2024ApJ...969...62S

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.