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

Abstract

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_H(1)≈ 7× 10²² cm^-2, N_H(2)≈ 6× 10²² cm^-2, and ionization parameters logξ(1)≈ 1.5 and logξ(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.