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15th of May 2019
The scintillating relativistic binary PSR J1141-6545
(by Reardon et al.)
Reardon et al. have observed the relativistic binary pulsar PSR J1141−6545 with the Parkes 64 m radio telescope in order to model the diffractive intensity scintillations and improve the accuracy of the astrometric timing model. The scintillation of pulsars at radio wavelengths is like the familiar twinkling of starlight. The intensity variations caused by interstellar scintillation are seen in all observations of radio pulsars at centimetre to metre wavelengths. They are caused by transverse fluctuations in the electron density of the turbulent ionised interstellar medium (IISM). The long-term scintillation of PSR J1141-6545, which shows orbital and annual variations, allows us to measure parameters that are difficult to measure with pulsar timing alone. The timescale of the scintillations depends on the relative motion of the pulsar and the IISM and, as the pulsar is in a binary system, sometimes it is moving in the same direction as the IISM (which slows down the scintillation timescale) and sometimes is is moving in the opposite direction as the IISM (which speeds up the scintillation timescale).

The image above shows the dynamic spectrum of four PSR J1141−6545 observations, covering a combined 2.2 pulsar orbits. Stretching of the scintles (in black) in time is evident (at e.g. 100 and 400 minutes) when the pulsar orbital velocity reaches a minimum. The vertical white bars are periods between the individual observations, while horizontal white bars and patches were removed because of radio-frequency interference. The greyscale shows the normalised flux with the black and white limits chosen to optimise the visualisation of scintles. Full results are published in the paper published in Monthly Notices of the Royal Astronomical Society.

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