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J. E. Krist (JPL), D. R. Ardila, D. A. Golimowski (JHU), M. Clampin (NASA-GSFC), H. Ford (JHU), G. D. Illingworth (UCO-Lick), G. Hartig (STScI), ACS Science Team
We present BVI multicolor images of the AU Microscopii debris disk taken with the Advanced Camera for Surveys coronagraph on the Hubble Space Telescope. AU Mic is a ~ 12 Myr-old M dwarf at a distance of 10 pc and is a member of the \beta Pictoris association. The optically-thin disk is viewed edge-on and can be seen to within 0.75'' (7.5 AU) of the star in the ACS images. The radial surface brightness profile indicates that there is a central clearing within 12 AU of the star, in agreement with thermal emission measurements. The clearing, along with small, localized variations in the apparent dust concentration, suggests a possible substellar perturber. The disk appears bowed at outer radii, and modelling indicates that this is due to a ~3\circ tilt along the line of sight of the outer disk from edge-on combined with foward scattering by the dust. The inner disk is within 1\circ of edge-on. The reflected light from the dust is bluer than the stellar light. This may indicate that there is a relative surplus of smaller grains compared to the grain size distributions in other debris disks, which appear either neutral or red compared to their stars. The surplus may be due to the lack of radiation pressure that would expel small grains in disks around more luminous stars.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.