2025ApJ...985...11R

We report on a single-pulse study of PSR J1239+0326 discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal Radio Astronomy FAST Survey. The observations were conducted at a central frequency of 1.25 GHz. The integrated pulse profile of PSR J1239+0326 shows four distinct components, implying a central line of sight traversing a presumed double cone core emission beam. We found correlations between intensities of the first and fourth components and the second and the core components, indicating that the charges emitted between the correlated components may be related. Based on rotating vector model fitting, we estimated the inclination angle between the magnetic and the rotational axes to be 10°. No nulls, giant pulses, or giant micropulses were detected during observation sessions. Outer-cone components are observed to display “even-odd” subpulse modulation with quasiperiodicity around 2P, where P is the rotational period of the pulsar. The trailing component exhibits energy modulation with quasiperiodicities of 19P and 26P. This two-mode modulation could result from the combination of sub-pulse drifts and the feedback between the voltage difference across the polar gap and surface thermal emission by backflowing charges.