Rapid polarisation variability in the VLBI structure of 0716+714

U. Bach, T.P. Krichbaum, A. Kraus, A. Witzel and J.A. Zensus (MPIfR)

To reveal the origin of the rapid IDV in 0716+714 a multi epoch VSOP
experiment was done in autumn 2000. The array consisted of 12 antennas
including the VLBA, Effelsberg and the HALCA Space antenna. To follow
the short term variability of the source the three epochs were spaced
by six days and by one day.  The resulting maps show a bright core and
a jet oriented to the north.  Simultaneous pointings with the 100m
Effelsberg telescope during the VSOP observations revealed variability
in total intensity and linear polarisation between the epochs. The
analysis of the VLBI data shows that the variations are caused by the
core component of 0716+714. The ground array and the VSOP maps show a
similar decrease of the flux densities in total intensity and linear
polarisation of the core component as the single dish measurements.
Further analysis of the data will help to discriminate whether the
variability is due to intrinsic variation of the source or if it is
introduced by the Inter Stellar Medium (ISM).