R136星团中有几颗恒星的质量大大超过了公认的150 Msun恒星质量极限
The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit
摘要：
本文介绍了用档案HST和VLT光谱学和高空间分辨率近红外光度学对年轻星团NGC 3603和R136中的富氢WN 5 -6星进行的光谱分析。我们推导出NGC 3603（T*~42+/-2 kK）和R136（T*~53+/-3 kK）中WN星的高T* 值加上聚集校正的dM/dt ~ 2- 5 × 10 ^-5 Msun/yr，这与理论预测非常吻合。这些恒星对它们的宿主星团的全球预算做出了不成比例的贡献。R136 a1单独提供整个30 Dor区域的~7%的N（LyC）。与主序星演化的85-500 Msun恒星模型的比较表明，NGC 3603中3个系统的年龄约为150万年M_init，范围为105 - 170 Msun，R136中4颗恒星的年龄为165-320 Msun。我们的高恒星质量得到了NGC 3603 A1组件的动力学质量测定的支持。我们考虑了R136星的预测L_X，如果它们是近距离碰撞风双星的话。R136 c与碰撞风双星系统一致。然而，短周期，碰撞风系统被排除在R136 a WN星，如果质量比的顺序统一。由于在如此稠密的环境中与其他大质量恒星的早期动力学相遇，广泛分离的系统预计会硬化。从模拟的星团，其成分是随机抽样的Kroupa IMF，这两个集群是一致的暂定上限质量约300 Msun。拱门星团要么太老了，表现出缺乏非常大质量的恒星，或者更可能的恒星质量被低估了-根据当代恒星和测光结果，拱门星团中最明亮的恒星的M_init接近200 Msun。在贫金属星系中，可能存在远超过150 Msun的恒星，这意味着这种对不稳定性的SNe可能发生在本地宇宙中，就像SN 2007 bi所声称的那样。
英文摘要：
Spectroscopic analyses of H-rich WN5-6 stars within the young star clusters NGC 3603 and R136 are presented, using archival HST & VLT spectroscopy, & high spatial resolution near-IR photometry. We derive high T* for the WN stars in NGC 3603 (T*~42+/-2 kK) & R136 (T*~53+/-3 kK) plus clumping-corrected dM/dt ~ 2-5x10^-5 Msun/yr which closely agree with theoretical predictions. These stars make a disproportionate contribution to the global budget of their host clusters. R136a1 alone supplies ~7% of N(LyC) of the entire 30 Dor region. Comparisons with stellar models calculated for the main-sequence evolution of 85-500 Msun suggest ages of ~1.5 Myr & M_init in the range 105 - 170 Msun for 3 systems in NGC 3603, plus 165-320 Msun for 4 stars in R136. Our high stellar masses are supported by dynamical mass determinations for the components of NGC 3603 A1. We consider the predicted L_X of the R136 stars if they were close, colliding wind binaries. R136c is consistent with a colliding wind binary system. However, short period, colliding wind systems are excluded for R136a WN stars if mass ratios are of order unity. Widely separated systems would have been expected to harden owing to early dynamical encounters with other massive stars in such a dense environment. From simulated star clusters, whose constituents are randomly sampled from the Kroupa IMF, both clusters are consistent with a tentative upper mass limit of ~300 Msun. The Arches cluster is either too old, exhibits a deficiency of very massive stars, or more likely stellar masses have been underestimated - M_init for the most luminous stars in the Arches cluster approach 200 Msun according to contemporary stellar & photometric results. The potential for stars greatly exceeding 150 Msun within metal-poor galaxies suggests that such pair-instability SNe could occur within the local universe, as has been claimed for SN 2007bi (abridged).
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