Method for Determining the Parameters of a Ring-Like Structure from the Visibility Function Shape

Black hole images obtained by very long baseline interferometry (VLBI) by the Event Horizon Telescope are a new tool for testing general relativity in super-strong gravitational fields. These images demonstrated a ring-like structure which can be explained as the black hole shadow image. To date, there are no reliable methods for determining the parameters of these ring-like structures, such as diameter, width, and asymmetry. In this paper, an algorithm for determining black hole image parameters is proposed using a Gaussian asymmetric ring as an example. Using the proposed method, the diameter and asymmetry parameters of the image of a supermassive black hole in the galaxy M87* were estimated based on observational data obtained by the Event Horizon Telescope group.