The Kepler light curve of DF Cyg is unparalleled in precision and cadence for any RV Tau star to date spanning a baseline of \sim 4 years and clearly displaying the signature pulsating behavior of alternating deep and shallow minima as well as the long-term trend indicative of an RVb-type variable .
We measure DF Cyg ’ s formal period ( the time interval between two successive deep minima ) to be 49.84 \pm 0.02 days .
The trend in the arrival times emulates that of the long-term period .
There appear to be precisely 16 deep+shallow minima cycles in one long-term cycle , suggesting a long-term cycle period of \approx 795 \pm 5 days .
We argue that binarity may naturally explain the long-term periodicity in DF Cyg .
The spectral energy distribution of DF Cyg features an infrared excess indicative of a disk possibly linked to a binary companion .
From a recent Gaia parallax measurement for DF Cyg , we calculated that it has a distance of 990 \pm 372 pc and a physical radius of R _ { \star } = 10.3 \pm 3.8 R _ { \odot } .
From kinematics and geometric arguments , we argue that the most likely interpretation for the decrease in flux from the long-period maximum to the long-period minimum , as well as the reduction of the short-term pulsation amplitude , is caused by an occulting body such as a disk surrounding DF Cyg and its binary companion .