Pulsar scattering in space and time

TL;DR

This paper presents a VLBI experiment studying pulsar scatter broadening in space and time, observing expanding rings and discussing calibration methods, advancing understanding of interstellar scattering effects.

Contribution

It introduces simultaneous spatial and temporal analysis of pulsar scattering using VLBI, providing first observational results of expanding rings and exploring calibration techniques.

Findings

Consistent detection of expanding scattering rings.

Observation of less broadened signals arriving earlier.

Discussion on amplitude calibration challenges.

Abstract

We report on a recent global VLBI experiment in which we study the scatter broadening of pulsars in the spatial and time domain simultaneously. Depending on the distribution of scattering screen(s), geometry predicts that the less spatially broadened parts of the signal arrive earlier than the more broadened parts. This means that over one pulse period the size of the scattering disk should grow from pointlike to the maximum size. An equivalent description is that the pulse profile shows less temporal broadening on the longer baselines. This contribution presents first results that are consistent with the expected expanding rings. We also briefly discuss how the autocorrelations can be used for amplitude calibration. This requires a thorough investigation of the digitisation and the sampler statistics and is not fully solved yet.