TOI-1710 HARPS-N radial velocity curve

Planets with scaled semi-major axes (a/R*) large enough to be unaffected by tidal alterations (tidally detached), offer a unique opportunity to study the original obliquity in which the system formed. We therefore observed TOI-1710 b (a/R*~36) in-transit using HARPS-N + GIANO-B, collecting high-precision radial velocities to measure the Rossiter-McLaughlin (RM) effect.

Spectral analysis of the H{alpha} and HeI triple lines was also pursued to evaluate atmospheric photoevaporation. Using our knowledge of the star rotation period (21.5+/-0.2d), we estimated a true obliquity of psi=149^+11^_-10_deg, which indicates a retrograde motion and places TOI-1710 b among the most misaligned systems -- and the only one known orbiting a cool star in retrograde motion. The strong misalignment favours a high-eccentricity migration (HEM) origin for this low-density super-Neptune planet in the savanna region, challenging previous findings that claimed a minor role of HEM in this period-radius(-density) domain.