Low Frequency Observations of the Subpulse Drifter PSR J0034-0721 with the Murchison Widefield Array

Abstract

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 (B0031-07), carried out with the Murchison Widefield Array at 185 MHz. We observe three distinct drift modes whose "vertical" drift band separations ($P_3$) and relative abundances are consistent with previous studies at similar and higher frequencies. The driftbands, however, are observed to change their slopes over the course of individual drift modes, which can be interpreted as a continuously changing drift rate. The implied acceleration of the intrinsic carousel rotation cannot easily be explained by plasma models based on ExB drift. Furthermore, we find that methods of classifying the drift modes by means of $P_3$ measurements can sometimes produce erroneous identifications in the presence of a changing drift rate. The "horizontal" separation between driftbands ($P_2$) is found to be larger at later rotation phases within the pulse window, which is inconsistent with the established effects of retardation, aberration, and the motion of the visible point. Longer observations spanning at least ~10,000 pulses are required to determine how the carousel rotation parameters change from one drift sequence to the next.

Accepted for publication in ApJ, 11 pages, 6 figures

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• PSRCHIVE and PSRFITS An Open Approach to Radio Pulsar Data Storage and Analysis
• The subpulse modulation properties of pulsars at 92 cm and the frequency dependence of subpulse modulation
• The High Time and Frequency Resolution Capabilities of the Murchison Widefield Array
• Visibility of pulsar emission: motion of the visible point
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Cited by in corpus (4)

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• Subpulse Drifting, Nulling and Mode changing in PSR J2006$-$0807 with Core emission
• Science with the Murchison Widefield Array: Phase I Results and Phase II Opportunities
• MWA tied-array processing III: Microsecond time resolution via a polyphase synthesis filter