Evolution of Swift J1727.8−1613 optical polarization and BVR magnitudes around the HIMS/SIMS state transition. The colored symbols correspond to the B (blue triangles), V (green diamonds), and R (red crosses) bands. Panel (a): AAVSO light curve (light green line) and the observed optical PD in three filters. Panel (b): observed PA. Panel (c): optical magnitudes calculated from DIPol-2 images as described in the text. The vertical dashed black line corresponds to MJD 60206, when the jet ejections were detected (Wood et al. 2025).