Relative Astrometry of Compact Flaring Structures in Sgr A* with Polarimetric VLBI

TL;DR

This paper introduces a polarimetric interferometry technique using VLBI to precisely locate and track compact flaring structures near Sgr A*, enabling high-resolution astrometry with current technology.

Contribution

The paper presents a novel method for extracting spatial and polarization information of flares in Sgr A* using polarimetric VLBI, improving imaging capabilities.

Findings

Achieves ~5 microarcsecond astrometry of flares near Sgr A*

Single baseline suffices for polarization and displacement of faint components

Multiple baselines enable 2D displacement reconstruction

Abstract

We demonstrate that polarimetric interferometry can be used to extract precise spatial information about compact polarized flares of Sgr A*. We show that, for a faint dynamical component, a single interferometric baseline suffices to determine both its polarization and projected displacement from the quiescent intensity centroid. A second baseline enables two-dimensional reconstruction of the displacement, and additional baselines can self-calibrate using the flare, enhancing synthesis imaging of the quiescent emission. We apply this technique to simulated 1.3-mm wavelength observations of a "hot spot" embedded in a radiatively inefficient accretion disk around Sgr A*. Our results indicate that, even with current sensitivities, polarimetric interferometry with the Event Horizon Telescope can achieve ~5 microarcsecond relative astrometry of compact flaring structures near Sgr A* on timescales of minutes.