| 12th of January 2023 |
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| Nulling in PSR J1401−6357 |
| by Chen et al. |
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Pulsars are like celestial lighthouses, emitting regular flashes of
radio waves. But occasionally the pulse emission quenches abruptly
for a period of time, which is referred to as nulling -- a phenomenon
that has been detected in more than 200 pulsars (of order 10% of the
known pulsar population). Pulse nulling appears to occur at all
frequencies and to all components simultaneously, but partial nulls
have also been detected. A variety of models have been proposed for
nulling, such as orbital companions, missing line of sight, switching
between curvature radiation and inverse Compton scattering, non-radial
oscillations, precessional torques, magnetic field instabilities,
switching between magnetospheric states, and the modification of
the surface magnetic field.
Chen et al. report on a detailed single pulse analysis of the radio emission from the pulsar J1401−6357 (B1358−63) based on data observed with the ultrawideband low-frequency receiver on the Parkes radio telescope, Murriyang. In addition to a weak leading component, the integrated pulse profile features a single-humped structure with a slight asymmetry. Well-defined nulls, with an estimated nulling fraction greater than 2%, are present across the whole frequency band. No emission is detected in the average pulse profile integrated over all null pulses. The observations also reveal the existence of sub-pulse drifting in this pulsar for the first time, providing further confirmation that the phenomena of pulse nulling and subpulse drifting are independent of observing frequency, and suggesting that they invoke changes on the global magnetospheric scale. The plot above shows a single pulse stacks for PSR J1401−6357 at one of eight different frequencies across the UWL band, with the corresponding average pulse profiles (blue) shown in the left hand side panel. The x-axis is the pulse number and the y-axis is longitude in degrees, with only the portion around the pulse shown. The three intervals of quenching emission are indicated by the white rectangles in each plot. The averaged null pulse profiles are shown with red lines. No significant emission is present in the null pulse profiles. |