High-resolution VLBI astrometry of pulsar scintillation screens with the θ - θ transform.

The recent development of |$\theta - \theta$| techniques in pulsar scintillometry has opened the door for new high-resolution imaging techniques of the scattering medium. By solving the phase retrieval problem and recovering the wavefield from a pulsar dynamic spectrum, the Doppler shift, time delay, and phase offset of individual images can be determined. However, the results of phase retrieval from a single dish are only known up to a constant phase rotation, which introduces extra parameters when doing astrometry using very long baseline interferometry. We present an extension to previous |$\theta - \theta$| methods using the interferometric visibilities between multiple stations to calibrate the wavefields. When applied to existing data for PSR B0834+06, we measure the effective screen distance and lens orientation with five times greater precision than was possible in previous work. [ABSTRACT FROM AUTHOR]