C IV absorption from hot gas inside supergiant shell LMC 4 observed with HST and IUE ⋆

High resolution ultraviolet spectra with HST-GHRS of two stars in the direction of the supergiant shell LMC 4 unambiguously show absorption by substantial quantities of C IV gas at velocities near the the sys-temic velocity of the LMC. In combination with the detection of diffuse X-rays from the LMC 4 by ROSAT and other supporting data, this demonstrates that the interior of LMC 4 is filled with tenuous hot gas. C IV interstellar absorption is seen over a large velocity range, having at least 2 components at about 280 and 320 km s −1. The strong component at 280 km s −1 has a width of 40 km s −1 and a column density in the order of 3 10 13 cm −2. The width of the absorption is best explained by bulk motions of C IV-containing gas clouds inside LMC 4. These hot clouds or layers around cold clouds have to have a relatively high filling factor inside LMC 4 to fit the observations. The characteristics of the C IV gas component at 320 km s −1 are such that they trace a blast wave from a recent supernova within the LMC 4 cavity. Galactic C IV absorption is also present, as to be expected for these lines of sight.