Observational signatures from supermassive black hole mimickers

Advanced interferometric techniques as those employed in the Event Horizon Telescope (EHT) and GRAVITY recently allowed to study the environment of the two nearest supermassive black hole candidates at horizon-scale resoluton. While current observations are consistent with accreting Kerr black holes, they also provide an excellent opportunity to look for signatures of compact objects beyond the Kerr hypothesis. We study the observational consequences of plasma accreting onto two kinds of black hole mimickers, namely, we consider models of gravastars and boson stars, as representatives of objects with and without a surface. To this end, we perform general relativistic magnetohydrodynamic simulations, which are then used to produce ray-trace and synthetic images, following a similar pipeline as that employed for model fitting within the EHT. Despite qualitative similarities in the images obtained, in general the models considered display significant differences in the mass estimates as compared to black holes, allowing them to be distinguished under very general assumptions.