Detecting Flaring Structures in Sagittarius A* with High-Frequency VLBI

The super-massive black hole candidate, Sagittarius A*, exhibitsvariability from radio to X-ray wavelengths on timescales thatcorrespond to 10 Schwarzschild radii. We survey the potential ofmillimeter wavelength very long baseline interferometry (VLBI) to detectand constrain time-variable structures that could give rise to suchvariations, focusing on a model in which an orbiting hot spot isembedded in an accretion disk. Nonimaging algorithms are developed thatuse interferometric closure quantities to test for periodicity, andapplied to an ensemble of hot spot models that sample a range ofparameter space. We find that structural periodicity in a wide range ofcases can be detected on most potential VLBI arrays using modern VLBIinstrumentation. Future enhancements of millimeter/submillimeter VLBIarrays including phased-array processors to aggregate VLBI stationcollecting area, increased bandwidth recording, and addition of new VLBIsites all significantly aid periodicity detection. The methods describedherein can be applied to other models of Sagittarius A*, including jetoutflows and magnetohydrodynamic accretion simulations.