We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant \rho Leo ( HD 91316 ) , deduced with the method of halo photometry .
This light curve reveals a dominant frequency of f _ { rot } = 0.0373 d ^ { -1 } and its harmonics .
This dominant frequency corresponds with a rotation period of 26.8 d and is subject to amplitude and phase modulation .
The K2 photometry additionally reveals multiperiodic low-frequency variability ( < 1.5 d ^ { -1 } ) and is in full agreement with low-cadence high-resolution spectroscopy assembled during 1800 days .
The spectroscopy reveals rotational modulation by a dynamic aspherical wind with an amplitude of about 20 km s ^ { -1 } in the H \alpha line , as well as photospheric velocity variations of a few km s ^ { -1 } at frequencies in the range 0.2 to 0.6 d ^ { -1 } in the Si III 4567Å line .
Given the large macroturbulence needed to explain the spectral line broadening of the star , we interpret the detected photospheric velocity as due to travelling super-inertial low-degree large-scale gravity waves with dominant tangential amplitudes and discuss why \rho Leo is an excellent target to study how the observed photospheric variability propagates into the wind .