Highly accurate photometry of the optical companion in $\gamma$-ray binary systems
has the potential to enable the exploration of previously unknown phenomena.
Here we report the discovery of repeated optical flares evolving on time scales of
about one day in the optical light curve of the well known system LS I +61 303. Their amplitude
does not exceed 0.01-0.02 magnitudes and, therefore, they are only within reach of
space observatories such as the Transiting Exoplanet Survey Satellite (TESS) in the
600-1000 nm bandpass. We tentatively propose that these flaring events are shock-powered
in nature as the compact object in LS I +61303 interacts with the circumstellar envelope of its Be star companion. TESS results dealing with other systems (MWC 148, MWC 656 and HD 3191) are also shortly addressed.