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More than two years ago the Event Horizon Telescope collaboration presentedthe first image reconstruction around the shadow for the supermassive blackhole in M87*. It gives an opportunity to evaluate the shadow size. Recently,the Event Horizon Telescope collaboration constrained parameters ("charges") ofspherical symmetrical metrics of black holes from an estimated allowed intervalfor shadow radius from observations of M87* in 2017. Earlier, analyticalexpressions for the shadow radius as a function of charge (including a tidalone) in the case of Reissner--Nordstr\"om metric have been obtained. Some timeago, Bin-Nun proposed to apply a Reissner--Nordstr\"om metric with a tidalcharge as an alternative to the Schwarzschild metric in Sgr~A*. If we assumethat a Reissner--Nordstr\"om black hole with a tidal charge exists in M87*,therefore, based on results of the shadow size evaluation for M87* done by theEvent Horizon Telescope collaboration we constrain a tidal charge. Similarly,we evaluate a tidal charge from shadow size estimates for Sgr~A*.

Constraints on a tidal charge of the supermassive black hole in M87* with the EHT observations in April 2017