H-FISTA: a hierarchical algorithm for phase retrieval with application to pulsar dynamic spectra

Osłowski, S.; Walker, Mark A.

doi:10.1093/mnras/stac3412

Cited by 4 publications

(4 citation statements)

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“…Secondary spectra were then created by taking the squared modulus of the two-dimensional Fourier transform (i.e., the power spectrum) of the corresponding 50 MHz dynamic spectrum and displaying it logarithmically (in decibels). While this is certainly one of the more commonly used methods for obtaining the secondary spectrum, alternative approaches have recently been explored (Osłowski & Walker 2023).…”

Section: Discussionmentioning

confidence: 99%

A Simultaneous Dual-frequency Scintillation Arc Survey of Six Bright Canonical Pulsars Using the Upgraded Giant Metrewave Radio Telescope

Turner,

Joshi,

McLaughlin

et al. 2024

ApJ

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We use the upgraded Giant Metrewave Radio Telescope (uGMRT) to measure scintillation arc properties in six bright canonical pulsars with simultaneous dual-frequency coverage. These observations, at frequencies from 300 to 750 MHz, allowed for detailed analysis of arc evolution across frequency and epoch. We perform more robust determinations of frequency dependence for arc curvature, scintillation bandwidth, and scintillation timescale, and comparison between arc curvature and pseudo-curvature than allowed by single-frequency-band-per-epoch measurements, which we find to agree with theory and previous literature. We find a strong correlation between arc asymmetry and arc curvature, which we have replicated using simulations, and attribute to a bias in the Hough transform approach to scintillation arc analysis. Possible evidence for an approximately week-long timescale over which a given scattering screen dominates signal propagation was found by tracking visible scintillation arcs in each epoch in PSR J1136+1551. The inclusion of a 155-minute observation allowed us to resolve the scale of scintillation variations on short timescales, which we find to be directly tied to the amount of interstellar medium sampled over the observation. Some of our pulsars showed either consistent or emerging asymmetries in arc curvature, indicating instances of refraction across their lines of sight. Significant features in various pulsars, such as multiple scintillation arcs in PSR J1136+1551 and flat arclets in PSR J1509+5531, that have been found in previous works, were also detected. The simultaneous multiple-band observing capability of the upgraded GMRT shows excellent promise for future pulsar scintillation work.

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Section: Discussionmentioning

confidence: 99%

A Simultaneous Dual-frequency Scintillation Arc Survey of Six Bright Canonical Pulsars Using the Upgraded Giant Metrewave Radio Telescope

Turner,

Joshi,

McLaughlin

et al. 2024

ApJ

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“…Studies to date have all been incoherent, attempting to measure the primary scintillation arc without full information of inverted arclets results from interfering pairs of images which arise in highly anisotropic screens. Phase retrie v al techniques such as holography (Walker et al 2008 ;Osłowski & Walker 2023 ), cyclic spectroscopy (Demorest 2011 ;Walker et al 2013 ), and the θ−θ transformation (Sprenger et al 2021 ;Baker et al 2022 ) can greatly increase the precision. In sources with discrete features, the mo v ement of features between observ ations gi ves another constraint on the average arc curvature in the between observations, and can be used as an additional precise constraint (Sprenger et al 2022 ).…”

Section: O N C L U S I O N S a N D F U T U R E P Ro S P E C T Smentioning

confidence: 99%

Variable scintillation arcs of millisecond pulsars observed with the Large European Array for Pulsars

Main

Antoniadis

Chen

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We present the first large sample of scintillation arcs in millisecond pulsars, analysing 12 sources observed with the Large European Array for Pulsars (LEAP), and the Effelsberg 100 m telescope. We estimate the delays from multipath propagation, measuring significant correlated changes in scattering timescales over a 10-year timespan. Many sources show compact concentrations of power in the secondary spectrum, which in PSRs J0613−0200 and J1600−3053 can be tracked between observations, and are consistent with compact scattering at fixed angular positions. Other sources such as PSRs J1643−1224 and J0621+1002 show diffuse, asymmetric arcs which are likely related to phase-gradients across the scattering screen. PSR B1937+21 shows at least three distinct screens which dominate at different times and evidence of varying screen axes or multi-screen interactions. We model annual and orbital arc curvature variations in PSR J0613−0200, providing a measurement of the longitude of ascending node, resolving the sense of the orbital inclination, where our best fit model is of a screen with variable axis of anisotropy over time, corresponding to changes in the scattering of the source. Unmodeled variations of the screen’s axis of anisotropy are likely to be a limiting factor in determining orbital parameters with scintillation, requiring careful consideration of variable screen properties, or independent VLBI measurements. Long-term scintillation studies such as this serve as a complementary tool to pulsar timing, to measure a source of correlated noise for pulsar timing arrays, solve pulsar orbits, and to understand the astrophysical origin of scattering screens.

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“…Previous attempts to infer the impulse response from observed data fall into two categories: phase retrieval using the dynamic spectrum (Walker et al 2008;Baker et al 2022), and using the cyclic nature of a pulsar signal to conduct cyclic spectroscopy (Demorest 2011;Walker et al 2013). Phase retrieval techniques usually assume that the impulse response is very sparse in some basis, and are ineffective otherwise (Osłowski & Walker 2022). Cyclic spectroscopy, on the other hand, assumes that the pulsar signal is a cyclostationary signal.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic Emission of PSR B1937+21 at 327 MHz

Mahajan,

van Kerkwijk

2024

ApJ

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At 327 MHz, the observed emission of PSR B1937+21 is greatly affected by scattering in the interstellar medium, on a timescale of order the pulse period. We use the bright impulsive giant pulses emitted by the pulsar to measure the impulse response of the interstellar medium and then recover the intrinsic emission of the pulsar by deconvolution—revealing fine structure on timescales not normally observable. We find that the intrinsic widths of the main pulse and interpulse in the pulse profile are similar to those measured at higher frequencies. We detect 60,270 giant pulses, which typically appear as narrow, ∼100 ns bursts consisting of one to a few nanoshots with widths ≲ 10 ns. However, about 10% of the giant pulses exhibit multiple bursts that seem to be causally related to each other. We also report the first detection of giant micropulses in PSR B1937+21, primarily associated with the regular main pulse emission. These are distinct from giant pulses not only in the phases at which they occur, but also in their larger widths, of order a microsecond, and steeper energy distribution. These measurements place useful observational constraints on emission mechanisms for giant pulses as well as the regular radio emission of millisecond pulsars.

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H-FISTA: a hierarchical algorithm for phase retrieval with application to pulsar dynamic spectra

Cited by 4 publications

References 50 publications

A Simultaneous Dual-frequency Scintillation Arc Survey of Six Bright Canonical Pulsars Using the Upgraded Giant Metrewave Radio Telescope

A Simultaneous Dual-frequency Scintillation Arc Survey of Six Bright Canonical Pulsars Using the Upgraded Giant Metrewave Radio Telescope

Variable scintillation arcs of millisecond pulsars observed with the Large European Array for Pulsars

Intrinsic Emission of PSR B1937+21 at 327 MHz

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