  We report the discovery of a deep, singular eclipse of the bona fide brown
dwarf Roque 12, a substellar member of the Pleiades. The eclipse was 0.65mag
deep, lasted 1.3h, and was observed with two telescopes simultaneously in
October 2002. No further eclipse was recorded, despite continuous monitoring
with Kepler/K2 over 70d in 2015. There is tentative (2sigma) evidence for
radial velocity variations of 5km/s, over timescales of three months. The best
explanation for the eclipse is the presence of a companion on an eccentric
orbit. The observations constrain the eccentricity to e>0.5, the period to
P>70d, and the mass of the companion to ~0.001-0.04Msol. In principle it is
also possible that the eclipse is caused by circum-sub-stellar material. Future
data releases by Gaia and later LSST as well as improved radial velocity
constraints may be able to unambiguously confirm the presence of the companion.
This would turn the system into one of the very few known eclipsing binary
brown dwarfs with known age.
