The Evolution and Erosion of AU Mic’s Debris Disk Imaged with Time Series Coronagraphy

Carol Anne Grady, John P. Wisniewski, Glenn H. Schneider, Jean-Charles Augereau, Anthony Boccaletti, John Debes, Dean Hines, Thomas Henning, Christopher Stark, Stephan Laos

<p style="margin: 0px; text-align: justify; font-stretch: normal; font-size: 12px; line-height: normal; font-family: Helvetica;">AU Mic (GJ 803, HD 197481) is one of the most interesting debris disk systems, with two planets, independently moving dust features and a very active, young, M-type star. An HST/STIS coronagraphic time series reveals changes in the SE arm features in shape, surface brightness and surface density, including development of partial cavities in the inner features. The outer features have bubble-like shapes which are partially detached from the midplane, and wings extending 4.5 au above and below the midplane. The NW arm features aren’t seen after 2017. The similar optical and millimeter sizes of the disk halo, and the absence of a trailing particle wake indicate low stellar radiation pressure. The belt is divided into 2 segments by a dark break crossing the midplane. The break moves at 0.1”/yr to the SE, is tilted to the SE above the midplane, but vertical below. This suggests that the sail-like appearance of feature B and the break are caused by a velocity gradient in the stellar wind above the disk midplane.</p><div><br></div>