Differential frequency-dependent delay from the pulsar magnetosphere
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Some radio pulsars show clear "drifting subpulses", in which subpulses are seen to drift in pulse longitude in a systematic pattern. Here we examine how the drifting subpulses of PSR B0809+74 evolve with time and observing frequency. We show that the subpulse period (P3) is constant on timescales of days, months and years, and between 14-5100 MHz. Despite this, the shapes of the driftbands change radically with frequency. Previous studies have concluded that, while the subpulses appear to move through the pulse window approximately linearly at low frequencies (<500 MHz), a discrete step of ~180° in subpulse phase is observed at higher frequencies (>820 MHz) near to the peak of the average pulse profile. We use LOFAR, GMRT, GBT, WSRT and Effelsberg 100-m data to explore the frequency-dependence of this phase step. We show that the size of the subpulse phase step increases gradually, and is observable even at low frequencies. We attribute the subpulse phase step to the presence of two separate driftbands, whose relative arrival times vary with frequency - one driftband arriving 30 pulses earlier at 20 MHz than it does at 1380 MHz, whilst the other arrives simultaneously at all frequencies. The drifting pattern which is observed here cannot be explained by either the rotating carousel model or the surface oscillation model, and could provide new insight into the physical processes happening within the pulsar magnetosphere.
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Low-frequency Observations of the Subpulse Drifter PSR J0034-0721 with the Murchison Widefield ArrayMcSweeney, S.; Bhat, Ramesh; Tremblay, Steven; Deshpande, A.; Ord, S. (2017)© 2017. The American Astronomical Society. All rights reserved.The phenomenon of subpulse drifting may hold the key to understanding the pulsar emission mechanism. Here, we report on new observations of PSR J0034-0721 ...
Karastergiou, A.; Johnston, S.; Andersson, N.; Breton, R.; Brook, P.; Gwinn, C.; Lewandowska, N.; Keane, E.; Kramer, M.; Macquart, Jean-Pierre; Serylak, M.; Shannon, R.; Stappers, B.; Van Leeuwen, J.; Verbiest, J.; Weltevrede, P.; Wright, G. (2014)The SKA will discover tens of thousands of pulsars and provide unprecedented data quality on these, as well as the currently known population, due to its unrivalled sensitivity. Pulsars are known to be variable on numerous ...
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