Validation of TOI-1221 b: A Warm Sub-Neptune Exhibiting Transit Timing Variations around a Sun-like Star

Abstract We present a validation of long-period ( 91.68278 − 0.00041 + 0.00032 days) transiting sub-Neptune planet, TOI-1221 b (TIC 349095149.01), around Sun-like m V = 10.5) star. This is one the few known exoplanets with period >50 days, and belongs to even smaller subset which have bright enough hosts for detailed spectroscopic follow-up. combine Transiting Exoplanet Survey Satellite light curves ground-based time-series photometry from Perth Telescope (0.3 m) Las Cumbres Observatory global telescope network (1.0 analyze transit signals rule out nearby stars as potential false-positive sources. High-contrast imaging Southern Astrophysical Research Gemini/Zorro stellar contaminants. Reconnaissance spectroscopy CHIRON sets planetary scale upper mass limit on object (1.1 3.5 M Jup at 1 σ 3 , respectively) shows no sign binary companion. determine radius ${R}_{{\rm{p}}}={2.91}_{-0.12}^{+0.13}{R}_{\oplus }$?> R p = 2.91 0.12 0.13 ⊕ placing it in regime. With insolation $S={6.06}_{-0.77}^{+0.85}\ {S}_{\oplus S 6.06 0.77 0.85 we calculate moderate equilibrium temperature T eq 440 K, assuming albedo perfect heat redistribution. find probability TRICERATOPS tool FPP 0.0014 ± 0.0003 well other qualitative quantitative evidence support statistical b. significant (>5 ) oscillatory timing variations, likely indicative an additional nontransiting planet.