Occultation Mapping of the Central Engine in the Active Galaxy MCG −6-30-15

The colossal power output of active galactic nuclei (AGN) is believed to befueled by the accretion of matter onto a supermassive black hole. This centralaccreting region of AGN has hitherto been spatially unresolved and itsstructure therefore unknown. Here we propose that a previously reported `deepminimum' in the X-ray intensity of the AGN MCG-6-30-15, was due to a uniqueX-ray occultation event and that it probes structure of the central engine onscales < 1e14 cm, or 1.4e-7 arcseconds. The data are consistent with a brightcentral source surrounded by a less intense ring, which we identify with theinner edge of an accretion disk. These may be the first direct measurements ofthe spatial structure and geometry of the accreting black-hole system in anactive galaxy.If the ring of X-ray emission is identified with the inner edgeof an accretion disk, upper limits on the BH mass can be derived. Ouroccultation interpretation is controversial in the sense that X-ray variabilityin AGNs is normally attributed to intrinsic physical changes in the X-rayemission region, such as disk or coronal instabilities.Comment: 15 pages, 2 Figures. Latex with separate postscript figure files. Accepted for publication in ApJ Letter