DOI

https://doi.org/10.48717/0dxb-5332

Project

EM156

Title

e-EVN: EN010A, EV023, EA065A, EM156A

Abstract

We propose a series of three astrometric measurements of the long-lived thermal tidal disruption event AT2019azh, aiming to determine the velocity of the radio-emitting outflow by measuring its astrometric shift over time. This will allow us to discriminate between different models for the radio emission, and, in combination with the existing radio spectra, determine the outflow geometry. The brightness, longevity and proximity of this tidal disruption event provide a unique opportunity to make such a measurement, with the source having gradually brightened over the past two years and now appearing to reach a peak at 1 GHz. To control the systematic uncertainties in the astrometry, we request an initial 2-hour e-EVN observation to find an appropriate in-beam calibrator within a few arcminutes. Once such a calibrator has been identified, we request three six-hour observations with the full EVN over the next two years. These observations will provide the first direct measurement of the outflow velocity in a thermal tidal disruption event, accurate to better than 0.1c.