On the Evolutionary Phase and Mass Loss of the Wolf-Rayet-like Stars in R136a*

摘要: We report on a systematic study of the most massive stars, in which we analyzed spectra four very luminous stars Large Magellanic Cloud. The lie 30 Doradus complex, three are located core compact cluster, R136a (R136a1, R136a3, and R136a5), fourth (Melnick 42), about 8'' north R136a. Low-resolution (<200 km s-1) these were obtained with GHRS FOS spectrographs Hubble Space Telescope. cover spectral range from 1200 to 1750 A, 3200 6700 A. derived fundamental parameters by fitting observations model calculated "ISA-WIND" code de Koter et al. find that all hot (~45 kK), luminous, rich hydrogen. Their positions HR-diagram imply they masses 60-90 M☉ 2 million years old at most, hence, O-type main-sequence still H-burning phase evolution. Nevertheless, two R136a3) mimic those Wolf-Rayet showing strong He II emission lines. According our calculations, this is natural consequence high mass-loss rate. conjecture R136a—those initial ~100 or more—are born as WR-like mass loss may perhaps be connected actual stellar formation process. Because observed rates up 3 times higher than assumed evolutionary models, post-main-sequence tracks will qualitatively different current models. rate 3.5-8 predicted analytical solutions for radiation-driven winds Kudritzki (1989). However, using sophisticated Monte Carlo calculations radiative driving unified atmospheres, show that—while cannot say sure what initiates wind—radiation pressure probably sufficient accelerate wind its terminal velocity, if one accounts effects multiple photon scattering dense investigated stars.