The pulsar/massive star binary system PSR B1259−63/LS 2883 is one of
the best-studied gamma-ray binary systems.
Using the Australian Long Baseline Array, Miller-Jones et al. have conducted
Very Long Baseline Interferometry (VLBI) observations of PSR B1259−63 over
4.4 years, fully sampling the 3.4-year orbital period.
The image above shows the motion of PSR B1259−63 on the sky over time,
in both Right Ascension (top) and Declination (bottom).
The motion is due to the motion of the pulsar in the binary orbit,
the motion of the binary system across the sky, and the motion
of the Earth around the Sun.
The black line shows the best-fitting astrometric
solution. The dashed and dotted vertical lines show the epochs of
periastron and apastron, respectively.
More details are given in
the paper published in
Monthly Notices of the Royal Astronomical Society.