The narrow-line quasar PHL 1092 was observed by XMM-Newton at two epochs
separated by nearly thirty months. Timing analyses confirm the extreme
variability observed during previous X-ray missions. A measurement of the
radiative efficiency is in excess of what is expected from a Schwarzschild
black hole. In addition to the rapid X-ray variability, the short UV light
curves (< 4 hours) obtained with the Optical Monitor may also show
fluctuations, albeit at much lower amplitude than the X-rays. In general, the
extreme variability is impressive considering that the broad-band (0.4-10 keV
rest-frame) luminosity of the source is ~10^45 erg/s. During at least one of
the observations, the X-ray and UV light curves show common trends, although
given the short duration of the OM observations, and low significance of the UV
light curves it is difficult to comment on the importance of this possible
correlation. Interestingly, the high-energy photons (> 2 keV) do not appear
highly variable. The X-ray spectrum resembles that of many narrow-line Seyfert
1 type galaxies: an intense soft-excess modelled with a multi-colour disc
blackbody, a power-law component, and an absorption line at ~1.4 keV. The ~1.4
keV feature is curious given that it was not detected in previous observations,
and its presence could be related to the strength of the soft-excess. Of
further interest is curvature in the spectrum above ~2 keV which can be
described by a strong reflection component. The strong reflection component,
lack of high-energy temporal variability, and extreme radiative efficiency
measurements can be understood if we consider gravitational light bending
effects close to a maximally rotating black hole.Comment: To appear in MNRAS. Submitted March 01, 2004. 9 page
