2025Natur.637...43M

Fast radio bursts (FRBs) last for milliseconds and arrive at Earth from cosmological distances. Although their origins and emission mechanisms are unknown, their signals bear similarities with the much less luminous radio emission generated by pulsars within our Miky Way Galaxy , with properties suggesting neutron star origins . However, unlike pulsars, FRBs typically show minimal variability in their linear polarization position angle (PA) curves . Even when marked PA evolution is present, their curves deviate significantly from the canonical shape predicted by the rotating vector model (RVM) of pulsars . Here we report on FRB 20221022A, detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst project (CHIME/FRB) and localized to a nearby host galaxy (about 65 Mpc), MCG+14-02-011. This FRB shows a notable approximately 130° PA rotation over its about 2.5 ms burst duration, resembling the characteristic S-shaped evolution seen in many pulsars and some radio magnetars. The observed PA evolution supports magnetospheric origins over models involving distant shocks , echoing similar conclusions drawn from tempo-polarimetric studies of some repeating FRBs . The PA evolution is well described by the RVM and, although we cannot determine the inclination and magnetic obliquity because of the unknown period or duty cycle of the source, we exclude very short-period pulsars (for example, recycled millisecond pulsars) as the progenitor.