The gravitationally lensed quasar APM 08279+5255 has the fastest claimed wind from any AGN , with velocities of 0.6–0.7 c , requiring magnetic acceleration as special relativisitic effects limit all radiatively driven winds to v < 0.3–0.5 c .
However , this extreme velocity derives from interpreting both the narrow and broad absorption features in the X-ray spectrum as iron absorption lines .
The classic ultrafast outflow source PDS 456 also shows similar absorption systems , but here the higher energy , broader feature is generally interpreted as an absorption edge .
We reanalyse all the spectra from APM 08279+5255 using a full 3-dimensional Monte Carlo radiative transfer disc wind model for the ionised wind at 0.1–0.2 c , together with complex absorption from lower ionisation material , and find that this is a better description of the data .
Thus there is no strong requirement for outflow velocities beyond 0.2 c , which can be powered by radiation driving .
We show that UV line driving is especially likely given the spectral energy distribution of this source which is intrinsically UV bright and X-ray weak .
While the peak of this emission is unobservable , it must be luminous enough to power the observed hot dust , favouring at least moderate black hole spin .