L’émission des disques protoplanétaires présente une grande diversité de structures qui semblent témoigner de la présence de planètes en formation dans leur disque. Malgré une moisson d’observations de grande qualité, notamment grâce à ALMA, la masse des disques protoplanétaires reste difficile à quantifier, que ce soit par l’émission des poussières ou du gaz. Dans cette communication, je présenterai une nouvelle idée pour contraindre la masse des disques dont la structure de l’émission suggère la présence de planètes massives. Cette idée repose sur le fait que les vitesses de migration planétaire et de dérive radiale des poussières varient de façon opposée avec la masse du disque. Un disque massif implique une migration planétaire rapide et rend moins probable l’interprétation planétaire des structures observées dans l’émission du disque. Un disque peu massif, à l’inverse, implique une dérive radiale rapide des poussières larges, ce qui peut être en tension avec le niveau de flux observé du disque dans le domaine radio. J’illustrerai ces contraintes pour le disque autour de l’étoile HD 163296 par des simulations hydrodynamiques d’interactions disque-planète post-traitées par des calculs de transfert radiatif dans la poussière.

Recent protoplanetary disc observations at high resolution, like in the DSHARP survey, have brought insights on the environment in which planets form. On the other hand, numerical simulations have the capacity to implement more and more complicated physics in our planet formation models. In this talk, I will present the results from two of our studies: first, we investigated how the potential natal disc of the Solar System could be seen if it was observed with ALMA. By computing synthetic ALMA images, we show that ALMA has the power to discover Solar System's protoplanetary disc analogs. Such high resolution observations will help us determine under which conditions giant planets form in the outer or inner regions of their discs. Another way to constrain the formation pathway of giant planets is by investigating how gas accreting giant planets shape their disc around them. With the help of hydrodynamical 2D simulations, we investigated how the mass is distributed between two gas accreting planetary cores forming in the same disc. After understanding the time evolution of their mass ratio, we compared it to the exoplanets' distribution: we found that, in order to explain the exoplanets' diversity, our planets *must* start accreting at different times and late in the gaseous disc lifetime. Future observations with the JWST can be of great help to constrain giant planet formation.

Les jeunes systèmes planétaires sont constitués de planètes, de petits corps, de poussières et de gaz circumstellaire. Les planètes sont détectées par les méthodes habituelles directes ou indirectes; les poussières sont détectées en lumière diffusée et en émission thermique et constituent la partie visible des disques de débris; le gaz circumstellaire est détecté par spectroscopie lorsque l'orientation du disque est favorable. Les petits corps (exocomètes, astéroïdes...) ne sont jamais observés directement, mais leur présence est rendue nécessaire comme source interne de poussières et de gaz. Ils sont donc au cœur de toutes les modélisations des disques de débris, en particulier leurs interaction dynamiques avec les planètes.

Le disque de Beta Pictoris est le prototype historique du disque de débris étudié depuis bientôt presque 40 ans. C'est aussi un des rares exemples de système avec à la fois un disque de débris et des exoplanètes connues dont on commence à connaître les orbites aujourd'hui (Beta Pictoris b & c deux exoplanètes géantes en orbite à 2.7 au et 9 au de l'étoile). La présence de planètes dans ce système avait été soupçonnée de manière indirecte par leurs effets sur le disque bien avant leur détection en 2009 et 2018). Un de ces effets est le scénario FEB (Falling Evaporating Bodies, autrement dit des exocomètes). Les observations du spectre de l'étoile on révélé depuis longtemps la présence de très nombreuses absorptions supplémentaire et temporaires, le plus souvent apparaissant sur le bord rouge des raies. Ces variations ont été attribuées et modélisées comme résultant du passage devant la ligne de visée de petits corps de type cométaire (les FEBs) qui s'évaporent au voisinage de l'étoile (Beust et al. 1990, 1996, 1998). La statistique fournie de ces événements spectraux a permis de proposer une origine dynamique à ce phénomène, liée à des résonances de moyen mouvement avec une (à l'époque) hypothétique planète géante en orbite vers ~10 au (Beust & Morbidelli 1996, 2000; Thébaut & Beust 2001).

La découverte de la planète Beta Pictoris b en 2009, qui correspondait presque exactement à la prédiction de 2001, a renforcé ce scénario. En revanche la découverte de la deuxième planète (Beta pic c) en 2018 complique le tableau, car elle peut constituer une barrière potentielle aux proto-FEBs résonnants en les éjectant avant d'atteindre le stade FEB proche de l'étoile. Je présente une nouvelle étude dynamique prenant en compte les deux planètes et une population de petits corps, et montre que ce sont les résonances de moyen mouvement avec Beta Pic c (et non Beta Pic b) qui sont susceptible d'envoyer des exocomètes vers l'étoile (Beust et al. 2023) de manière tout aussi efficace. Mieux, la présence de Beta Pic b à l'extérieur entretient le phénomène FEB en maintenant l'excitation du disque de planétésimaux et en faisant perpétuellement entrer de nouveaux corps dans les résonances avec Beta Pic c, qui sinon se retrouveraient vidées très rapidement. Le scénario FEB proposé initialement il y a 30 ans se trouve donc complètement remanié par la présence de ces deux planètes.

