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arXiv 1707.09883astro-ph.SRastro-ph.GA
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V346 Nor星包层到盘的质量输运：一个FUor型年轻爆发星光度问题的个例研究

Mass transport from the envelope to the disk of V346 Nor: a case study for the luminosity problem in an FUor-type young eruptive star

Á. Kóspál, P. Ábrahám, T. Csengeri, O. Fehér, M. R. Hogerheijde, Ch. Brinch, M. M. Dunham, E. I. Vorobyov, D. M. Salter, Th. Henning

备注：
16 pages, 8 figures, published in ApJ
发表信息：
The Astrophysical Journal, Volume 843, Issue 1, article id. 45, 12 pp. (2017)
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摘要：

低质量恒星形成的一个长期存在的开放问题是光度问题：大多数原恒星的亮度低于理论预测。一个可能的解决办法是吸积过程是间歇性的。FU Ori-type星（FUors）被认为是高吸积态天体的可见例子。FUOR通常被大质量的包层所包围，这些包层补充了盘的物质，使盘能够产生吸积爆发。然而，我们没有足够的信息，信封动力学在FUOR，在哪里以及如何从信封到磁盘的质量转移发生。在这里，我们提出的ALMA观测的FUor型恒星V346也不是在1.3毫米连续和不同的CO旋转线。我们绘制了其包络的密度和速度结构，并使用通道图，位置-速度图和光谱天文测量方法分析结果。我们发现，V346也不是被包围的气态物质在10000金规模，其中一个突出的外流腔被雕刻。在中心$\sim$ 700 au内，拱星物质形成一个扁平的伪盘，其中物质以守恒的角动量下落。在$\sim$ 350天文单位内，速度分布更符合围绕中心恒星为0.1 $M_{\odot}$的开普勒旋转盘。我们确定了从信封到磁盘的6 $\times$ 10 $^{-6}\,M_{\odot}$年$^{-1}$，一个比从磁盘到恒星的静态吸积率高几个因素的下降率，暗示了作为爆发原因的下降率和吸积率之间的不匹配。

英文摘要：

A long-standing open issue of the paradigm of low-mass star formation is the luminosity problem: most protostars are less luminous than theoretically predicted. One possible solution is that the accretion process is episodic. FU Ori-type stars (FUors) are thought to be the visible examples for objects in the high accretion state. FUors are often surrounded by massive envelopes, which replenish the disk material and enable the disk to produce accretion outbursts. However, we have insufficient information on the envelope dynamics in FUors, about where and how mass transfer from the envelope to the disk happens. Here we present ALMA observations of the FUor-type star V346 Nor at 1.3 mm continuum and in different CO rotational lines. We mapped the density and velocity structure of its envelope and analyze the results using channel maps, position-velocity diagrams, and spectro-astrometric methods. We found that V346 Nor is surrounded by gaseous material on 10000 au scale in which a prominent outflow cavity is carved. Within the central $\sim$700 au, the circumstellar matter forms a flattened pseudo-disk where material is infalling with conserved angular momentum. Within $\sim$350 au, the velocity profile is more consistent with a disk in Keplerian rotation around a central star of 0.1 $M_{\odot}$. We determined an infall rate from the envelope onto the disk of 6$\times$10$^{-6}\,M_{\odot}$yr$^{-1}$, a factor of few higher than the quiescent accretion rate from the disk onto the star, hinting for a mismatch between the infall and accretion rates as the cause of the eruption.

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