Properties of the radio jet emission of four gamma-ray Narrow Line
  Seyfert 1 galaxies
  The detection of gamma rays from a small number of Narrow Line Seyfert 1
galaxies by the LAT instrument onboard Fermi seriously challenged our
understanding of AGN physics. Among the most important findings associated with
their discovery has been the realisation that smaller-mass black holes seem to
be hosted by these systems. Immediately after their discovery a radio multi-
frequency monitoring campaign was initiated to understand their jet radio
emission. Here the first results of the campaign are presented. The light
curves and some first variability analyses are discussed, showing that the
brightness temperatures and Doppler factors are moderate. The phenomenologies
are typically blazar-like. The frequency domain on the other hand indicates
intense spectral evolution and the variability patterns indicate mechanisms
similar to those acting in the jets of BL Lacs and FSRQs. Finally, the linear
polarisation also reveals the presence of a quiescent, optically thin jet in
certain cases.
