Presentation #109.04 in the session IXPE.
X-ray binary systems consist of a main sequence star and a compact object — a white dwarf, neutron star or black hole — in close orbit. Because these systems cannot be resolved by current X-ray telescopes, they have instead been studied using X-ray spectroscopy and timing. X-ray polarimetry can probe the geometry of these systems where the other techniques cannot, for example constraining the orbital parameters. This has finally become possible thanks to the recent launch of the Imaging X-ray Polarimetry Explorer (IXPE) observatory, as I will show in this contribution.