ALMA observations of the supergiant B[e] star Wd1-9
ALMA observations of the supergiant B[e] star Wd1-9
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ALMA 对超巨星 B[e] 星 Wd1-9 的观测
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
R. Blomme
中科院分区：
文献类型：
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作者：
D. Fenech;J. Clark;R. Prinja;J. Morford;S. Dougherty;R. Blomme
大质量恒星的质量损失在它们的演化中起着关键作用，尽管精确的机制-辐射驱动风，脉冲喷射和/或二元相互作用-仍然不确定。在这封信中，我们介绍了超巨星B[e]星星Wd 1 -9的阿塔卡马大型毫米/亚毫米阵列线和连续观测，Wd 1 -9是一个位于星暴星团Westerlund 1（Wd 1）内的大质量主序后天体。我们发现它是天空中最亮的恒星点源之一，波长为毫米，发射（偶然发现）在H41α射电复合线。我们将这些特性归因于低速（约100 km s-1）电离风，其极端质量损失率为约6.4 × 105（d/5 kpc）1.5百万年。在它的外部是一个扩展的非球面喷射星云，这表明在之前的阶段有大量的质量损失。总的来说，Wd 1 -9的毫米性质与高亮度恒星源MWC 349 A的毫米性质非常相似。我们的结论是，这些对象是相互作用的二进制演变远离主序列，并经历快速的情况下，A质量转移。因此，它们--以及更广泛的超巨星B[e]星--可能为研究一个过程的物理学提供了一个独特的窗口，这个过程塑造了双星系统中70%的大质量恒星的生命周期。
Mass-loss in massive stars plays a critical role in their evolution, although the precise mechanism(s) responsible – radiatively driven winds, impulsive ejection and/or binary interaction – remain uncertain. In this Letter, we present Atacama Large Millimetre/Submillimeter Array line and continuum observations of the supergiant B[e] star Wd1-9, a massive post-main-sequence object located within the starburst cluster Westerlund 1 (Wd1). We find it to be one of the brightest stellar point sources in the sky at millimetre wavelengths, with (serendipitously identified) emission in the H41α radio recombination line. We attribute these properties to a low velocity (∼100 km s-1 ) ionized wind, with an extreme mass-loss rate ≳6.4 × 105(d/5 kpc)1.5 Mȯyr-1. External to this is an extended aspherical ejection nebula indicative of a prior phase of significant mass-loss. Taken together, the millimetre properties of Wd1-9 show a remarkable similarity to those of the highly luminous stellar source MWC349A. We conclude that these objects are interacting binaries evolving away from the main sequence and undergoing rapid case-A mass transfer. As such they – and by extension the wider class of supergiant B[e] stars – may provide a unique window into the physics of a process that shapes the life-cycle of ∼70 per cent of massive stars found in binary systems.