Expansion of methanol maser rings

Ring-like sources of 6.7 GHz methanol maser emission were discovered a decade ago with the European VLBI Network. In the past years we have been incessantly working to understand the nature of these rings. In general, the methanol rings do not coincide with H II regions nor they show 22 GHz water maser emission. Here, we present a proper motion study over a time baseline up to 10.5 years for the first sub-sample of methanol maser rings. Our findings suggest that in three targets G23.207-00.377, G23.389+00.185, and G23.657-00.127, such rings form in outflows or even in winds close to the central sources, and the masers trace slow proper motions of a few km s^-1 typically.