High-fidelity Imaging of the Inner AU Mic Debris Disk: Evidence of Differential Wind Sculpting?

John P. Wisniewski, Adam F. Kowalski, James R.A. Davenport, Glenn Schneider, Carol A. Grady, Leslie Hebb, Kellen D. Lawson, Jean Charles Augereau, Anthony Boccaletti, Alexander Brown, John H. Debes, Andras Gaspar, Thomas K. Henning, Dean C. Hines, Marc J. Kuchner, Anne Marie Lagrange, Julien Milli, Elie Sezestre, Christopher C. Stark, Christian Thalmann

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

We present new high-fidelity optical coronagraphic imagery of the inner ∼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 2018 July 26-27. This new imagery reveals that "feature A," residing at a projected stellocentric separation of 14.2 au on the southeast 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 Transiting Exoplanet Survey Satellite 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 misalignment of the stellar and disk rotational axes, we suggest that the disk could still be sculpted by the differential equatorial versus polar wind that it sees with every stellar rotation.

Original languageEnglish (US)
Article numberL8
JournalAstrophysical Journal Letters
Volume883
Issue number1
DOIs
StatePublished - Sep 20 2019
Externally publishedYes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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