DOES THE DEBRIS DISK AROUND HD 32297 CONTAIN COMETARY GRAINS?Based on observations made at the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: the University of Arizona on behalf of the Arizona University system; Istituto Nazionale di Astrosica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; the Ohio State University, and the Research Corporation, on behalf of the University of Notre Dame, University of Minnesota and University of Virginia., Based on observations made using the Large Binocular Telescope Interferometer (LBTI). LBTI is funded by the National Aeronautics and Space Administration as part of its Exoplanet Exploration program.

We present an adaptive optics imaging detection of the HD 32297 debris disk at L′ (3.8 μm) obtained with the LBTI/LMIRcam infrared instrument at the Large Binocular Telescope. The disk is detected at signal-to-noise ratio per resolution element ∼3-7.5 from ∼0.″3 to 1.″1 (30-120 AU). The disk at L′ is bowed, as was seen at shorter wavelengths. This likely indicates that the disk is not perfectly edge-on and contains highly forward-scattering grains. Interior to ∼50 AU, the surface brightness at L′ rises sharply on both sides of the disk, which was also previously seen at Ks band. This evidence together points to the disk containing a second inner component located at ≲50 AU. Comparing the color of the outer (50 <r/AU <120) portion of the disk at L′ with archival Hubble Space Telescope/NICMOS images of the disk at 1-2 μm allows us to test the recently proposed cometary grains model of Donaldson et al. We find that the model fails to match this disk's surface brightness and spectrum simultaneously (reduced chi-square = 17.9). When we modify the density distribution of the model disk, we obtain a better overall fit (reduced chi-square = 2.87). The best fit to all of the data is a pure water ice model (reduced chi-square = 1.06), but additional resolved imaging at 3.1 μm is necessary to constrain how much (if any) water ice exists in the disk, which can then help refine the originally proposed cometary grains model. [ABSTRACT FROM AUTHOR]