Detection of Echoes in PSR B1508+55 at Frequencies below 100 MHz Using the LWA1

Bansal, Karishma; Taylor, G. B.; Stovall, K.; Dowell, Jayce

doi:10.3847/1538-4357/ab76bc

Cited by 10 publications

(11 citation statements)

References 29 publications

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“…component at 650 MHz. Bansal et al (2020) note that the nondetection above 300 MHz by previous observations is due to its steep spectral index. Another possibility to consider is that the deflection angle (320 mas at < 100 MHz), which is quadratic in wavelength, is insufficient to refract the component into the line of sight at shorter wavelengths.…”

Section: Possible Scenariosmentioning

confidence: 56%

“…Further LOFAR observations have now revealed the presence of multiple images (Wucknitz 2019) roughly aligned along the proper motion vector, suggesting that the pulsar is moving towards perhaps linearly aligned refracting structures. Bansal et al (2020) report the detection of these echoes at frequencies below 100 MHz.…”

Section: Psr B1508+55mentioning

confidence: 93%

“…While these pulsed were detected in the LOFAR observations, we do not detect them in the GMRT 550-750 MHz observations. Additionally, Bansal et al (2020) measure a distance of ∼ 251 pc to a lens based on their observations of B1508+55 at frequencies < 100 MHz.…”

Section: Possible Scenariosmentioning

confidence: 99%

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Scintillation of PSR B1508+55 -- the view from a 10,000-km baseline

Marthi,

Simard,

Main

et al. 2020

Preprint

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We report on the simultaneous Giant Metrewave Radio Telescope (GMRT) and Algonquin Radio Observatory (ARO) observations at 550-750 MHz of the scintillation of PSR B1508+55, resulting in a ∼10,000-km baseline. This regime of measurement lies between the shorter few 100-1000 km baselines of earlier multi-station observations and the much longer earth-space baselines. We measure a scintillation cross-correlation coefficient of 0.22, offset from zero time lag due to a ∼ 45 s traversal time of the scintillation pattern. The scintillation time of 135 s is 3× longer, ruling out anisotropic as well as strictly 1D scattering. Hence, the low cross-correlation coefficient is indicative of highly anisotropic but 2D scattering. The common scintillation detected on the baseline is confined to low delays of 1𝜇s, suggesting that this correlation may not be associated with the prominent parabola detected at GMRT. Detection of pulsed echoes and their direct imaging with the Low Frequency Array (LOFAR) by a different group enable them to measure a distance of 120 pc to the screen causing these echoes. These previous measurements, alongside our observations, lead us to propose that there are two scattering screens: the closer 120 pc screen causing the prominent parabola detected at GMRT, and a screen further beyond causing the scintillation detected on the GMRT-ARO baseline. We advance the hypothesis that the 120-pc screen partially resolves the speckle images on the screen beyond and that their scattering axes are mutually misaligned, resulting in a two-dimensional scattered disc, to explain the low cross-correlation coefficient.

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Section: Possible Scenariosmentioning

confidence: 56%

Section: Psr B1508+55mentioning

confidence: 93%

See 1 more Smart Citation

Scintillation of PSR B1508+55 -- the view from a 10,000-km baseline

Marthi,

Simard,

Main

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…1 Further Low-Frequency Array (LOFAR) observations have now revealed the presence of multiple images (Wucknitz 2019) roughly aligned along the proper motion vector, suggesting that the pulsar is moving towards perhaps linearly aligned refracting structures. Bansal et al (2020) report the detection of these echoes at frequencies below 100 MHz.…”

Section: Psr B1508+55mentioning

confidence: 93%

“…While these pulses were detected in the LOFAR observations, we do not detect them in the GMRT 550-750 MHz observations. Additionally, Bansal et al (2020) measure a distance of ∼251 pc to a lens based on their observations of B1508+55 at frequencies < 100 MHz.…”

Section: Multiple Scattering Screens: Possible Scenariosmentioning

confidence: 99%

Scintillation of PSR B1508+55 – the view from a 10 000-km baseline

Marthi

Simard

Main

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We report on the simultaneous Giant Metrewave Radio Telescope (GMRT) and Algonquin Radio Observatory (ARO) observations at 550-750 MHz of the scintillation of PSR B1508+55, resulting in a ∼10,000-km baseline. This regime of measurement lies between the shorter few 100-1000 km baselines of earlier multi-station observations and the much longer earth-space baselines. We measure a scintillation cross-correlation coefficient of 0.22, offset from zero time lag due to a ∼45 s traversal time of the scintillation pattern. The scintillation time of 135 s is 3 × longer, ruling out isotropic as well as strictly 1D scattering. Hence, the low cross-correlation coefficient is indicative of highly anisotropic but 2D scattering. The common scintillation detected on the baseline is confined to low delays of ≲ 1μs, suggesting that this correlation may not be associated with the parabolic scintillation arc detected at the GMRT. Detection of pulsed echoes and their direct imaging with the Low Frequency Array (LOFAR) by a different group enable them to measure a distance of 125 pc to the screen causing these echoes. These previous measurements, alongside our observations, lead us to propose that there are at least two scattering screens: the closer 125 pc screen causing the scintillation arc detected at GMRT, and a screen further beyond causing the scintillation detected on the GMRT-ARO baseline. We advance the hypothesis that the 125-pc screen partially resolves the speckle images on the screen beyond leading to loss of coherence in the scintillation dynamic spectrum, to explain the low cross-correlation coefficient.

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Double-lens scintillometry: the variable scintillation of pulsar B1508 + 55

Sprenger

Main

Wucknitz

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We report on observations of PSR B1508+55’s scintillation at the Effelsberg 100-m telescope spanning from early 2020 to early 2022. In the autumn of 2020, close to the time the pulsar was predicted to cross echoes in its pulse profile, a sudden transition in the scintillation arcs from peculiar stripe-like features to parabolic arclets was observed. To infer a geometric model of the scattering we measure the effects of the annual velocity curve of Earth, of the relative movement of the line of sight, and of the projection of points on a second scattering screen and develop novel methods to do so. The latter phenomenon was discovered by this study and strongly indicates a two-screen scattering geometry. We derive an analytical two-screen model and demonstrate in a Markov Chain Monte Carlo analysis as well as simulations that it can be successfully applied to explain the observations by interpreting the transition as a change of relative amplitudes of images as well as a shift in the orientation of anisotropy. The collection of methods we demonstrate here is transferable to other pulsars with the potential to strongly improve constraints on scattering models.

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Detection of Echoes in PSR B1508+55 at Frequencies below 100 MHz Using the LWA1

Cited by 10 publications

References 29 publications

Scintillation of PSR B1508+55 -- the view from a 10,000-km baseline

Scintillation of PSR B1508+55 -- the view from a 10,000-km baseline

Scintillation of PSR B1508+55 – the view from a 10 000-km baseline

Double-lens scintillometry: the variable scintillation of pulsar B1508 + 55

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