A rapidly spinning supermassive black hole at the centre of NGC 1365. (arXiv:1302.7002v1 [astro-ph.HE])

A rapidly spinning supermassive black hole at the centre of NGC 1365. (arXiv:1302.7002v1 [astro-ph.HE]):
Broad X-ray emission lines from neutral and partially ionized iron observed
in active galaxies have been interpreted as fluorescence produced by the
reflection of hard X-rays off the inner edge of an accretion disk. In this
model, line broadening and distortion result from rapid rotation and
relativistic effects near the black hole, the line shape being sensitive to its
spin. Alternative models in which the distortions result from absorption by
intervening structures provide an equally good description of the data, and
there has been no general agreement on which is correct. Recent claims that the
black hole (2E6 solar masses) at the centre of the galaxy NGC 1365 is rotating
at close to its maximum possible speed rest on the assumption of relativistic
reflection. Here we report X-ray observations of NGC 1365 that reveal the
relativistic disk features through broadened Fe line emission and an associated
Compton scattering excess of 10-30 keV. Using temporal and spectral analyses,
we disentangle continuum changes due to time-variable absorption from
reflection, which we find arises from a region within 2.5 gravitational radii
of the rapidly spinning black hole. Absorption-dominated models that do not
include relativistic disk reflection can be ruled out both statistically and on
physical grounds.