20 s Cadence TESS Photometry of HR 8799

Abstract 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.