# High Fidelity Imaging of the Inner AU Mic Debris Disk: Evidence of Differential Wind Sculpting?

## TL;DR

This study uses high-resolution HST imagery and TESS photometry to analyze the AU Mic debris disk, revealing a loop-like feature and suggesting that stellar wind and magnetic field misalignment influence disk sculpting.

## Contribution

It provides the first high-fidelity optical imaging of the inner AU Mic debris disk and proposes a novel wind sculpting mechanism linked to stellar magnetic field orientation.

## Key findings

- Discovery of a loop-like feature at 14.2 au in the disk.
- Evidence of starspot complexes and magnetic axis offset.
- Implication of stellar wind influence on disk morphology.

## Abstract

We present new high fidelity optical coronagraphic imagery of the inner $\sim$50 au of AU Mic's edge-on debris disk using the BAR5 occulter of the Hubble Space Telescope Imaging Spectrograph (HST/STIS) obtained on 26-27 July 2018. This new imagery reveals that "feature A", residing at a projected stellocentric separation of 14.2 au on SE-side of the disk, exhibits an apparent "loop-like" morphology at the time of our observations. The loop has a projected width of 1.5 au and rises 2.3 au above the disk midplane. We also explored TESS photometric observations of AU Mic that are consistent with evidence of two starspot complexes in the system. The likely co-alignment of the stellar and disk rotational axes breaks degeneracies in detailed spot modeling, indicating that AU Mic's projected magnetic field axis is offset from its rotational axis. We speculate that small grains in AU Mic's disk could be sculpted by a time-dependent wind that is influenced by this offset magnetic field axis, analogous to co-rotating Solar interaction regions that sculpt and influence the inner and outer regions of our own Heliosphere. Alternatively, if the observed spot modulation is indicative of a significant mis-alignment of the stellar and disk rotational axes, we suggest the disk could still be sculpted by the differential equatorial versus polar wind that it sees with every stellar rotation.