Stellar encounters with the beta Pictoris planetesimal system

We use data from the Hipparcos catalog and the Barbier-Brossat & Figon cata log of stellar radial velocities to test the hypothesis that the beta Pic p lanetesimal disk was disrupted by a close stellar encounter. We trace the s pace motions of 21,497 stars and discover 18 that have passed within 5 pc o f beta Pic in the past 1 Myr. beta Pie's closest encounter is with the K2 U T star HIP 27628 (similar to0.6 pc), but dynamically the most important enc ounter is with the F7 V star HIP 23693 (similar to0.9 pc). We calculate the velocity and eccentricity changes induced by the 18 perturbations and conc lude that they are dynamically significant if planetesimals exist in a beta Pic Oort cloud. We provide a first-order estimate for the evolutionary sta te of a beta Pic Oort cloud and conclude that the primary role of these ste llar perturbations would be to help build a comet cloud rather than destroy a preexisting structure. The stellar sample is similar to 20% complete and motivates future work to identify less common close interactions that woul d significantly modify the observed circumstellar disk. For future radial v elocity study, we identify six stars in the Hipparcos catalog that may have approached beta Pic to within 0.1 pc and therefore remain as candidate dis k perturbers.