Artefacts of circumpolar cartography in radio pulsar polarization

Dyks, J.

doi:10.1093/mnrasl/slaa073

Cited by 12 publications

(6 citation statements)

References 23 publications

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“…We tested whether such a passage is present within our data by visually inspecting the position angle and corresponding ellipticity angle distributions plotted on the Poincaré sphere in Figure 9. Most of the polarization distribution is concentrated in a blob centred near (2Ψ, 2𝜒) = (45 • , −15 • ), however the low-density distribution with negative values of Ψ, i.e values associated with the downward drifting branch, appears to trace out a rough circular pattern similar to those presented in Figures 2 and 3 of Dyks (2020). This suggests the pulses associated with the downward-drifting PA branch are not associated with the reversed PA swing detected on MJD 59062.…”

Section: Polarization Modesmentioning

confidence: 54%

The dynamic magnetosphere of Swift J1818.0$-$1607

Lower,

Johnston,

Shannon

et al. 2020

Preprint

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Radio-loud magnetars display a wide variety of radio-pulse phenomenology seldom seen among the population of rotationpowered pulsars. Spectropolarimetry of the radio pulses from these objects has the potential to place constraints on their magnetic topology and unveil clues about the magnetar radio emission mechanism. Here we report on eight observations of the magnetar Swift J1818.0−1607 taken with the Parkes Ultra-Wideband Low receiver covering a wide frequency range from 0.7 to 4 GHz over a period of 5 months. The magnetar exhibits significant temporal profile evolution over this period, including the emergence of a new profile component with an inverted spectrum, two distinct types of radio emission mode switching, detected during two separate observations, and the appearance and disappearance of multiple polarization modes. These various phenomena are likely a result of ongoing reconfiguration of the plasma content and electric currents within the magnetosphere. Geometric fits to the linearly polarized position angle indicate we are viewing the magnetar at an angle of ∼99 • from the spin axis, and its magnetic and rotation axes are misaligned by ∼112 • . While conducting these fits, we found the position angle swing had reversed direction on MJD 59062 compared to observations taken 15 days earlier and 12 days later. We speculate this phenomena may be evidence the radio emission from this magnetar originates from magnetic field lines associated with two co-located magnetic poles that are connected by a coronal loop.

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Section: Polarization Modesmentioning

confidence: 54%

The dynamic magnetosphere of Swift J1818.0$-$1607

Lower,

Johnston,

Shannon

et al. 2020

Preprint

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“…Occasional departures from the smooth PA swing are detected in individual epochs, an example of which is shown in the top-right panel of Figure 1. The relatively smooth evolution of the PA swing persists at higher observing frequencies where the effects of interstellar scattering are negligible, indicating these features are due to either an unusually smooth transition between two orthogonal polarization modes or the result of birefringent propagation effects in the near-field environment (Dyks 2020). Birefringent propagation effects would also explain the unusually high circular polarization fraction (up to |V |/I = 0.54) as well as changes in handedness between observations.…”

Section: Radio Disappearance and Reactivationmentioning

confidence: 93%

The 2022 high-energy outburst and radio disappearing act of the magnetar 1E 1547.0-5408

Lower¹,

Younes²,

Scholz³

et al. 2023

Preprint

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We report the radio and high-energy properties of a new outburst from the radio-loud magnetar 1E 1547.0−5408. Following the detection of a short burst from the source with Swift-BAT on 2022 April 7, observations by NICER detected an increased flux peaking at (6.0±0.4)×10 −11 erg s −1 cm −2 in the soft X-ray band, falling to the baseline level of 1.7 × 10 −11 erg s −1 cm −2 over a 17-day period. Joint spectroscopic measurements by NICER and NuSTAR indicated no change in the hard non-thermal tail despite the prominent increase in soft X-rays. Observations at radio wavelengths with Murriyang, the 64-m Parkes radio telescope, revealed that the persistent radio emission from the magnetar disappeared at least 22 days prior to the initial Swift-BAT detection and was re-detected two weeks later. Such behavior is unprecedented in a radio-loud magnetar, and may point to an unnoticed slow rise in the high-energy activity prior to the detected short-bursts. Finally, our combined radio and X-ray timing revealed the outburst coincided with a spin-up glitch, where the spin-frequency and spin-down rate increased by 0.2 ± 0.1 µHz and (−2.4 ± 0.1) × 10 −12 s −2 respectively. A linear increase in spin-down rate of (−2.0 ± 0.1) × 10 −19 s −3 was also observed over 147 d of post-outburst timing. Our results suggest that the outburst may have been associated with a reconfiguration of the quasi-polar field lines, likely signalling a changing twist, accompanied by spatially broader heating of the surface and a brief quenching of the radio signal, yet without any measurable impact on the hard X-ray properties.

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“…Following the theoretical expectation that an orthogonal jump takes place when there is a change in dominance between the two orthogonal modes of emission, we would expect "true" orthogonal jumps to be accompanied by a drop of the polarization to zero. As described by Dyks (2020), apparent orthogonal jumps in PA will also result from the polarization state transitioning across the Poincaré sphere and passing close to the Stokes 𝑉 pole. In these cases, the polarization does not drop to zero, instead it is rotated from 𝐿 into 𝑉.…”

Section: Categorization Of Profile Polarization Featuresmentioning

confidence: 96%

Pulsar polarization: a broad-band population view with the Parkes Ultra-Wideband receiver

Oswald,

Johnston,

Karastergiou

et al. 2023

Preprint

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The radio polarization properties of the pulsar population are only superficially captured by the conventional picture of pulsar radio emission. We study the broadband polarization of 271 young radio pulsars, focusing particularly on circular polarization, using high quality observations made with the Ultra-Wideband Low receiver on Murriyang, the Parkes radio telescope. We seek to encapsulate polarization behaviour on a population scale by defining broad categories for frequency-and phase-dependent polarization evolution, studying the co-occurrences of these categorizations and comparing them with average polarization measurements and spin-down energy ( 𝐸). This work shows that deviations of the linear polarization position angle (PA) from the rotating vector model (RVM) are linked to the presence of circular polarization features and to frequency evolution of the polarization. Polarization fraction, circular polarization contribution and profile complexity all evolve with 𝐸 across the population, with the profiles of high-𝐸 pulsars being simple and highly linearly polarized. The relationship between polarization fraction and circular contribution is also seen to evolve such that highly polarized profiles show less variation in circular contribution with frequency than less strongly polarized profiles. This evolution is seen both across the population and across frequency for individual sources. Understanding pulsar radio polarization requires detailed study of individual sources and collective understanding of population-level trends. For the former, we provide visualizations of their phase-and frequency-resolved polarization parameters. For the latter, we have highlighted the importance of including the impact of circular polarization and of 𝐸.

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Artefacts of circumpolar cartography in radio pulsar polarization

Cited by 12 publications

References 23 publications

The dynamic magnetosphere of Swift J1818.0$-$1607

The dynamic magnetosphere of Swift J1818.0$-$1607

The 2022 high-energy outburst and radio disappearing act of the magnetar 1E 1547.0-5408

Pulsar polarization: a broad-band population view with the Parkes Ultra-Wideband receiver

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