Context : We have re-analyzed the X-ray spectra of the gravitational lensed high-redshift BAL QSO APM 08279+5255 , observed with the XMM-Newton and Chandra observatories .
Previous studies ( Hasinger et al .
2002 ; Chartas et al .
2002 ) detected unusual , highly-ionized iron absorption features , but differed in their interpretation of these features , regarding the kinematical and ionization structure .

Aims : We seek one physical model that can be successfully applied to both observations .

Methods : For the first time we have performed detailed photoionization modeling on the X-ray spectrum of APM 08279+5255 .

Results : The absorbing gas in APM 08279+5255 can be represented by a two-absorbers model with column densities N _ { H } ( 1 ) \approx 7 \times 10 ^ { 22 } { cm } ^ { -2 } , N _ { H } ( 2 ) \approx 6 \times 10 ^ { 22 } { cm } ^ { -2 } , and ionization parameters \log \xi ( 1 ) \approx 1.5 and \log \xi ( 2 ) \approx 3 , with one of them ( the high-ionization component ) outflowing at v \approx 0.18 ( \pm 0.01 ) c , carrying large amount of gas out of the system .
We find that the Chandra spectrum of APM 08279+5255 requires the same Fe/O ratio overabundance ( previously ) indicated by the XMM-Newton observation , showing that both absorber components underwent similar chemical evolution and/or have similar origin .

Conclusions :