Depolarization Induced by Rapid Polarization Angle Swings: A Common Feature of Pulsars and Fast Radio Bursts?

The polarization angle (PA) of pulsars and fast radio bursts (FRBs) provides a useful diagnostic of the magnetic fields in their emission regions and is therefore crucial for understanding their radiation and origins. Within a general geometric framework for polarized emission from a rotating neutron star, we suggest a possible anti-correlation between the degree of linear polarization L and d PA/dt, the time derivative of the PA, as a common feature of pulsars and FRBs. The depolarization arises from the incoherent superposition of radiation with different polarization directions within the observable part of the emission region, and is detectable only when the PA swing is steep enough. We test this conjecture using a sample of radio pulsars and find possible evidence for the expected anti-correlation in a subset of pulsars. Whether this relation holds in FRBs remains uncertain due to limited observational data. Identification of this feature would not only provide insights into the rotating magnetospheric origin of FRBs, but also place constraints on the spin periods and geometric parameters of the neutron stars that power these mysterious bursts.