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24th of April 2018
Determining the distance to PSR J0437-4715
Li et al. have recently studied PSR J0437−4715, the nearest millisecond pulsar and the brightest at radio wavelengths. To explore the feasibility of achieving a parallax distance accuracy of one light-year, comparable to the recent timing result, with the technique of differential astrometry, they searched for compact radio sources quite close to PSR J0437−4715. Using existing data from the Very Large Array and the Australia Telescope Compact Array, they detected two sources with flat spectra, relatively stable flux densities of 0.9 and 1.0 mJy at 8.4 GHz and angular separations from the pulsar of 13 and 45 arcseconds.

With a network consisting of the Australian Long Baseline Array and the Kunming 40-m radio telescope, they found that both sources have a point-like structure and a high brightness temperatures consistent with them being the compact radio cores of extragalactic active galactic nuclei rather than Galactic radio stars. The finding of these two radio active galactic nuclei will enable high distance accuracy to be achieved with the in-beam phase-referencing very-long-baseline interferometric observations and provide one of the most stringent constraints on the time variability of the gravitational constant, G, in the near future.

More details are given in the paper, published in Monthly Notices of the Royal Astronomical Society.

As tomorrow is the ANZAC day public holiday in Australia, the next ADAP will be on April 26th.

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