X-ray emission from wind blown interstellar bubbles - IV. ROSAT HRI observations of NGC 6888

The interaction of fast stellar winds with the surrounding interstellar medium produces large amounts of hot X-ray emitting gas. Scarce previous observations indicated substantial differences between simple one-dimensional models and the data. We have obtained ROSAT images of several wind blown interstellar bubbles. In this first paper we present an X-ray map of the prototype ring nebula NGC 6888. Although we confirm previous total flux determinations and the possibility to reconcile these values with theory by introducing ionization non-equilibrium, our map demonstrates that the assumed geometry (a thick shell) is far from reality