ALMA Compact Array observations of the Fried Egg nebula: Evidence for large-scale asymmetric mass-loss from the yellow hypergiant IRAS 17163-3907.
ALMA Compact Array observations of the Fried Egg nebula: Evidence for large-scale asymmetric mass-loss from the yellow hypergiant IRAS 17163-3907.
复制标题
煎蛋星云的 ALMA 致密阵列观测：黄超巨星 IRAS 17163-3907 大规模不对称质量损失的证据。
DOI：
10.1051/0004-6361/201628416
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发表时间：
2016
影响因子：
6.5
通讯作者：
A. Zijlstra
中科院分区：
文献类型：
--
作者：
S. Wallström;E. Lagadec;S. Muller;J. Black;N. Cox;N. Cox;R. Galván;K. Justtanont;S. Longmore;H. Olofsson;R. D. Oudmaijer;G. Quintana;R. Szczerba;W. Vlemmings;H. V. Winckel;A. Zijlstra
黄色超巨星非常罕见，代表了大质量恒星的快速演化阶段。这个进化阶段的特点是质量损失非常严重，对此的理解仍然非常有限。在这里，我们报告ALMA紧凑型阵列观测到的一个50″-马赛克朝向煎蛋星云，围绕着银河系中为数不多的黄色超巨星IRAS 17163-3907。12CO J=2-1谱线、H30α重组谱线和连续谱线的发射以~8″的分辨率成像，揭示了恒星周围分子环境的形态。连续体发射是无法分辨的，在恒星的位置达到峰值。射电重组线H30α显示了该恒星未解析的发射，其近似高斯光谱以速度为21±3 km s-1为中心，宽度为57±6 km s-1。相比之下，CO - 2-1的排放是复杂的，分解成几个组分，超出了视线内星际气体的污染。朝向恒星的CO光谱是一个宽阔的平台，中心为系统速度+18 km s-1，膨胀速度为100±10 km s-1。假设各向同性和恒定的质量损失，我们估计质量损失率为8±1.5 ×10-5 M⊙年-1。在距离恒星25″的半径处，我们探测到与赫歇尔先前拍摄的尘埃环有关的CO排放。然而，这个环的运动学与膨胀壳不一致，但显示出速度梯度为vsys±20 km s-1。此外，我们还发现了一个令人费解的明亮特征，以相对于恒星的+40 km s-1的速度将恒星与CO环呈放射状连接起来。这个突波特征可以追溯到恒星的单向抛射事件。我们的ACA观测揭示了IRAS 17163周围复杂的形态，并说明了ALMA将为大质量恒星演化领域带来的突破。
Yellow hypergiants are rare and represent a fast evolutionary stage of massive evolved stars. That evolutionary phase is characterised by a very intense mass loss, the understanding of which is still very limited. Here we report ALMA Compact Array observations of a 50″-mosaic toward the Fried Egg nebula, around one of the few Galactic yellow hypergiants IRAS 17163-3907. The emission from the 12CO J=2-1 line, H30α recombination line, and continuum is imaged at a resolution of ~8″, revealing the morphology of the molecular environment around the star. The continuum emission is unresolved and peaks at the position of the star. The radio recombination line H30α shows unresolved emission at the star, with an approximately gaussian spectrum centered on a velocity of 21±3 km s-1 with a width of 57±6 km s-1. In contrast, the CO 2-1 emission is complex and decomposes into several components beyond the contamination from interstellar gas in the line of sight. The CO spectrum toward the star is a broad plateau, centered at the systemic velocity of +18 km s-1 and with an expansion velocity of 100±10 km s-1. Assuming isotropic and constant mass-loss, we estimate a mass-loss rate of 8±1.5 ×10-5 M⊙ yr-1. At a radius of 25″ from the star, we detect CO emission associated with the dust ring previously imaged by Herschel. The kinematics of this ring, however, is not consistent with an expanding shell, but show a velocity gradient of vsys ±20 km s-1. In addition, we find a puzzling bright feature radially connecting the star to the CO ring, at a velocity of +40 km s-1 relative to the star. This spur feature may trace a unidirectional ejection event from the star. Our ACA observations reveal the complex morphology around IRAS 17163 and illustrate the breakthroughs that ALMA will bring to the field of massive stellar evolution.
年轻星团 RSGC2 中红超巨星的 GIANO-TNG 光谱
影响因子：
6.5
作者：
Origlia L
通讯作者：
Origlia L