Left panel: predicted evolution of the surface velocity as a function of the surface gravity for 1.7 M_⊙ stellar models along the red giant branch with and without planet engulfment. Different initial rotations on the ZAMS are considered for models without engulfment: Ω_ini/ Ω_crit = 0.3, 0.5, 0.6, 0.7, 0.8, 0.9, and 0.95 (alternate black continuous and dashed lines). The time-averaged surface velocities during the main-sequence phase of the models vary between about 30 and 240 km s^-1. The model with planet engulfment (blue continuous line, the dotted blue line is the model without engulfment) initially had Ω_ini/ Ω_crit =0.1 and a 15 M_J planet orbiting at a distance equal to 0.5 au. The engulfment occurs when the surface gravity of the star is around 2.2. Right panel: evolution of the Rossby number as a function of the surface gravity for the same stellar models along the red giant branch with and without a planet engulfment.