As direct imaging is making progress, more multiple planetary systems are being discovered, the characterization of which provides constraints on their architecture. Among these, the famous HR8799 system occupies a special place as it was the first multiple system imaged and is composed of at least 4 young giant planets in resonant configuration, and a debris disk arranged in several belts. HR8799 has been extensively observed from the ground with extreme AO at near IR and in the submillimeter range. After introducing the contrast performance of the MIRI coronagraphs, we will present the very first recent images of this planetary system observed with MIRI/JWST in mid IR filters and provide a first taste of atmospheric characteristics of the planets as well as some features observed in the debris disk.

Because of the wealth of informations related to atmospheric dynamics and tidal interactions they contain, non-transiting exoplanets phase-curve modulations have an important potential for spatial photometric and spectroscopic surveys, in optical and infrared wavelength. Although the analysis of data obtained from transiting systems has been widely privileged over the past decades, granting the additional knowledge transits and eclipses are able to provide, the characterisation of non-transiting exoplanets is a challenge that needs to be undertaken by modern exoplanetary science in order to broaden our understanding of both exoplanetary system dynamics and tidally-induced variability in solar-type stars. This can only be achieved by putting together an accurate knowledge of the stellar properties with a comprehensive description of the exoplanet intrinsic dynamics as well as of its interactions with the host star. In order to demonstrate the perspectives offered by these non-transiting systems, we consider the detection of a stable short-period photometric modulation in the 4-year light curve of a Kepler solar-type pulsator. The most plausible explanation for this signal is by far the presence of a non-transiting exoplanet in close orbit around the host star. This allows us to combine photometry, asteroseismology, and high-resolution spectroscopy from a HARPS-N follow-up campaign to characterise the system. From photometry, we obtain the stellar surface rotation period while seismology provides a constraint on the stellar inclination and, combined with spectroscopic surface parameters, enables a precise modelling of the stellar structure and evolution. We also show from spectroscopy that stellar activity indicators are de-correlated from the planet orbital period. In order to get better constraints on the planetary parameters, we model the light reflection and emission from the planet atmosphere, taking into account albedo and energy redistribution. We discuss how star-planet tidal interactions shape the configuration of the system during its evolution, which is supposed to be mainly driven by inertial waves dissipation in the convective envelope of the star. We finally emphasise that non-transiting-system observations will greatly benefit from the abilities of JWST, ARIEL, and PLATO.  

The characterization of exoplanets is inherently linked to our ability to characterize their host stars. M dwarfs have been identified as privileged targets for searching planets in the habitable zone of their host star, and several instruments, such as SPIRou, were built specifically for their observation in the near-Infrared domain. Deriving accurate estimates of atmospheric parameters for such stars remains challenging, however. One of the best options at our disposal is the comparison of high-resolution spectra to state-of-the-art synthetic models. This approach may however be limited in its application to magnetic targets as the shape of stellar lines can be significantly affected by the presence of magnetic fields. In this talk, we present the results of an analysis performed with a new tool, ZeeTurbo, based on Turbospectrum, and capable of solving the polarized radiative transfer equation. With this code, we compute a grid of synthetic spectra computed for various magnetic field strengths and develop a process to simultaneously constrain the effective temperature ($T_{\rm eff}$), the surface gravity ($\log{g}$), metallicity ([M/H]), alpha-enhancement ($\alpha/Fe$) and average magnetic flux. We apply our tools to a few key magnetic targets monitored in the context of the SPIRou Legacy Survey, and retrieve estimates consistent with the literature.

Les observations d'atmosphères d'exoplanètes par le JWST ont commencé et promettent des découvertes inédites, notamment grâce à sa gamme spectrale immense et sa sensibilité. Cependant, les observations à basse et moyenne résolution ont leur limites et possèdent des dégénérescences intrinsèques. Le meilleur moyen pour lever ces dégénérescences est de coupler les études depuis l'espace avec des observations à haute résolution depuis le sol, par des instruments tels que SPIRou au CFHT ou NIRPS à La Silla. Ces observations peuvent aussi servir en préparation des études JWST en identifiant les meilleures cibles (large atmosphère, faible couverture nuageuse ...) et en cherchant des effets dynamiques, inaccessibles en basse résolution, si possible en 2 ou 3 dimensions.

Dans cette présentation, je ferai le point sur l'état de l'art de la spectroscopie à haute résolution et de la façon dont elle peut se coupler aux observations JWST. Je détaillerai les cibles intéressantes pour le futur, ainsi que la contribution française à cet objectif. Enfin, j'expliquerai comment se couplent en pratique basse et haute résolution, et ce que les premières études couplées nous ont appris de plus sur les atmosphères d'exoplanètes. 

HD 95086 is a young (~13 Myr), nearby Solar-System analog hosting a 4-5 MJup, directly-imaged exoplanet: HD 95086 b. The planet orbits at ~57 au from the star between an inner and an outer debris belt located at 7-10 au and 106-320 au, respectively. Previous studies have suggested that the size of the broad cavity between the two belts requires the presence of one or more additional planets at a closer separation (<30 au).

In this talk, we present the results of a long-term, in-depth follow-up monitoring of the HD 95086 planetary system with direct-imaging observations from the VLT/SPHERE instrument combined with archival data from the VLT/NACO and Gemini/GPI instruments (Desgrange et al., 2022). Our work aims to explore the orbital and atmospheric properties of HD 95086 b, and look for the presence of additional planet(s). In particular, we extract the JH low-resolution spectrum of HD 95086 b for the first time, and confirm its very red spectral energy distribution. Our analysis indicates that it could be explained by the presence of a circumplanetary debris disk around the planet b or a super-solar metallicity atmosphere.

