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Session 53 - SNs, Planetaries and Circumstellar Disks.
Display session, Wednesday, June 10
Atlas Ballroom,
Many nearby otherwise normal main sequence stars have far-IR excesses attributable to orbiting circumstellar grains. It is clear that the grains must be second-generation grains released from larger parent bodies such as asteroids or comets because the grain lifetimes are much shorter than the system ages. In the well-known prototypes \alpha Lyr, \alpha Piscis Australis, \beta Pictoris and \epsilon Eridani, the circumstellar disks appear to be comparable in scale to the Kuiper Belt of our solar system and to contain relatively empty central regions with sizes similar to the planetary zone of our system.
We present new models for the 4 prototype disks and 6 other systems using the best available information on the far-IR angular sizes plus spectral energy distributions from IRAS and other photometric data. Our analyses of the source sizes include convolution of source models with IRAS diffraction functions and detector spatial response maps.
The general trends seen in the prototypes extend to the fainter systems: grains smaller than 100 \mum lying a few 10s to 100s of AU from the central stars, with optical depths more than 10^2 times that of our system's zodiacal cloud, and with deficits of warm emission implying significant central low-density regions.
