Time Domain Coronagraphy: Diagnosing the Stripping of AU Mic's Debris Disk
Résumé
Boccaletti et al. 2015 discovered sub-structures moving within the starlight-scattering AU Mic (M1V, d = 9.79 pc, 23±3 Myr) debris disk at super-Keplerian tangential velocities in spatially resolved imagery of the disk. To date, these are the only moving features seen in spatially resolved imagery of any debris disk. The surface brightness, number, morphology, and velocities of these moving features constrain their physical location and mass, and thus are critical quantities needed to elucidate the origin of this dynamical phenomenon. We are now following up our epoch 2010/2011 and 2017/2018 HST/STIS visible-light coronagraphic observations of the AU Mic disk (Schneider et al. 2014, Wisniewski et al. 2019; HST/GO programs 12228 and 15219, respectively), in three contiguous HST cycles just commenced by investigating the multiple feature temporal evolution with revisits to the system at six epochs over the next three years (initially HST/GO 15907 in cycle 27). With these new observations we aim to determine: (a) What are the surface brightnesses of all features, and how do the surface brightness and morphology of features change over time? b) What are the detailed vertical motions of the features? c) Do the amplitudes of the motions depend on stellocentric distance? c) What are the motions of the newly discovered features (NW-gamma and NW-delta) on the NW-side of the disk? These data will be used to test hypotheses that suggest such features may be caused by the stellar wind expelling grains originating from a parent body that orbits at 8±2 au (Sezestre et al. 2017) or by interaction between the star's wind and repeated dust avalanche events (Chiang & Fung 2017). Herein we summarize the program plan for the next three years and report on preliminary observational results from the first epoch of anticipated observations (if executed prior to this meeting).