Microquasars are Black Hole X-ray binaries (BHXB) which can eject material in the form of a
bipolar jet, similarly to quasars, but at much smaller scales. Their high-energy emission comes
from an accretion disk (∼1 keV) and from a hot ‘corona’ near the black hole that up-scatters
photons from the disk in the hard X-ray domain (1–100 keV). A high-energy component above
150 keV has been detected in bright sources and its precise origin is still unknown: it could come
either from Compton scattering of disk photons on coronal relativistic non-thermal electrons (a.k.a
hybrid Comptonization), or from the synchrotron emission from the very base of the compact jet.
The measurement of polarization above 150 keV can provide valuable insights into the processes
at play as we expect higher polarization fraction due to synchrotron emission from the jets (up to
70% with a very ordered magnetic field)