Giant Exo-Planet Atmosphere, oRigin and Dynamics – GuEPARD

On a competitive international scene with on-going planet search surveys at Gemini, Keck and Subaru telescopes, our ANR10-GuEPARD project allowed us to strengthen our leadership in the field of detection and characterization of giant exoplanets. Large-scale systematic surveys were initiated using a multi-techniques approach to explore and characterize the environment of nearby stars. The direct imaging and radial velocities techniques were mainly used and combined to explore the giant planet population at all periods. Our results offer a more global view of the planetary system architecture and physical properties to constrain the relevant formation mechanisms at play. This work was also combined with the modeling of the stellar activity that currently limits the detection performances of close-in planets, as well as with the modeling of planetary atmospheres to interpret and study the key physical processes observed in young planetary atmospheres, such as the formation and sedimentation of clouds, the effect of low-gravity conditions, and of the dynamical mixing and convective motions.

Breakthrough Results: The ANR-GuEPARD project led to various breakthrough discoveries and results between 2011 and mid-2015 including:
• key observational discoveries: the first direct observation of a giant exoplanet revolution around its stellar host in the ß Pictoris system, the first direct evidence of planet disk interaction in a young planetary system in the same system, the image of the lightest exoplanet HD95086b ever imaged, the first detection of a planetary mass companion around a binary star, the discovery of thin dusty ring around the binary HD106906 that hosts a planetary mass companion, the discovery of fast-moving features in the debris disk around AU Microscopii possibly related to interactions between a hidden planet and the disk,
• key astrophysical studies: the creation of a reference near-IR spectral library of young exoplanets and brown dwarfs, one of the first comparative study of the occurrence of giant planets at wide orbits with predictions of planetary formation theories, the first search for close-in giant exoplanets at short periods around young stars, a serie of dedicated papers on the impact of activity for the detection of Earth-like planets,
• key modeling developments: the development of Hydrodynamics Radiative simulations in 2D and 3D and of clouds formation model including the most up-to-date physical processes at play (super-saturation, nucleation, condensation, sedimentation, size distribution effects, impact of convection) to model cool atmospheres on a large range of physical conditions (effective temperature, pressure, metallicity) for low-mass stars to brown dwarfs and exoplanets.

Key results obtained during our ANR have been published and presented in international conferences. Our work strengthened our leadership on a very competitive international scene, enabled us to optimally exploit current instrumentation dedicated to direct imaging and radial velovity studies, finally to prepare the future exploitation of upcoming instruments and spatial missions dedicated to explore the origin and the physics of giant exoplanets and planetary architectures.

Scientific Publications and Outreach: Our project success can be quantified by more than 110 publications in international journals (A&A, ApJ, Nature, Science, SPIE), including 44 publications involving several partners, the participation to more the 50 international and national conferences to present our results including up to 17 invited reviews, more than 10 national and international press releases, finally various public outreach communications.

Since the discovery of the first EGP around the star 51 Peg in 1995, our understanding of the origin and properties of EGPs has fundamentally evolved. The existence of Hot Jupiters has revealed the premise of an unexpected variety of planetary systems. Planetary systems have been confirmed to not be rare. Their occurrence actually depends on the host star properties such as the metallicity, and possibly the mass and the multiplicity. Multiple planetary systems have been discovered. The atmosphere and the structure of giant irradiated planets have even been probed and studied. Finally, the ultimate performances of current instrumentation led to the discovery of telluric planets or Super-Earths. However, despite this success, fundamental questions remain to be answered about their formation, their evolution and the physics of their interior and atmosphere. We still do not know if several formation mechanisms can operate at different location around the star or how they depend on the stellar properties such as mass and multiplicity. During our ANR05 program, data processing and analysis tools have been developed and demonstrated for the detection and characterization of giant planets using both direct imaging and radial velocity observing techniques. Whereas radial velocity is nowadays the most successful technique to detect close-in EGPs at short periods, less than 10 years, direct imaging is unique for the detection and the characterization of wide orbit giant planets through the analysis of actual planetary photons. Based on this program our expertise has been more than confirmed with the discoveries of the first planetary mass companion in direct imaging, the first close-in giant planet around a massive star, the characterization of the stellar activity impact on planet surveys and the development of dynamical atmosphere models. On a very competitive international scene and in the perspective of the next generation of planet finder instruments (SPHERE and ESPRESSO at VLT), our ANR10-GuEPARD project, for “Giant Exo-Planet Atmosphere, oRigins and Dynamics”, aims at strengthening our leadership in the field of giant planet detection and characterization. We want to initiate a phase of systematic multi-techniques observations and characterization of the environment of nearby stars. We will fully exploit our expertise to provide invaluable constraints to model the large variety of properties for EGPs, including their frequency, their physical and orbital characteristics (distribution of mass, period and eccentricity). We will probe the diversity of the planetary systems and study the evolution of their properties with the star characteristics (metallicity, lithium abundance, multiplicity, age and mass). Finally, the use of direct imaging will enable us to witness the first phases of planetary formation and evolution directly into the planetary disks. Based on a solid expertise developed during our prvious project and in the perspective of future planet finder instruments, our project is a mandatory step that will lead to a more global view and understanding of the formation and the physics of giant planets.