In addition, this young emblematic system will be observed in the context of the JWST GTO program with several instruments. We will discuss as well what information the JWST may give us on the system HD 95086, both considering the planet b and possible additional planets. 

Over the past two decades, transit spectroscopy has led to the detection of various species in exoplanet atmospheres. Improvements in resolution and sensitivity however revealed the potential biases induced by the stellar lines locally occulted by the planet along its transit chord. Our goals are to investigate the implications of centre-to-limb variations and stellar rotation in the biases induced in absorption spectra by planetary-occulted stellar lines, and to interpret atmospheric absorption signatures in the presence of these stellar contamination. We use a forward modelling approach with the EVaporating Exoplanets (EVE) code to calculate stellar spectra during the transit of an exoplanet and its atmosphere, accounting for the system geometry, the profile of the local stellar lines, and their variations over the stellar surface. We use the local planetary spectrum as a reference to compute absorption spectra and derive an unaffected atmospheric absorption signature. We then use this signature as a benchmark to identify clearly the biases induced in absorption spectra by centre-to-limb variation and stellar rotation when using an inappropriate proxy to estimate the planet-occulted stellar lines during the transit. As soon as the spectral profile of the proxy that is used departs from the real planet-occulted stellar line profiles, distortions were created in the absorption spectra of our test planet. For both moderate to fast rotators the distortions affected the atmospheric signature significantly, especially when the planetary radial orbital velocity is close to the radial velocity of the occulted stellar surface. The amplitude of distortions induced by centre-to-limb variations can reach a few tenths of % and thus be significant when searching for faint atmospheric signatures. Studying planetary transit absorption signatures remains a complicated task without an accurate estimate of the impact of stellar rotation and center-to-limb variations on the local stellar spectrum. We wish to demonstrate how using forward modelling with codes such as EVE can help us to dissect and understand the observed absorption signatures and eventually lead to better characterisations of exoplanet atmospheres

The James Webb Space Telescope (JWST) Mid-InfraRed Instrument (MIRI) with its Low-Resolution Spectrometer (LRS) already have and will carry out primary and secondary transit spectroscopy of exoplanet atmospheres with an unprecedented sensitivity, in an almost uncharted wavelength range (from 5 to 12 μm). Among the 77 programs for cycle 1 of transiting exoplanet observation proposed for Early Release Science (ERS), Guaranteed Time Observation (GTO) and General Observations (GO), 43 of them have or will be observed with the MIRI instrument including 17 with the LRS mode. These proposals with MIRI LRS are mainly focused on small planets. As a matter of fact, MIRI is the most suited instrument to observe the thermal emission of hot rocky or sub-Neptune planets. The scientific impact of these observations is very high as no atmosphere has ever been probed around rocky temperate exoplanets. During the past few months, both Commissioning results and observations revealed key insights in exoplanetary atmospheres, leading to strong detections of molecules in the L-band. In this talk we (1) present the latest update of the MIRI LRS instrument performances based on Commissioning results and our work on instrumental systematics in collaboration with the Space Telescope Science Institute. (2) We provide a complete review of MIRI LRS observations and their scientific insights, including Commissioning target Super-Earth L168-9b transit spectroscopy and ERS target Hot-Jupiter WASP-43b phase-curve spectroscopy. (3) We show the outcomes of our MIRI LRS simulation pipeline based on Commissioning calibration on predictions of past and future observations, thus providing tools and recommendations for JWST Cycle 2 proposals. Finally, we highlight the fact that JWST performances are beyond ground-based expectations and further work on Cycle 1 performances will improve our understanding of the instrument, therefore guaranteeing strong scientific results in the next decades.

Session hands-on sur le JWST MIRI-LRS pour apprendre à faire de la réduction de données.

Over recent years and in the near future, space and ground telescopes have increased the precision of their observations of exoplanets.

With the new capabilities of JWST notably, it may be possible to extract a more exact information as to the composition of exoplanet atmospheres.

It may be even possible to study their interior for example through the outgassing of magma oceans.

In this presentation, we will focus on the effects of outgassing on observations, relative to the concentration of hydrogen in the magma ocean.

Our model relies on a Gibbs free-energy minimization to find the vapor composition in equilibrium with the magma ocean (a modified version of the CEA/NASA code (Gordon & McBride (1996)).

The vapor composition is then used in an atmospheric model, ATMO (Amundsen et al. 2014), which solves for the pressure-temperature profile by finding the energy flux balance in each layer of the model.

ATMO can also generate synthetic emission and transmission spectra from this pressure-temperature profile.

We confirm previous results such as the thermal inversion of silicate atmospheres, the dominant opacity source coming from SiO, MgO, Na, K, ... (Ito et al. 2015, Zilinskas et al. 2022). We find a SiO feature at 9 μm similarly to Ito et al. (2015).

We also show how the inclusion of hydrogen slowly reduces the inversion, for increasing temperatures, and hint at observability of various molecules.

The evolution and current state of an atmosphere depend on how it responds to stellar irradiation. Such a response depends on a combination of atmospheric properties (in particular composition, and overall irradiation) and stellar properties (in particular, the high-energy spectrum of the star). Following the launch of JWST, and its unprecedented sensitivity and spectral coverage, the coming years will likely see a shift in the community's focus from big, hydrogen-dominated planets to smaller planets with a likely diversity of atmospheric compositions. This presentation will describe ongoing work on the collisional-radiative behaviour of water-rich atmospheres, which is of fundamental importance to understand the nature of such objects at both the population-wise level and for individual cases.

