On the deep minimum state in the Seyfert galaxy MCG-6-30-15

We present a detailed spectral analysis of the first observation of the Seyfert I galaxy MCG-6-30-15 by the European Photon Imaging Camera on board the XMM-Newton observatory, together with contemporaneous data from the Proportional Counter Array on the Rossi X-ray Timing Explorer. Confirming our previously published result, we find that the presence of extremely broadened reflection features from an ionized relativistic accretion disc is required even when one employs the latest X-ray reflection models and includes the effect of complex absorption. The extremely broadened reflection features are also present if the primary continuum is modelled with a thermal Comptonization spectrum rather than a simple power-law continuum. With this fact established, we examine these data using a relativistic smearing function corresponding to a 'generalized thin accretion disc' model. We find strong evidence for torquing of the central parts of the accretion disc (presumably through magnetic interactions with the plunging region of the disc and/or the rotating black hole itself). Indeed, within the context of these torqued disc models, this system appears to be in a torque-dominated (or 'infinite-efficiency') state at the time of this observation. In addition, we find marginal evidence that the X-ray emitting corona radiates a greater fraction of the total dissipated energy in the inner portions of the disc. We also perform a study of spectral variability within our observation. We find that the disc reflection features maintain roughly a constant equivalent width with respect to the observed continuum, as predicted by simple reflection models. Taken together with other studies of MCG-6-30-15 that find disc features to possess constant intensity at higher flux states, we suggest that the flux of disc features undergoes a saturation once the source emerges from a deep minimum state. We discuss the implications of these results for the physics of the deep minimum 'state transitions'.