Reduced χ² maps for the location of GG Tau Ab2 in the new PIONIER observations presented here. In the 2013 epoch, solution “a” is both the most likely from a pure likelihood perspective, and it is also the most plausible based on the motion observed between the 2012 and 2014 Keck observations (see Sect. 2.1). The second and third highest likelihood solutions (labelled “b” and “c”), located to the West-Southwest of the primary solution, are also illustrated in Fig. 4.