Physical and kinematical properties of the X-ray absorber in the broad absorption line quasar APM 08279+5255

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, ApJ, 573, L77; Chartas et al. 2002, ApJ, 579, 169) 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 $N_{\rm H}(1)$≈ 7$\times$ 1022 cm-2, $N_{\rm H}(2)$≈ 6$\times$ 1022 cm-2, and ionization parameters $\log\xi(1)$≈ 1.5 and $\log\xi(2)$≈ 3, with one of them (the high-ionization component) outflowing at v≈ 0.18(± 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