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

TL;DR

This study analyzes XMM-Newton, Swift, and ROSAT observations of the quasar LBQS 0102-2713, revealing its steep soft X-ray spectrum, high luminosity, and properties consistent with Comptonized UV emission, indicating an extremely high Eddington ratio.

Contribution

First comprehensive multi-instrument analysis of LBQS 0102-2713 confirming its steep X-ray spectrum and high luminosity, with spectral modeling suggesting Comptonized UV emission and an exceptionally high Eddington ratio.

Findings

Steep soft X-ray photon index between 3.35 and 4.41.

Luminosity of approximately 6.2 x 10^47 erg/s.

Eddington ratio estimated at 18 (+33, -12).

Abstract

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+-0.2)x10^47 erg s^(-1) and alpha_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 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.