Scintillation of PSR B1508+55 – the view from a 10 000-km baseline. Issue 4 (19th July 2021)

• Record Type: Journal Article
• Authors: Marthi, V R; Simard, D; Main, R A; Pen, U-L; van Kerkwijk, M H; Vanderlinde, K; Gupta, Y; Roberts, C; Quine, B M
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 506:Issue 4(2021)
• Page Start: 5160
• Page End: 5169
• Publication Date: 2021-07-19
• Subjects: scattering -- methods: observational -- techniques: interferometric -- pulsars: B1508+55 -- radio continuum: ISM; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1970
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: 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 an ∼10 000-km baseline. This regime of measurement lies between the shorter few 100- to 1000-km baselines of earlier multistation 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 one-dimensional scattering. Hence, the low cross-correlation coefficient is indicative of highly anisotropic but two-dimensional 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.