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

TL;DR

This study analyzes the pulsation patterns of the star WASP-33, revealing tidally perturbed modes influenced by its exoplanet, and confirms its hybrid pulsator nature through gravity-darkened stellar modeling.

Contribution

It demonstrates the impact of star-planet interactions on stellar pulsations and incorporates gravity darkening into the analysis of a misaligned exoplanet system.

Findings

Identification of tidally perturbed pulsation modes near orbital harmonics

WASP-33 confirmed as a gamma Dor - delta Sct hybrid pulsator

Transit modeling supports gravity darkening and consistent planetary parameters

Abstract

WASP-33 is one of the few $\delta$ 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. We made use of the Transit and Light Curve Modeller (TLCM) to solve the light curve from the Transiting Exoplanet Survey Satellite (TESS). We include gravity darkening into our analysis. 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 $3$rd, $12$th and $25$th orbital harmonics ($f_{orb} \sim 0.82$ d$^{-1}$). Also, there is a prominent overabundance of pulsational frequencies rightwards of the orbital harmonics, being 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 $\delta$ Sct and $\gamma$ Dor ranges of the Fourier spectrum, implying that WASP-33 is a $\gamma$ Dor -- $\delta$ 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.