The interstellar lines and the energetics of the inner Doradus nebulafrom the ultraviolet spectrum of R 136a.

An IUE short and long wavelength absorption line spectrum (1150 - 3000 Å) of the central superluminous object in the 30 Doradus nebula, R 136a, is analysed. Radial velocities and equivalent widths of the Magellanic interstellar components are given. The Magellanic interstellar components fall into four well-separated groups. The same groups show up in the velocity components of all interstellar LMC emission and absorption lines so far observed. Their average velocities are given. They can be explained by a model of the inner part of 30 Dor consisting of shells and bubbles, and warp material above the plane of the LMC. The power of R 136a alone is sufficient to energize the multitude of the 30 Dor shells and to structure the whole nebula.