X-ray polarization measurements of Swift J1728.8-1613 in different accretion states

Black hole X-ray binaries represent ideal sources to probe accretion physics in strong gravitational field and X-ray polarization allows to put constraints on the geometry of the accretion disk and X-ray corona responsible for up-scattering of X-ray thermal photons. Swift J1728.8-1613 is a uniquely bright black-hole X-ray binary allowing to measure X-ray polarization across the entire outburst. The IXPE observed the source during its bright hard state and its transition to the soft state. New observations started in February 2024 to measure the X-ray polarization in the decaying soft state to probe how the X-ray polarization signal and geometry of X-ray emitting regions vary with different accretion states. I will report on the new results of IXPE measurements of Swift J1728.8-1613.