Single-pulse behaviours and fast radio burst-like micropulses in FAST wide-band observations of eight pulsars

Abstract

ABSTRACTWe searched for evidence of subpulse drifting and micropulses from eight pulsars. Our observations were carried out using the ultra-wide-bandwidth receiver installed on the Five-hundred-meter Aperture Spherical radio Telescope (FAST), as part of the pilot program for the Commensal Radio Astronomy FAST Survey (CRAFTS). For three pulsars (PSRs J0426+4933, J0815+4611, J1529+40), we detected single pulses for the first time. Four pulsars [PSRs J0426+4933, J0815+4611, J1529+40, J1945−0040 (B1942–00)] were observed to undergo subpulse drifting. Notable features include bimodal behaviour in the nulling of PSR J0034−0721 (B0031–07). For this pulsar, short-duration (≲10 period) null events were shown to be frequency-dependent, whereas long-duration null events were frequency-independent. The driftings of the pulse components for this pulsar overlapped in time, and the integrated profiles of the drift modes are shown to be distinct, indicating a different energy distribution. Subpulse drifting is detected for PSR J0426+4933 at ∼400 MHz, but becomes undetectable above 600 MHz, probably becuase of the disappearance of one pulse component. Microstructures have been detected in pulses from PSRs J0034−0721 and J0151−0635 (B0148–06). The quasi-periodic microstructure emission in PSR J0034−0721 was detectable at low observing frequencies. The duration of the micropulses was found to be frequency-dependent. In a similar fashion to fast radio bursts, the detected micropulses were bandwith-limited, with a characteristic bandwidth of 128.4 ± 31.6 MHz for PSR J0034−0721 and of 93.3 ± 3.2 MHz for PSR J0151−0635.