SIZE OF THE VELA PULSAR'S EMISSION REGION AT 18 cm WAVELENGTH

Gwinn, C. R.; Johnson, Michael D.; Jauncey, D. L.; Tzioumis, A. K.; Hirabayashi, H.; Kobayashi, Hideyuki; Murata, Yasuhiro; Edwards, P. G.; Dougherty, S. M.; Carlson, Brent; Rizzo, D. Del; Quick, J.; Flanagan, C. S.; McCulloch, P. M.

doi:10.1088/0004-637x/758/1/7

Cited by 10 publications

(5 citation statements)

References 79 publications

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“…The y-intercept of the fit is close to the noise level estimated for the empty spectral range of this gate, discussed in Section 5.1 below. The figure also shows, as a dotted line, results for noise in a fit to the global distribution of visibility discussed in Gwinn et al (2012). The two techniques usually agree well, for gates and spectral ranges with high amplitude, so that leakage of noise into adjacent bins is small, and the distribution can be characterized well.…”

Section: Observations: Noise On a Short Baselinementioning

confidence: 75%

“…Alternative analyses, involving a model for the distribution of flux density of the scintillating source, avoid use of bins completely and so eliminate "noise leakage." Such analyses can estimate all parameters, including noise parameters, simultaneously (as in Gwinn et al 2012;. These methods are also insensitive to correlations between spectral channels.…”

Section: Effects Of Scintillation Variability Correlation and Binnmentioning

confidence: 99%

“…Thus, the 3-parameter model is excellent. If we adopt the parameters from Gwinn et al (2012) shown by the dashed lines in Figure 4, the mean square residual is 3.3 × 10 −3 .…”

Section: Observations: Noise On a Short Baselinementioning

confidence: 99%

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Noise in the Cross-Power Spectrum of the Vela Pulsar

Gwinn¹,

Johnson²,

Jauncey³

et al. 2012

ApJ

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We compare the noise in interferometric measurements of the Vela pulsar from ground-and space-based antennas with theoretical predictions. The noise depends on both the flux density and the interferometric phase of the source. Because the Vela pulsar is bright and scintillating, these comparisons extend into both the low and high signal-to-noise regimes. Furthermore, our diversity of baselines explores the full range of variation in interferometric phase. We find excellent agreement between theoretical expectations and our estimates of noise among samples within the characteristic scintillation scales. Namely, the noise is drawn from an elliptical Gaussian distribution in the complex plane, centered on the signal. The major axis, aligned with the signal phase, varies quadratically with the signal, while the minor axis, at quadrature, varies with the same linear coefficients. For weak signal, the noise approaches a circular Gaussian distribution. Both the variance and covariance of the noise are also affected by artifacts of digitization and correlation. In particular, we show that gating introduces correlations between nearby spectral channels.

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Section: Observations: Noise On a Short Baselinementioning

confidence: 75%

Section: Effects Of Scintillation Variability Correlation and Binnmentioning

confidence: 99%

See 1 more Smart Citation

Noise in the Cross-Power Spectrum of the Vela Pulsar

Gwinn¹,

Johnson²,

Jauncey³

et al. 2012

ApJ

Self Cite

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“…("Stars twinkle, planets do not.") The depth of modulation reveals the size of the emission region (Cohen et al 1966;Readhead & Hewish 1972;Hewish et al 1974;Gwinn et al 2012b;Johnson et al 2012b). More precisely, source size affects the distribution of flux density for a scintillating source.…”

Section: Propagation Effectsmentioning

confidence: 99%

Radio Pulsars

et al. 2015

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Almost 50 years after radio pulsars were discovered in 1967, our understanding of these objects remains incomplete. On the one hand, within a few years it became clear that neutron star rotation gives rise to the extremely stable sequence of radio pulses, that the kinetic energy of rotation provides the reservoir of energy, and that electromagnetic fields are the braking mechanism. On the other hand, no consensus regarding the mechanism of coherent radio emission or the conversion of electromagnetic energy to particle energy yet exists. In this review, we report on three aspects of pulsar structure that have seen recent progress: the self-consistent theory of the magnetosphere of an oblique magnetic rotator; the location, geometry, and optics of radio emission; and evolution of the angle between spin and magnetic axes. These allow us to take the next step in understanding the physical nature of the pulsar activity.

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“…In many pulsars, the scintillation pattern is different for different parts of the pulse profile, evidence that the interstellar screen re-solves the pulsar emission region (e.g. Backer 1975;Smirnova et al 1996;Gupta et al 1999;Gwinn et al 2000Gwinn et al , 2012Johnson et al 2012;Pen et al 2014;Main et al 2017). In order to place physical sizes and separations on pulse components using these measurements, one must have an understanding of the scattering geometry, particularly the distances to and the resolving powers of the scattering screens.…”

mentioning

confidence: 99%

Disentangling interstellar plasma screens with pulsar VLBI: combining auto- and cross-correlations

Simard

Pen

Marthi

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Pulsar scintillation allows a glimpse into small-scale plasma structures in the interstellar medium, if we can infer their properties from the observed scintillation pattern. With Very Long Baseline Interferometry, and working in delay-delay rate space (after a Fourier transform of the dynamic spectra) where the contributions of pairs of images to the interference pattern become localized, the scattering geometry and distribution of scattered images on the sky can be determined if a single, highly-anisotropic scattering screen is responsible for the scintillation. However, many pulsars are subject to much more complex scattering environments where this method cannot be used. We present a novel technique to reconstruct the scattered flux of the pulsar and solve for the scattering geometry in these complex cases by combining interferometric visibilities with cross-correlations of single-station intensities. This takes advantage of the fact that, considering a single image pair in delay-delay rate space, the visibilities are sensitive to the sum of the image angular displacements, while the cross-correlated intensities are sensitive to the difference, so that their combination can be used to localize both images of the pair. We show that this technique is able to reconstruct the previously published scattering geometry of PSR B0834+06, then apply it to simulations of more complicated scattering systems, where we find that it can distinguish features from different scattering screens even when the presence of multiple screens is not obvious in the Fourier transform of the visibilities. This technique will allow us to both better understand the distribution of scattering within our local interstellar medium and to apply current scintillometry techniques, such as modelling scintillation and constraining the location of pulsar emission, to sources for which a current lack of understanding of the scattering environment precludes the use of these techniques.

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SIZE OF THE VELA PULSAR'S EMISSION REGION AT 18 cm WAVELENGTH

Cited by 10 publications

References 79 publications

Noise in the Cross-Power Spectrum of the Vela Pulsar

Noise in the Cross-Power Spectrum of the Vela Pulsar

Radio Pulsars

Disentangling interstellar plasma screens with pulsar VLBI: combining auto- and cross-correlations

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