Transits of PH3 b, c, and d through January, 2019

We report the discovery of one newly confirmed planet (P=66.06 days, R_P_=2.68+/-0.17 R_{Earth}_) and mass determinations of two previously validated Kepler planets, Kepler-289 b (P=34.55 days, R_P_=2.15+/-0.10 R_{Earth}_) and Kepler-289-c (P=125.85 days, R_P_=11.59+/-0.10 R_{Earth}_), through their transit timing variations (TTVs). We also exclude the possibility that these three planets reside in a 1:2:4 Laplace resonance.

The outer planet has very deep (~1.3%), high signal-to-noise transits, which puts extremely tight constraints on its host star's stellar properties via Kepler's Third Law. The star PH3 is a young (~1 Gyr as determined by isochrones and gyrochronology), Sun-like star with M_*_=1.08+/-0.02 M_{sun}_, R_*_=1.00+/-0.02 R_{sun}_, and T_eff_=5990+/-38 K. The middle planet's large TTV amplitude (~5 hr) resulted either in non-detections or inaccurate detections in previous searches.