  55 Cnc e is a transiting super-Earth (radius $1.88\rm\,R_\oplus$ and mass
$8\rm\, M_\oplus$) orbiting a G8V host star on a 17-hour orbit. Spitzer
observations of the planet's phase curve at 4.5 $\mu$m revealed a time-varying
occultation depth, and MOST optical observations are consistent with a
time-varying phase curve amplitude and phase offset of maximum light. Both
broadband and high-resolution spectroscopic analyses are consistent with either
a high mean molecular weight atmosphere or no atmosphere for planet e. A long
term photometric monitoring campaign on an independent optical telescope is
needed to probe the variability in this system. We seek to measure the phase
variations of 55 Cnc e with a broadband optical filter with the 30 cm effective
aperture space telescope CHEOPS and explore how the precision photometry
narrows down the range of possible scenarios. We observed 55 Cnc for 1.6
orbital phases in March of 2020. We designed a phase curve detrending toolkit
for CHEOPS photometry which allows us to study the underlying flux variations
of the 55 Cnc system. We detected a phase variation with a full-amplitude of
$72 \pm 7$ ppm but do not detect a significant secondary eclipse of the planet.
The shape of the phase variation resembles that of a piecewise-Lambertian,
however the non-detection of the planetary secondary eclipse, and the large
amplitude of the variations exclude reflection from the planetary surface as a
possible origin of the observed phase variations. They are also likely
incompatible with magnetospheric interactions between the star and planet but
may imply that circumplanetary or circumstellar material modulate the flux of
the system. Further precision photometry of 55 Cnc from CHEOPS will measure
variations in the phase curve amplitude and shape over time this year.
