50 pico arcsecond astrometry of pulsar emission

TL;DR

This paper demonstrates ultra-precise VLBI astrometry of pulsar emission, achieving sub nanoarcsecond accuracy to measure emission region size and altitude, opening new possibilities for pulsar distance and motion studies.

Contribution

The study introduces a novel VLBI technique using interstellar speckle patterns to measure pulsar emission regions with unprecedented precision.

Findings

Measured pulsar emission region at a few hundred km altitude.

Achieved sub nanoarcsecond astrometric accuracy.

Found emission region much closer to the star than the light cylinder.

Abstract

We use VLBI imaging of the interstellar scattering speckle pattern associated with the pulsar PSR 0834+06 to measure the astrometric motion of its emission. The ~ 5AU interstellar baselines, provided by interference between speckles spanning the scattering disk, enable us to detect motions with sub nanoarcsecond accuracy. We measure a small pulse deflection of ~18+/-2 km (not including geometric uncertainties), which is 100 times smaller than the native resolution of this interstellar interferometer. This implies that the emission region is small, and at an altitude of a few hundred km, with the exact value depending on field geometry. This is substantially closer to the star than to the light cylinder. Future VLBI measurements can improve on this finding. This new regime of ultra-precise astrometry may enable precision parallax distance determination of pulsar binary displacements.