We present evidence for the rapid variability of the high velocity iron K-shell absorption in the nearby ( z = 0.184 ) quasar PDS 456 .
From a recent long Suzaku observation in 2013 ( \sim 1 Ms effective duration ) we find that the the equivalent width of iron K absorption increases by a factor of \sim 5 during the observation , increasing from < 105 eV within the first 100 ks of the observation , towards a maximum depth of \sim 500 eV near the end .
The implied outflow velocity of \sim 0.25 c is consistent with that claimed from earlier ( 2007 , 2011 ) Suzaku observations .
The absorption varies on time-scales as short as \sim 1 week .
We show that this variability can be equally well attributed to either ( i ) an increase in column density , plausibly associated with a clumpy time-variable outflow , or ( ii ) the decreasing ionization of a smooth homogeneous outflow which is in photo-ionization equilibrium with the local photon field .
The variability allows a direct measure of absorber location , which is constrained to within r = 200 - 3500 r _ { g } of the black hole .
Even in the most conservative case the kinetic power of the outflow is \gtrsim 6 \% of the Eddington luminosity , with a mass outflow rate in excess of \sim 40 \% of the Eddington accretion rate .
The wind momentum rate is directly equivalent to the Eddington momentum rate which suggests that the flow may have been accelerated by continuum-scattering during an episode of Eddington-limited accretion .