  We briefly review and extend our discussion of the ROSAT detection of the
extraordinarily luminous (>10^{42} erg/s) partly extended (> 30 kpc diameter)
X-ray emission from the double-nucleus ultraluminous infrared galaxy NGC 6240.
The ROSAT spectrum can be well fit by emission from two components in roughly
equal proportions: a thermal optically thin plasma with kT \sim 0.6 keV and a
hard component that can be represented by a canonical AGN powerlaw. Source
counts appear to have dropped by 30% within a year. Altogether, these findings
can be well explained by a contribution of radiation from an AGN essentially
hidden at other wavelengths. Fits of ASCA spectra, conducted by various groups,
corroborate this result, revealing a high-equivalent width FeK blend which
again is straightforwardly interpreted by scattered AGN light.
  If radiating at the Eddington limit, the central black hole mass does not
exceed 10^7 M_sun. We discuss implications for the formation of this AGN.
However, the luminosity in the remaining extended thermal component is still at
the limits of a pure starburst-wind-induced source. We suggest that the deeply
buried starburst has switched to a partially dormant phase so that heating of
the outflow is diminished and a cooling flow could have been established. This
flow may account for the extended shock heating traced by LINER-like emission
line ratios and the extremely luminous H_2 emission from the central region of
this galaxy. Next-generation X-ray telescopes will be able to test this
proposal.