Les exoplanètes orbitant très proche de leur étoile subissent des niveaux d'irradiation extrêmes conduisant à un échappement atmosphérique hydrodynamique et à la formation d'un vent planétaire. La perte de masse planétaire est régie par plusieurs mécanismes physiques dont la photoionisation qui peut impacter l'évolution des exo-atmosphères. A l'aide de PLUTO, nous étudions par l'intermédiaire de simulations hydrodynamiques 1D et 2D l'effet de l'ionisation secondaire par les photoélectrons sur l'ionisation et le chauffage du gaz différentes masses planétaires. En effet, l'énergie résultante déposée sous forme de chaleur dépend à la fois de l'énergie des électrons primaires (électron résultant de l'interaction entre un photon et un atome d'hydrogène), de la fraction d'ionisation et aussi des ions créés lors du processus d'ionisation secondaire (lorsque le photoélectron interagit avec un autre atome d'hydrogène). Nos résultats rapportent une diminution importante jusqu'à 50% du taux de perte de masse atmosphérique pour tous les systèmes planétaires lorsque les photoélectrons sont pris en compte. Ces estimations révisées des taux de perte de masse des exoplanètes chaude est importante pour l'interprétation physique des manifestations observables de ces vents planétaires.

Dans les dix prochaines années, il sera essentiel de pouvoir détecter des terres jumelles par photométrie et vitesses radiales. Le signal de telles planètes est de l'ordre de 10 cm/s et 80 ppm, et leur détection n'est pas limitée par le bruit de photon des instruments, mais par leur systématiques et les signaux provenant de l'activité stellaire. Pour repousser les limites de détection il faut de nouvelles méthodes d'analyse permettant d'exploiter à fond les données. Dans cet exposé, je montrerai comment l'analyse des données peut être séparée en plusieurs étapes auxquelles on peut apporter une solution optimale dans un certain sens. En particulier, je montrerai comment on peut obtenir une représentation réaliste des signaux d'activité stellaire. 

With the first observations having been carried out by the JWST, the great potential of this long awaited instrument is at last coming to fruition. For exoplanetary characterisation in particular, it has already shown great promise for tremendous discoveries, having captured the first clear evidence for CO2 in an exoplanet’s atmosphere. Still limited in resolution however, coupling it with ground-based observations would optimise results. The near-infrared spectropolarimeter SPIRou located at the Canada-France-Hawaii Telescope (CFHT) is one of if not the best for atmospheric characterisation from the ground, due to its properties and location. It observed the exoplanet WASP-76b as part of the ATMOSPHERIX project, motivated by a reported and confirmed asymmetry in the limbs of the atmosphere of this ultra hot Jupiter, detected through observations in the visible (Ehrenreich et al. 2020, Kesseli et Snellen 2021). This has led to extensive theoretical and observational work around this planet to understand its peculiarity. In acquiring infrared data of this atmosphere, different pressure layers are expected to be probed, which could reveal a different temperature and dynamical profile of the atmosphere. In this talk, I will detail my study of the characterisation of the atmosphere of WASP-76b using SPIRou infrared data, reduced so as to maximise the atmospheric signal. By using a combination of simulated atmospheric models and statistical methods to analyse it, this led to the first detection of H2O and CO in high-resolution infrared data of this planet at the expected theoretical Doppler shift due to the planet’s orbital motion. With such detections opening a new window into the understanding of the circulation and composition of WASP-76b, the prospect of coupling observations in different wavelength ranges and at different resolutions (like JWST) appears an exciting opportunity to better understand the physics and chemistry of ultra-hot planetary atmospheres.

The Juno mission has completely revolutionised our vision of the interior of Jupiter. One of the main findings of Juno, thanks to very accurate measurements of Jupiter's gravity field, is the presence of a dilute core inside the planet. However, the size of this dilute core is still a matter of debate and constraining its extent is key to understand the formation and evolution of the planet.

Since Jupiter is mostly composed of hydrogen and helium, it is essential to use an appropriate equation of state to precisely access the structure of the planet. While linear mixing is usually employed in interior models, it is important to take the non-ideal mixing effects into account to properly model the behaviour of a H-He mixture. We propose a new equation of state that includes the H-He interactions and remains valid for any mixture of hydrogen and helium.

We ran MCMC simulations to study a wide range of interior models of Jupiter. I will present results of interior models including uncertainties in the equation of state and in the deep atmospheric entropy. We obtain a relatively wide range of dilute cores extending between about 15% to 60% of Jupiter’s mass. We are thus able to find solutions in relatively good agreement with formation models as well as Saturn interior models, which favour small dilute cores. This work on Jupiter's interior and the H-He equation of state has direct consequences to the study of exoplanets, notably on the mass-radius relationship.

The Characterizing Exoplanets Satellite (CHEOPS) is the first ESA space mission dedicated primarily to the study of exoplanetary systems. Since its first light in January 2020, and through its nominal mission of 3.5 years, CHEOPS is performing ultra-high precision photometry of bright stars known to host extrasolar planets. Next to searching for transits of planets known from radial velocities and measuring precise radii of known transiting planets, CHEOPS is performing characterization of exoplanet atmospheres. In this talk, I will briefly describe the space mission and its scientific objectives, I’ll then present some of its most important results, and detail how the instrument can reveal the properties of planetary atmospheres through optical light occultations and planetary phase curves.  In particular, I will present the observations of the secondary eclipses of the ultra-hot Neptune LTT9779b and illustrate how these complement ongoing and future observations from the ground and space.

