Evidence for a radiatively driven disc-wind in PDS 456?
  We present a newly discovered correlation between the wind outflow velocity
and the X-ray luminosity in the luminous ($L_{\rm bol}\sim10^{47}\,\rm
erg\,s^{-1}$) nearby ($z=0.184$) quasar PDS\,456. All the contemporary
XMM-Newton, NuSTAR and Suzaku observations from 2001--2014 were revisited and
we find that the centroid energy of the blueshifted Fe\,K absorption profile
increases with luminosity. This translates into a correlation between the wind
outflow velocity and the hard X-ray luminosity (between 7--30\,keV) where we
find that $v_{\rm w}/c \propto L_{7-30}^{\gamma}$ where $\gamma=0.22\pm0.04$.
We also show that this is consistent with a wind that is predominately
radiatively driven, possibly resulting from the high Eddington ratio of
PDS\,456.
