# Multiple Rings of Millimeter Dust Emission in the HD 15115 Debris Disk

## TL;DR

High-resolution ALMA observations of the HD 15115 debris disk reveal two rings separated by a gap, providing insights into disk structure and potential planetary influence, with no millimeter evidence for the asymmetry seen in scattered light.

## Contribution

First millimeter-wave high-resolution imaging of HD 15115 revealing detailed disk structure and a gap, constraining potential planet mass and disk morphology.

## Key findings

- Disk inner edge at ~44 AU, outer edge at ~92 AU.
- A gap at ~59 AU with high fractional depth.
- Estimated planet mass sculpting the gap is ~0.16 Jupiter masses.

## Abstract

We present observations of the HD 15115 debris disk from ALMA at 1.3 mm that capture this intriguing system with the highest resolution ($0.\!\!^{\prime\prime}6$ 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 $43.9\pm5.8$ AU ($0.\!\!^{\prime\prime}89\pm0.\!\!^{\prime\prime}12$) and $92.2\pm2.4$ AU ($1.\!\!^{\prime\prime}88\pm0.\!\!^{\prime\prime}49$), respectively, with a gap located at $58.9\pm4.5$~AU ($1.\!\!^{\prime\prime}2\pm0.\!\!^{\prime\prime}10$) with a fractional depth of $0.88\pm0.10$ and a width of $13.8\pm5.6$ AU ($0.\!\!^{\prime\prime}28\pm0.\!\!^{\prime\prime}11$). 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 $0.16\pm0.06$ $M_\text{Jup}$.