Pulsation-driven mass loss observed in action from ground and space

It is believed that pulsation plays a substantial role in the mass loss mechanism operating in Be stars, acting on top of rotation to lift material off the photosphere to feed the circumstellar disks. The causal relation between the combination of different non-radial pulsation modes and mass ejection is already well established. The next step forward will be given when the ejecta, which are the building blocks of the disks, are studied to determine their mass and angular content. To address this question, one must combine observations that probe the photospheric changes (photometry and spectroscopy of photospheric lines) with observations that track the ejecta proper (spectroscopy of emission lines). We are analyzing TESS data for what is by far the largest sample of Be stars observed from space to study their pulsational properties and circumstellar variability. This effort is aided by years of ground-based photometry, archival spectroscopy, and, most importantly, a campaign that is acquiring time-series Echelle spectra simultaneous with TESS observations. With the contemporaneous spectra, we are measuring changes in the photosphere and the evolution of the circumstellar environment at the same time, and establishing links between stellar and circumstellar variability. We find dramatic changes in the spectral features that probe the very inner regions of the disk on timescales of hours and days, which are correlated with signals seen by TESS when stars are actively ejecting material. Studying the star-disk interface in this way is of fundamental importance in understanding the elusive mass ejection mechanism of Be stars.