The following document lists the file abstract/DBACKMAN_DISK_UH1.abs
from catalogue VI/111.
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===================================================================== ===================================================================== We propose a series of studies of an optically thin edge-on disk discovered around the star BD +31 643 in the open cluster and star-forming region IC 348 by our co-investigator Kalas using visual coronagraph imaging. This disk is a large (d > 12000 AU = 40 arcsec) analog to the beta Pic disk, surrounding a close binary pair of B5 main sequence stars. The IR properties of this system are nearly unknown so we are requesting time with all 4 of ISO's instruments. This 2nd-call proposal is an extension of our ISO program RSTENCEL.VEGADIS. The new disk is embedded in a 2x3 arcmin reflection nebulosity that is also powered by the B stars. The disk has a central region with lower surface brightness than an inward extrapolation of the outer disk density, similar in character to the profile of the beta Pic disk (with much larger scale), indicating a central region of significantly depleted dust density. The new disk has optical depth of order 10^-3 to 10^-2, similar to or somewhat larger than beta Pic's. The lifetimes of micron-sized grains at the outer edges of the central zones in the beta Pic and BD +31 643 disks are substantially shorter than the system ages, indicating that the grain disks must be continually replenished, perhaps by collisions of planetesimals or cometary activity. We plan to test via maps at 3 wavelengths with CAM and PHT whether the color temperature and IR surface brightness of the disk are symmetric about the B stars and decrease with radius at rates consistent with expectations for plausible-sized particles, and whether the central depletion reveals itself in the spectral energy distribution. We also plan SWS and LWS spectra in search of clues to composition and excitation of the disk in reflectance.