Interstellar scintillations of PSR B1919+21: space-ground interferometry

Abstract

We carried out observations of pulsar PSR B1919+21 at 324 MHz to study the distribution of interstellar plasma in the direction of this pulsar. We used the RadioAstron (RA) space radiotelescope together with two ground telescopes: Westerbork (WB) and Green Bank (GB). The maximum baseline projection for the space-ground interferometer was about 60000 km. We show that interstellar scintillation of this pulsar consists of two components: diffractive scintillations from inhomogeneities in a layer of turbulent plasma at a distance $z_1=440$ pc from the observer or homogeneously distributed scattering material to pulsar; and weak scintillations from a screen located near the observer at $z_2=0.14\pm 0.05$ pc. Furthermore, in the direction to the pulsar we detected a prism that deflects radiation, leading to a shift of observed source position. We show that the influence of the ionosphere can be ignored for the space-ground baseline. Analysis of the spatial coherence function for the space-ground baseline (RA-GB) yielded the scattering angle in the observer plane: ${\theta }_{scat}$ = 0.7 mas. An analysis of the time-frequency correlation function for weak scintillations yielded the angle of refraction in the direction to the pulsar: ${\theta }_{ref,0}$ = 110 ms and the distance to the prism $z_{prism}\le 2$ pc.

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• Revealing compact structures of interstellar plasma in the Galaxy with RadioAstron
• Disentangling interstellar plasma screens with pulsar VLBI: Combining auto- and cross-correlations
• Probing the ionosphere by the pulsar B0950+08 with help of RadioAstron ground-space baselines
• Uncertainty in Measurements of the Distances of Scattering Screens in Pulsar Observations
• Interstellar scintillation of sources B0821+394 and B1812+412 as observed by the LPA LPI radio telescope