TOI-1695 is a V-mag=13 M-dwarf star from the northern hemisphere at 45 pc from the Sun, around which a 3.134-day periodic transit signal from a super-Earth candidate was identified in TESS photometry. With a transit depth of 1.3 mmag, the radius of candidate TOI-1695.01 was estimated by the TESS pipeline to be 1.82 REarth with an equilibrium temperature of ~620 K. We successfully detect a reflex motion of the star and establish it is due to a planetary companion at an orbital period consistent with the photometric transit period thanks to a year-long radial-velocity monitoring of TOI-1695 by the SPIRou infrared spectropolarimeter. We use and compare different methods to reduce and analyse those data. We report a 5.5-sigma detection of the planetary signal, giving a mass of 5.5+/-1.0 MEarth and a radius of 2.03+/-0.18 REarth. We derive a mean equilibrium planet temperature of 590+/-90 K. The mean density of this small planet of 3.6+/-1.1 g cm^(-3) is similar (1.7-sigma lower) than that of the Earth. It leads to a non-negligible fraction of volatiles in its atmosphere with f_[H,He]=0.28(+0.46)(-0.23)% or f_water=23+/-12%. TOI-1695 b is a new sub-Neptune planet at the border of the M-dwarf radius valley that can help test formation scenarios for super-Earth/sub-Neptune-like planets.

The search for exoplanets at radio long wavelengths (or low frequencies), typically beyond a few meters (below a few 100 MHz) has been a rising research field for the past decades. This search, based on expectations derived from auroral radio emissions of magnetized planets of the solar system, is motivated by the unique informations that a radio detection would provide on exoplanets and their interaction with the host star (planet/star magnetic field, rotation/revolution periods etc.). It lies among the main science objectives of giant, high sensitivity, ground-based radiotelescopes such as LOFAR (in Europe), NenuFAR (in Nançay) or SKA (Australia). Beyond exoplanets, for which clues of detection accumulate, tens of ultracool dwarves and active stars have already been detected. In this presentation, I will review recents efforts spent on this topic of the french community spent on LOFAR, NenuFAR and SKA.

We will present the results of new SPHERE data processing project (ANR DDISK) using methods dedicated to  the reconstruction of the circumstellar environments. For total intensity we use the REXPACO algorithm, Flasseur+2021 to recover their morphology. The method formalize the challenging imaging tasks within an inverse problem framework embedding a statistics-based model of the stellar leakages combined with a physics-based forward model of the instrumental effects. Beyond the significant gain in sensitivity, a major feature of the unsupervised REXPACO algorithm is its ability to reconstruct faithful images of the circumstellar environment, and to provide reliable astro-photometric estimates. Because the combination of intensity and polarimetry is critial to acess the physics of the dust composing the circumstellar disks, we will also present new SPHERE polarimetric data processing using RHAPSODIE algorithm, Denneulin+2020. This unsupervised method, also based on an inverse problems framework, demonstrates significantly better sensitivity, and gives access to an unprecedented resolution thanks to its forward modeling of the instrumental effects (including deconvolution).
These two different processing methods constitute state-of-the-art capabilities in the field, and we will discussed their efficiency using a large sample of observational and synthetic data.

Young giant exoplanets are the best targets for characterization with direct imaging. The Medium Resolution Spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) of the recently launched James Webb Space Telescope gives access to the first spectroscopic data for direct imaging above 5 microns with unprecedented sensitivity at a spectral resolution up to 3700. This provides a valuable complement to near-infrared data from ground-based instruments for characterizing these objects. At mid-infrared wavelengths, the star-to-planet flux ratio is more favorable than in the near-infrared and it provides access to molecular signatures that are relevant to characterize exoplanet atmospheres. Simulating data for the MRS, which covers a large spectral range from 5 to 28 microns, we are investigating the feasibility to detect molecules in the atmosphere of exoplanets with the so-called molecular mapping method. Taking advantage of the spectral difference between the star and the planets, this integral field spectrograph allows to disentangle the light from the star and that of the planet using cross-correlation with planetary atmospheric models. We will present the results of performance estimation based on simulations of MIRI observations. Simulating many known direct imaged systems, we detect and retrieve molecules such as CO, CH4, NH3, H2O, PH3, HCN, and using a large grid of Exo-REM atmospheric models, we are exploring the sensitivity of the method to determine atmospheric parameters. Finally, we will present a parametric analysis of MIRI/MRS detection capacity, studying the impact of the spectral type and the angular separation on the method's performance. Once combined with near IR data or coronographic data, MIRI/MRS will have the capacity to improve the characterization of exoplanetary atmospheres and to derive constraints on planetary formation.

A recent evolution, both theoretical and observational, in the understanding of protoplanetary disks dynamics points toward a low turbulence level; when turbulence is modelled by viscosity, this translates into a low viscous parameter. This new paradigm modifies our understanding of the dust dynamics in these disks and therefore the first steps of planet formation. Does it help planetesimal formation? Does it modify how the dust is distributed in the disk?
To address such questions, we performed a systematic parameter study of 2D Keplerian turbulence and particles dynamics in these flows. In this talk, an introduction to turbulence as well as new tools and methods adapted to study dust dynamics will be presented before to discuss the conditions resulting in particle clustering, the first step towards planetesimal gravitational collapse.
These results open new paths toward a model for planetesimal formation, and may open discussions on observational interpretations of dusty disks.

