We present the results of a closure phase analysis of 3 mm very long baseline interferometry
measurements performed on Sagittarius A* (Sgr A*).We have analysed observations made in
2015 May using the Very Long Baseline Array, the Robert C. Byrd Green Bank Telescope and
the Large Millimeter Telescope Alfonso Serrano and obtained non-zero closure phase measurements
on several station triangles – indicative of a non-point-symmetric source structure.
The data are fitted with an asymmetric source structure model in Sgr A*, represented by a
simple two-component model, which favours a fainter component due east of the main source.
This result is discussed in light of a scattering screen with substructure or an intrinsically
asymmetric source.