  We study the collisional evolution of km-sized planetesimals in tight binary
star systems to investigate whether accretion towards protoplanets can proceed
despite the strong gravitational perturbations from the secondary star. The
orbits of planetesimals are numerically integrated in two dimensions under the
influence of the two stars and gas drag. The masses and orbits of the
planetesimals are allowed to evolve due to collisions with other planetesimals
and accretion of collisional debris. In addition, the mass in debris can evolve
due to planetesimal-planetesimal collisions and the creation of new
planetesimals. We show that it is possible in principle for km-sized
planetesimals to grow by two orders of magnitude in size if the efficiency of
planetesimal formation is relatively low. We discuss the limitations of our
two-dimensional approach.
