Recent discoveries have demonstrated that planetary systems routinely survive the post-main sequence evolution of their host stars , leaving the resulting white dwarf with a rich circumsteller environment .
Among the most intriguing of such hosts is the hot white dwarf GD 394 , exhibiting a unique 1.150 \pm 0.003 d flux variation detected in Extreme Ultraviolet Explorer ( EUVE ) observations in the mid 1990s .
The variation has eluded a satisfactory explanation , but hypotheses include channeled accretion producing a dark spot of metals , occultation by a gas cloud from an evaporating planet , or heating from a flux tube produced by an orbiting iron-cored planetesimal .

We present observations obtained with the Transiting Exoplanet Survey Satellite ( TESS ) of GD 394 .
The space-based optical photometry demonstrates a 0.12 \pm 0.01 % flux variation with a period of 1.146 \pm 0.001 d , consistent with the EUVE period and the first re-detection of the flux variation outside of the extreme ultraviolet .
We describe the analysis of the TESS light curve and measurement of the optical variation , and discuss the implications of our results for the various physical explanations put forward for the variability of GD 394 .