Differential frequency-dependent delay from the pulsar magnetosphere

Hassall, T. E.; Stappers, B. W.; Weltevrede, P.; Hessels, J. W. T.; Alexov, A.; Coenen, T.; Karastergiou, A.; Krämer, M.; Keane, E. F.; Kondratiev, V. I.; Leeuwen, J. van; Noutsos, A.; Pilia, M.; Serylak, M.; Sobey, C.; Zagkouris, K.; Fender, R. P.; Bell, M. E.; Broderick, J. W.; Eislöffel, J.; Falcke, H.; Grießmeier, Jean-Mathias; Kuniyoshi, M.; Miller-Jones, J. C. A.; Wise, Michael; Wucknitz, O.; Zarka, Philippe; Asgekar, A.; Batejat, F.; Bentum, Marinus Jan; Bernardi, G.; Best, P. N.; Bonafede, A.; Breitling, F.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Gasperin, F. de; Reijer, Jan Pieter de; Duscha, S.; Fallows, R. A.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Gunst, A. W.; Heald, G.; Hoeft, M.; Juette, E.; Maat, P.; McKean, J. P.; Norden, M. J.; Pandey-Pommier, M.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H. J. A.; Sluman, J.; Tang, Y.; Tasse, C.; Vermeulen, R. C.; Weeren, R. J. van; Wijnholds, Stefan J.; Yatawatta, S.

doi:10.1051/0004-6361/201220764

Cited by 27 publications

(16 citation statements)

References 41 publications

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“…Similar frequency-dependent effects have also been observed in PSR B0809+74 by Hassall et al (2013) and PSR B0943+10 by Bilous (2018). The latter argue that the evolution (in phase) of the drift bands can be understood in terms of the radius-to-frequency mapping (RFM; whereby the opening angle of the beam emerging from the same surface sparks increases at lower frequencies), affecting the projected phases at which the beamlets pass through the line of sight.…”

Section: Effect Of Finite Spark Sizesupporting

confidence: 59%

On the Geometry of Curvature Radiation and Implications for Subpulse Drifting

McSweeney

Bhat

Tremblay

et al. 2019

ApJ

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The phenomenon of subpulse drifting offers unique insights into the emission geometry of pulsars, and is commonly interpreted in terms of a rotating carousel of "spark" events near the stellar surface. We develop a detailed geometric model for the emission columns above a carousel of sparks that is entirely calculated in the observer's inertial frame, and which is consistent with the well-understood rotational effects of aberration and retardation. We explore the observational consequences of the model, including (1) the appearance of the reconstructed beam pattern via the cartographic transform and (2) the morphology of drift bands and how they might evolve as a function of frequency. The model, which is implemented in the software package PSRGEOM, is applicable to a wide range of viewing geometries, and we illustrate its implications using PSRs B0809+74 and B2034+19 as examples. Some specific predictions are made with respect to the difference between subpulse evolution and microstructure evolution, which provides a way to further test our model.

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Section: Effect Of Finite Spark Sizesupporting

confidence: 59%

On the Geometry of Curvature Radiation and Implications for Subpulse Drifting

McSweeney

Bhat

Tremblay

et al. 2019

ApJ

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“…Owing to the broadband nature of our observations, we were able to detect a so-called frequency-dependent phase delay, first discovered for PSR B0809+74 by Hassall et al (2013). In addition to variation within the on-pulse window, single pulses at different parts of the observing band have different drift phases at the same time.…”

Section: Introductionmentioning

confidence: 68%

“…4. Such folds are called "modfolds" or "driftbands" in the literature (Backus et al 2011;Hassall et al 2013).…”

Section: P 3 Folds In B Modementioning

confidence: 99%

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

Bilous

2018

A&A

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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 strongly 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 contradicted the almost aligned rotator model of PSR B0943+10. We analyse the properties of drifting subpulses in the Bright mode and report on the short-scale (minutes) 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 the 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 of subpulse separation 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.

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“…Pulsar B0809+74 shows drifting sub-pulses and has a frequency-dependent profile. It is discussed in detail in Hassall et al (2013). Pulsar B1133+16 shows two components where the separation, the amplitudes, and widths are frequency-dependent.…”

Section: Detected Pulsarsmentioning

confidence: 99%

A census of the pulsar population observed with the international LOFAR station FR606 at low frequencies (25–80 MHz)

Bondonneau

Grießmeier

Theureau

et al. 2020

A&A

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Context. To date, only 69 pulsars have been identified with a detected pulsed radio emission below 100 MHz. A LOFARcore LBA census and a dedicated campaign with the Nançay LOFAR station in stand-alone mode were carried out in the years 2014−2017 in order to extend the known population in this frequency range. Aims. In this paper, we aim to extend the sample of known radio pulsars at low frequencies and to produce a catalogue in the frequency range of 25-80 MHz. This will allow future studies to probe the local Galactic pulsar population, in addition to helping explain their emission mechanism, better characterising the low-frequency turnover in their spectra, and obtaining new information about the interstellar medium through the study of dispersion, scattering, and scintillation. Methods. We observed 102 pulsars that are known to emit radio pulses below 200 MHz and with declination above −30 • . We used the the Low Band Antennas (LBA) of the LOw Frequency ARray (LOFAR) international station FR606 at the Nançay Radio Observatory in stand-alone mode, recording data between 25-80 MHz. Results. Out of our sample of 102 pulsars, we detected 64. We confirmed the existence of ten pulsars detected below 100 MHz by the LOFAR LBA census for the first time (Bilous et al. 2019) and we added two more pulsars that had never before been detected in this frequency range. We provided average pulse profiles, DM values, and mean flux densities (or upper limits in the case of non-detections). The comparison with previously published results allows us to identify a hitherto unknown spectral turnover for five pulsars, confirming the expectation that spectral turnovers are a widespread phenomenon.

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Differential frequency-dependent delay from the pulsar magnetosphere

Cited by 27 publications

References 41 publications

On the Geometry of Curvature Radiation and Implications for Subpulse Drifting

On the Geometry of Curvature Radiation and Implications for Subpulse Drifting

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

A census of the pulsar population observed with the international LOFAR station FR606 at low frequencies (25–80 MHz)

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