We present an analysis of the joint XMM-Newton and NuSTAR observations of the radio-quiet quasar QSO B2202–209 .
Using an optical observation from the Hale Telescope at the Palomar Observatory , we revise the redshift of the source from the previously reported z = 1.77 to z = 0.532 , and we estimate the mass of the central black hole , \log ( M _ { BH } / M _ { \odot } ) = 9.08 \pm 0.18 .
The X-ray spectrum of this source can be well described by a power-law of photon index \Gamma = 1.82 \pm 0.05 with E _ { cut } = 152 _ { -54 } ^ { +103 } { keV } , in the rest frame of the source .
Assuming a Comptonisation model , we estimate the coronal temperature to be kT _ { e } = 42 \pm 3 { keV } and kT _ { e } = 56 \pm 3 { keV } for a spherical and a slab geometry , respectively .
The coronal properties are comparable to the ones derived for local AGN , despite a difference of around one order of magnitude in black hole mass and X-ray luminosity ( L _ { 2 - 10 } = 1.93 \times 10 ^ { 45 } { erg s ^ { -1 } } ) .
The quasar is X-ray loud , with an unusually flat observed optical-to-X-ray spectral slope \alpha _ { OX } = 1.00 \pm 0.02 , and has an exceptionally strong optical [ \ion Oiii ] line .
Assuming that both the X-ray emission and the [ \ion Oiii ] line are isotropic , these two extreme properties can be explained by a nearly edge-on disk , leading to a reduction in the observed UV continuum light .