On the origin of the X - ray emission from a narrow - line radioquasar at z > 1

We present new XM M − N ewton X-ray observations of the z = 1.246 narrow-line radioquasar RX J1011.2+5545 serendipitously discovered by ROSAT. The flat X-ray spectrum previously measured by ROSAT and ASCA is shown to be the result of a steep Γ ∼ 1.8 power law spectrum seen through a moderate intrinsic absorbing column (N H ∼ 4 × 10 21 cm −2). The position of the X-ray source is entirely coincident with the nucleus of the radio source that we have resolved in new sensitive V LA observations at 3.6 and 6 cm, implying that scattering in the radio lobes is not responsible for the bulk of X-ray emission. In the EPIC pn image, a faint patch of X-ray emission is apparent 14 " to the NE of the main X-ray source. The former is positionally coincident with an apparently extended optical object with R ∼ 21.9, but there is no associated radio emission, thus ruling out the possibility that this represents a hotspot in a jet emanating from the primary X-ray source. No reflection features are detected in the X-ray spectrum of the narrow-line radioquasar, although an Fe line with equivalent width of up to 600 eV cannot be ruled out.