  We study the behaviour of heavy inertial particles in the flow field of two
like-signed vortices. In a frame co-rotating with the two vortices, we find
that stable fixed points exist for these heavy inertial particles; these stable
frame-fixed points exist only for particle Stokes number $St<St_{cr}$. We
estimate $St_{cr}$ and compare this with direct numerical simulations, and find
that the addition of viscosity increases the $St_{cr}$ slightly. We also find
that the fixed points become more stable with increasing $St$ until they
abruptly disappear at $St=St_{cr}$. These frame-fixed points are between fixed
points and limit cycles in character.
