Multifrequency study of a double-double radio galaxy J1706+4340
  We report the outcome of multifrequency radio observations of a double-double
radio source J1706+4340 carried out with the Very Large Array and Giant
Metrewave Radio Telescope. After supplementing our own data with those
available in the literature, we collected a considerable set of radio
measurements covering the range from 74 to 8460 MHz. This has enabled us to
perform a comprehensive review of physical properties of the source and its
dynamical evolution analysis. In particular, we found that, while the age of
the large-scale outer lobes is in the range 260-300 Myr, the renewal of the jet
activity, which is directly responsible for the double-double structure, took
place only about 12 Myr ago after about 27-Myr long period of quiescence.
Another important property of J1706+4340 we found is that the injection
spectral indices and the jet powers for the inner and the outer doubles are
very similar. This implies that it is the spin of the supermassive black hole
rather than e.g. an instability of the accretion disc that is likely
responsible for the jet production and its properties.
