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We present an analysis of the Suzaku observations of the prototype wind-blownbubble NGC 6888 which is based both on use of standard spectral models and on adirect comparison of theoretical models with observations. The X-ray spectra ofNGC 6888 are soft and most of the X-rays are in the (0.3 - 1.5 keV) energyrange. But, hard X-rays (1.5 - 4.0 keV) are also detected (~10% of the observedflux). The corresponding spectral fits require a relatively cool plasma with kT< 0.5 keV but much hotter plasma with temperature kT > 2.0 keV is needed tomatch the observed hard X-ray emission. We find no appreciable temperaturevariations within the hot bubble in NGC 6888. The derived abundances (N, O, Ne)are consistent with those of the optical nebula. This indicates a common originof the X-ray emitting gas and the outer cold shell: most of the X-ray plasma(having non-uniform spatial distribution: clumps) has flown into the hot bubblefrom the optical nebula. If the electron thermal conduction is efficient, thiscan naturally explain the relatively low plasma temperature of most of theX-ray emitting plasma. Alternatively, the hot bubble in NGC 6888 will beadiabatic and the cold clumps are heated up to X-ray temperatures likely byenergy exchange between the heavy particles (hot ions diffusing into the coldclumps).

Suzaku Observations of the Prototype Wind-Blown Bubble NGC 6888