We have observed the luminous ( L _ { 2 - 10 ~ { } keV } \simeq 6 \times 10 ^ { 44 } erg s ^ { -1 } ) radio–quiet quasar RBS 1124 ( z = 0.208 ) with Suzaku .
We report the detection of a moderately broad iron ( Fe ) line and of a weak soft X–ray excess .
The X–ray data are very well described by a simple model comprising a power law X–ray continuum plus its reflection off the accretion disc .
If the inner disc radius we measure ( r _ { in } \leq 3.8 gravitational radii ) is identified with the innermost stable circular orbit of the black hole spacetime , we infer that the black hole powering RBS 1124 is rotating rapidly with spin a \geq 0.6 .
The soft excess contribution in the 0.5–2 keV band is \sim 15 per cent , about half than that typically observed in unobscured Seyfert 1 galaxies and quasars , in line with the low disc reflection fraction we measure ( R _ { disc } \simeq 0.4 ) .
The low reflection fraction can not be driven by disc truncation which is at odds not only with the small inner disc radius we infer but , most importantly , with the radiatively efficient nature of the source ( L _ { Bol } / L _ { Edd } \simeq 1 ) .
A plausible explanation is that the X–ray corona is the base of a failed jet ( RBS 1124 being radio–quiet ) and actually outflowing at mildly relativistic speeds .
Aberration reduces the irradiation of the disc , thus forcing a lower than standard reflection fraction , and halves the inferred source intrinsic luminosity , reducing the derived Eddington ratio from \simeq 1 to \simeq 0.5 .
A partial covering model provides a statistically equivalent description of the 0.3–10 keV data , but provides a worse fit above 10 keV .
More importantly , its properties are not consistent with being associated to the Fe emission line , worsening the degree of self–consistency of the model .
Moreover , the partial covering model implies that RBS 1124 is radiating well above its Eddington luminosity , which seems unlikely and very far off from previous estimates .