  We present results from multi-epoch spectral analysis of XMM-Newton and
Chandra observations of the broad absorption line (BAL) quasar APM 08279+5255.
Our analysis shows significant X-ray BALs in all epochs with rest-frame
energies lying in the range of ~ 6.7-18 keV. The X-ray BALs and 0.2-10 keV
continuum show significant variability on timescales as short as 3.3 days
(proper time) implying a source size-scale of ~ 10 r_g, where r_g is the
gravitational radius. We find a large gradient in the outflow velocity of the
X-ray absorbers with projected outflow velocities of up to 0.76 c. The maximum
outflow velocity constrains the angle between the wind velocity and our line of
sight to be less than ~ 22 degrees. We identify the following components of the
outflow: (a) Highly ionized X-ray absorbing material (2.9 < logxi < 3.9) and a
column density of log N_H ~ 23 outflowing at velocities of up to 0.76 c. (b)
Low-ionization X-ray absorbing gas with log N_H ~ 22.8. We find that flatter
spectra appear to result in lower outflow velocities. Based on our spectral
analysis of observations of APM 08279+5255 over a period of 1.2 years (proper
time) we estimate the mass-outflow rate and efficiency of the outflow to have
varied between 16(-8,+12) M_solar yr^-1 and 64(-40,+66) M_solar yr^-1 and
0.18(-0.11,+0.15) to 1.7(-1.2+1.9), respectively. Assuming that the outflow
properties of APM 08279+5255 are a common property of most quasars at similar
redshifts, our results then imply that quasar winds are massive and energetic
enough to influence significantly the formation of the host galaxy, provide
significant metal enrichment to the interstellar medium and intergalactic
medium, and are a viable mechanism for feedback at redshifts near the peak in
the number density of galaxy mergers.