Le comité exoplanète transverse, créé par l'INSU en 2020, sera présenté (contexte INSU, rôles). Ce contexte sera suivi d'un
résumé des actions effectuées par le CET depuis sa création. L'accent sera ensuite mis sur la préparation de l'exercice de prospective
INSU/AA qui démarrera en 2023, en particulier le calendrier, les différents chantiers à venir (organisationnel, instruments...) et
les points de vigilance. Cette présentation courte servira de point de départ à des discussions afin de construire cette prospective
dans les meilleures conditions.

Il est maintenant admis que l'activité stellaire est un frein majeur à la détection par la méthode des vitesses radiales de planètes de petites masses autour d'étoiles de type solaire. L'impact des taches et plages est bien connu, via différents processus (contraste des structures, inhibition du blueshift convectif), mais l'impact des champs de vitesse à différentes échelles dans la photosphère l'est beaucoup moins. Ces processus, opérant à différentes échelles spatiales et temporelles, impactent cependant significativement les mesures en vitesses radiales du fait de leur variabilité. En nous appuyant sur notre connaissance du Soleil, nous avons étudié l'impact de l'ensemble de ces contributions pour des étoiles de type solaire. Un large échantillon de séries synthétiques réalistes a été généré pour des étoiles de type spectral F6-K4 de différents niveaux d'activité, et ont permis de réaliser des tests en aveugle afin de caractériser l'incertitude sur les masses estimées par la méthode des vitesses radiales pour des planètes de type Terre orbitant en zone habitable, et pour estimer les taux de détection et de faux positifs lors de recherche de planètes dans le cadre de relevés.

Hot giant exoplanets are very exotic objects with no equivalent in the Solar system which allow us to study the behavior of atmospheres under extreme conditions. Their day-night thermal and chemical dichotomy associated with extreme wind dynamics make them intrinsically 3D objects. Thus, the simple 1D assumptions must be avoided in order to be able to explain in a consistent way hot and ultra hot Jupiter atmospheres and their evolution. I will present a review paper (submitted) where we highlight the importance of these 3D considerations, how they impact transit, eclipse and phase curve observations. We also analyze how the models must adapt in order to remain self-consistent, consistent with the observations and sufficiently accurate to avoid bias or errors. We particularly insist on the synergy between models and observations in order to be able to carry out atmospheric characterizations with data from the new generation of instruments that are currently in operation or will be in the near future.

Satellites alter the spin-axis precession rate of their host planet. The tidal migration of moons is therefore an efficient driver of resonance crossing between the spin-axis and orbital precession modes of a planet. Once the planet is captured in resonance, the migration of its moons produces a large obliquity increase over billions of years -- for instance, this mechanism is responsible for Saturn's axis tilt. When the planet's obliquity reaches 90°, however, the migrating moon becomes unstable and can be disrupted into a ring of debris. In transit data, such a very oblique ring can be misinterpreted as an extended atmosphere ("super-puff exoplanet"). This phenomenon is a viable alternative to the -- otherwise unexplained -- very low density of HIP41378 f.

With a sample of more than 5000 objects at hand, exoplanet demographics is starting to unveil how the complex process of planet formation has produced the multifaceted hues of observed exoplanetary architectures. However, the two most successful detection techniques, namely transits and radial velocities, are biased towards old planets orbiting close to their stars. Complementing them, direct imaging is preferentially sensitive to young giant planets in wide orbits, offering unique insights into the critical stages of giant planet formation and early evolution. Here I will present intriguing recent results from the ongoing B-star Exoplanet Abundance Study (BEAST) operated at SPHERE@VLT, the first survey looking for planets around young B stars (M>2.4 M_sun): setting the record for the most massive planet-hosting stars to date, the unexpected detection of already two ~10-15 M_J companions around two distinct ~6-10 M_sun systems has provided evidence for the possibility of giant planet formation around massive stars, urging the extension of planet formation models – classically restricted to solar-like stellar hosts – up to this stellar mass regime. Yet, many questions remain to be answered. Supplementing the exploratory work enabled by ground-based facilities, space-borne missions like Gaia and JWST can crucially contribute to a more thorough characterization of the newly-found substellar objects. In particular, JWST follow-up observations in the NIR and MIR regimes are expected to provide crucial spectral information, paving the way to a deeper understanding of how giant planets and brown dwarfs can come into being under such exotic conditions. Even more intriguingly, a comparison with free-floating objects of the same size targeted by ongoing and future dedicated JWST programs will clarify whether a distinction can be operated between “planet-like” and “star-like” giant planet and brown-dwarfs, and the possible interplay between dynamical capture and ejection.

Understanding the atmospheric circulation, radiative transfer and atmospheric chemistry of exoplanets is crucial for the characterization of these objects.

In particular, Hot Jupiters are among the most observed type of exoplanets and have no equivalent in our Solar System. During the last decade, observational and modeling efforts have been made to begin the atmospheric characterization of these exoplanets.

We set out to use the generic Planetary Climate Model (generic PCM), a 3D Global Climate Model developed for paleoclimate and temperate exoplanet studies to simulate the atmosphere of Hot Jupiter. As a case study, we chose to model WASP-43 b, a Hot Jupiter with an orbital period of 19.5 hours and an equilibrium temperature of 1400 K. This planet has already been observed by the Hubble Space Telescope and the Spitzer Space Telescope, yielding crucial information about key atmospheric processes but also raising substantial questions about cloudiness, chemistry and wind patterns. Moreover, this planet has been observed by JWST on December 1^st 2022, providing astounding data in the mid-infrared.

