2005A&A...433..455S

We present the analysis of XMM-Newton observations of three X-ray weak quasars: PG 1001+054, PG 1535+547 and PG 2112+059. All objects are absorbed by ionized material showing high column densities, N_H=2.9x10²²cm^–2 to N_H=1.9x10²³cm^–2, and ionization parameters, ξ=147erg.cm/s to ξ=542erg.cm/s. The spectra of PG 1535+547 require an additional partial covering by neutral material with a column density of N_H≃9x10²²cm^–2 at a covering factor of ≃0.96. The spectra of PG 1535+547 show systematic residuals in the energy range from ∼4keV to ∼6keV, which are inconsistent with K_α-fluorescence-emission of neutral or ionized iron under the assumption of a Gaussian line profile. They can be described with a relativistic disk line (Laor) and establish therefore the second X-ray weak quasar with such a spectral characteristic. Our results together with the findings of Brinkmann et al. (2004A&A...414..107B) and Piconcelli et al. (2004MNRAS.351..161P), indicate that warm absorbers characterized by high column densities and ionization parameters are typical of X-ray weak quasars. The occurrence of a variable relativistic broad Fe K_α fluorescence line in two out of the five well studied X-ray weak quasars might indicate a second general characteristic of the entire object class. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.