Short-term variability and mass loss in Be stars VI. Frequency groups in $\gamma$ Cas detected by TESS

In photometry of γ Cas (B0.5 IVe) from the Solar Mass Ejection Imager (SMEI) and the BRIght Target Explorer (BRITE)-Constellation satellites, indications of low-order non-radial pulsation have recently been found, which would establish an important commonality with the class of classical Be stars at large. New photometry with the Transiting Exoplanet Survey Satellite (TESS) has detected three freq...