Phenomenological Extension for Tidal Charge Black Hole

Abstract

A simple phenomenological extension of the black hole solution with tidal charge is proposed. Empirical data on the Sgr A* is consistent with the suggested metric which serves as a generalisation of the Reissner-Nordström one. Such a generalisation includes the leading effects beyond general relativity so, the discussed metric can explain wider range of gravitational effects. We discuss physical features of an object described by the proposed metric, namely, the size of its shadow and the innermost stable circular orbit radius.

Shadows from spinning black holes in extended gravity

“…5). As we demonstrated earlier [19] in minimally extended BH model the shadow sizes less than 4R Sw appear. Such BH does not exist in Kerr-Newman model and could be the indication of extended gravity appearance.…”

“…In the vanishing inclination (θ i = 0) case the shadow becomes circularly symmetrical (like in the non-rotating case) but slightly compressed due to the rotation. Previously [19] we demonstrated that two non-rotating BHs with different parameters could have the same shadow size. In the rotating case each point of the shadow edge can be treated as the image of the BH's potential since it corresponds to the unique photon orbit radius r 0 .…”

“…Earlier, in Ref. [19] we investigated the consequences of a shadow model extension for the non-rotating BH. Now we generalize the model by including of the BH rotation.…”

Calculating black hole shadows: Review of analytical studies

“…( 26) in [62]. We also refer to Alexeyev et al [63] for possible generalizations. With known b cr , the angular radius α sh of the shadow can now be found for an arbitrary position of the observer using eq.…”

Black Holes and Wormholes in Extended Gravity

“…Since for solar and bigger than solar masses of the black hole the solution does not differ from Schwarzschild, no observable effects can make the solution distinguishable, although in the microphysics the difference could be detectable [46]. Additional constraints on the "tidal charge" could be placed by considering circular orbits and the black hole shadows [48,49].…”