20 s Cadence TESS Photometry of HR 8799

We analyzed 20 s cadence Transiting Exoplanet Survey Satellite time-series photometry of the exoplanet host star HR 8799 collected in Sector 56. The amplitude spectrum shows Gamma Doradus (γ Dor) pulsations consistent with previous space-based photometry from MOST. Assuming that HR 8799 is a representative of γ Dor stars in the Kepler sample, the dominant dipole mode at 1.98 cycles day^-1 implies a core rotation period of ~0.7 day, which combined with $v\sin i$ and stellar radius measurements would result in a preliminary stellar inclination of ~28° assuming rigid rotation. We find no significant residual photometric variation after removing the pulsation signal aside from a ~9 days trend that is likely a systematic effect or an artifact from performing aggressive frequency subtraction in the presence of red noise.