Resolving Structure in the Debris Disk around HD 206893 with ALMA

TL;DR

This study uses ALMA to resolve and model the debris disk around HD 206893, revealing a gap that suggests potential planetary companions, advancing understanding of disk structures and planet formation.

Contribution

First high-resolution ALMA imaging of HD 206893's debris disk, identifying a significant gap indicative of possible planetary influence.

Findings

Detected a broad debris disk extending from <51 au to 194 au.

Identified a gap at approximately 70 au, with a width of about 31 au.

Gapped structures are common in ALMA-resolved debris disks, hinting at planetary presence.

Abstract

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.