XMM-Newton detection of a Comptonized accretion disc in the quasar PKS 0558-504
Dadina, M.; O'Brien, P. T.; Reeves, J. N.; Brinkmann, W.; Stephen, J. B.; Pounds, K. A.; Turner, M. J. L.; Page, M.; Gliozzi, M.
United Kingdom, Germany, Italy
Abstract
We present XMM-Newton observations of the bright quasar PKS 0558-504. 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 PKS 0558-504 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.