Constraining the Flaring Region of Sagittarius A* By 1.3mm VLBI Measurements

We use a model of an accretion flow coupled with an emergent flare to interpret the latest 1.3mm VLBI measurements for Sagittarius A*. The visibility data constrained the distances from the flare center to the black hole center as $d_{\mathrm{E}\mathrm{W}}\lesssim 20{\mathrm{R}}_{\mathrm{g}}$ and $d_{\mathrm{N}\mathrm{S}}\lesssim 80{\mathrm{R}}_{\mathrm{g}}$ in the East-West and North-South directions, respectively. If interpreted by the hot-spot model, the flare was preferred to pass in front of the black hole at a radius much larger than $d_{\mathrm{E}\mathrm{W}}$. If interpreted by the episodic jet launched from a nearly edge-on hot accretion flow, the flare was preferred to be ejected with ${\theta }_{\mathrm{j}}\gtrsim {40}^{\circ }$ off the black hole rotating axis. This method can be generalized to help us understand future sub-millimeter VLBI observations, and study the millimeter/sub-millimeter variabilities in the vicinity of the Galactic Center supermassive black hole.