We present observations of the HD 15115 debris disk from ALMA at 1.3 mm that capture this intriguing system with the highest resolution ( 0 \farcs 6 or 29 AU ) at millimeter wavelengths to date .
This new ALMA image shows evidence for two rings in the disk separated by a cleared gap .
By fitting models directly to the observed visibilities within a MCMC framework , we are able to characterize the millimeter continuum emission and place robust constraints on the disk structure and geometry .
In the best-fit model of a power law disk with a Gaussian gap , the disk inner and outer edges are at 43.9 \pm 5.8 AU ( 0 \farcs 89 \pm 0 \farcs 12 ) and 92.2 \pm 2.4 AU ( 1 \farcs 88 \pm 0 \farcs 49 ) , respectively , with a gap located at 58.9 \pm 4.5 AU ( 1 \farcs 2 \pm 0 \farcs 10 ) with a fractional depth of 0.88 \pm 0.10 and a width of 13.8 \pm 5.6 AU ( 0 \farcs 28 \pm 0 \farcs 11 ) .
Since we do not see any evidence at millimeter wavelengths for the dramatic east-west asymmetry seen in scattered light , we conclude that this feature most likely results from a mechanism that only affects small grains .
Using dynamical modeling and our constraints on the gap properties , we are able to estimate a mass for the possible planet sculpting the gap to be 0.16 \pm 0.06 M _ { \text { Jup } } .