  We investigate theoretically the motion of tiny heavy passive particles
transported in a plane inviscid flow consisting of two point vortices, in order
to understand particle dispersion and trapping during vortex interaction. In
spite of their large density, particles are not necessarily centrifugated away
from vortices. It is observed that they can have various equilibrium positions
in the reference frame rotating with the vortices, provided the particle
response time and the vortex strength ratio lie in appropriate ranges. A
stability analysis reveals that some of these points can be asymptotically
stable, and can therefore trap particles released in their basin of attraction.
A complete trapping diagram is derived, showing that any vortex pair can
potentially become a dust trap, provided the vortex strength ratio is different
from 0 (single vortex) and -1 (translating symmetrical vortices). Trapping
exists for both co-rotating or contra-rotating vortex pairs. In the latter
case, particle trapping on a limit cycle is also observed, and confirmed by
using Sapsis and Haller's method [Chaos, 20, 017515, 2010] generalized to
non-inertial reference frames.
