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STIS spectroscopy of newborn massive stars in SMC N81

M. Heydari-Malayeri·M. R. Rosa·D. Schaerer·F. Martins·V. Charmandaris
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Abstract

Using Hubble Space Telescope observations with STIS, we study the main exciting stars of N81, a high excitation compact Hii region in the Small Magellanic Cloud (SMC). These far UV observations are the first spectroscopic measurements of stars in such a region and reveal features characteristic of an O6-O8 stellar type. The astonishing weakness of their wind profiles and their sub-luminosity (up to ~ 2 mag fainter in Mv than the corresponding dwarfs) make these stars a unique stellar population in the Magellanic Clouds. Our analysis suggests that they are probably in the Hertzsprung-Russell diagram locus of a particularly young class of massive stars, the so-called Vz luminosity class, as they are arriving on the zero age main sequence.

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M. Heydari-Malayeri, M. R. Rosa, D. Schaerer, F. Martins, V. Charmandaris. 2001-10-26. STIS spectroscopy of newborn massive stars in SMC N81. https://doi.org/10.1051/0004-6361%3A20011574

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