SIMBAD references

We have obtained ROSAT observations of several wind blown interstellar bubbles. In this paper we present the results of the PSPC observations of S 308 which optically shows a spherically symmetric shell with only slight hints on developing instabilities. It should therefore be a prototypical object for 1d and spherical 2d models. The X-ray surface brightness is very low. We have determined a total luminosity of L_x≃3.7x10³³erg/s and plasma temperatures in the range T=(1.5 ... 28)x10⁶K. The emitting volume is a thick shell with a ratio of inner to outer radius of ≃0.5. Both L_x and the observed count rate surface profiles do not compare very well with predictions from current models. Also, the observed wind power is two orders of magnitude greater than needed as input by the models to produce the observed bubble. This stellar wind strength problem is similar to the one Garcia-Segura and MacLow found in their numerical models for NGC 6888.