Program: GS-2005A-Q-34

The ISO mission revealed an array of sharp crystalline silicate emission features longwards of 17um in the spectra of many evolved sources. While some of these objects have O-rich exciting stars, as expected, a surprising number have C-rich exciting stars as well as strong PAH-like features shortwards of 14um - these have been dubbed dual-dust chemistry objects. Current interpretations point to binarity as being a key common thread, with previous evolutionary phases having resulted in the creation of compact disks or tori that harbour the cold crystalline silicates. To confirm this scenario and to distinguish it from alternatives in which the cold crystalline silicates are located in outflows or in Oort Clouds at much larger radii, high spatial resolution spectroscopy in the 20um region is required. Only an 8-m telescope can provide the required angular resolution. We request 24 hours of TReCs time for 10- and 20-um long-slit spectra and direct images of 5 bright sources (from a list of 10 sources) that exhibit strong crystalline silicate features in their 20um ISO spectra.