Speaker
Description
Zakharov et al. (2005a) predicted an opportunity to reconstruct a shadow in Sgr A$^*$ with ground based or space-ground interferometer acting in mm or sub-mm band (the Millimetron was mentioned for such needs). The prediction was realized in May 2022 since the Event Horizon Telescope (EHT) Collaboration presented results of a shadow reconstruction for our Galactic Center (earlier the shadow around the supermassive black hole in M87 was reconstructed in 2019). These reconstructions were based on EHT observations done in 2017. For Reissner--Nordstr$\ddot{\text{o}}\text{m}$ metric Zakharov et al. (2005b) derived analytical expressions for shadow size as a function of charge and later these results were generalized for a tidal charge case (Zakharov, 2014). We discuss opportunities to evaluate parameters of alternative theories of gravity with shadow size estimates done by the EHT Collaboration, in particular, a tidal charge could be estimated from these observations (Zakharov, 2022). We also discuss opportunities to use Millimetron facilities for shadow reconstructions in M87$^*$ and Sgr A$^*$. In our recent studies (Zakharov, 2024) we discuss shadow formations for cases where naked singularities or wormholes substitute black holes in galactic centers.
References
Zakharov A. F., Nucita A. A., De Paolis F., Ingrosso G. (2005a) New Astron., 10, 479
Zakharov A. F., De Paolis F., Ingrosso G., Nucita A. A. (2005b) A & A 442, 795
Zakharov A. F. (2014) Phys. Rev. D 90, 062007
Zakharov A. F. (2022) Universe 8(3), 141
Zakharov A.F. (2024, in press)
