  Irrotational relativistic vortex configurations in uniform subsonic motion
with respect to a surrounding perfect fluid are analysed for the purpose of
application to superfluid layers in neutron stars. Asymptotic solutions are
found by asymptotically expanding the flow equation at large distances from the
vortex core and then by solving it order by order. The asymptotic effective
tension and energy density that are needed for an averaged macroscopic
description are thus obtained as functions of the vortex velocity, the vortex
circulation, the asymptotic chemical potential and of parameters depending on
the equation of state.
