The R136 star cluster dissected with Hubble Space Telescope/STIS - II. Physical properties of the most massive stars in R136
The R136 star cluster dissected with Hubble Space Telescope/STIS - II. Physical properties of the most massive stars in R136
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用哈勃太空望远镜/STIS-II 解剖 R136 星团。
DOI：
10.1093/mnras/staa2801
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发表时间：
2020
影响因子：
4.8
通讯作者：
Bestenlehner J
中科院分区：
文献类型：
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作者：
Bestenlehner J
我们提出了一个光学分析的55名成员的R136，在大麦哲伦星云的蜘蛛星云的中央集群。我们的样本是用哈勃太空望远镜上的STIS观测到的，完整的样本低至约40 M <$，包括7颗质量超过100 M <$的超大质量恒星。我们进行了光谱分析，以得出它们的物理特性。利用演化模型，我们发现R136中大质量恒星的初始质量函数是头重脚轻的，幂律指数γ = 2 ± 0.3，但不能排除更陡的指数。R136的年龄在100万到200万年之间，中位年龄约为160万年。比logL/L <$= 6.3更亮的恒星是氦富集的，它们的演化主要是由质量损失决定的，但是仍然需要旋转混合或其他形式的混合来解释表面的氦成分。质量大于40 M的恒星光谱质量大于演化质量。假设恒星风不成团，风-光度关系的斜率为2.41 ± 0.13，比通常得到的斜率（1.8）要陡。R136的电离（）和机械（）输出主要由质量最大的恒星（）控制。R136为蜘蛛星云的总预算贡献了大约四分之一的电离通量和大约五分之一的机械反馈。为了对蜘蛛星云区域的大质量恒星进行普查，我们将我们的结果与VLT火焰蜘蛛星云调查以及其他光谱研究相结合。我们观察到缺乏演化的沃尔夫-拉叶星和发光的蓝、红超巨星。
We present an optical analysis of 55 members of R136, the central cluster in the Tarantula Nebula of the Large Magellanic Cloud. Our sample was observed with STIS aboard theHubble Space Telescope, is complete down to about 40 M⊙, and includes seven very massive stars with masses over 100 M⊙. We performed a spectroscopic analysis to derive their physical properties. Using evolutionary models, we find that the initial mass function of massive stars in R136 is suggestive of being top-heavy with a power-law exponent γ ≈ 2 ± 0.3, but steeper exponents cannot be excluded. The age of R136 lies between 1 and 2 Myr with a median age of around 1.6 Myr. Stars more luminous than logL/L⊙= 6.3 are helium enriched and their evolution is dominated by mass-loss, but rotational mixing or some other form of mixing could be still required to explain the helium composition at the surface. Stars more massive than 40 M⊙have larger spectroscopic than evolutionary masses. The slope of the wind–luminosity relation assuming unclumped stellar winds is 2.41 ± 0.13 which is steeper than usually obtained (∼1.8). The ionizing () and mechanical () output of R136 is dominated by the most massive stars (). R136 contributes around a quarter of the ionizing flux and around a fifth of the mechanical feedback to the overall budget of the Tarantula Nebula. For a census of massive stars of the Tarantula Nebula region, we combined our results with the VLT-FLAMES Tarantula Survey plus other spectroscopic studies. We observe a lack of evolved Wolf–Rayet stars and luminous blue and red supergiants.