  We present new results from our study of the X-rayed outflow of the z = 3.91
gravitationally lensed broad absorption line (BAL) quasar APM 08279+5255. These
results are based on spectral fits to all the long exposure observations of APM
08279+5255 using a new quasar-outflow model. This model is based on cloudy
simulations of a near-relativistic quasar outflow. The main conclusions from
our multi-epoch spectral re-analysis of Chandra, XMM-Newton and Suzaku
observations of APM 08279+5255 are: 1) In every observation we confirm the
presence of two strong features, one at rest-frame energies between 1-4 keV,
and the other between 7-18 keV. 2) We confirm that the low-energy absorption
(1-4 keV rest-frame) arises from a low-ionization absorber with logNH~23 and
the high-energy absorption (7-18 keV rest-frame) arises from highly ionized
(3>log xi>4; where xi is the ionization parameter) iron in a near-relativistic
outflowing wind. Assuming this interpretation, we find that the velocities on
the outflow could get up to ~0.7c. 3) We confirm a correlation between the
maximum outflow velocity and the photon index and find possible trends between
the maximum outflow velocity and the X-ray luminosity, and between the total
column density and the photon index. We performed calculations of the force
multipliers of material illuminated by absorbed power laws and a
Mathews-Ferland SED. We found that variations of the X-ray and UV parts of the
SEDs and the presence of a moderate absorbing shield will produce important
changes in the strength of the radiative driving force. These results support
the observed trend found between the outflow velocity and X-ray photon index in
APM 08279+5255. If this result is confirmed it will imply that radiation
pressure is an important mechanism in producing quasar outflows.
