B0943+10: low-frequency study of subpulse periodicity in the Bright mode with LOFAR

Abstract

We use broadband sensitive LOFAR observations in the 25-80 MHz frequency range to study the single-pulse emission properties of the mode-switching pulsar B0943+10. We review the derivation of magnetospheric geometry, originally based on low-frequency radio data, and show that the geometry is less constrained than previously thought. This may be used to help explain the large fractional amplitudes of the observed thermal X-ray pulsations from the polar cap, which contradict the almost aligned rotator model of PSR B0943+10. We analyse the properties of drifting subpulses in the Bright mode and report on the minutes-long variations of the drift period. We searched for the periodic amplitude modulation of drifting subpulses, which is a vital argument for constraining several important system parameters: the degree of aliasing, the orientation of the line-of-sight vector with respect to magnetic and spin axes, the angular velocity of the carousel, and thus, the gradient of the accelerating potential in the polar gap. The periodic amplitude modulation was not detected, indicating that it may be a rare or narrow-band phenomenon. Based on our non-detection and review of available literature, we chose to leave the aliasing order unconstrained and derived the number of sparks under different assumptions about the aliasing order and geometry angles. Contrary to the previous findings, we did not find a large (of the order of 10%) gradual variation of the separation between subpulses throughout Bright mode. We speculate that this large variation may be due to the incorrect accounting for the curvature of the line of sight within the on-pulse window. Finally, we report on the frequency-dependent drift phase delay, which is similar to the delay reported previously for PSR B0809+74. We provide a quantitative explanation of the observed frequency-dependent drift phase delay within the carousel model.

updated to match the accepted version (A&A); added polarisation discussion and language corrections

References in corpus (12)

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• The origin of the frequency-dependent behaviour of pulsar radio profiles
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Cited by in corpus (10)

• A NICER view of PSR J0030+0451: evidence for a global-scale multipolar magnetic field
• The frequency-dependent behaviour of subpulse drifting: I. Carousel geometry and emission heights of PSR B0031-07
• Thermal emission and magnetic beaming in the radio and X-ray mode-switching PSR B0943+10
• PSR B0943+10: Mode Switch, Polar Cap Geometry, and Orthogonally Polarized Radiation
• PSR J0026-1955: A curious case of evolutionary subpulse drifting and nulling
• Expected imprints of the carousel in multi-frequency pulsar observations and new evidence for multi-altitude emission
• The Discovery of Transitive Phenomenon in the Radio Emission of the mode-switcher PSR B0943+10
• Testing the circularity of PSR B0818-41's carousel
• On the Geometry of Curvature Radiation and Implications for Subpulse Drifting
• Independent discovery of a nulling pulsar with unusual sub-pulse drifting properties with the Murchison Widefield Array