Confronting the Superbubble Model with X‐Ray Observations of 30 Doradus C

We present an analysis of XMM-Newton observations of the superbubble 30 Dor Cand compare the results with the predictions from the standard wind-blownbubble model. We find that the observed X-ray spectra cannot be fittedsatisfactorily with the model alone and that there is evidence for nonthermalX-ray emission, which is particularly important at > 4 keV. The totalunabsorbed 0.1-10 keV luminosities of the eastern and western parts of thebubble are ~3 10^36 erg/s and ~5 10^36 erg/s, respectively. The unabsorbed0.1-10 keV luminosity of the bubble model is 4 10^36 erg/s and so the power-lawcomponent contributes between 1/3 and 1/2 to the total unabsorbed luminosity inthis energy band. The nature of the hard nonthermal emission is not clear,although recent supernovae in the bubble may be responsible. We expect thatabout one or two core-collapse supernovae could have occured and are requiredto explain the enrichment of the hot gas, as evidenced by the overabundance ofalpha-elements by a factor of 3, compared to the mean value of 0.5 solar forthe interstellar medium in the Large Magellanic Cloud. As in previous studiesof various superbubbles, the amount of energy currently present in 30 Dor C issignificantly less than the expected energy input from the enclosed massivestars over their lifetime. We speculate that a substantial fraction of theinput energy may be radiated in far-infrared by dust grains, which are mixedwith the hot gas because of the thermal conduction and/or dynamic mixing.Comment: 25 pages, 4 figures. To appear in The Astrophysical Journal, August 20, 2004 issu