THE INTERACTION OF NGC-6888 AND HD-192163 WITH THE SURROUNDING INTERSTELLAR-MEDIUM

We investigate the neutral gas distribution and kinematics in the surr oundings of the WR star HD 192163 and the ring nebula NGC 6888, based on HI 21 cm line observations carried out with the Synthesis Telescope of the DRAO, A detailed analysis of the HI distribution at low positi ve velocities allowed us to identify two different structures very pro bably related to the star and the ring nebula. From inside to outside they are: (1) an elliptical shell, 11.8X6.3 pc in size, that embraces the ring nebula (labeled inner shell); and (2) a distorted HI ring, 28 pc in diameter, also detected in IR emission (outer shell). The borde rs of the inner shell strikingly follows the brightest regions of NGC 6888, showing the sites where the interaction between the nebula and t he surrounding gas occurs. A third structure, the external feature, is a broken are detected at slightly higher velocities than the former s hells. We propose a scenario in which the strong stellar wind of HD 19 2163, expanding in an inhomogeneous interstellar medium, blew the oute r shell during the main sequence phase of the star. Later, the materia l ejected by the star during the LBV (or RSG) and WR phases created NG C 6888. This material encountered the innermost wall of the outer shel l originating the inner shell. The association of the external feature with the star and the nebula is not clear. (C) 1996 American Astronom ical Society.