Variability, polarimetry, and timing properties of single pulses from PSR J2222-0137 using FAST

In our work, we analyse 5 × 10⁴ single pulses from the recycled pulsar PSR J2222-0137 in one of its scintillation maxima observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). PSR J2222-0137 is one of the nearest and best studies of binary pulsars and a unique laboratory for testing gravitational theories. We report single pulses' energy distribution and polarization from the pulsar's main-pulse region. The single-pulse energy follows the lognormal distribution. We resolve a steep polarization swing, but at the current time resolution ($64\ \mu {\rm s}$), we find no evidence for the orthogonal jump in the main-pulse region, as has been suspected. We find a potential sub-pulse drifting period of $P_{3} \sim 3.5 P$. We analyse the jitter noise from different integrated numbers of pulses and find that its σ_j is $270\pm {9}\ {\rm ns}$ for 1-h integration at 1.25 GHz. This result is useful for optimizing future timing campaigns with FAST or other radio telescopes.