Program: GS-2005A-Q-2

We propose to image with T-ReCS, using payback ("guaranteed") time, at 10 and 18 microns a sample of 14 circumstellar debris disks observed by Rieke et al. using Spitzer. These observations, along with proposed MICHELLE open-time observations of 10 northern debris disks also observed by Rieke et al., will initiate our exploration of the relationship between disk brightness, structure, and the occurrance of catastrophic planetesimal collisions and other types of major events and processes. Our previous Gemini imaging of Beta Pic showed that its debris disk has a strong wavelength-dependent brightness asymmetry, which we attribute to the release into the disk of a distinct population of dust particles by the recent catastrophic breakup of a planetesimal. We have proposed that the sudden increase in the number of particles and/or type of dust particles has caused the Beta Pic disk to flare in brightness, with the central disk asymmetry being a result and important signature of the initially localized event. The Rieke et al. Spitzer sample shows that the 24-micron emission attributable to a debris disk typically decreases with disk age, but within each age bin, they found a large range in the excess, which they propose is associated with stochastic processes, such as collisional planetesimal breakup, in the disks. Our Beta Pic study and that by Rieke et al. suggest that significant relationships may exist between disk mid-IR brightness (due, e.g., to the sudden creation of numerous small particles) and disk structure (e.g., asymmetries). The proposed observations will look at somewhat brighter members of the the Rieke et al. sample to begin to explore the properties of this sample in this new context.