Speaker
Description
The discovery of planets orbiting at less than 1 au from their host star and less massive than Saturn in various exoplanetary systems revolutionized our theories of planetary formation. The fundamental question is whether these close-in low-mass planets could have formed in the inner disc interior to 1 au, or whether they formed further out in the planet-forming disk and migrated inwards. Exploring the role of additional giant planet(s) in these systems may help to pinpoint their global formation and evolution. We carried out a direct imaging survey with VLT/SPHERE to look for outer giant planets and brown dwarf companions in 27 systems hosting close-in low-mass planets discovered by radial velocity. Our sample is composed of very nearby (<20pc) planetary systems, orbiting G-, K- and M-type mature stellar hosts. Our final direct imaging detection performances, ranging from 5 to 30 MJup beyond 2 au, were considered together with radial velocity and astrometric sensitivity. We recovered the emblematic very cool T-type brown dwarf GJ229B, but did not find any new bound companion among our 337 point-source detections. Our pilot study (Desgrange et al. 2023) opens the way to a multi-technique approach for the exploration of very nearby exoplanetary systems which will be prime targets for future ground-based and space observatories (ELT, HWO) and also the current JWST observatory.
