Observational optical constraints of regular black holes

In this work, we consider two recently introduced novel regular black hole solutions and investigate the circular null geodesics to find the connection between the photon sphere, the horizon and the black hole shadow radii. We also study the energy emission rate for these solutions and discuss how the parameters of models affect the emission of particles around the black holes. Furthermore, we compare the resulting shadow of these regular black holes with observational data of the Event Horizon Telescope and find the allowed regions of the model parameters for which the obtained shadow is consistent with the data. Finally, we employ the correspondence between the quasinormal modes in the eikonal limit and shadow radius to study the scalar field perturbations in these backgrounds.