  Motivated by recent IceCube observations we re-examine the idea that
microquasars are high energy neutrino emitters. By stretching to the maximum
the parameters of the Fermi engine we show that the nearby high-mass X-ray
binary LS 5039 could accelerate protons up to above about 20 PeV. These highly
relativistic protons could subsequently interact with the plasma producing
neutrinos up to the maximum observed energies. After that we adopt the spatial
density distribution of high-mass X-ray binaries obtained from the deep
INTEGRAL Galactic plane survey and we assume LS 5039 typifies the microquasar
population to demonstrate that these powerful compact sources could provide a
dominant contribution to the diffuse neutrino flux recently observed by
IceCube.
