Integral and XMM-Newton help to find X-ray engine inside mysterious supernova
The ATLAS telescope in Hawaii first spotted an unprecedentedly bright
and rapidly evolving stellar explosion that suddenly appeared in the sky
on 16 June 2018: they named it AT2018cow (see
ATel
#11727). In only two days the object exceeded the brightness of any
previously observed supernova.
Broad band X-ray spectral evolution of the remarkable transient in its
first 40 days of evolution. At early times INTEGRAL and NuSTAR
observations revealed the presence of a "hump" of emission above 10 keV,
that later disappeared. INTEGRAL was able to map the fading of the
hump with time. This Compton hump is completely unprecedented among
explosive transients, but common among accreting black holes.
In AT2018cow one associates the presence of the hump with radiation from
the cow central engine reprocessed by asymmetric ejecta that expands
with time into the medium and progressively becomes less and less
efficient in reprocessing the inner engine radiation.
