Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales

Understand

The Galactic Center black hole Sagittarius A* (Sgr A*) is a prime observing target for the Event Horizon Telescope (EHT), which can resolve the 1.3 mm emission from this source on angular scales comparable to that of the general relativistic shadow.

• Previous EHT observations have used visibility amplitudes to infer the morphology of the millimeter-wavelength emission.
• Potentially much richer source information is contained in the phases.
• We report on 1.3 mm phase information on Sgr A* obtained with the EHT on a total of 13 observing nights over 4 years.