Examples for planet-to-star interactions

Planet-star interactions are considered to have a Janus-faced character. Most of the known forms belong to star-to-planet interactions, for which well-known examples are the stellar irradiation, rotation and stellar activity affecting the planet. We can only rarely see planet-to-star scenarios, mostly because of the smaller planets can less affect the stellar physics. In this talk, we review three examples for such scenarios, including commensurabilities between the stellar spin and the planetary orbit, excitation of stellar activity, and stellar oscillations suffering planetary perturbations. The observational basis of our examples, Kepler-13A, AU Mic and WASP-33 also cover the three major exoplanet missions: Kepler, CHEOPS and TESS, nicely showing how the space-based exoplanet photometry started revealing the (almost) hidden face of Janus.