Recently, evidence for synchrotron emission in both black-hole (BH) and neutron star X-ray\nbinaries has been mounting, from optical/infrared spectral, polarimetric, and fast timing signatures.\nThe synchrotron emission of jets can be highly linearly polarised, depending on the configuration of\nthe magnetic field (B-field). Optical and infrared (OIR) polarimetric observations of X-ray binaries are\npresented in this brief review. The OIR polarimetric signature of relativistic jets is detected at levels of\nâË?¼1ââ?¬â??10%, similarly to for active galactic nuclei (AGN) cores. This reveals that the magnetic geometry\nin the compact jets may be similar for supermassive and stellar-mass BHs. The B-fields near the jet\nbase in most of these systems appear to be turbulent, variable and on average, aligned with the jet\naxis, although there are some exceptions. These measurements probe the physical conditions in the\naccretion (out)flow and demonstrate a new way of connecting inflow and outflow, using both rapid\ntiming and polarisation. Variations in polarisation could be due to rapid changes of the ordering of\nthe B-field in the emitting region, or in one case, flares from individual ejections or collisions between\nejecta. It is predicted that in some cases, variable levels of X-ray polarisation from synchrotron\nemission originating in jets will be detected from accreting galactic BHs with upcoming spaceborne\nX-ray polarimeters.
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