XMM-Newton, Swift, and ROSAT Observations of LBQS 0102-2713

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 Hubble Space Telescope and optical spectroscopic observations. The first XMM-Newton observations carried out in 2009 December 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 Ultra-Violet/Optical Telescope and the XMM-Newton/ROSAT data which results in a huge luminosity of (6.2 ± 0.2) × 10⁴⁷ erg s^–1 and α_ox values ranging between (–1.87 ± 0.11) and (–2.11 ± 0.12). The nature of the soft X-ray emission can be explained as local Comptonized emission of the UV disk 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 θ = kT _e/m _ec² we derive an upper limit of about 10 keV.