Optical polarization curve of the transitional millisecond pulsar PSR J1023+0038 during an X-ray flaring mode.

This data collection contains an optical polarimetric curve obtained with FORS2 at the Very Large Telescope in the R_special band for PSR J1023+0038, the prototype of the transitional millisecond pulsar class.Simultaneous observations were also performed with the IXPE X-ray polarimeter and the VLA in the radio band. The data reveal a clear anti-correlation between polarization and flux across all frequencies, with polarization decreasing as flux increases. This behavior is associated with powerful multi-band flares, enabling us to demonstrate that the origin of the flaring activity is linked to an unpolarized process, most likely due to ejections.