  Planets are thought to form at the early stage of stellar evolution when the
mass accretion is still ongoing. RY Tau is a T Tauri type star at the age of a
few Myr, with accretion disc seen at high inclination, so that line of sight
crosses both the wind and the accretion gas flows. In a long series of
spectroscopic monitoring of the star in 2013-2020, we detected variations in
H-alpha and NaI D absorptions at radial velocities of infall (accretion) and
outflow (wind) with a period of about 22 days. The absorptions in the infalling
and the outflowing gas streams vary in anti-phase: an increase of infall is
accompanied by a decrease of outflow, and vice versa. These flip-flop
oscillations retain phase over several years of observations. We suggest that
this may result from the MHD processes at the disk-magnetosphere boundary in
the propeller mode. Another possibility is that a massive planet modulates some
processes in the disc and provides the observed effects. The period, if
Keplerian, corresponds to a distance of 0.2 AU, which is close to the dust
sublimation radius in this star. The presence of the putative planet may be
confirmed by radial velocity measurements: expected amplitude is > 90 m/s if a
planet mass is > 2 Mj.
