Positions of all the water maser spots measured with the VLBA in the region VLA 3-N in epochs 2001–2002 (plus signs; this paper, Table A1) and in epochs 2008–2009 (filled circles; Sanna et al. 2012). The colour scale represents the LSR radial velocity of the masers. The arrows (solid and dashed lines for epochs 2001–2002 and 2008–2009, respectively) represent the proper motion vectors of the maser features listed in Tables 1 and 2. The length of the arrows corresponds to the estimated proper motions over the total time span of 7 yr [time span between our VLBA observations and those of Sanna et al. (2012)]. Note that the positions of all the maser spots detected in 2001–2002 fall within the area circumscribed by the masers detected in 2008–2009. The northern and southern bow-shock structures are separated from each other by ∼100 mas (∼330 au) for epochs 2001–2002, and by ∼120 mas (∼400 au) for epochs 2008–2009 (see Sections 3 and 4).