XMM-Newton Detection of a Comptonized Accretion Disc in the Quasar   PKS0558-504
  We present XMM-Newton observations of the bright quasar PKS0558-504. The 0.2-10 keV spectrum is dominated by a large, variable soft X-ray excess. The fastest flux variations imply accretion onto a Kerr black hole. The XMM-Newton data suggest the presence of a `big blue bump' in PKS0558-504 extending from the optical band to ~3 keV. The soft X-ray spectrum shows no evidence for significant absorption or emission-line features. The most likely explanation for the hot big blue bump is Comptonization by the multi-temperature corona of a thermal accretion disc running at a high accretion rate. 
P.T. O'Brien (1), J.N. Reeves (1), M.J.L. Turner (1), K.A. Pounds (1),   M. Page (2), M. Gliozzi (3), W. Brinkmann (3), J.B....