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The binary pulsar J2222-0137 is an enigmatic system containing a partially recycled millisecond pulsar and a companion of unknown nature. Whilst the low eccentricity of the system favors a white dwarf companion, an unusual double neutron star system is also a possibility, and optical observations will be able to distinguish between these possibilities. In order to allow the absolute luminosity (or upper limit) of the companion object to be properly calibrated, we undertook astrometric observations with the Very Long Baseline Array to constrain the system distance via a measurement of annual geometric parallax. With these observations, we measure the parallax of the J2222-0137 system to be 3.742 +0.013 -0.016 milliarcseconds, yielding a distance of 267.3 +1.2 -0.9 pc, and measure the transverse velocity to be 57.1 +0.3 -0.2 km/s. Fixing these parameters in the pulsar timing model made it possible to obtain a measurement of Shapiro delay and hence the system inclination, which shows that the system is nearly edge-on (sin i = 0.9985 +/- 0.0005). Furthermore, we were able to detect the orbital motion of J2222-0137 in our VLBI observations and measure the longitude of ascending node. The VLBI astrometry yields the most accurate distance obtained for a radio pulsar to date, and is furthermore the most accurate parallax for any radio source obtained at low radio frequencies (below ~5 GHz, where the ionosphere dominates the error budget). Using the astrometric results, we show the companion to J2222-0137 will be easily detectable in deep optical observations if it is a white dwarf. Finally, we discuss the implications of this measurement for future ultra-high-precision astrometry, in particular in support of pulsar timing arrays.
The PSR J2222-0137 binary system is a unique laboratory for testing gravity theories. To fully exploit its potential for the tests, we aim to improve the measurements of its physical parameters: spin, orbital orientation, and post-Keplerian parameter
We describe a data reduction pipeline for VLBI astrometric observations of pulsars, implemented using the ParselTongue AIPS interface. The pipeline performs calibration (including ionosphere modeling), phase referencing with proper accounting of refe
Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars, and multiwavelength observations of their companion stars. Very Long Baseline Interferometry (VLBI) a
With the publication of Gaia DR2, 1.3 billion stars now have public parallax and proper motion measurements. In this contribution, we compare the results for sources that have both optical and radio measurements, focusing on circumstellar masers. For
IRAS 16293-2422 is a very well studied young stellar system seen in projection towards the L1689N cloud in the Ophiuchus complex. However, its distance is still uncertain with a range of values from 120 pc to 180 pc. Our goal is to measure the trigon