IS THERE A PLANET AROUND BETA-PICTORIS - PERTURBATIONS OF A PLANET ONA CIRCUMSTELLAR DUST DISK

The beta Pictoris circumstellar disk, like others, seems to exhibit an inner clearing zone, at typical distances of 1-50 AU from the star. W e investigate the possibility that this void is caused by a planet emb edded in the disk. We have implemented on a Connection Machine a code which simultaneously integrates the motions of 8192 particles. These a re submitted to Poynting-Robertson (PR) drag, while being perturbed by a planet orbiting at 20 AU from the star. The free parameters are the planetary mass, the planetary orbital eccentricity, and the particle size. Above a critical planet mass of approximately 10(-5) stellar mas ses (approximately 5 Earth masses, or 1/3 Uranian masses), the planet is able to trap particles in outer mean motion resonances, for time sc ales comparable to, or larger than, the PR decay time. No permament tr apping is observed, however. Once they escape the resonances, the part icles rapidly decay onto the star, on highly eccentric orbits. A moder ate planetary orbital eccentricity (10(-2)) can create large arclike s tructures in the disk. A depleted region corotating with the planet, a nd just outside it, is also observed. We show finally that these proce sses can create a steady state clearing zone extending inside the plan et orbit. We emphasize that the structures excited on the disk by a pl anet could be a way to reveal bodies otherwise invisible by direct ima gery. C 1994 Academic Press, Inc.