Tidal disruption of a super-Jupiter by a massive black hole
  Aims: A strong, hard X-ray flare was discovered (IGR J12580+0134) by INTEGRAL
in 2011, and is associated to NGC 4845, a Seyfert 2 galaxy never detected at
high-energy previously. To understand what happened we observed this event in
the X-ray band on several occasions. Methods: Follow-up observations with
XMM-Newton, Swift, and MAXI are presented together with the INTEGRAL data. Long
and short term variability are analysed and the event wide band spectral shape
modelled. Results: The spectrum of the source can be described with an absorbed
(N_H ~ 7x10^22 cm^{-2}) power law (\Gamma \simeq 2.2), characteristic of an
accreting source, plus a soft X-ray excess, likely to be of diffuse nature. The
hard X-ray flux increased to maximum in a few weeks and decreased over a year,
with the evolution expected for a tidal disruption event. The fast variations
observed near the flare maximum allowed us to estimate the mass of the central
black hole in NGC 4845 as ~ 3x10^5 Msun. The observed flare corresponds to the
disruption of about 10% of an object with a mass of 14-30 Jupiter. The hard
X-ray emission should come from a corona forming around the accretion flow
close to the black hole. This is the first tidal event where such a corona has
been observed.
