  Debris disks are tenuous, dusty belts surrounding main sequence stars
generated by collisions between planetesimals. HD 206893 is one of only two
stars known to host a directly imaged brown dwarf orbiting interior to its
debris ring, in this case at a projected separation of 10.4 au. Here we resolve
structure in the debris disk around HD 206893 at an angular resolution of 0.6"
(24 au) and wavelength of 1.3 mm with the Atacama Large
Millimeter/submillimeter Array (ALMA). We observe a broad disk extending from a
radius of <51 au to 194^{+13}_{-2} au. We model the disk with a continuous,
gapped, and double power-law model of the surface density profile, and find
strong evidence for a local minimum in the surface density distribution near a
radius of 70 au, consistent with a gap in the disk with an inner radius of
63^{+8}_{-16} au and width 31^{+11}_{-7} au. Gapped structure has been observed
in four other debris disks -- essentially every other radially resolved debris
disk observed with sufficient angular resolution and sensitivity with ALMA --
and could be suggestive of the presence of an additional planetary-mass
companion.

Earth and Planetary Astrophysics;Solar and Stellar Astrophysics