Using black hole imaging to test general relativity in a regime where gravity is strong and yet non-dynamical poses a significant challenge: disentangle the astrophysical effects of the radiating source from the purely gravitational ones. In this talk, I will present an extensive parameter estimation survey of astrophysical models where the predicted general relativity's photon ring, a narrow ring-shaped feature predicted by general relativity but not yet observed, can be recovered. Our analysis uses the numerical framework AART to simulate black hole movies of stochastic, non-stationary, non-axisymmetric equatorial sources. Our results provide further evidence that, despite the astrophysical uncertainty, measurements of the photon ring can perform a stringent null test of the Kerr hypothesis.
Paolo Pani