Orbital phase-resolved polarization of Cyg X-1 in the hard state. Left panel: Variation of the normalized Stokes parameters. The numbers represent the orbital phase bins from 1 to 10 and the colors correspond to the superorbital phase (right color bar). Right panel: PD and PA as a function of orbital phase. Solid black lines in both panels correspond to the best-fit model described in Sect. 4.1.