Gravity darkening and tidally perturbed stellar pulsation in the misaligned exoplanet system WASP-33

Abstract

Aims. WASP-33 is one of the few δ Sct stars with a known planetary companion. By analyzing the stellar oscillations, we search for possible star-planet interactions in the pattern of the pulsation. Methods. We made use of the Transit and Light Curve Modeller to solve the light curve from the Transiting Exoplanet Survey Satellite. We include gravity darkening in our analysis. Results. The stellar oscillation pattern of WASP-33 clearly shows signs of several tidally perturbed modes. We find that there are peaks in the frequency spectrum that are at or near the 3rd, 12th, and 25th orbital harmonics (forb ∼ 0.82 d−1). Also, there is a prominent overabundance of pulsational frequencies rightward of the orbital harmonics, a characteristic of a tidally perturbed stellar pulsation, which is an outcome of star-planet interactions in the misaligned system. There are peaks in both the δ Sct and γ Dor ranges of the Fourier spectrum, implying that WASP-33 is a γ Dor – δ Sct hybrid pulsator. The transit light curves are best fitted by a gravity-darkened stellar model, and the planet parameters are consistent with earlier determinations.