Top panel: mean rotation period of Kepler-17 vs. time for our tidal evolution model computed with Q′ = 10⁷ (dotted line) and Q′ = 10⁸ (solid line). The evolution of the stellar spin without any tidal torque and assuming a period of 12.01 days at an age of 1.8 Gyr is plotted as the dot-dashed line. The vertical dashed line indicates the adopted age of the star. Middle panel: as in the top panel, but for the orbit semimajor axis. Lower panel: radius of the star adopted to compute the tidal evolution vs. time.