The Stability of Planets in the Alpha Centauri system
  This paper investigates the long-term orbital stability of small bodies near the central binary of the Alpha Centauri system. Test particles on circular orbits are integrated in the field of this binary for 32000 binary periods or approximately 2.5 Myr. In the region exterior to the binary, particles with semi-major axes less than roughly three times the binary's semi-major axis are unstable. Inside the binary, particles are unstable if further than 0.2 binary semimajor axes from the primary, with stablility closer in a strong function of inclination: orbits inclined near 90 degrees are unstable in as close as 0.01 binary semimajor axes from either star. 
Paul A. Wiegert (University of Toronto), Matt Holman (Canadian   Institute for Theoretical Astrophysics)