Polarization Profiles of Globular Cluster Pulsars from FAST. I. 25 Profiles from Previously Known Pulsars

Abstract We present a polarization study of 25 globular cluster (GC) pulsars observed with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), including 15 profiles measured for the first time. The pulse width–period relationships for millisecond pulsars (MSPs) in GCs follow power-law indices of −0.268 (W10) and −0.330 (W50), consistent with normal pulsars. Only 20% of the sample exhibit clear S-shaped position angle curves-significantly fewer than in the normal pulsar population. Rotation Measures (RMs) for these pulsars suggest that GCs near the Galactic plane show higher RMs, in agreement with former studies. Polarization ratios were measured, with M53A showing the highest linear polarization (56%) and M15H the highest absolute circular polarization (37%). On average, GC pulsars exhibit lower circular (−1%) and absolute circular (11%) polarization compared to normal pulsars observed with Parkes (5% and 32%, respectively). However, their polarization distributions align with MSPs in the Galactic plane, suggesting GC environments do not drastically alter emission properties.