H_2_O masers in AFGL 2591 VLA 3-N

We measured the proper motions of 33 water maser features, which have an average proper motion velocity of ~1.3mas/yr (~20km/s). The morphology and the proper motions of this cluster of water masers show systematic expanding motions that could imply one or two different centres of star formation activity. We made a detailed model for the southern structure, proposing two different kinematic models to explain the three-dimensional spatio-kinematical distribution of the water masers: (1) a static central source driving the two bow-shock structures and (2) two independent driving sources, one of them exciting the northern bow-shock structure, and the other one, a young runaway star moving in the local molecular medium exciting and moulding the remarkably smoother southern bow-shock structure.

Future observations will be necessary to discriminate between the two scenarios, in particular by identifying the still unseen driving source(s).