The exciting star of the small bubble N 120A in the Large Magellanic Cloud

Abstract

UV characteristics of the star BI 141 show that it is the exciting star of the nebula N 120A of the LMC. We determine its UV spectral classification as O_9.5_I and we derive the terminal velocity and mass-loss rate of its stellar wind, in agreement with the usual values found for galactic supergiants of the same spectral type. The energetic balance between the power of the stellar wind and the measured energetic input into the surrounding gas shows that the wind is largely the dominant factor for driving the bubble. The best model for the sustained bubble is the model with conservation of energy, (nonradiative shocked stellar winds). The discrepancy between the visible spectral classification B_3_I and the UV classification opens the questions of either the multiplicity or the variability of BI 141, and of its stellar wind.