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arXiv 2203.05036astro-ph.SRastro-ph.GA
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关于M17恒星形成区近距离大质量双星的起源

On the origin of close massive binaries in the M17 star-forming region

E. Bordier, A. J. Frost, H. Sana, M. Reggiani, A. Mérand, A. Rainot, M. C. Ramírez-Tannus, W. J. de Wit

摘要:

对年轻星团和OB星协中的O型星进行的光谱多重性巡天显示,这些大质量恒星(M $_{i}$ $\gt$ 15 $M_{\odot}$)中有很大一部分($\sim$ 70%)属于近距离短周期双星(物理距离d $\lt$很少au)。尽管最近取得了重大进展,但导致这种紧密的大规模多系统的形成机制仍有待阐明。因此,年轻的大质量密近双星(或高阶多重系统)是研究大质量恒星配对机制的独特实验室。我们提出了第一个VLTI/重力观测的六个年轻的O型星在M17恒星形成区($\lesssim$ 1百万年)和两个额外的前景星。从能见度振幅和闭合相位的干涉模型拟合,我们寻找同伴和测量它们的位置和流量比。结合大气模型和演化轨迹的大小差异,我们进一步限制了单个组件的质量。所有六颗大质量恒星都位于多个星系中,多重性分数(MF)为100%,68%的置信区间为94- 100%。我们检测到的9个同伴与分离高达120 au的总数。包括以前确定的光谱同伴,同伴分数的年轻O型星在我们的样本达到2.3 $\pm$ 0.6。导出的质量跨越从2.5到50 $M_{\odot}$的宽范围,具有大的倾向于高质量的同伴。虽然基于一个适度的样本,我们的结果清楚地表明,高度的多重性的起源是植根于他们的恒星形成机制。没有明确的证据之一的竞争概念的大质量恒星的形成(核心吸积或竞争吸积)可以found. However,我们的结果是兼容的迁移作为一个方案的形成密切的大质量双星。

英文摘要:

Spectroscopic multiplicity surveys of O stars in young clusters and OB associations have revealed that a large portion ($\sim$ 70%) of these massive stars (M$_{i}$ $\gt$ 15 $M_{\odot}$) belong to close and short-period binaries (physical separation d $\lt$few au). Despite the recent and significant progress, the formation mechanisms leading to such close massive multiple systems remain to be elucidated. As a result, young massive close binaries (or higher-order multiple systems) are unique laboratories to figure out the pairing mechanism of high-mass stars. We present the first VLTI/GRAVITY observations of six young O stars in the M17 star-forming region ($\lesssim$ 1 Myr) and two additional foreground stars. From the interferometric model fitting of visibility amplitudes and closure phases, we search for companions and measure their positions and flux ratios. Combining the resulting magnitude difference with atmosphere models and evolutionary tracks, we further constrain the masses of the individual components. All of the six high-mass stars are in multiple systems, leading to a multiplicity fraction (MF) of 100%, yielding a 68% confidence interval of 94-100%. We detect a total number of 9 companions with separations up to 120 au. Including previously identified spectroscopic companions, the companion fraction of the young O stars in our sample reaches 2.3$\pm$0.6. The derived masses span a wide range from 2.5 to 50 $M_{\odot}$, with a great tendency towards high-mass companions. While based on a modest sample, our results clearly indicate that the origin of the high degree of multiplicity is rooted in their star formation mechanism. No clear evidence for one of the competing concepts of massive star formation (core accretion or competitive accretion) could be found. However, our results are compatible with migration as a scenario for the formation of close massive binaries.

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