Serendipitous AGN in the XMM-Newton fields of Markarian 205 and QSO 0130 403

The X-ray spectra of serendipitously observed AGN in the XMM-Newton fields of Mrk 205 and QSO 0130 403 are analysed. The sample consists of 23 objects, none of which is detected at radio frequencies, with a median X-ray luminosity of �4×10 44 erg s 1 and redshifts ranging from �0.1 to just over 3. The mean photon index was found to be 1.89 ± 0.04. In contrast to past ASCA and ROSAT observations of high-redshift radio-loud quasars, we find little evidence for excess intrinsic absorption in these radio-quiet objects, with only three sources requiring a column density in excess of the Galactic value. Comparing the measured spectral indices over the redshift range, we also find there is no X-ray spectral evolution of QSOs with time, up to redshift 3. Within the sample there is no evidence for evolution of the optical to X-ray spectral index, �ox, with redshift, the mean value being 1.66 ± 0.04. However, upon comparing the values from the Bright Quasar Survey at low redshift (z < 0.5) and