Our simulation are able to replicate the already known atmospheric patterns of the atmosphere of Hot Jupiters, that we will present during this talk. We show that cloudless simulations are unable to reproduce the aforementioned data.

Thus, we developed a scheme to simulate the formation of clouds and to take into account their radiative feedback in a fully coherent manner. Our results show better agreements with already published data. We will discuss the impact of clouds on the dynamics and the observables during this talk.

This study is dedicated to provide more realistic tools to interpret protoplanetary disk observations with microwave scattering experiments, where our dust analogs are geometrically controlled thanks to additive manufacturing, using a refractive index similar to astronomical silicate. The size of these analogs is chosen to be proportional to real dust compared to the used wavelengths to do the observations, in order to respect the electromagnetic scale invariance rule and thus reproduce similar scattering behaviors as real dust.   
    
In this work we studied the scattering parameters (in the Mie scattering regime) such as the phase function, degree of linear polarization and other Mueller matrix elements of three dust morphologies, e.g. fractal aggregates, and two families of grains with different types of roughness. The goal was to understand their scattering properties and thus give insights or tools to understand the indirect information that is gathered with scattered light observations.

Measurements of dust analog were performed in the anechoic chamber of CCRM and cross-validated with numerical simulations. Thanks to the multi-orientation and multi-wavelength that our setup provides, two types of analyses were performed with the three types of morphologies: first, scattering parameters averaged over several orientations of analogs at different wavelengths, and second, scattering parameters including a power-law size distribution. Based on these two analyses, we were able to identify characteristic scattering properties of each morphology, showed with their scattering parameters.  We identified the differences of their scattering parameters within a given morphology and between the different morphologies, and we compared them with scattering parameters of similar morphologies found in literature, verifying the coherence of our results.

Based on our results, we proved that the control of geometry, refractive index and orientation of our analogs are key to interpret their scattering properties, providing unique scattering measurements thanks to our microwave experiment in CCRM and to the additive manufacturing. Furthermore, these results suggest that porosities of our aggregates and roughness of our compact grains clearly affect in specific ways their scattering properties. Moreover, we showed the interest to continue the instrumental development of telescopes to obtain more than the total scattered intensity (phase function) and degree of linear polarization. Indeed, the other scattering parameters (which are related to the non-sphericity, the degree of circular polarization and the polarization at 45°) can give more clues about the morphology of dust in protoplanetary disks. Finally, we suggested to increase the size of our analogs and test other refractive indices to obtain closer scattering parameters to observations of forming disks, as well as to perform measurements at backscattering angles.

Ça y est, nous y sommes enfin ! Le JWST est lancé, déployé, et maintenant en pleine opération. Près de 200h d’observations ont été obtenues lors du cycle 1 d’observations du JWST pour caractériser les atmosphères des 7 planètes TRAPPIST-1, principalement par spectroscopie de transit, mais aussi par éclipses secondaires. Certaines de ces observations ont maintenant déjà été effectuées, les spectres sont en cours d’analyse voire pour certains déjà analysés, les premiers papiers sont en cours d’écriture, certains sont peut-être même déjà soumis. Dans cette présentation, je propose de faire un tour d’horizon (plus ou moins accéléré, selon le temps alloué) de ce que l’on sait à ce jour des planètes du système TRAPPIST-1, notamment concernant leurs atmosphères et leur habitabilité potentielle, aussi bien à partir de résultats d’observations que de travaux en modélisation. Ce tour d’horizon s’appuie en partie sur un article de revue que nous avons récemment publié (https://link.springer.com/article/10.1007/s11214-020-00719-1). Je présenterai quelques exemples clés – à partir de spectres d’observations simulés – illustrant les capacités du JWST à caractériser les atmosphères des 7 planètes TRAPPIST-1. Ces observations ont un potentiel formidable pour faire de la climatologie comparée avec les planètes telluriques du système solaire et notamment la Terre.

Le télescope spatial Roman (RST) de la NASA, prévu pour un lancement à l'horizon 2027, embarquera un démonstrateur technologique d'imageur à très haut contraste, le Coronagraph Instrument (CGI), qui permettra d'effectuer les toutes premières détections d'exoplanètes géantes en lumière réfléchie dans le visible. Il combinera pour cela un ensemble de briques technologiques qui permettront d'atteindre des contrastes compris entre 10^-7 (spécification) et 10^-9 (but). Après une phase de démonstration technologique d'une durée de 3 mois répartie durant la première année de la mission, CGI aura la possibilité de réaliser un programme scientifique d'une durée équivalent à 20-25% du temps scientifique de l'observatoire. La validation globale du fonctionnement de CGI et de ses performances servira de précurseur pour le développement d'un instrument capable d'imager des exo-Terres sur un futur grand observatoire spatial après le JWST. L'équipe instrumentale de CGI sera épaulée par l'équipe scientifique du Coronagraph Community Participation Program (CPP) pour la validation et l'exploitation du démonstrateur. Aux Etats-Unis, la sélection de l'équipe du CPP se fera via un appel compétitif de la NASA courant 2023. Côté français, le CNES est un des quatre partenaires internationaux de RST/CGI et disposera à ce titre d'une représentation officielle dans le CPP. Il y a donc une opportunité pour la communauté française de s'impliquer dans CGI et de valoriser son expertise dans le domaine des exoplanètes (instrumentation, détection, caractérisation, modélisation). Je présenterai les enjeu de la mission et du démonstrateur, ainsi que les opportunités offerte à notre communauté grâce à la participation du CNES dans la mission.

