AAS 205th Meeting, 9-13 January 2005
Session 11 Brown Dwarfs and Exoplanets
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

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[11.20] The Diversity of Debris Disks Around A Stars

G. H. Rieke, K. Y. S. Su, J. A. Stansberry, D. Trilling (University of Arizona), G. Bryden (Jet Propulsion Laboratory), J. Muzerolle, E. T. Young (University of Arizona), C. A. Beichman, K. R. Stapelfeldt (Jet Propulsion Laboratory)

Combined Spitzer, ISO, and IRAS observations now characterize nearly 300 debris disks around stars of about 2.5 solar masses. A surprising result is that these systems display a huge range of properties. For example, their spectral energy distributions between 24 and 70 microns have a wide range slopes, and the slopes show no recognizable pattern as a function of the stellar age, or other parameters that might be relevant. Some of the systems contain large amounts of small dust grains, even close to the star. In these cases, the lifetime of the grains is short, and for them to dominate the radiometric properties of the system requires a very high replenishment rate. In the cases of beta Pic and Vega, detailed models indicate that small grains are being ejected by radiation pressure, a process that acts over a time scale of 1000 years or less. In such cases, estimates of the mass requirements for continuous replenishment of the grains over the life of the star suggest that the total would be forbiddingly large. We interpret these systems, and the variety of debris disk properties generally, in terms of recent models that suggest that the radiometric properties of such systems may be dominated over a significant fraction of the life of the star by the results of single, catastrophic planetestimal collisions.

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