Differential interferometry of close binary of supermassive black holes
  in an elliptical configuration
  The Very Large Telescope Interferometer (VLTI), and the Extremely Large
Telescope (ELT) will be a robust astrophysics suite offering the opportunity of
probing the structure and dynamics of CB-SMBH at high spectral and angular
resolution. Here, we explore and illustrate the application of differential
interferometry on unresolved the CB-SMBH systems in elliptical orbital
configurations and a single SMBH with clouds in elliptical orbital motion.
Photocenter displacements between each SMBH and regions in their disc-like
broad line regions (BLR) appear as small interferometric differential phase
variability. To investigate the application of interferometric phases for the
detection of CB-SMBH systems, we simulate a series of differential
interferometry signatures, based on our model comprising ensembles of clouds
surrounding each of supermassive black hole in a CB-SMBH. Setting model to the
parameters of a single SMBH with elliptical cloud motion, we also calculated a
series of differential interferometry observables for this case. We found
various deviations from the canonical S-shaped of CB-SMBH phases profile for
elliptically configured CB-SMBH systems. The amplitude and specific shape of
the interferometry observables depend on orbital configurations of the CB-SMBH
system. We get distinctive results when considering antialigned angular momenta
of cloud orbits regarding total CB-SMBH angular momentum. Some simulated
spectral lines from our model closely resemble observations of Pa \alpha line
got from near-infrared AGN surveys. We found differences between differential
phases zoo of a single SMBH and CB-SMBH systems. The differential phases zoo
for a single SMBH comprises deformed S shape. We also showed how their
differential phase shape, amplitude, and slope evolve with various sets of
cloud orbital parameters and observer position.
