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

In our work, we analyse $5\times {10}^4$ 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 log-normal distribution. We resolve a steep polarization swing, but at the current time resolution ($64\mu \mathrm{s}$), 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 $P_3\sim 3.5P$. We analyse the jitter noise from different integrated numbers of pulses and find that its ${\sigma }_j$ is $270\pm 9\mathrm{n}\mathrm{s}$ for 1-hr integration at 1.25 GHz. This result is useful for optimizing future timing campaigns with FAST or other radio telescopes.