  Stable massive neutral particles emitted by astrophysical sources undergo
deflection under the gravitational potential of our own galaxy. The deflection
angle depends on the particle velocity and therefore non-relativistic particles
will be deflected more than relativistic ones. If these particles can be
detected through neutrino telescopes, cosmic ray detectors or directional dark
matter detectors, their arrival directions would appear aligned on the sky
along the source-lens direction. On top of this deflection, the arrival
direction of non-relativistic particles is displaced with respect to the
relativistic counterpart also due to the relative motion of the source with
respect to the observer; this induces an alignment of detections along the sky
projection of the source trajectory. The final alignment will be given by a
combination of the directions induced by lensing and source proper motion. We
derive the deflection-velocity relation for the Milky Way halo and suggest that
searching for alignments on detection maps of particle telescopes could be a
way to find new particles or new astrophysical phenomena.
