Cleaning the TESS observations of WASP-33 b transits from the host star photometric variability

Based on the TESS observations of a $\delta$ Scuti variable WASP-33 obtained in 2019 and 2022, we thoroughly investigate the power spectrum of its photometric flux and construct a statistically exhaustive model for its variation. This model contains 30 robustly justified harmonics, the red noise, and quasiperiodic noise components. This compound model allows us to greatly improve the transit timing accuracy of the exoplanet WASP-33 b. The rms of its transit timing variation residuals is drastically reduced by a factor of 3.5, from 63 s to 18 s.