Short-period, low-mass planets have been found to often display inflated atmospheres [1]. Here, we investigate the interior structure of such planets with a moderate water budget using a fully self-consistent planet interior model [2, 3], where water can exist in supercritical state.

This has been done by increasing the working range of an existing interior model, allowing us to explore the 0.2-2.3 Earth mass range. We consider planets with water mass fractions (WMF) ranging from 0.01% to 5% and irradiation temperatures between 500 and 2000K. Moreover, we consider three possible internal compositions; a pure rocky interior, an Earth-like core mass fraction (0.325) and a Mercury-like core mass fraction (0.7). We find that at higher masses, the planet radius increases with the planet mass, and the radii for planets with supercritical water are greater than if water was in a condensed phase. An important mass of water can also result in a notable compression of the refractory layers (up to 0.1 Earth radius for a WMF of 5%). At lower masses, we find that the steam atmosphere inflates, and becomes gravitationally unstable when the scale height of the atmosphere exceeds ~0.1 times the planetary radius. We propose to use this H/Rp ratio as a stability criterion for steam atmospheres. Our data can be used to estimate the maximum WMF that can be retained by a planet given its mass, irradiation temperature and interior composition. For a given mass and temperature, a large part of the planets considered here can be stable even if constituted of 100% water. As the temperature increases or as the mass decreases, the surface gravity of a 100% water planet becomes too weak to retain the steam atmosphere. It is then possible to estimate the maximum WMF under which the atmosphere is stable.Our results show that planets under 0.9 Earth masses should typically present unstable hydrospheres.

We also find that a sharp transition exists between a planet able to hold a 100% water atmosphere and an unstable one, as the H/Rp stability criterion exceeds 0.1. Additionally, we note that this class of planets is a viable explanation of the current Super-Puff category without invoking instrumental limitations, as the mass of water molecules induces a more inflated atmosphere than H/He planets.

References:

[1] Turbet, M., Bolmont, E., Ehrenreich, D., et al. 2020, A&amp;A, 638, A41

[2] Aguichine, A., Mousis, O., Deleuil, M., et al. 2021, ApJ, 914, 84

[3] Vivien, H.G., Aguichine, A., Mousis, O., et al. 2022, ApJ

Les modèles d’interaction planète-disque reposent principalement sur des simulations 2D et 3D purement hydrodynamiques. L’accrétion y est souvent prescrite par un paramètre alpha qui modélise classiquement le transport radial turbulent de masse dans le disque. Ce scénario d’accrétion est depuis quelques années questionné par un paradigme qui implique l’évacuation verticale de moment cinétique par des vents magneto-hydrodynamiques. L’objectif est ici d'étudier l’impact d’une protoplanète massive dans un disque magnétisé en présence d'un vent MHD. Pour ce faire, nous avons réalisé avec le nouveau code GPU IDEFIX des simulations MHD non-idéale (avec diffusion ambipolaire) à haute résolution d’un disque de gaz, avec planète en orbite circulaire fixe, et baigné dans un champ magnétique vertical à grande-échelle. En particulier, j'illustrerai le lien entre la formation d'un sillon planétaire, la dynamique des lignes de champ magnétique et le comportement du vent dans le sillon. Seront également abordés quelques résultats additionnels concernant l'asymétrie du sillon, l'accrétion dans le disque, mais également l'évaluation du couple gravitationnel exercé par le disque sur la planète.

As planets age, they evacuate internal energy as such their thermal profile changes as well as the effective entropy. This temporal evolution will lead to changes in observed luminosity and radius of a planet. The modeling of the thermal evolution requires a planetary model with rigorous equations of state for the composition. The equations of state with a hydrostatic equilibrium model help give the radius of a planet for a given thermodynamic configuration. Work on this by Marley & al. (2006) or Fortnay & al. (2009) showed that one can estimate the evolution of the radius of a Jupiter like planet over time given an initial starting entropy and with the H/He equation of state by Saumon et al. (1995). However, these models uniquely evaluate the radii without considering the complex atmosphere equilibrium essential from an observational point of view. Subsequent models such as by Marley et al. (2021) couple atmosphere models with more rigorous interieur equations of state which act as a boundary condition. By doing this, one has access to the temporal evolution of the spectra as well as the radius. We propose a similar approach where we seek to link the 1D self-consistent radiative convective atmosphere model, Exorem (Blain et al.), with a planetary interieur model, Exoris (Mazevet et al.). By linking the thermal profiles of these two models we can have a complete model considering the high pressure and temperature conditions of the interieur and the complex radiative and chemical properties of the atmosphere. Exorem gives us the added possibility of exploring the impact of parameters such as clouds and stellar irradiation on the evolution of the spectrum and radius. Exorem also disposes of a disequilibrium chemistry model, rendering the atmospheric modeling more precise. Exoris allows us to create more complex interiors combining radial shells with different compositions. By linking precisely, the thermal profiles we can get an insight into the planetary interior. We shall first explore how the atmosphere and interior models function before showing how they can be linked. Finally, we will look at the type of results that we can obtain from this combined model. We will notably explore how these results fit into the type of observations we can hope to obtain with JWST for Jupiter and sub-Jupiter like planets.