Towards constraining the central black hole's properties by studying its   infrared flares with the GRAVITY instrument
  The ability of the near future second generation VLTI instrument GRAVITY to constrain the properties of the Galactic center black hole is investigated. The Galactic center infrared flares are used as probes of strong-field gravity, within the framework of the hot spot model according to which the flares are the signature of a blob of gas orbiting close to the black hole's innermost stable circular orbit. Full general relativistic computations are performed, together with realistic observed data simulations, that lead to conclude that GRAVITY could be able to constrain the black hole's inclination parameter. 
F. H. Vincent, T. Paumard, G. Perrin, E. Gourgoulhon, F. Eisenhauer,   S. Gillessen
astro-ph.GA