  Aims. We aim to study the structure and kinematics of the two filaments
inside the subsonic core Barnard 5 in Perseus using high-resolution ($\approx$
2400 au) NH3 data and a multi-component fit analysis.
  Methods. We used observations of NH3 (1,1) and (2,2) inversion transitions
using the Very Large Array (VLA) and the Green Bank Telescope (GBT). We
smoothed the data to a beam of 8'' to reliably fit multiple velocity components
towards the two filamentary structures identified in B5.
  Results. Along with the core and cloud components, which dominate the flux in
the line of sight, we detected two components towards the two filaments showing
signs of infall. We also detected two additional components that can possibly
trace new material falling into the subsonic core of B5.
  Conclusions. Following comparison with previous simulations of filament
formation scenarios in planar geometry, we conclude that either the formation
of the B5 filaments is likely to be rather cylindrically symmetrical or the
filaments are magnetically supported. We also estimate infall rates of
$1.6\times10^{-4}\,M_\odot\,yr^{-1}$ and $1.8\times10^{-4}\,M_\odot\,yr^{-1}$
(upper limits) for the material being accreted onto the two filaments. At these
rates, the filament masses can change significantly during the core lifetime.
We also estimate an upper limit of $3.5\times10^{-5}\,M_\odot\,yr^{-1}$ for the
rate of possible infall onto the core itself. Accretion of new material onto
cores indicates the need for a significant update to current core evolution
models, where cores are assumed to evolve in isolation.
