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We report on radio observations of four magnetars SGR 0501+4516, Swift 1834.9–0846, 1E 1841–045, SGR 1900+14, and a magnetar-like pulsar PSR J1846–0258 with the Five-hundred-meter Aperture Spherical radio Telescope at 1250 MHz. Notably, PSR J1846–0258 was observed 1 month after its 2020 X-ray outburst. The data from these observations were searched for periodic emissions and single pulses. No radio emission was detected for any of our targets. After accounting for the effect of red noise, the nondetections yield stringent upper limits on the radio flux density, with S _1250 ≤ 16.9 μ Jy for the four magnetars and the magnetar-like pulsar, along with constraints on single-pulse flux densities. Our deep radio observations suggest that these magnetars and the magnetar-like pulsar are indeed radio-quiet sources or unfavorably beamed. The resulting flux upper limits, along with previous findings, are discussed, highlighting the significance of further radio observations of radio-quiet magnetars and the high-B magnetar-like pulsar.

Careful scrutiny of the single pulse emissions from PSR B2110+27 has been conducted through highly sensitive observations using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at a central frequency of 1250 MHz. Our investigation revealed significant subpulse drift behavior and nulling in this pulsar. Moreover, we observed that the nulling events tend to be of short duration, with an estimated overall nulling fraction of approximately 27% ± 3%. It is noteworthy that the drift direction of the subpulses exhibits abrupt changes, occasionally transitioning into a steady state or displaying a low drift rate. Analysis using longitude resolved fluctuation spectra indicates the presence of two distinct repetition periods for the pulsar: P _3 = (10.8 ± 2.5)P and P _3 = (31.6 ± 4.2)P, where P denotes the pulsar period. Our investigation revealed that the subpulse separation remains consistent across different drift patterns, with P _2 = 2.°3 ± 0.°2. A more comprehensive analysis indicates that the unique drift behavior observed can be explained by a carousel model of the dipole field. Minor changes in P _2 and drift rate caused significant variations in the apparent P _3 and abrupt shifts in the drift direction, while the true repetition period (assuming first-order aliasing) changed by only ∼10%. We observe a drift band memory and apparent phase memory across the null state in this pulsar, as well as variations in the drift rate and drift direction across the null state, though we have not detected significant periodicity of the nulling itself. This suggests that these phenomena may arise from random null pulses intersecting with the frequently aliased drift bands.

We report on the radio eclipse properties of spider pulsar J1816+4510 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The high-sensitivity FAST observations will allow us to probe much deeper into the eclipse region of this pulsar at higher frequencies >1 GHz. The duration of the full eclipse, eclipse ingress, and egress at 1100, 1200, 1300, and 1400 MHz are measured, respectively. The variation of eclipse duration with frequency is studied by splitting the FAST observations into four subbands. It is found that the eclipse egress of PSR J1816+4510 takes longer than the ingress and becomes more symmetrical with increasing frequency. The variations of the durations with the frequency for the full eclipse, eclipse ingress, and egress follow a power-law decay pattern with different indices. The pulse profile variations near the eclipse are studied. It is found that the broadening of pulse profiles becomes more prominent with deepening into the eclipse region due to the scattering from the companion star. Moreover, the pulse smearing induced by the scattering and the rapid dispersion measure (DM) fluctuations within a subintegration during the eclipse egress at different frequencies and orbital phases is comparatively studied. It is found that the scattering plays a more important role than the DM fluctuations for the pulse smearing of the eclipse. The observations of this paper will provide important clues for the theoretical studies of the radio eclipse mechanism of the spider pulsar systems.