The Black Hole Photon Ring II: Astrophysical Fluctuations*

Using black hole images to test general relativity in the dynamical, strong-field regime poses a significant challenge: how can the effects of the gravitational field be disentangled from the astrophysical details of the radiating source? The photon ring, whose angle-dependent diameter follows a shape predicted by general relativity, is a promising observable with a weak dependence on astrophysics. In this talk, I will present an extensive parameter-estimation survey of astrophysical models in which this ring shape can be recovered with high precision. The analysis was carried out using the numerical framework AART to simulate black hole movies of stochastic, non-stationary, non-axisymmetric equatorial sources. These results are relevant to the ongoing effort to develop space-based, very-long-baseline-interferometry missions targeting the photon rings of supermassive black holes.