The Polarization of Radiation coming from Windy Black Hole Accretion Disks

X-ray polarimetry is becoming a key tool for investigating stellar-mass black hole binaries, providing new insights into accretion physics and their relativistic effects in strong gravitational fields. However, recent observations have revealed polarization degrees higher than predicted by standard disk models. These discrepancies can be explained if the disk emission interacts with an outflowing plasma in the form of a magnetically driven wind. To explore this possibility, we combined a physically motivated MHD wind model with photo-ionization and Monte Carlo radiative transfer simulations to study how winds can modify the polarization of X-ray radiation emerging from accretion disks. Our results show two clear signatures. First, the polarization degree Π increases systematically with photon energy, with characteristic differences between Schwarzschild and Kerr black holes and a localized minimum near the iron K edge. Second, polarization is minimized at intermediate viewing angles while the polarization angle remains nearly constant across both energy and inclination angles. The first trend qualitatively reproduces the observed increase of polarization with energy reported in recent IXPE observations of 4U 1630–47, although our predicted values are significantly lower, possibly reflecting the simplifying assumptions of our setup. The main contribution of this work is the first modeling of polarization from a realistic MHD wind including both scattering and absorption processes. These findings indicate that winds imprint distinct polarization signatures, which in future X-ray polarimetry campaigns could be used to place constraints on the geometry and dynamics of accretion flows in black hole systems.