The WINE survey. A transiting 100-day exo-Saturn with a companion in the Habitable Zone

The Warm gIaNts with tEss collaboration (WINE) is at the forefront of detecting, confirming, and characterizing long-period giant exoplanets from TESS. These warm giants provide a key population to constrain planet formation and evolution theories. Our systematic search for transits (including single transits) in the TESS light curves has given rise to hundreds of transiting giant candidates with periods larger than 10 days, out to hundreds of days. Our efficient ground-based radial-velocity and photometric follow-up of the southern skies has already confirmed several tens of these candidates.

In this work, we present our latest exciting results, focussing on the spectroscopic confirmation of the warm giant TOI-199 b, which we first identified in TESS photometry as a single transitter. We confirm and characterize the planet using TESS photometry (Sectors 1-13 and 27-36), ground-based photometry from ASTEP in Antarctica, and radial velocities from FEROS, HARPS, CORALIE, and CHIRON. Orbiting a G-type star, TOI-199 b has a 104.83-day period, a mass of 0.12M_J, and a radius of 0.8R_J. It is the first exo-Saturn in this period range with a precisely determined mass and radius. The TESS and ASTEP transits also show strong transit timing variations, pointing to the existence of a second, non-transiting planet in the system. The analysis of the radial velocities and TTVs reveals TOI-199 c to have a period of 279.92 days, and a minimum mass of 0.51M_J. This period places it within the inner edge of the optimistic Habitable Zone.