X-rays from superbubbles in the Large Magellanic Cloud

We find diffuse X-ray emission not associated with known supernova remnants (SNRs) in seven Large Magellanic Cloud H II complexes encompassing 10 OB associations: N44, N51D, N57A, N70, N154, N157 (30 Dor), and N158. Their X-ray luminosities range from 7 × 10³⁴ ergs s^-1 in N57A to 7 × 10³⁶ ergs s^-1 in 30 Dor. All, except 30 Dor, have simple ring morphologies, indicating shell structures. Modeling these as superbubbles, we find that the X-ray luminosities expected from their hot interiors fall an order of magnitude below the observed values. SNRs close to the center of a superbubble add very little emission, but we calculate that off-center SNRs hitting the ionized shell could explain the observed emission.