GRAIN DYNAMICS IN DEBRIS DISKS: CONTINUOUS OUTWARD FLOWS AND EMBEDDED PLANETS

This study employs grain dynamic models to examine the density distribution of debris disks, and discusses the effects of the collisional time intervals of asteroidal bodies, the maximum grain sizes, and the chemical compositions of the dust grains of the models, in order to find out whether a steady outmoving flow with an l/R profile could be formed. The results showed that a model with new grains every 100 years, a smaller maximum grain size, and a composition C400 has the best fit to the l/R profile because: (1) the grains have larger values of β on average, therefore, they can be blown out easily and (2) the new grains are generated frequently enough to replace those that have been blown out. With the above two conditions, some other models can have a steady out-moving flow with an approximate l/R profile. However, those models in which new grains are generated every 1000 years have density distributions far from the profile of a continuous out-moving flow. Moreover, the analysis on the signatures of planets in debris disks showed that there are no indications when a planet is in a continuous out-moving flow, however, the signatures are obvious in a debris disk with long-lived grains.