Measuring the black hole parameters in the galactic center with RADIOASTRON

Shadow of a rotating braneworld black hole

“…The first one is a space-based radio telescope launched in July 2011. It will be capable of carrying out measurements with high angular resolution, about 1 − 10 µas [28,33]. On the other hand, the MAXIM project is a space-based X-ray interferometer with an expected angular resolution of about 0.1 µas (see [34] for further details).…”

“…Rotating black holes present apparent shapes or shadows with an optical deformation due to the spin [19,20], instead of being circles as in the case of non-rotating ones. This topic has been reexamined by several authors in the last few years [17,[21][22][23][24][25][26][27][28], with the expectation that the direct observation of black holes will be possible in the near future [28]; therefore the study of the shadows will be useful for measuring the properties of astrophysical black holes. Optical properties of rotating braneworld black holes were studied by Schee and Stuchlik [29].…”

Graviton mass evaluation with trajectories of bright stars at the Galactic Center

“…spectral line structure [1,2,3] 8 (see also more recent reviews [11,12] on the subject). Another phenomenon, where one really needs a strong gravitational field approach, is simulations of a shadow formation started since [13,14,15,16] (see also calculations of shadows for different cases [17,18,19,20,21,22] and recent reviews on the subject [23,24]). The problem is connected with attempts to resolve the smallest spot at the Galactic Center with VLBI interferometry in mm-band [25].…”

Shadow of a Kaluza-Klein rotating dilaton black hole

“…The shadows (or apparent shapes) of nonrotating black holes are circular, but rotating ones present a deformation caused by the spin [12,13]. This topic has been recently considered by several authors [10,[14][15][16][17][18][19][20][21][22][23][24][25], both in Einstein gravity and in modified theories, since it is expected that direct observation of black holes will be possible in the near future [25][26][27]. In that case, the analysis of the shadows will be a useful tool for obtaining properties of astrophysical black holes and comparing different gravitational theories.…”