Evolution in the AU Microscopii Debris Disk
          Stanimir Metchev, Caltech
          Joshua Eisner, Caltech
          Lynne Hillenbrand, Caltech
          Sebastian Wolf, Max-Planck, Heidelberg, Germany
          We discuss multi-wavelength high-contrast scattered light observations of the debris disk around the nearby young star AU Mic.  From its 0.6 - 1.6 micron color, the disk shows evidence for decreasing grain size with increasing orbital radius.  The trend is reflected in a gradually steepening surface brightness profile - a feature also observed in the beta Pic debris disk.  From the apparent homology between the two systems, and from the scaling of their physical parameters, we infer that the trend is due to dynamical evolution of the disk on the Poynting-Robertson and/or collisional time scale.
          From modeling of the combined multi-wavelength imaging and spectral energy distribution data for AU Mic, we constrain the radius of the inner clearing in the disk to approximately 10 AU.  Inner disk radii as small as 1 AU are also possible however, indicating that absence of 10-25 micron excess may not be a reliable indicator of the lack of warm dust in debris disks.