Speaker
Description
Cygnus X-1 is the prototype black hole high-mass microquasar.
As a persistent and bright X-ray source is considered an optimal candidate
to study the disk-jet coupling. It displays the typical soft and hard X-ray
spectral states of black hole binaries where the emission is dominated by
the thermal black body radiation and by non-thermal emission from the inner
part of the disk and the relativistic jets, respectively. We report the detection of a
8-sigma excess, above 60 MeV, spatially coincident with Cygnus X-1 by using
7.5 yr of Fermi-LAT data and the latest Pass8 software version. The point-like
signal is clearly associated to the microquasar since the emission correlates
with the hard X-ray state. In addition, there is a hint
of orbital flux variability with most of the emission coming around the
superior conjunction. The high energy emission is most likely associated
with the jets. We will discuss the possible mechanisms at work and the
constraints on the emission regions that can be derived.
