Title:
The destruction and recreation of the X-ray corona in an accreting massive black hole

Abstract:
In my talk I will discuss the strange case of 1ES 1927+654, a nearby AGN 
in which a changing-look event drastically transformed its X-ray properties. 
After a optical/UV outburst the power- law component, typically associated to 
the X-ray corona, completely disappeared, and the spectrum is dominated by 
blackbody- like emission. This implies that the corona, ubiquitously found in AGN, 
was destroyed in the event. Our ∼ 450 day long X-ray monitoring campaign shows that, 
as the X-ray luminosity of the source increases, the X-ray corona is re-created, 
and a soft power-law component re-appears and dominates the emission 
for 0.3-2 keV luminosities >5x10^43 erg/s. This behaviour could be associated with 
the tidal disruption of a star by the accreting black hole, which is expected to destroy 
the innermost regions of the accretion flow.