EVOLUTION OF DUST IN CIRCUMSTELLAR DISKS

it is now established that premain sequence stars are often surrounded by circumstellar disks, some of which are thought to be protoplanetary disks. we propose to study the evolution of the dust in the disks by studying the co and co2 absorption bands in dust grains. since co2 is produced by surface processing of co, the abundance of co2 with respect to co is a direct measure of the amount of surface processing undergone by the grains. our spectra will cover the 4.27 micron band, by far the strongest fundamental band of co2. this band has been inobservable until now because it is located in a region completely inaccessible to groundbased telescopes and airborne platforms. iso provides the first opportunity to study co2 in dust grains. our proposed research differs from the guaranteed time proposals in that our observations will provide the high resolution spectra necessary for modeling. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]