using the CARMENES spectrograph.
[Transmis par Salomé Grouffal]
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3. Reminder: Roman Coronagraph School Europe 2026
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**** The deadline is in one month ****
Roman Coronagraph School Europe 2026
9-13 March 2026, Villa Clythia, Fréjus (France)
In 2027, the Coronagraph Instrument from the Nancy Grace Roman Space Telescope (RST) will provide the very first images of mature giant exoplanets and circumstellar disks in reflected light in the visible. This unique science will be enabled by reaching contrast levels 2 to 3 orders of magnitude better than current state-of-the-art visible or near-infrared coronagraphs, thanks to the combination of several high-contrast imaging technologies for the first time in space. Beyond the technological demonstration, the Roman Coronagraph is expected to enable ground-breaking science and offer unique science opportunities to the community. The Community Participation Program (CPP) team is currently hard at work to prepare the target list, observations, planning tools, data simulation and reduction pipelines, and tools to support for several key observing modes. It ambitions to provide the community with all the information and tools needed to make the best out of the public Roman Coronagraph data.
The Roman Coronagraph is led by NASA, but with a strong participation from international agencies (CNES, MPIA, ESA, and JAXA). This participation means that the European astronomical community can play an important role in the preparation of the mission and then in the scientific exploitation of the data provided by the coronagraph. This school intends to provide to 20 PhD students and postdocs all the necessary background and tools to be ready to reduce, analyse and interpret the first Roman Coronagraph data.
The school is organised over five days, 9-13 March 2026, at Villa Clythia in Fréjus (France). It will consist in classes on high-contrast imaging, exoplanet atmosphere modelling, debris disks, and exoplanet demographics. A large part of the school will be dedicated to hands-on sessions to get familiar with simulation tools, reduction pipeline, and modelling and retrieval tools.
Important dates:
• May 2025: Announcement of the school and opening of the applications
• 17 October 2025: End of applications
• Mid-November 2025: Announcement of the selected participants
• March 2026: School
All the relevant information, including invited speakers and instructions on how to apply, can be found on the website:
https://romanschool2026.sciencesconf.org/
[Transmis par Arthur Vigan]
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Pour transmettre vos annonces ou résultats scientifiques que vous souhaitez diffuser à la communauté, écrivez-nous à l’adresse <newsletter-at-exos@services.cnrs.fr>