THE EXCITING STAR OF THE SMALL BUBBLE N-120A IN THE LARGE MAGELLANIC CLOUD

UV characteristics of the star BI 141 show that it is the exciting sta r of the nebula N 120A of the LMC. We determine its UV spectral classi fication as 09.5I and we derive the terminal velocity and mass-loss ra te of its stellar wind, in agreement with the usual values found for g alactic supergiants of the same spectral type. The energetic balance b etween the power of the stellar wind and the measured energetic input into the surrounding gas shows that the wind is largely the dominant f actor for driving the bubble. The best model for the sustained bubble is the model with conservation of energy, (nonradiative shocked stella r winds). The discrepancy between the visible spectral classification B3I and the UV classification opens the questions of either the multip licity or the valiability of BI 141, and of its stellar wind.