  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. We seek one physical model that can be successfully
applied to both observations. For the first time we have performed detailed
photoionization modeling on the X-ray spectrum of APM 08279+5255. The absorbing
gas in APM 08279+5255 can be represented by a two-absorbers model with column
densities N_H(1)~7x10^{22} cm^-2, N_H(2)~6x10^{22} cm^-2, and ionization
parameters logxi(1)~1.5 and logxi(2)~3, with one of them (the high-ionization
component) outflowing at v~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.
