The supergiant shell LMC 2. II. Physical properties of the 10⁶ K gas

LMC 2 has the highest X-ray surface brightness of all known supergiant shells in the Large Magellanic Cloud (LMC). The X-ray emission peaks within the ionized filaments that define the shell boundary but also extends beyond the southern border of LMC 2 as an X-ray bright spur. ROSAT HRI images reveal the X-ray emission from LMC 2 and the spur to be truly diffuse, indicating a hot plasma origin. We have obtained ROSAT PSPC and ASCA SIS spectra to study the physical conditions of the hot (≥10⁶ K) gas interior to LMC 2 and the spur. Raymond-Smith thermal plasma model fits to the X-ray spectra, constrained by H I 21 cm emission line measurements of the column density, show the plasma temperature of the hot gas interior of LMC 2 to be kT ∼ 0.1-0.7 keV and of the spur to be kT ∼ 0.1-0.5 keV. We have compared the physical conditions of the hot gas interior to LMC 2 with those of other supergiant shells, superbubbles, and supernova remnants (SNRs) in the LMC. We find that our derived electron density for the hot gas inside LMC 2 is higher than the value determined for the supergiant shell LMC 4, comparable to the value determined for the superbubble Nil, and lower than the values determined for the superbubble N44 and a number of SNRs.