We have analyzed the first XMM-Newton , Swift and archival ROSAT PSPC observations of the quasar LBQS 0102-2713 .
The object was selected from the ROSAT archive as being notable due to the steep soft X-ray photon index and due to the UV brightness based on HST and optical spectroscopic observations .
The first XMM-Newton observations carried out in December 2009 and the first Swift observations from 2010 have confirmed the steepness of the soft X-ray photon index , which ranges between 3.35 and 4.41 for the different XMM-Newton and ROSAT detectors , the UV brightness of the source and the absence of significant absorption by neutral hydrogen .
The new data allow a combined spectral fitting to the Swift UVOT and the XMM-Newton/ROSAT data which results in a huge luminosity of ( 6.2 \pm 0.2 ) \times 10 ^ { 47 } erg s ^ { -1 } and \alpha _ { ox } values ranging between ( -1.87 \pm 0.11 ) and ( -2.11 \pm 0.12 ) .
The nature of the soft X-ray emission can be explained as local comptonized emission of the UV disc photons in the pseudo-Newtonian potential .
The black hole mass is estimated from the Mg II line and translates into an Eddington ratio of L / L _ { edd } = 18 ^ { +33 } _ { -12 } .
For the dimensionless electron temperature of the plasma cloud \theta = kT _ { e } / m _ { e } c ^ { 2 } we derive an upper limit of about 10 keV .