Multi-Faceted Emission Properties of PSR J2129+4119 Observed with FAST

Despite locating well below the traditional death line, the pulsar exhibits sustained and multi-modal emission behavior, including nulls, weak pulses, regular emission, and occasional bright pulses. The nulling fraction is measured to be 8.13% +/- 0.51%, with null durations typically under four pulse periods.

Fluctuation spectral analysis reveals both phase-modulated subpulse drifting and intermittent beat-like modulation. At the same time, polarization profiles show high linear polarization and stable polarization position angle (PPA) swings consistent with a near-tangential sightline geometry. Quasi-periodic microstructures are detected in 11.54% of regular pulses, with a mean periodicity and width of 4.57 ms and 4.30 ms, respectively.