# HD 106906: A Case Study for External Perturbations of a Debris Disk

## TL;DR

This study investigates how an exterior planetary-mass object can influence the shape of a debris disk, using HD 106906 as a case example, highlighting the importance of considering external perturbers in disk morphology analysis.

## Contribution

It demonstrates that external companions can cause observable asymmetries in debris disks, expanding the understanding of disk-perturber interactions beyond interior planets.

## Key findings

- The observed disk asymmetry is consistent with perturbations from the exterior companion.
- External perturbers can significantly influence debris disk morphology.
- Models including external perturbers better explain observed disk features.

## Abstract

Models of debris disk morphology are often focused on the effects of a planet orbiting interior to or within the disk. Nonetheless, an exterior planetary-mass perturber can also excite eccentricities in a debris disk, via Laplace-Lagrange secular perturbations in the coplanar case or Kozai-Lidov perturbations for mutually inclined companions and disks. HD 106906 is an ideal example of such a system, as it harbors a confirmed exterior 11 M_Jup companion at a projected separation of 650 au outside a resolved, asymmetric disk. We use collisional and dynamical simulations to investigate the interactions between the disk and the companion, and to use the disk's observed morphology to place constraints on the companion's orbit. We conclude that the disk's observed morphology is consistent with perturbations from the observed exterior companion. Generalizing this result, we suggest that exterior perturbers, as well as interior planets, should be considered when investigating the cause of observed asymmetries in a debris disk.