Observations by Gwinn, Moran, and Reid of the proper motions of water masers in W49N show that they have an elongated distribution expanding from a common center. Features with high space velocity only occur far from the center, while low-velocity features occur at all distances. It is proposed that water masers in star-forming regions occur in expanding shells swept up by high-velocity winds from young, massive stars during the early phases of the expansion. In W49N, confinement of the bubble by a density distribution with an axial cavity can explain both the velocity field and the shape of the maser distribution. A fully dynamical calculation of the expanding bubble is presented which provides a satisfactory fit for the observations and suggests that this system is only ~250 yr old. Thus these observations may show the very first stages of the formation of a jet from a young stellar object.

Document Type


Publication Date


Notes/Citation Information

Published in The Astrophysical Journal Letters, v. 393, no. 1, p. L33-L36.

©1992. The American Astronomical Society. All rights reserved.

The copyright holder has granted permission for posting the article here.

Digital Object Identifier (DOI)